PHILOSOPHICAL ISSUES ARISING FROM CEREBRAL COMMISSUROTOMY BY DALE ROSS BARKMAN B . A . , U n i v e r s i t y of B r i t i s h Columbia , 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES (PHILOSOPHY) We accept t h i s t h e s i s as conforming to the r e q u i r e d s tandard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1978 Dale Ross Barkman, 1978 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Co lumb ia , I a g ree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s tudy . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d tha t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i thout my w r i t t e n p e r m i s s i o n . The U n i v e r s i t y o f B r i t i s h Co lumbia 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 Depa rtment i i ABSTRACT This thesis discusses the philosophical positions that have arisen out of the research with cerebral commissurotomy patients. Following this discussion we develop and defend a position of our own. The f i r s t chapter discusses the operation and the postoperative tests that were conducted. Evidence is set out that makes i t prima facie plausible that these patients have two minds. This evidence i s basically evidence that the two hemispheres are not capable of pooling their informational content in special situations. Evidence for this non integration is found in a l l the senses except taste. This chapter also discusses hemispheric specialization, language in the minor hemi-sphere and the cuing mechanisms of the s p l i t hemispheres. The second chapter is devoted to Puccetti and Bogen who argue that normal humans have two minds. Their evidence for this comes from the evidence for two minds in the cerebral commissurotomy patients. Puccetti argues that i f two minds were not present to start with, a simple operation would not e l i c i t two minds from one. Puccetti also discusses tests on normal humans that are to support his position. These arguments are discussed and rejected. The third chapter discusses additional evidence for only one mind in normal humans. Puccetti's arguments are not only inadequate in that they do not prove their point but they ignore a great deal of evidence that there is only one mind in normal humans. This evidence comes from interference that two different tasks cause for each other. There is i i i also evidence that the two hemispheres work together on one task and that their specialization i s complimentary, resulting in functional dependence, rather than being duplicative. The fourth chapter i s devoted to Eccles' attempt to reduce the minor hemisphere to an unconscious, computer l i k e entity. He argues from what he calls, 'the unity of consciousness' and on epistomological grounds concerning evidence for a mind other than one's own. The argu-ment from the unity of consciousness, however, begs the question and his epistomological considerations leave him in grave danger of solipsism. Chapter five discusses Dewitt's attempt to mediate between Eccles and Puccetti. Dewitt believes that Puccetti i s right in asserting that these patients have two minds. On the other hand he i s impressed with Eccles theory that the lack of language i n the minor hemisphere causes a great disparity between the minor hemisphere and the major hemisphere. He therefore concludes that the patients have two minds, one of which does not qualify for personhood. Dewitt, however, has gravely under-estimated the a b i l i t y of the minor hemisphere. It has more language capacity than he believes and gives every evidence of being a person. It i s also questionable whether or not language is a necessary condition for the self-awareness that goes with personhood. Chapter six looks at Robinson's attempts to undermine the two mind interpretation of the evidence. He does this mainly by trying to find tiimilar counter examples that resist a two mind interpretation. His program f a i l s due to the dissimilarity of the counter examples and the cerebral commissurotomy results. i v Chapter seven considers Nagel's contention that the patients have an uncountable number of minds. Nagel does not believe that there is a strange uncountable number of minds that these patients actually have. Instead he believes that i t i s impossible to say how many minds they do have because we do not know how to count them. Nagel reasons that we have good evidence to believe that the patients have one mine and good evidence that they have two. Since both cannot be true we do not know what to say about these patients. Nagel believes that the above consid-erations make i t d i f f i c u l t for us to understand these patients' mental lives. We agree with Nagel that there are times when i t i s d i f f i c u l t i f not impossible to say how many minds the commissurotomy patient has. We disagree that this i s always the case. Our problem with counting i s not, however, a failure to understand something about the patients' mental lives, but i s due to a counting problem when two hemispheres are only pa r t i a l l y integrated. We agree with a suggestion from Nagel that an unusual connection between the hemispheres does not settle the ques-tion of how many minds the patient might be said to have. The hemispheres do seem to be able to integrate or pool their information using sophisti-cated muing mechanisms. Our position i s that the patients usually have one mind that inte-grates the two hemispheres of the brain by cuing. The testing situations, however, interfere with this cuing and thereby cause a temporary, partial nonintegration between the hemispheres. During this time we, therefore do not know how many minds the patient can be said to have. V TABLE OF CONTENTS Page ABSTRACT i i - i v ACKNOWLEDGEMENTS v i i i Chapter I. PHENOMENA SURROUNDING THE SURGICAL SEPARATION OF THE TWO HEMISPHERES OF THE BRAIN 1 The Operation 1 Behavioral Results Following ' Cerebral Commissurotomy 3 Tactual Symptoms 4 Visual Symptoms 7 Olfactory Symptoms . 9 Audio Symptoms 10 Cross-modal Integration 11 Hemispheric Specialization 12 Language in the Minor Hemisphere 17 Cuing Mechanisms 18 Conclusion 22 II. ARGUMENTS FOR TWO MINDS IN NORMAL HUMANS 24 Introduction 24 The Arguments Presented: Different Informational Content 25 Questions Concerning Mind Splitting 27 Amytal Experiments with Normal Subjects 29 v i The Shape of the Brain 30 Arguments from the Functional Independence of the Hemispheres 31 Consideration of the Arguments for Two Minds in the Normal Human 32 Different Information Content 32 Questions About Splitting the Mind . . . . . . . . . 36 Amytal and Normal Subjects 39 The Shape of the Brain 43 Functional Independence of the Hemispheres 44 III. ONE MIND IN NORMAL HUMANS 47 Introduction 47 Interference 47 Two Hemispheres Working on One Task 51 Evidence from Hemispheric Specialization 53 IV. ARGUMENTS FOR ONE MIND IN BRAIN BISECTED PATIENTS . . . 56 Introduction 56 Unconscious Behavior 56 The Unity of Consciousness 59 Epistomological Considerations 60 Objections to Eccles 61 Another Look at Unconscious Behavior 61 The Unity of Consciousness 63 Eccles' Epistomological Grounds For Postulating Conscious States 65 y i i V. AN ATTEMPT TO MEDIATE BETWEEN PUCCETTI AND ECCLES . . . 68 Introduction 68 Humans and Personhood 69 Dewitt's Criterion of Personhood 71 The Failure of Dewitt's Program 73 Self-Awareness and the Minor Hemisphere 75 Language i n the Minor Hemisphere, 77 VI. FURTHER ATTEMPTS TO SEE SPLIT-BRAIN PATIENTS AS HAVING ONE MIND 78 Counter Examples . 78 Commissurotomy Symptoms as an Instance of a Larger Agnosias Class 81 The Split-Mind Thesis Defended 82 VII. AN UNRESOLVABLE PROBLEM 88 Introduction 88 The Problem With the Positions 89 Mental Unity 93 Counting Complex Entities 95 Problems with Counting 95 Reworking the Position that Asserts Two Minds only During the Tests 98 CONCLUSION 105 FOOTNOTES 106-112 BIBLIOGRAPHY 113-117 v i i i Acknowledgements I would l i k e to thank Gary Wedeking and James Dybikowski f o r t h e i r p a t i e n c e and a d v i c e as I wrote t h i s t h e s i s . They gave me w ise c o u n c i l on what to l eave out and what needed to be i n c l u d e d . I would a l s o l i k e to thank my aunt , Mable Epp, f o r going over the t e x t w i t h me to c o r r e c t s p e l l i n g and s t y l i s t i c e r r o r s . My t y p i s t , Joyce Welwood, was most h e l p f u l i n p o i n t i n g out s i m i l a r e r r o r s . The e r r o r s tha t remain a r e , of course my own. 1 CHAPTER I PHENOMENA SURROUNDING THE SURGICAL SEPARATION OF THE TWO HEMISPHERES OF THE BRAIN The Operat ion When J . E. Bogen and P. J . Vogel f i r s t s e c t i o n e d the corpus ca l losum of a f o r t y - e i g h t year o l d man i t was not a new concept ion i n surgery .^ R. W. Sperry had been do ing e x t e n s i v e r e s e a r c h w i t h animals whose commissures had been s p l i t and cases of the o p e r a t i o n i n v o l v i n g humans had been repor ted as e a r l y as 1944. S p e r r y ' s exper iments had been done ma in l y to d i s c o v e r how the d i f f e r e n t hemispheres were r e l a t e d to one another . The e a r l i e r human cases had been performed to h e l p cure c e r t a i n e p i l e p t i c symptoms but the r e s u l t s of the o p e r a t i o n had been i n c o n c l u s i v e . Bogen and V o g e l , however, on l o o k i n g a t the r e s u l t s of the e a r l i e r o p e r a t i o n s noted tha t at l e a s t four of the human p a t i e n t s had shown some s i g n of improvement. Fur thermore , on l y one of the p a t i e n t s had the a n t e r i o r commissure s e c t i o n e d . S i n c e t h i s commissure was c l e a r l y important i n c e r t a i n e p i l e p t i c s e i z u r e s the d o c t o r s f e l t tha t the o p e r a t i o n cou ld have some chance of success f o r the c o n t r o l of c e r t a i n k i n d s of severe e p i l e p t i c c o n d i t i o n s . W. J . , t h e i r p a t i e n t , had f i r s t been i n j u r e d d u r i n g the war a t the age of t h i r t y . He was unconscious f o r about f o r t y - e i g h t hours and taken c a p t i v e . In c a p t i v i t y he had been h i t w i t h a r i f l e b u t t and l o s t one hundred pounds. H i s f i r s t c o n v u l s i o n occur red i n 1951 d u r i n g an emergency o p e r a t i o n . In 1956 he had a minimum of two to th ree 2 convulsions per day and one seizure that year lasted almost a week. Because the patient's condition could not be controlled through medica-tion his desperate situation caused the doctors to consider every possible solution to the problem. Finally on February 6, 1962 the corpus callosum down to the anterior commissure was sectioned in an attempt to control his epilepsy. The procedure of operation was simple in conception. Once into the skull the right hemisphere was l i f t e d away from the l e f t and the commissures were sectioned with a small suction needle. This procedure minimizes the brain damage although some damage may be done by l i f t i n g the right side. The amount of damage is d i f f i c u l t to estimate because W. J., like a l l the patients since, have suffered previous brain damage. Following the operation W. J. seemed to be paralized on the l e f t side of his body while the right side had hyperactive reflexes. The patient remained mute for a week and could not feed himself. The patient recovered rapidly so that at the end of a month his only symptoms were a sensory d e f i c i t and a persistent tonic grasp reflex on the l e f t side. After four months the patient was able to perform bimanual tasks without impairment and could walk. Furthermore, his epileptic seizures came under control without the heavy medication that was used before. The patient, who had also been chronically underweight, gained forty pounds and began to lead a normal l i f e . W. J. is typical of the cerebral commissurotomy patients in that a l l suffer from some brain damage and the operation is only a last resort. Not a l l are as damaged as W. J. nor do they a l l take as long to recover. Other variations center around deciding which half of the 3 b r a i n w i l l be exposed. J u s t r e c e n t l y the o p e r a t i o n has been changed so tha t i t does not s e c t i o n the e n t i r e corpus c a l l o s u m . Th is procedure i s found to c o n t r o l the symptoms as e f f e c t i v e l y as a f u l l s e c t i o n i n g . At the same t ime i t does not r e s u l t i n the unusual symptoms of d i s s o c i a t i o n tha t s p l i t - b r a i n p a t i e n t s m a n i f e s t . B e h a v i o r a l R e s u l t s F o l l o w i n g C e r e b r a l Commissurotomy The most remarkable t h i n g about these p a t i e n t s i s , how normal they appear to be . They were so normal that i n the n i n e t e e n f o r t i e s i t was s p e c u l a t e d tha t the s o l e f u n c t i o n of the .corpus ca l losum was to keep the hemispheres from s a g g i n g . The p a t i e n t s are capable of l i v i n g normal l i v e s a t home and c o u l d , a f t e r a s u i t a b l e r e c o v e r y , even pass a m e d i c a l exam w i thout showing any abnormal e f f e c t s . Through cases of b r a i n surgery i t has been known f o r a long t ime tha t the l e f t hemisphere i s u s u a l l y i n c o n t r o l of the r i g h t s i d e of the body and the r i g h t h e m i -sphere c o n t r o l s the l e f t s i d e . These p a t i e n t s , however, have no problem w a l k i n g , t y p i n g , swimming, b u t t o n i n g up t h e i r s h i r t or a wide range of o ther manouvers tha t r e q u i r e the two hemispheres to work i n harmony. F o l l o w i n g recovery from c e r e b r a l commissurotomy i n monkeys, Sperry remarks tha t they " a r e h a r d l y d i s t i n g u i s h a b l e from normal animals i n 2 t h e i r l a b o r a t o r y b e h a v i o r . " Most p a t i e n t s , a l s o , do not compla in of l o s s of s e n s a t i o n from e i t h e r s i d e or of an incomplete v i s u a l f i e l d . Those who do complain of l o s s of s e n s a t i o n on the l e f t s i d e u s u a l l y have e x t e n s i v e r i g h t hemisphere damage tha t would account f o r the s low recovery of t h i s s e n s a t i o n . 4 Most brain bisected patients also seem to .have voluntary control of a l l their limbs. In test situations they move either arm at w i l l and only in rare circumstances complain that one arm seems to be moving on i t s own. The patient might not know why he pointed at a certain object but the effort to move the arm i s a voluntary, conscious effort. In this regard the patient seems to be a normal unitary person. Tactual Symptoms Upon closer examination, especially in closely controlled situations, the patients do show remarkable abnormalities. The symptoms are reported 3 by Gazzaniga, Bogen and Sperry. They blindfolded the patient so that he could not see where he was being touched. The patient would then be touched lightly with something like a pencil and was required to point with his finger to the place where he was touched. At times he was told to use either his l e f t or his right hand while at other times he could choose either hand. The results indicated that the patient could consistently identify the spot stimulated " i f both the stimulus and the response were kept to 4 the same side of the body." That is i f the l e f t leg, arm, or trunk of the body was stimulated a finger on the l e f t hand could identify the spot. The case was similar for the right side of the body. These responses were without hesitation and could also be performed i f a delay of five, ten or twenty seconds was imposed. Under free hand use the patient usually used the l e f t hand for the l e f t side of his body and the right hand for the right side. The only exception came when stimulus was in the f a c i a l and neck areas. In these areas either hand was used freely, regardless of which side of the face 5 or neck was involved. The problem came when the patient was asked to indicate the stimulated area with the l e f t hand when the right side was involved or vice versa. This was even true after some refinement of the test, with areas close to the left-right divisional center of the body. With the le f t hand there were times when the right leg would be stimulated and the l e f t hand would make no attempt at a l l to find the point. The problem, therefore, was not just that the place indicated was grossly inaccurate but the stimulation was missed completely. Similar results were obtained when the other side was tested. At times the le f t hand would indicate the place stimulated even after being ordered not to respond. The right side did not seem to be aware of either the stimu-lation or the response of the l e f t hand as i t did not make any attempt to respond. When the patient was asked why he had not responded he replied that he had not been touched. Another type of test required the patient to tap with his fingers the number of times that he was touched. The same sort of result was seen. If the right hand was used for touches on the l e f t , the response was never above the chance level. Other tests found the same result for temperature. The patient would be given a glass of cold water in the right hand. If asked to find a glass of the same temperature he could do this with his right hand but his l e f t hand performed at chance levels. The areas of the face and neck did not show this left-right syndrome. One hand could not even indicate the position a pencil was held in the other hand. A pencil would be placed in one hand of the patient and 6 t i l t e d . The patient was then to take the other hand and touch the end of the p e n c i l . I t turned out that he was not able to do t h i s with any accuracy. An i n t e r e s t i n g r e s u l t occurred when the patient was asked f o r a verb a l report of some of the sensations that he had been subjected to. It i s known independently of these tests that the brain i s l a t e r a l i z e d for speech. In the vast majority of right-handed people the l e f t hemisphere i s capable of speech while the r i g h t side i s not. When asked about the stimulus the patient was able to c o r r e c t l y i d e n t i f y what was happening on the r i g h t side of h i s body but unable to t e l l what was happening on the l e f t . When the limbs of the patient were put at d i f f e r e n t angles by the doctors the patient could t e l l what p o s i t i o n the r i g h t limbs and j o i n t s were i n . On the le f t , the p o s i t i o n of the l e f t shoulder could be reported along with the positi o n s of the knee and ankle. The positions of the toes, elbow, fingers and wrist however, could not be reported. While the patient might not be able to t e l l the p o s i t i o n of h i s limbs i p s i l a t e r a l l y there i s some evidence that the hemispheres can pick out ki n e s t h e t i c movements b i l a t e r a l l y . Levy, Nebes, and Sperry"* report a patient who was t o l d to touch some p l a s t i c l e t t e r s that s p e l l e d a word. The patient would brush h i s l e f t hand over the l e t t e r s . He was not able to v e r b a l l y t e l l what the word was. He was then asked to write the word out with h i s l e f t hand. Aft e r the word was written the patient was capable of v e r b a l l y i d e n t i f y i n g the word. The examiners suggested that t h i s behavior i s evidence that the major hemisphere can pick out the f i n e k i n e s t h e t i c movements of the hand and even the fingers 7 on the i p s i l a t e r a l side but that i t cannot pick out tactual stimulation i p s i l a t e r a l l y . Therefore the major hemisphere was not able to identify the word when i t was just touched but could pick i t out when i t was written. Many similar types of tests have been done that show that the l e f t hemisphere does not seem to be aware of what is going on in the opposite hemisphere. Since the brain basically gains bodily information contra-l a t e r a l ^ , stimulus to the l e f t of the body goes to the right hemisphere and vice versa. Tests like the above seem to indicate that only one hemisphere gains the information. More complex tests are possible. For instance, the patient i s asked to feel an object out of sight and later identify i t by pointing to i t or by picking i t up. When the l e f t hand has done the i n i t i a l identification i t can also point to the object. If the right hand is required to identify what object the l e f t f e l t i t cannot do so manually or verbally. If the right hand does attempt to identify the object i t performs at chance levels. The hemispheres therefore do not seem to be able to convey tactual information between themselves under these circumstances. Pain and kinesthetic stimulus however, is represented bilaterally in both hemispheres. Visual Symptoms The same basic results are obtained for visual stimulus. The patient's optic chiasms are not s p l i t so each eye directs information into each hemisphere. It seems, however, that each eye sends the l e f t visual f i e l d information to the right hemisphere and the right visual f i e l d information to the l e f t hemisphere. Thus the eye's retina i s divided into two reporting sections. The l e f t half of the retina 8 reports to the l e f t hemisphere and v i c e versa. The c o n t r a l a t e r a l i t y of the hemisphere to the v i s u a l f i e l d i s accomplished through the i n v e r t i n g e f f e c t of the lens of the eye. Gazzaniga reports that the patients were subjected to a test i n which a se r i e s of l i g h t s were flashed, each l i g h t at one tenth of a second, across the v i s u a l f i e l d from l e f t to r i g h t . The patient was then asked what he had seen. Each patient only "reported that l i g h t s had been flashed i n the r i g h t h a l f of the v i s u a l f i e l d . " ' ' A s i m i l a r r e s u l t was obtained when flashes were presented at random i n the v i s u a l f i e l d . Flashes i n the r i g h t v i s u a l f i e l d were reported while l e f t v i s u a l f i e l d flashes were not reported and i n f a c t were v e r b a l l y denied.^ Since the r i g h t hemisphere i s not capable of speech a verbal response i s impossible unless i t somehow sent the information to the l e f t hemisphere. I t was found that when the r i g h t hemisphere was able to respond i n a non-verbal manner to v i s u a l stimulus that i t performed at the same l e v e l as the l e f t hemisphere. The f a i l u r e to report flashes i n the l e f t v i s u a l f i e l d therefore i s explained because the r i g h t hemi-sphere cannot give a verbal response. Any conscious area of the mind a v a i l a b l e f o r verbal recognition does not seem to be aware of the stimulus. I t seems therefore that the r i g h t hemisphere has not been able to inform the l e f t hemisphere of the information that i t has obtained. This lack of i n t e g r a t i o n , however, would seem to i n d i c a t e that the mind of the patient had been s p l i t with the sectioning of the corpus callosum. The two hemispheres i n the case of touch and sight do not seem to be connected i n a way that they are aware of what i s 9 happening in the other hemisphere. Visual tests that require some integration of the information of both hemispheres showed the same sort of lack of integration. A continuous line would extend from the left to the right with a break in the middle of the visual field. To see this break the patient would of course have to see the line and the other line start. The patient's visual field on the one side, however, ends at the middle of the visual field. The patient was not able to t e l l that there was a break in the line. Similarly they could not te l l i f the two lines met at an angle if they met at the middle point. Thus the hemispheres could not pool their visual information. Olfactory Symptoms The sense of smell is also lateralized in these patients. This lateralization is ipsilateral. The right nostril reports to the right hemisphere and the left nostril reports to the left hemisphere. As with tactual and visual stimuli there does not seem to be free access of olfactory information between the hemispheres. The tests in this 9 area were done by Sperry and H. W. Gordon. Vials containing different olfactory stimuli would be presented to one of the nostrils for identi-fication. The patient would have to either say what the odour smelled like or respond by pointing to the type of object giving the smell, depending on the examiner's instructions. The examiners found i t was necessary not only to block off the patient's nostril that was not being tested but right after the presentation of the stimulus the other nostril had to be blocked off. When this was not done the turbulence in the sinus cavities seemed to allow some cross feeding of the odour to the other nostril. 10 What was found was that when a stimulus was presented to the r i g h t n o s t r i l the patient would report that he had smelled nothing. Occasion-a l l y i f the substance had a p a r t i c u l a r l y bad smell he could i n d i c a t e that the smell was repugnant but he could not i d e n t i f y i t . On the other hand i f a manual response was c a l l e d f o r the patient could point to the stimulus with h i s l e f t hand. Gordon and Sperry t e l l of a case where the v i a l presented to the r i g h t n o s t r i l contained coffee. The l e f t "hemisphere 'forgot' to keep s i l e n t and gave the response 'water'. Simultaneously, the l e f t hand immediately reached out toward the coffee cup.""*"^ When asked about her response she apologized for speaking but reminded them that they had t o l d her to say 'water' i f she smelled nothing. She explained the response of the l e f t hand by saying that "she had simply l e t the hand go where i t wanted, adding the comment that sometimes i t seemed to 'have a mind of i t s own'."^ Thus the sense of smell i s also l a t e r a l i z e d i n the hemispheres. The hemispheres of b r a i n bisected patients are not able to communicate with each other what smells are being smelled by each r e s p e c t i v e l y . Audio Symptoms Hearing i s represented i n the hemispheres i n a somewhat more com-plex manner than touch, v i s i o n and smell. With the appropriate experiments, however, the same sort of data can be obtained. The complexity arises due to the f a c t that each ear feeds both hemispheres with audio information. What allowed the experiments to succeed was that the ear transmitted a stronger s i g n a l to the c o n t r a l a t e r a l hemisphere than to the i p s i l a t e r a l one. Thus i f both ears were simultaneously given c o n f l i c t i n g s t i m u l i the hemispheres would tend to ignore the 11 weaker i p s i l a t e r a l input and concentrate on the contralateral input. An example of a test was one in which six digits were presented to the patient. Three were given i n one ear and the other three were given simultaneously to the other ear. It was found that the callosum-sectioned patients were "unable to report with any great accuracy those 12 presented to the l e f t ear." Another test is more sophisticated. Two nonsense words are presented simultaneously, one to each ear. For instance, one ear would hear 'rahduct' while the other would hear 'pahduct'. Normal subjects would identify the word as 'product' since the mind would fuse the two stimuli into the one word. One cerebral commissurotomy patient, however, did not hear the fused word. Instead 13 he only reported "the word presented to the right ear." The other patient who was tested reported the fused word. Gazzaniga speculates that the difference could be in some unknown difference in the extent of the surgery. It could also be that the latter patient was more adept at using the weaker i p s i l a t e r a l input along with the contralateral. Cross-modal Integration Although cross-modal integration has not been specifically commented on or tested i t has been presumed to be normal by the examiners. That i s , of course, as long as the integration i s restricted to one side. For instance, at times the patient has been asked to feel an unseen object with his l e f t hand. Then a number of objects are shown to him visually and he is asked to point with his l e f t hand to the object that he touched. He has no problem completing this task even though the input was tactual while the output required visual recognition. The 12 same type of response was r e q u i r e d f o r t e s t s to do w i t h s m e l l . The p a t i e n t smelled something he could not see and then picked the object out of a number of objects that he could see. There was no problem w i t h t h i s s o r t of i n t e g r a t i o n . The only time when t h i s presented a problem was when d i f f e r e n t hemispheres were i n v o l v e d i n the i n t e g r a t i o n . I f the l e f t hand-right hemisphere touched an obje c t the r i g h t h a n d - l e f t hemisphere could not i d e n t i f y i t by touch. At the same time i t could not i d e n t i f y i t by speech, or by p o i n t i n g to i t w i t h the r i g h t hand. The problem was not only one of cross-modal i n t e g r a t i o n but arose even on the l e v e l of inter-modal i n t e g r a t i o n . There was a t a c t u a l - t a c t u a l agnosia as w e l l as a t a c t u a l - v i s u a l agnosia. Yet i f the l e f t hemisphere was e x c l u -s i v e l y i n v o l v e d i n the i n t e g r a t i o n everything i n t e g r a t e d normally. I t woul'd seem th e r e f o r e that as f a r as cross-modal i n t e g r a t i o n went that these p a t i e n t s are normal. The l a c k of i n t e g r a t i o n when d i f f e r e n t hemispheres are i n v o l v e d i s b e t t e r explained by saying that the hemispheres are cut o f f from each other than to say that some k i n d of modal i n t e g r a t i n g agnosia i s at work. The p a t i e n t s ane too able to i n t e g r a t e cross-modal i n f o r m a t i o n to make such a response p l a u s i b l e . Hemispheric S p e c i a l i z a t i o n As has already been mentioned one hemisphere, u s u a l l y the l e f t , i s s p e c i a l i z e d f o r speech. This i s not the only f u n c t i o n that t h i s hemi-sphere i s dominant i n . I t i s a l s o the hemisphere that i s capable of mathematical and l o g i c a l reasoning. The best that the other hemisphere seems to be able to do i n t h i s area i s to count and perhaps perform minor a d d i t i o n s and s u b t r a c t i o n s . Having f u l l c a p a c i t y f o r speech, the 13 speech, or dominant hemisphere, i s capable of a wide range of a c t i v i t i e s . I t i s capable of abstract t h i n k i n g , reasoning and car ry ing on the high l e v e l of human a c t i v i t i e s that our soc ie ty demands of i t . Since we value th i s sort of capaci ty to such a high degree we tend to overlook other c a p a c i t i e s . With these pat ients there was even some i n i t i a l doubt as to what the other hemisphere r e a l l y d i d . I t c e r t a i n l y was capable of sensory process ing but that forms a rather p r i m i t i v e r o l e i n our day to day mental l i f e . The specula t ion was that the speech hemisphere was the dominant one and the other hemisphere ju s t tagged along as a s i l e n t and not too g i f t e d par tner . The 'minor ' hemisphere was seen as a non-act ive p a r t i c i p a n t i n one's day to day a f f a i r s . That p i c t u r e has now changed. The s i l e n t hemisphere might s t i l l be thought to be the minor hemisphere, but i t i s recognized that i t d i f f e r s from the major hemisphere i n that i t i s s p e c i a l i z e d for a d i f f e r e n t range of mental processes . These processes were missed at f i r s t because they were not thought to be as important as the other more l o g i c a l capac-i t i e s . In f a c t , however, they are extremely important to our day to day l i f e . One area i n which the minor hemisphere has a c lear advantage over the other hemisphere i s i n i t s a b i l i t y to recognize non-descr ipt 14 pat terns . J . Levy, C. Trevarthen and Sperry devised tests to show th i s advantage of the minor hemisphere. They took four d i f f e r e n t types of patterns to be i d e n t i f i e d . There were faces , a n t l e r s , drawings of f a m i l i a r objects ( i . e . , roses , . eyes and bees) and patterns of squares and crosses . The patterns were then arranged so that they were s p l i t down the middle . I f faces were used one ha l f of the pa t tern would be h a l f of one face whi le the other h a l f would be the other s ide of another 14 face. The pattern would look l i k e a complete pattern with the exception that there was no symmetry between the sides. When the patient was exposed to the pattern for a brief instance one half face would be projected into one hemisphere while the other half face would be pro-jected into the other. The hemispheres presumably f i l l e d out the miss-ing half of the face in a manner appropriate to the half face that i t already saw. The examiners knew which pattern had been fed into each hemisphere. The response that the patient made would therefore t e l l which hemisphere was responding. The results were very interesting. With each of the different patterns the patients were tested with the l e f t hand pointing, the right hand pointing and a vocal naming of the object. When the l e f t hand identified faces that were seen 89% of the responses indicated the face flashed to the l e f t visual f i e l d . 10% indicated the face i n the right visual f i e l d and 1% of the responses were in error. The right hand, however, pointed 75% of the time to ,the faces flashed to the l e f t visual f i e l d , 20% of the responses were for right visual f i e l d and 5% of the responses were wrong. It seems by these results that the right hemisphere seems to be better able to recognize non-descript patterns such as faces than the l e f t hemisphere. Furthermore, i t also seems that the minor hemisphere is able to gain control of the i p s i l a t e r a l motor system and respond with the right hand. The right hand's response cannot be seen as evidence for some cross integration of information between the hemispheres. This was seen when the subject was required to name the face. The subject f i r s t was required to memorize the names of three faces. These faces were 15 made to be e a s i l y d i s t i n g u i s h a b l e i n tha t one had g l a s s e s and another had a moustache. The p a t i e n t s t i l l had a g reat d e a l of d i f f i c u l t y memorizing these names and d i d so by the a s s o c i a t i o n of ' D i c k ' w i t h g l a s s e s , ' P a u l ' w i t h moustache, e t c . Once t h i s task was l e a r n e d the above experiment was t r i e d . 49% of the responses named the f a c e f l a s h e d to the r i g h t v i s u a l f i e l d , 36% of the responses went to the l e f t v i s u a l f i e l d and 15% were i n e r r o r . S i m i l a r types of responses were ob ta ined i n each of the other types of p a t t e r n s . The d i f f e r e n c e between the v o c a l response and the r i g h t hand p o i n t i n g would seem to i n d i c a t e tha t d i f f e r e n t hemispheres were c o n t r o l l i n g the two responses . I t would seem, t h e r e f o r e , t h a t the r i g h t hemisphere has a c l e a r advantage over the l e f t i n r e c o g n i z i n g n o n - d e s c r i p t p a t t e r n s . Not on ly d i d the r i g h t hemisphere immediately l e a r n the p a t t e r n s , but i t d i d b e t t e r a t p o i n t i n g , w i thout p r i o r memor izat ion than the l e f t d i d a f t e r much study and a g o n i z i n g . The f a c t t h a t t h e r e were v o c a l and p o i n t i n g responses to the s i d e that cou ld be presumed to be cut o f f from the hemisphere r e s p o n d i n g , cou ld be e x p l a i n e d by the f a c t tha t these p a t i e n t s were a l r e a d y f a i r l y good a t cu ing the other hemisphere i n . Therefore the l e f t hemisphere might c o r r e c t l y name the f a c e seen by the r i g h t because the r i g h t was a b l e to cue i t i n . I t i s e v i d e n t , however, tha t the r i g h t hemisphere responded through the r i g h t hand s i n c e the p e r c e n -tage of r i g h t v i s u a l f i e l d responses to a p a t t e r n jumped from a low of 4% w i t h the r i g h t hand p o i n t i n g to a h i g h of 63% when a v e r b a l response was c a l l e d f o r . D i f f e r e n t hemispheres seem to be doing the responding h e r e . B. M i l n e r and L. Taylor"'""' f i n d the same s o r t of r i g h t hemispher ic 16 s u p e r i o r i t y and also f i n d evidence that the r i g h t hemisphere i s capable of nonverbal memory. Milner and Taylor had t h e i r subjects f e e l a non-sense wire pattern that was out of sight. The patient was then to pick out the pattern from among four such patterns. The same hand was used f o r both receiving the stimulus and t e s t i n g the memory. If the patient succeeded with one hand that hand was then given the same task only t h i s time a f t e r an i n t e r v a l of f i f t e e n seconds. Further delays of t h i r t y , s i x t y and one hundred and twenty seconds were imposed. Out of the seven patients f i v e were unable to i d e n t i f y the pattern with t h e i r r i g h t hand at a l l . One was able to i d e n t i f y i t i f there was no delay and one succeeded a f t e r a s i x t y second delay. With the l e f t hand, however, one was capable of i d e n t i f i c a t i o n a f t e r a 15 second delay, another reached the 30 second delay and four reached a l e v e l of 120 second delay. The same patient that was capable of a s i x t y second delay with the r i g h t hand was also stopped at the same point with h i s l e f t . I t seems evident that the r i g h t hemisphere i s capable of storing a non-verbal type of memory and that i t i s more capable of t h i s type of recognition than the l e f t hemisphere. The r i g h t hemisphere i s also more capable of comprehending three dimensional objects. If asked to match cardboard cutouts with a three dimensional object that the cutouts could be folded up i n t o , the l e f t hand would respond immediately to the task and approach i t i n a d i r e c t manner. When forced to do the task with the l e f t hemisphere, however, the patient would attack the problem h e s i t a n t l y and with a verbal read-out of how i t was working the problem out."^ The two hemispheres, therefore, seem to approach the matter i n fundamentally d i f f e r e n t ways. 17 The minor hemisphere seems to take a w h o l i s t i c approach while the major hemisphere looks f o r l a b e l s and a way to work the problem out. When the problem or pattern defies d e s c r i p t i o n the major hemisphere's perform-f ance drops dramatically while the minor hemisphere's r i s e s to the point of sometimes even being able to take over the i p s i l a t e r a l motor system. Language i n the Minor Hemsiphere The minor hemisphere has l i t t l e i f any a b i l i t y to speak v e r b a l l y . A f t e r the s u r g i c a l removal of the major hemisphere i t seems capable of e x p l i c a t i v e s and other short, highly patterned responses. While t h i s output i s rather meager there i s evidence of some language capacity. Levy, Nebes and Sperry did some work i n t h i s f i e l d using p l a s t i c 17 l e t t e r s . The patients would be given one or two l e t t e r s i n h i s l e f t hand and t o l d that i t could s p e l l a word i f he arranged them c o r r e c t l y . The patient responded'correctly i n a l l s i x of the cases. Another te s t presented the l e t t e r s i n the correct order already. The patient was asked what word was s p e l l e d . He was not able to i d e n t i f y the word so he was then t o l d to write the word with h i s l e f t 18 hand. He got nine of the ten words correct. In another t e s t an item from a s e r i e s of household items was presented out of sight to the l e f t hand. The patient was then asked to write the word for what was i n that hand. This was a d i f f i c u l t task and was done l a b o r i o u s l y . When handed a pipe he started to write the 'p' and the ' i ' . At t h i s point the writing became much more relaxed and the word ' p e n c i l ' was written. He then paused, stroked out the l a s t four l e t t e r s and s a i d he did not know what the object was. He was capable of 19 drawing the object, however, when he was asked to. 18 These p a t i e n t s t h e r e f o r e do seem to be a b l e to comprehend some words and can produce the a p p r o p r i a t e ones by w r i t i n g i f not v e r b a l l y . 20 Gazzaniga and S . H i l l y a r d r e p o r t tha t the p a t i e n t s ' minor hemispheres are good on s imple nouns l i k e 'boy ' and ' g i r l ' but are not good at combining these s imple nouns i n t o sentences w i t h v e r b s . They do not seem to be a b l e to recogn i ze the c o r r e c t use of the f u t u r e t e n s e , nor 21 were they a b l e to p i c k the c o r r e c t use of the p l u r a l . The o n l y h i g h e r grammat ica l d i s c r i m i n a t i o n they d i d seem to be a b l e to make was between the a f f i r m a t i v e and the n e g a t i v e . The p a t i e n t s do , however, seem to be ab le to comprehend enough language to be a b l e to f o l l o w the i n s t r u c t i o n s of t h e i r t e s t e r s . P a t i e n t s who on ly have a minor hemisphere are a b l e to keep appointments and understand what i s be ing s a i d to them to a h i g h degree. The minor hemisphere t h e r e f o r e has a g r e a t e r c a p a c i t y f o r unders tand ing than i t does f o r p r o d u c t i o n of language. I t i s n o t , however, on the same l e v e l w i t h the major hemisphere. Cuing Mechanisms I t was soon found tha t the hemispheres were very apt a t cu ing each o ther i n on the i n f o r m a t i o n tha t they h a d . The t e s t s dev ised to show that there was a s p l i t between the hemispheres had to become i n c r e a s i n g l y more s o p h i s t i c a t e d to avo id t h i s manner of c r o s s - c o m m u n i c a t i o n . There are many d i f f e r e n t ways tha t t h i s cu ing i s done. One method of cu ing seems to come from something l i k e the emot ions . A good or repugnant f e e l i n g i n one hemisphere t r a n s f e r s to the other even though the l a t t e r hemisphere has no i d e a of what causes the emot ion . Gazzaniga g i v e s an example where a p i c t u r e of a nude was f l a s h e d to the 19 l e f t v i s u a l f i e l d . The p a t i e n t s m i l e d and chuck led but cou ld not t e l l what had been seen . Ins tead she s a i d that the "machine was funny , or 22 s o m e t h i n g . " Something l i k e t h i s was a l s o seen above i n the s e c t i o n on o l f a c t o r y responses . The r i g h t n o s t r i l was exposed to a bad s m e l l . The l e f t hemisphere knew that the s m e l l was repugnant but i t cou ld not i d e n t i f y the s t i m u l u s . There i s some s p e c u l a t i o n tha t t h i s type of i n f o r m a t i o n t r a n s f e r i s accompl ished through the i n t a c t b r a i n stem. Both hemispheres are connected to t h i s stem and i t i s b e l i e v e d tha t the emotions a r i s e i n t h i s area of the b r a i n . Whi le emotions u s u a l l y have a c o g n i t i v e component we are a l s o s u b j e c t to vague unexp la ined f e e l i n g s . The b r a i n stem cou ld t r a n s f e r the vague f e e l i n g and thus the emotion would a r i s e w i t h -out the c o g n i t i v e i n p u t . Another p o s s i b l e e x p l a n a t i o n i s tha t the emotions are t r a n s f e r r e d through the f a c i a l musc les . Both hemispheres can c o n t r o l and r e c e i v e i n f o r m a t i o n from the f a c e and neck a r e a s . In the above cases the minor hemisphere would presumably s m i l e and chuck les when p l e a s e d , and c o n t o r t the f a c e a t the bad s m e l l . The major hemisphere would n o t i c e t h a t i t s f a c e was s m i l i n g or c o n t o r t i n g and would search f o r an e x p l a n a t i o n . S ince i t does not acknowledge the minor hemisphere i t must f i n d the cause of t h i s behav ior w i t h i n i t s e l f . I t has no i d e a of the c o g n i t i v e b a s i s f o r i t s response , but i t knows tha t the response must have been caused by something good or bad . I t , t h e r e f o r e , r e p o r t s the vague answer and would s t a r t to f e e l the a p p r o p r i a t e emotion t h a t i s be ing expressed by i t s f a c i a l m u s c l e s . Gazzaniga r e p o r t s another cu ing method. Whi le t e s t i n g p a t i e n t s ' 20 responses to f l a s h e s of l i g h t examiners d i scovered tha t the p a t i e n t s e v e n t u a l l y were a b l e to v e r b a l l y r e p o r t f l a s h e s i n the l e f t v i s u a l f i e l d . They d i scovered the cu ing method by c a r e f u l o b s e r v a t i o n of the p a t i e n t . A f t e r the f l a s h the p a t i e n t ' s eyes would dar t to focus on the area of the f l a s h . The f l a s h was shor t enough tha t i t was over be fo re the eyes cou ld focus on i t , so the major hemisphere cou ld not have d i r e c t l y exper ienced the f l a s h . Yet i t cou ld r e p o r t i t s i n c e i t knew where the eyes had f o c u s e d . A f t e r some time the major h e m i -sphere would subconsc ious l y come to b e l i e v e that i t a c t u a l l y saw the 23 f l a s h . The above cu ing hypothes i s was t e s t e d by p r e s e n t i n g two s i m u l -taneous f l a s h e s to the r i g h t and l e f t hemispheres . The eyes could not d a r t t t o both so the cu ing method was s topped . In t h i s case on ly the f l a s h to the r i g h t v i s u a l f i e l d was v e r b a l l y r e p o r t e d . The f l a s h to the o ther f i e l d cou ld on ly be repor ted n o n - v e r b a l l y w i t h the l e f t s i d e of the body. A s i m i l a r type of cu ing i s a l s o used by the hemispheres when the c o r r e c t ob jec t must be p i c k e d out of a number of o b j e c t s . I f the minor hemisphere r e c e i v e d the o r i g i n a l s t i m u l u s and thus knew the c o r r e c t answer i t would focus the eyes on the c o r r e c t o b j e c t . The major hemisphere would then s t a r t to f e e l good about that ob jec t and c o r r e c t l y p i c k i t . I f a wrong answer was g i ven the major hemisphere cou ld know that due to the d i s g u s t expressed by the minor hemisphere v i a the f a c i a l musc les . A more p r i m i t i v e , but h i g h l y e f f e c t i v e , means of cu ing was found by 21 G a z z a n i g a , Bogen and S p e r r y . In t h e i r t a c t u a l t e s t s d e s c r i b e d i n the t a c t u a l s e c t i o n above, they found tha t they had to be c a r e f u l w i t h t h e i r s t i m u l a t i o n when they came c l o s e to the d i v i d i n g a rea of the body. I t seemed that the p a t i e n t p i c k e d up a u d i t o r y and other types of cues which s p o i l e d the t e s t s . A f t e r t a k i n g t h i s cu ing i n t o account they s t i m u l a t e d the same areas and found tha t the s t i m u l u s was r e s t r i c t e d to one h e m i -sphere . As was n o t e d , e a r l i e r , p a i n and k i n e s t h e t i c s t i m u l u s i s represented b i l a t e r a l l y . Such c a p a c i t i e s are u s e f u l i n c u i n g . I t has a l ready been r e p o r t e d how the minor hemisphere cou ld cue the major hemisphere by w r i t i n g out the word tha t the major hemisphere was to r e p o r t . P u c c e t t i r e p o r t s a cu ing example where the minor hemisphere used the b i l a t e r a l p a i n mechanisms. The p a t i e n t h e l d a p e n c i l i n h i s l e f t hand. The major hemisphere was v a i n l y guess ing what o b j e c t was h e l d . As i t d i d t h i s the l e f t hand s l o w l y took the p e n c i l , turned i t so t h a t the p o i n t of i t was a t h i s thumb and pressed h a r d . The major hemisphere f e l t the p a i n , knew that the ob jec t was sharp and t h e r e f o r e knew that the o b j e c t was a p e n c i l . Thus the b i l a t e r a l p a i n r e p r e s e n t a t i o n was used to cue the major hemisphere. 25 Gazzaniga and H i l l y a r d found another form of behav io r tha t c a l l e d f o r some k i n d of cu ing mechanism. An unexpected number was f l a s h e d to the l e f t v i s u a l f i e l d . The p a t i e n t was asked what number he had seen . Gazzaniga and H i l l y a r d observed tha t the response took longer when the number was l a r g e r . In f a c t the r e s u l t s cou ld be put on a graph and i t was found t h a t there was a d i r e c t r a t i o between the t ime of response and the s i z e of the number. Th is suggested tha t some s o r t of rhythm method 22 was being used to get the c o r r e c t answer. When asked how he d i d i t the p a t i e n t r e p l i e d tha t "What I d o . . . i s to count up u n t i l I h i t a number 26 tha t ' s t i c k s o u t ' . Then I stop and t e l l you what i t i s . " Th is cu ing mechanism seems to be h i g h l y s o p h i s t i c a t e d . I t i s u n c l e a r e x a c t l y how i t works but there i s some communication between the hemispheres t h a t a l l o w s the i n f o r m a t i o n to t r a n s f e r . The two hemispheres t h e r e f o r e seem to be a b l e to t r a n s f e r a good d e a l of i n f o r m a t i o n between themselves . They w i l l use s imp le methods when such methods are a v a i l a b l e but they are a l s o capable of u s i n g methods tha t are s o p h i s t i c a t e d and almost i m p o s s i b l e to stop w i t h our present t e s t i n g methods. The tendency i s f o r the hemispheres to become more adapted to u s i n g these cu ing methods as t ime goes o n . Cuing t h e r e -f o r e becomes extremely important to these p a t i e n t s . C o n c l u s i o n I t would seem from what has been s a i d tha t s e c t i o n i n g the corpus c a l l o s u m r e s u l t s i n the p a t i e n t hav ing two separated consc ious spheres . N e i t h e r sphere i s capable of i n d i c a t i n g what i s i n the other sphere u n -l e s s i t has been cued i n i n some way. I t i s t h e r e f o r e pr ima f a c i e reasonab le to conclude tha t these p a t i e n t s have two minds each g a i n i n g i n p u t from separate areas of the body except from the neck and f a c e where both hemispheres are r e p r e s e n t e d . Fur thermore , except i n excep -t i o n a l cases each hemisphere i s i n c o n t r o l of the c o n t r a l a t e r a l p o r t i o n of the body except f o r the f a c e and neck . These two minds a l s o approach problems i n d i f f e r e n t ways. The major hemisphere i s capable of speech , l o g i c , mathematics and o ther a b s t r a c t 23 r e a s o n i n g s . The minor hemisphere i s dominant f o r r e c o g n i t i o n of n o n -d e s c r i p t p a t t e r n s , a r t i s t i c a b i l i t y , and the l i k e . The two hemispheres are t h e r e f o r e very d i f f e r e n t i n t h e i r s p e c i a l i z a t i o n . 24 CHAPTER II ARGUMENTS FOR TWO MINDS IN NORMAL HUMANS Introduction Puccetti and Bogen agree that the evidence of the last chapter indicates that these patients have two minds. They believe, however, that this evidence i s also evidence for two minds in every human being even i f the normal connecting links between the hemispheres are intact. They believe that each hemisphere of the brain represents a whole mind. The links between the hemispheres are seen as communicating links be-tween two cooperating minds. Each of us would then consist of two minds, each of which would have a l l the properties necessary for person-hood. We would be like an airplane with two pilots instead of only one. Several arguments are advanced for this position. Puccetti pro-duces arguments to show that the informational content of the two hemi-spheres i s always different. Puccetti also argues that the separation of the hemispheres either through commissurotomy or hemispherectomy does not result in half persons as he believes a mind spl i t t i n g would re-quire. On the other hand i f the mind i s not s p l i t he finds i t puzzling that a simple operation should create a new mind. He also cites exper-iments that show the type of phenomena in the normal patient that con-vinced us of two minds in the bisected patient. Bogen's arguments depend more on the physical separateness of the two hemispheres, their specialized functions and the hemispheres' functional independence. 25 The Arguments P r e s e n t e d : D i f f e r e n t I n f o r m a t i o n a l Content The experiment that P u c c e t t i c i t e s to show that the hemispheres always have d i f f e r e n t i n f o r m a t i o n a l content depends on r e a c t i o n t i m e . A normal sub jec t i s b r i e f l y exposed to a n o n d e s c r i p t f i g u r e i n e i t h e r v i s u a l f i e l d . S ince the f i g u r e i s n o n d e s c r i p t the minor hemisphere must p rocess the i n f o r m a t i o n b e f o r e the major hemisphere can v e r b a l l y i d e n t i f y the o b j e c t . I t was t h e r e f o r e s p e c u l a t e d that i f the f i g u r e was f i r s t p resented to the major hemisphere, the i d e n t i f y i n g response would take l o n g e r , s i n c e the i n f o r m a t i o n would have to be sent to the minor hemisphere f o r p r o c e s s i n g be fo re a response cou ld be made. I f the f i g u r e was presented d i r e c t l y to the minor hemisphere, the p r o c -e s s i n g cou ld proceed wi thout de lay and the i d e n t i f i c a t i o n cou ld be made sooner . Th is i s i n f a c t what happened. When the f i g u r e was presented to the minor hemisphere the v e r b a l i d e n t i f i c a t i o n took f o u r t e e n m i l l i -seconds l e s s than when i t was f i r s t p resented to the major hemisphere. P u c c e t t i c l a i m s t h a t t h i s experiment shows t h a t t h e r e " w i l l always be some d i f f e r e n c e i n the i n f o r m a t i o n content of each b r a i n " or hemisphere. I t i s not at a l l c l e a r t h a t the experiment d e s c r i b e d above r e a l l y does show what P u c c e t t i says tha t i t does . P u c c e t t i r e q u i r e s an a r g u -ment tha t shows that one hemisphere i s consc ious of some i n f o r m a t i o n b e f o r e the other one i s . B r a i n p r o c e s s i n g , of c o u r s e , i s always l o c a l -i z e d , but P u c c e t t i must show that consc iousness i s a l s o l o c a l i z e d . In the above experiment the d i f f e r e n c e i n r e a c t i o n t ime i s e x p l a i n e d by the f a c t that the major hemisphere has to send the i n f o r m a t i o n to the minor hemisphere f o r p r o c e s s i n g . Presumably the r e a c t i o n t ime i s the 26 same from the time that the minor hemisphere gains the information to the verbal response. In this experiment the right hemisphere gains the information directly in one case and through the major hemisphere in the other. For the reaction time to count as evidence for different infor-mational content in the two hemispheres the major hemisphere would have to be conscious of the information before the right hemisphere became aware of i t . If this were so, the l e f t hemisphere should have been aware of the figure before minor hemisphere processing, but only respond-ed to i t sometime later. The response in this case could, therefore, not be a good indication of the conscious content of the l e f t hemisphere. The response however, was to indicate this consciousness. Against Puccetti, one would expect that the type of processing that results i n the difference of reaction time in this case would be explained better by preconscious brain processing rather than by an explanation that postulates consciousness of the whole process. Puccetti needs a different kind of experiment to prove his point. There are experiemnts that have shown that normal subjects react faster to a stimulus in their l e f t visual f i e l d with their l e f t hand than with their right hand. If the response of the hand i s taken as an indication of the hemisphere becoming aware of the stimulus, this would show that when a stimulus was presented to the right hemisphere, the right hemi-sphere was aware of the stimulus before the l e f t hemisphere. Therefore the informational content of the two hemispheres would be different. Given that the informational content of the two hemispheres i s different Puccetti can argue, with some i n i t i a l p l a u s i b i l i t y , that they do not belong to one mind. They cannot be identical since they do not 27 have the same information. Therefore there are two separate spheres of consciousness i n the normal human being. Two spheres of consciousness count of course for two minds in the human. Questions Concerning Mind Splitting Puccetti believes that one w i l l be caught on the horns of a dilemma i f one believes that the brain bisected patient had one mind before the operation and two after the operation. Someone believing this w i l l have severe d i f f i c u l t i e s regardless of whether he thinks the operation split s the mind or does not s p l i t i t . The latter horn would have the operation somehow create a new mind while the former would require the presence of two half minds after the operation. The side of the horn assuming that minds cannot be s p l i t runs into d i f f i c u l t y because two minds are present where only one was before. Which of the two minds would be the new one? Whichever position one would take would be arbitrary. The two minds would be associated with the two hemispheres. Both hemispheres, however, were functioning before the operation and continue their specialized tasks in much the same man-ner as they did before. How could one of them count as a new mind? Furthermore, how can a simple operation somehow create a mind? This position therefore holds no promise for one who wishes to affirm that the cerebral commissurotomy patient had one mind before the operation and two after. If, on the other hand, minds are splittable and this operation splits one mind into two, i t w i l l not do to ask which mind i s the new mind. The breaking of one stick into two does not create a new stick, i t simply splits the stick. Puccetti's problem with the mind-splitting 28 position i s that one never finds half a mind. Not only do these pa-tients not have half a mind but patients with one hemisphere removed also do not have half a mind. No matter how severe an operation, the patient w i l l never be l e f t with half a mind. But then how could an operation s p l i t the mind into two half minds? Puccetti's argument depends on the application of the distinction between count and mass nouns to minds. Mass noun objects are splittable into two parcels of the same stuff. When one divides a glass of water between two glasses, both parcels of water are water. Count noun ob-jects, on the other hand, do not survive such s p l i t t i n g . When one splits a chair in two, no chair remains. Instead of two chairs, one has two half chairs but no complete chair. It seems obvious that minds should be placed into the count noun category since they are f a i r l y easy to individuate. Any splitting of the mind therefore should result in half minds and not whole minds. Half minds, however, are inconceivable, so minds, according to Puccetti, are not splittable. Therefore, the horn of the dilemma that assumed that minds were splittable is also not tenable. According to Puccetti then, the position that the normal human being has one mind and that cerebral commissurotomy results in two minds is untenable. We shall take up the mass noun-count distinction again later in this chapter. Puccetti's position avoids the dilemma described above. The normal human being has two minds. Commissurotomy therefore does not create a new mind nor does i t s p l i t a whole mind. A l l commissurotomy does is to separate the communication links between two separate minds. This disrupts the minds' attempts to cooperate with each other. 29 Amytal Exper iments w i t h Normal Sub jec ts 2 In 'A Reply to P r o f e s s o r M a r g o l i s ' P u c c e t t i advances a very power fu l argument f o r two minds i n the normal human b e i n g . He c i t e s exper imenta l data t h a t i n v o l v e s human beings w i t h normal commissure c o n n e c t i o n s . These p a t i e n t s need a b r a i n o p e r a t i o n on t h e i r r i g h t hemisphere. S i n c e speech i s so important to our l i f e as humans i t i s important f o r the surgeons to know which s i d e of the b r a i n i s l a t e r a l -i z e d f o r speech. S ince speech i s u s u a l l y found i n the l e f t hemisphere the doc to r i n j e c t s Amytal i n t o the l e f t c a r o t i d a r t e r y . Th is r e s u l t s i n the l e f t hemisphere going to s l e e p . The p a t i e n t i s then asked ques t ions tha t demand a v e r b a l response . I f the p a t i e n t cannot respond v e r b a l l y the surgeon knows tha t the p a t i e n t ' s speech i s l a t e r a l i z e d to the l e f t hemisphere. In s e v e r a l of these t e s t s at C o r n e l l M e d i c a l School the p a t i e n t was g i v e n a c i g a r e t t e i n the l e f t hand w h i l e the l e f t hemisphere was s t i l l a s l e e p . Be fo re the l e f t hemisphere awoke the c i g a r e t t e was taken away. Once f u l l y awake the p a t i e n t was asked what was p laced i n h i s hand d u r i n g the t e s t . He r e p l i e d that he d i d not know. He was then shown a s e r i e s of o b j e c t s and was aga in asked which of the o b j e c t s he was g i v e n d u r i n g the t e s t . J u s t as "he s t a r t s to repeat tha t he d o e s n ' t 3 know, h i s l e f t hand immediate ly p o i n t s to the c i g a r e t t e . " The response of t h i s p a t i e n t i s of the same k i n d tha t we d i s c u s s e d i n the l a s t c h a p t e r . I t shows t h a t there i s a severe i n f o r m a t i o n a l gap between the l e f t and r i g h t hemispheres . The r i g h t hemisphere i s c o n -s c i o u s of hav ing h e l d the c i g a r e t t e . I t can i d e n t i f y the c i g a r e t t e and p o i n t to i t independent ly of the major hemisphere. At the same t ime the 30 l e f t hemisphere denies a l l knowledge of the p r e v i o u s event and i s i n c a p a b l e of any response . Th is seems to i n v o l v e the two hemispheres i n a deep s p l i t . I f the person i n the t e s t i s thought to have one mind , then i t would appear tha t h a l f of tha t mind i s aware of the c i g -a r e t t e and can c o n s c i o u s l y ac t on that knowledge w h i l e the other h a l f i s t o t a l l y unaware of what happened. P u c c e t t i ' s p o i n t , of c o u r s e , i s that such a d i s s o c i a t i o n between the hemispheres i s so severe tha t the p e r -son cannot be s a i d to have one mind . S i n c e t h i s p a t i e n t has normal commissure l i n k s between the hemispheres P u c c e t t i c l a i m s tha t even normal humans have two minds . The Shape of the B r a i n P u c c e t t i i s i n f l u e n c e d to a g reat ex tent by J . Bogen. One of 4 Bogen's arguments f o r two minds i n the normal person stems from the obvious d u a l i t y of the b r a i n . The b r a i n has two hemispheres and t h e r e -f o r e i t i s not s t r u c t u r a l l y u n i t e d i n appearance. Bogen comments tha t " t h i s d u a l i t y i s so apparent to the most c a s u a l i n s p e c t i o n tha t i t has i n t r i g u e d n e u r o l o g i s t s f o r c e n t u r i e s , e s p e c i a l l y s i n c e i t o c c a s i o n a l l y happens t h a t one hemisphere i s dest royed w i t h p r e s e r v a t i o n of the p e r s o n a l i t y . Bogen uses t h i s f a c t a long w i t h an argument tha t the ' twolhemi-spheres are capable of independent e x i s t e n c e to argue f o r two minds i n the normal p e r s o n . The shapes of the b r a i n , however, does lend some p l a u s i b i l i t y to h i s argument on i t s own grounds. When we l o o k a t o ther organs of the body the shape of them has a g reat d e a l to do w i t h how many we t h i n k there a r e . We have two k idneys even though both of them do the same job and i n a sense a re even connected through t h e i r s e c r e t i o n 31 i n t o the same b l a d d e r . The k idneys cou ld even be j o i n e d by common communication l i n k s ( i . e . , l i n k s g i v i n g s i g n a l s when to operate e t c . ) and s t i l l be cons idered two. On the o ther hand, i f the two had formed one shape tw ice the s i z e of each s e p a r a t e l y , we would not say tha t we had two k i d n e y s . The hear t on the o ther hand has four chambers w i t h d i f f e r e n t f u n c t i o n s ye t no one t h i n k s that we have f o u r h e a r t s . The d u a l i t y of the b r a i n , t h e r e f o r e , cou ld count as ev idence f o r two b r a i n s and thus two minds . Arguments from the F u n c t i o n a l Independence of the Hemispheres The q u o t a t i o n above c o n t a i n s another of Bogen's arguments, t h i s t ime depending on the f u n c t i o n a l independence of the hemispheres . As has been shown by numerous a c c i d e n t s or o p e r a t i o n s tha t r e q u i r e d the removal of a hemisphere due to a tumor, each hemisphere can remain consc ious and t y p i c a l l y human wi thout the other hemisphere. Each h e m i -sphere i s capable of be ing consc ious independent ly of the o t h e r . S i n c e on ly one hemisphere i s necessary f o r the p o s s e s s i o n of a mind i t i s s t r a i g h t f o r w a r d l y t r u e that p o s s e s s i n g two hemispheres should make i t p o s s i b l e to have two minds. Bogen a l s o emphasizes tha t these hemispheres a re d i f f e r e n t . The human b r a i n i s l a t e r a l i z e d w i t h each hemisphere hav ing d i f f e r e n t f u n c -t i o n a l s p e c i a l i z a t i o n s . Therefore each hemisphere t h i n k s d i f f e r e n t l y than the o t h e r . S i n c e the hemispheres are capable of e x i s t i n g w i thout each o t h e r , and s i n c e they a l s o t h i n k d i f f e r e n t l y , Bogen contends tha t normal humans have two minds i n s t e a d of one. 32 I f t h e two h e m i s p h e r e s r e a l l y a r e f u n c t i o n a l l y i n d e p e n d e n t o f e a c h o t h e r , P u c c e t t i and B o g e n w o u l d h a v e us s e e t h e c o m m i s s u r e l i n k s b e t w e e n t h e h e m i s p h e r e s as m e r e l y i n f o r m a t i o n a l l i n e s . Thus t h e c o r p u s c a l l o s u m w o u l d n o t h a v e a n i n t e g r a t i n g f u n c t i o n b u t a f u n c t i o n o f r e l a y i n g m e s s a -g e s b e t w e e n two i n d e p e n d e n t m i n d s . T h e h e m i s p h e r e s w o u l d t r a d e s e n s o r y i n f o r m a t i o n a n d o c c a s i o n a l l y h e l p e a c h o t h e r i n a r e a s o f t h e i r own s p e c i a l i z a t i o n . T h i s , h o w e v e r , w o u l d be c o m m u n i c a t i o n i n s t e a d o f i n t e -g r a t i o n . I f t h e h e m i s p h e r e s a r e as i n d e p e n d e n t o f e a c h o t h e r as P u c c e t t i and B o g e n w o u l d h a v e us t h i n k , t h e h e m i s p h e r e s c a n more e a s i l y be s e e n as two c o o p e r a t i n g m i n d s t h a n twomparts o f one g r e a t e r m i n d . T h e m i n d s c a n g e t a l o n g w i t h o u t e a c h o t h e r b u t i t i s t o t h e i r a d v a n t a g e t o c o o p e r a t e . A C o n s i d e r a t i o n o f t h e A r g u m e n t s f o r Two M i n d s i n t h e N o r m a l Human D i f f e r e n t I n f o r m a t i o n C o n t e n t We saw e a r l i e r t h a t P u c c e t t i ' s e x p e r i m e n t a l d a t a f o r h i s argument p r o v i n g t h a t t h e h e m i s p h e r e s h a d d i f f e r e n t i n f o r m a t i o n a l c o n t e n t was n o t c o n c l u s i v e . T h e r e a r e , h o w e v e r , a l s o p r o b l e m s w i t h t h e b e t t e r e x p e r i -ment t h a t we g a v e t o h i m . An e x p e r i m e n t v e r y much l i k e t h i s i s r e p o r t e d by D . E . B r o a d b e n t . I t c o n s i s t s o f v i s u a l l y p r e s e n t i n g two d i f f e r e n t s t i m u l i t o t h e s u b j e c t . G i v e n s t i m u l u s A t h e s u b j e c t i s t o r e s p o n d w i t h h i s l e f t h a n d . S t i m u l u s B i s t o be r e s p o n d e d t o w i t h t h e r i g h t h a n d . E i t h e r s t i m u l u s c o u l d be p r e s e n t e d a t any t i m e and i n e i t h e r t h e l e f t o r r i g h t v i s u a l f i e l d . On i n i t i a l l y c o n d u c t i n g t h e e x p e r i m e n t t h e r e s u l t s w e r e v e r y s i m i l a r t o t h o s e d e s c r i b e d e a r l i e r . I f s t i m u l u s A a p p e a r e d i n t h e l e f t v i s u a l 33 f i e l d the l e f t - h a n d e d response was f a s t e r than i f s t i m u l u s A was p r e -sented i n the r i g h t v i s u a l f i e l d . The same was the case f o r s t i m u l u s B except tha t t h i s t ime i t was the r i g h t hand t h a t responded f a s t e r when B was presented i n the r i g h t v i s u a l f i e l d i n s t e a d of the l e f t . Thus, i f the hemisphere tha t was to respond obta ined the i n f o r m a t i o n d i r e c t l y , i t became aware of the i n f o r m a t i o n f a s t e r than i f the other hemisphere got i t f i r s t . T h e r e f o r e , one hemisphere would be aware of the i n f o r m a -t i o n b e f o r e the o t h e r . The exper imenters now took another approach to c o n f i r m t h e i r r e -s u l t s . The s u b j e c t was to c ross h i s hands. The key on the l e f t , how-e v e r , was s t i l l to be pressed i n response to s t i m u l u s A and the one on the r i g h t f o r s t i m u l u s B. The r i g h t hand, however, would be p r e s s i n g on t h e ' l e f t and the l e f t would p ress on the r i g h t . I t was expected t h a t i f s t i m u l u s B was presented i n the l e f t v i s u a l f i e l d t h a t the key on the r i g h t would be pressed f a s t e r by the l e f t hand than i f the s t i m u l u s came i n the r i g h t f i e l d . Th is would g i v e the advantage to a hemisphere that both c o n t r o l l e d the response and r e c e i v e d the i n f o r m a -t i o n d i r e c t l y . As i t turned o u t , however, i t "was always the key on the same s i d e as the s t i m u l u s that was pressed f a s t e r . . . " ^ Th is was e x a c t l y the o p p o s i t e of what was expected . Broadbent suggests t h a t r e a c t i o n t ime does not depend on which hemisphere f i r s t ga ins the i n f o r m a t i o n and then responds . Ins tead i t i s much more complex and i s c o n t r o l l e d more by how the mind sees i t s environment. In any case the e x p l a n a t i o n of r e a c t i o n t ime i s not as s t r a i g h t f o r w a r d as P u c c e t t i would l i k e to t h i n k . Th is experiment would a l s o i n d i c a t e that c o n s c i o u s -ness cannot be l o c a l i z e d i n the same way t h a t b r a i n p r o c e s s i n g can be . 34 Consciousness i s b e t t e r a s c r i b e d to the t o t a l b r a i n , or the se t of b r a i n areas c o o p e r a t i n g f o r an e x p e r i e n c e , than to the i n d i v i d u a l p a r t s of the b r a i n . P u c c e t t i , t h e r e f o r e , cannot appeal to r e a c t i o n t ime to show that the two hemispheres have d i f f e r e n t i n f o r m a t i o n a l , c o n t e n t . Even i f we grant P u c c e t t i h i s c l a i m t h a t the consc ious content of the two hemispheres i s always d i f f e r e n t and presume w i t h him that c o n -s c i o u s n e s s i s l o c a l i z e d w i t h b r a i n p r o c e s s i n g , i t i s not obvious t h a t t h i s w i l l prove h i s p o i n t . P u c c e t t i wishes to argue tha t t h i s d i f f e r e n c e i n content proves that we have two minds . U n f o r t u n a t e l y , i f we were .to accept t h i s i t would prove much more than P u c c e t t i would have us t h i n k . The mind has many d i f f e r e n t f u n c t i o n a l a b i l i t i e s . These f u n c t i o n a l a b i l i t i e s are o f t e n l i n k e d to s p e c i f i c areas of the b r a i n . For i n -s t a n c e , s i g h t i s i n one a r e a ; h e a r i n g i n another ; and speech , i n y e t another . Under P u c c e t t i ' s assumptions i t would seem that a l l these areas are c o n s c i o u s . At the same t ime they are separated from each o ther so t h e r e w i l l always be some t ime d i f f e r e n c e b e f o r e one a r e a can t r a n s m i t i t s i n f o r m a t i o n to any other a r e a . Thus there w i l l be a d i f -fe rence i n i n f o r m a t i o n a l content between each of the areas of the b r a i n . Us ing P u c c e t t i ' s argument we would have ev idence f o r a host of d i f f e r e n t minds . He only b e l i e v e s tha t there are two but he g i v e s no reason why h i s argument cannot be expanded to g i v e us many. To p o s t u l a t e t h i s l a r g e number of minds , however, g i v e s us too many minds to be a p l a u s i b l e account of how we w i s h to d e s c r i b e o u r s e l v e s . A d i f f e r e n t account of how the d i f f e r e n t areas of the mind come together to form one mind i s needed. That w i l l be the work of the next c h a p t e r . What i s important now i s tha t P u c c e t t i ' s argument would l e a v e us w i t h too many minds to be 35 a p l a u s i b l e account of our menta l e x p e r i e n c e . Perhaps P u c c e t t i cou ld defend h i m s e l f by contending tha t the d i f -fe rence between h i s account of the two hemispheres and the account of the many 'minds ' even w i t h i n one hemisphere, i s tha t w i t h two there i s d u p l i c a t i o n of thought w h i l e w i t h i n one hemisphere t h e r e i s n o t . The a rea f o r h e a r i n g does not become aware of v i s u a l sense d a t a or v i c e v e r s a . Each hemisphere however, does have v i s u a l i n f o r m a t i o n from the other hemisphere and there i s d u p l i c a t i o n . P u c c e t t i cou ld argue tha t t h i s d u p l i c a t i o n i s the b a s i s of the c l a i m t h a t there a r e two minds . There i s a . s i g n i f i c a n t d i f f e r e n c e between the d i f f e r e n t i n f o r m a t i o n a l content between the hemispheres than there i s between the v a r i o u s areas of a hemisphere , because one i n v o l v e s d u p l i c a t i o n and the o ther does n o t . I s t h i s f a i r ? Under the model of b r a i n o p e r a t i o n t h a t i s be ing presumed, the a rea of the b r a i n tha t i s s p e c i a l i z e d i n s i g h t becomes aware of the v i s u a l sense data b e f o r e the o ther areas t h a t i n c o r p o r a t e t h i s i n f o r m a t i o n i n t o t h e i r response to the w o r l d . Thus i f a motor response i s r e q u i r e d due to a v i s u a l s t i m u l u s , the v i s u a l a rea of the b r a i n i s aware of the v i s u a l i n f o r m a t i o n b e f o r e the motor response a r e a i s . The f a c t t h a t the motor response area ga ins the i n f o r m a t i o n i n a d i f f e r e n t form than the v i s u a l a rea i s i r r e l e v a n t . D u p l i c a t i o n i s not the i s s u e , but the t r a n s f e r of i n f o r m a t i o n from one hemisphere to the o t h e r . P u c c e t t i would be as w i l l i n g to accept the t ime d i f f e r e n c e argument i f the t r a n s f e r of i n f o r m a t i o n d i d not r e s u l t i n d u p l i c a t i o n of the exact k i n d of thought than i f i t was a mere d u p l i c a t i o n . Another approach cou ld a l s o be t a k e n . Each hemisphere c o n t r i b u t e s i t s i n f o r m a t i o n and the t o t a l b r a i n o rgan i zes the i n f o r m a t i o n i n t o a 36 coherent whole. The l e f t hemisphere can only contribute right visual f i e l d information and the right hemisphere can only contribute informa-tion from the l e f t f i e l d . At this stage there i s no duplication. The only stage where duplication of thought could be seen to arise i s when the information is entered into the memory. At this stage, however, the mind has a functional purpose for entering the information into two memory banks. The two memory banks treat the information in s i g n i f i -cantly different ways, both of which are necessary for the functioning of the total mind. The duplication of functional areas i n the brain a l l have a functional use. Thus the model i s not one of two minds doing the same thing, but is more on the model of a single mind with different functional capacities. Questions About Splitting the Mind Puccetti i s right in insisting that the operation does not create any new mind. Such a conclusion is just too absurd to be taken seriously. He is not on as safe ground, however, when he asserts that any s p l i t must result i n half minds instead of whole minds. One won-ders why this should be so. A stick broken in half results in two halves of the stick but neither of the pieces i s half a stick i n i t s own right. Both halves are sticks as much as the original one that they came from. Similarly with an amoeba: both of the amoebae that result from the s p l i t are amoebae. There is very l i t t l e sense i n say-ing that they are half amoebae. Puccetti asserts that the "Amoeba-like man who divides... would not be a man." He does not, however, give any reason why we should hold this view. Amoebae and sticks divide i n 37 two and yet we need not look for half amoebae or half sticks. Why then should we expect half minds when minds are s p l i t i n two? Puccetti needs some theory about the relationship between the complexity or non-uniformness of a substance, and what can be said about the splitting of the substance. For instance, M. Furth attributes 9 something l i k e this to Aristotle's biological works. Aristotle i s seen to distinguish between uniform and non-uniform parts of animals. This distinction i s roughly seen to follow the mass noun-count noun distinc-tion. Examples of uniform parts of animals are substances lik e milk, flesh, blood and the li k e . A part of a portion of milk is s t i l l milk and a part of a portion of blood is s t i l l blood. With non-uniform parts, however, a part of the whole is not the same thing as the whole. A part of a face is not a face and a part of a skeleton is not a skeleton.^ Between these two classifications there is a transitional stage consisting of parts that could be seen to f i t into either category. This i s a 'delicate point; for about here occurs the beginning of an interface between the mass-system prevailing below, and the count-system prevailing above."''""'" Parts lik e blood vessels can be counted in this category. A part of a blood vessel is s t i l l a blood vessel, but there comes a time when i t is dissected enough that a part of what is s t i l l a blood vessel is no longer one. These categories are then to f i t into a hierarchy with the uniform parts being the matter out of which the non-uniform parts can be b u i l t . For instance, the skeleton i s b u i l t out of bones which are in the transitional stage. The bones, however, are b u i l t out of matter that 38 is more uniform in nature. The substances of which i t i s true that a part of the whole is s t i l l a whole, form the matter of the substances where a part of the whole is not a whole. Furth sees the distinction as following the mass noun-count noun distinction. Where does this get Puccetti? Sticks f i t in the transitional stage and i t is not clear where amoebae f i t . They are, therefore, not the best counter examples to his theories of mind spl i t t i n g . Puccetti obviously wants minds to f i t into something l i k e a non-uniform part category. Thus a part of a mind would not be a mind. Minds belong i n the count system. They are obviously very complex and nothing lik e uniform substances so i t seems plausible that they should be like non-uniform substances. There are problems,however, with the distinction as i t stands. For one thing i t does not consider substances that are as complex as a mind can be. Even something as complex as a skeleton must reach a certain level of complexity before i t is considered a skeleton. There does not seem to be any reason though why the skeleton could not become a great deal more complex, so that a division of the skeleton would result in two minimal skeletons that lack the complexity of the original. For instance, to be imaginative, consider an animal that had evolved in such a way that one of i t s parts would be a complete skeleton of a lesser animal. One of the parts of the animal might be a fi s h - l i k e appendage to help the animal swim. Then a part of the skele-ton would be a skeleton when separated from the rest. More plausible examples can be raised. For instance, a computer has a wide range of a b i l i t i e s . One can have a computer with just a few a b i l i t i e s and one can have a much more complex one. If one divided the 39 complex computer in such a way as to leave two machines each sharing some of the functional capacities of the original, the resulting machines would s t i l l be minimal computers. Thus what was part of the original computer would s t i l l be a computer. If this i s correct one need not cease using the count-system and the mass-system. One need only assert that not everything that f i t s into the count-noun category is unsplittable into parts of the same type of thing. If some theory about what happens to count noun substances when they s p l i t i s the basis of one's criterion for counting something as a count noun sub-stance, then one may have to change the c r i t e r i a . It seems obvious that we can have a mind that i s so complex that a division of i t s functional capacities w i l l result i n two minds and not a half mind. Puccetti's dilemma therefore f a i l s to exhaust the pos s i b i l i t i e s . Amytal and Normal Subjects The results of the Amytal experiment are very d i f f i c u l t to explain. The biggest problem i s that there i s no theory that explains the data. It seems to be a case of two connected hemispheres that are disconnected. Since the hemispheres are connected, the minor hemisphere should be able to communicate the correct answer to the major hemisphere. It does not appear able to do this. The subject i s conscious of both l e f t and right hemispheres on the whole and yet is cut off from part of the right hemisphere. The patient i s conscious with the minor hemi-sphere yet he does not have access to some information in i t . One would be tempted to allocate the unreachable information to the large category 40 of brain events that are unconscious. This, however, is untenable since the patient has shown appropriate behavioral evidence that he is conscious of the information. One can perhaps get a feeling for what could be happening above, by considering what would be the case i f i t were possible to deprive each hemisphere of direct access to the visual information i n the other. For example, l e f t visual f i e l d information would go to the right hemisphere alone and vice versa. Thus neither hemisphere would have direct access to the whole f i e l d , yet the hemispheres would be integrated normally in a l l other functions and senses. The experiments of the last chapter could then be tried with interesting results. If the patient f e l t something he would know i t with both hemispheres, but i f the information was flashed visually to one hemisphere the other hemisphere would not have direct access to i t . Thus the hemispheres would be integrated and acting as one except for sight. This integration might allow for some indirect knowledge of visual information. Thus i f there was a book on my l e f t I might pro-ceed to pick i t up with f u l l confidence, but s t i l l not be aware of direct visual contact with the book. It i s puzzling how this would work, but something like i t i s possible when someone works on a jigsaw puzzle. In this case one can often pick up a piece and insert i t knowing beforehand that i t would f i t and yet not know how one knew i t . The minor hemisphere probably was the source of this information and the confidence that went with i t . It would s t i l l be a s k i l l of whose working we were not aware. 41 The sight s p l i t person is s t i l l a puzzle though. How can only half a mind be aware of certain input and the rest not have access to it? The claim seems to be that we are not conscious of what half of our mind i s conscious of. The situation was described as i f one were blind when i t came to sensing the data yet functionally able to see. The problem, however, is more complex than that, since there is a part of the mind that does sense the sense data. The man i s integrated, yet s p l i t . To heal the s p l i t a l l one has to do is blind the man. One is puzzled about how to describe the situation. One need not feel this same puzzle just because the links between the two hemispheres do not connect a l l the different areas of the 12 hemispheres. To f u l f i l l i t s specialized function one hemisphere might need specialized areas that the other does not. These areas could be seen as f u l f i l l i n g necessary functions for the use of the higher specialized function. In a sense they would be connected to the other hemisphere, but at a higher level when their combined work was raised to a conscious level. Not every area of the brain need be connected with each of the others. A l l that is needed is some integration so that the disconnected area eventually becomes integrated with the rest of the brain. This is plausible i f the area disconnected i s not thought to be conscious. The normally disconnected areas do not give evidence of being conscious. If functional integration i s achieved for two conscious areas of the hemisphere without conscious integration, the situation i s harder to describe. We shall return to this in chapter seven. 42 Puccetti's case is a puzzle. A l l the normal links between the hemispheres are intact. The minor hemisphere wishes to inform the major hemisphere of the events that took place during the major hemi-sphere's recent sleep. If i t did not wish to relay information i t would not point to the cigarette in the test. When the hemispheres are disconnected the hemispheres are ingenious at getting the other hemisphere to know what is going on. Yet i n this case even though the connections are normal the minor hemispheres cannot relay information to the major. Something seems to be missing in our account of how these connections work. Perhaps the connecting links should be seen in a different light. It seems to be that they can only relay information during the time of the sensory input. After that time the information i s perhaps either coded differently so that i t could not transfer, or the transfer needs some memory or other help from the receiving hemisphere. In any case, i f the one hemisphere is not aware of the information at the time of input, the receiving hemisphere does not seem able to send the informa-tion later on. This i s a puzzling communication system but there does not seem to be any other way of describing i t that accounts for the amytal experiment. Perhaps the amytal experiment can now be explained without con-cluding that normal humans a l l have two minds. First?of a l l , the amytal can be seen to be temporarily splitting the hemispheres. The s p l i t i s effected by anesthetizing one of the hemispheres. This has the same effect as a temporary hemispherectomy. It is no puzzle why the major hemisphere does not receive the information while under the 43 amytal. Later however, after i t has awakened, the normal connections cannot inform i t of a l l that went on while i t was asleep. A temporary s p l i t has been effected with certain lingering results due to how the brain's communicating links operate. Puccetti's case i s , therefore, one that takes a normal brain and spli t s i t temporarily. We can then expect the usual split-brain phenomena. The. normal human mind, how-ever, has never been s p l i t , so how is this to count as evidence that normal humans are two minded? Furthermore, the s p l i t i n the amytal experiment is only temporary so this man has really one mind except for a few lingering results that arise from the time of the experiment. The amytal experiment does not show that the normal human being has two minds. The Shape of the Brain Bogen and Puccetti are impressed by the fact that the brain comes in two hemispheres. Two hemispheres, both of which are conscious, suggest two brains and thus two minds. The best response to this type of argument i s that when i t comes to minds, the shape of the brain i s irrelevant. We usually l i k e to think that we have as many brains as minds, so since we only have one mind we only have one brain. To i l l u s t r a t e that shape is irrelevant to the number of minds to be counted, imagine two functionally equivalent minds but correlated to brains with different shapes. One, for instance, could be correlated to a brain that has i t s functional areas scattered throughout the body. The speech area could be near the mouth, the visual, near the eyes and motor control could be placed somewhere in the chest. The other mind 44 would be correlated with a brain that occupied one area of the body and would not be divided into hemispheres. Since the two minds are equiva-lent in how they experience the world and react to i t , one does not wish to say that the one man has many minds and the other only has one. Each of these men would only have one mind. We might wish to stop counting brains on the basis of how many minds one had. That i s , we might wish to think that the one man had many brains but only one mind. This, however, would not be necessary. The scattered brain could be considered as one. This last point could be illustrated by another example. Consider two radios, the one a small transistor and the other b u i l t by a radio enthusiast who wanted the parts of the radio to be scattered throughout the house. Its tuning d i a l could be i n the bedroom, the receiver on the roof, the speaker in the li v i n g room and the other works appropri-ately scattered. Yet since this radio was functionally equivalent to the small transistor, one would not wish to think that the scattered set consisted of more than one radio. Shape makes no difference to the countability of radios. It also makes no difference to how many minds we may think that we have. Functional Independence of the Hemispheres Bogen emphasized that since either hemisphere can survive on i t s own that we are potentially two minded. This i s somehow to count as an argument for the assertion that each of us has two minds in fact. Thus he jumps from what can be the case, to assert that this i s the case. This i s not valid. For instance, take a water container that i s capable 45 of having a partition placed in the middle and separated. Thus I have a container that i s potentially capable of being two water containers. If I destroy one side of the container I s t i l l have a container. Yet when the container does not have the partition in place that would make i t two, i t is only one container. Its potential for being two does not make i t two. The hemispheres can be seen as the containers. If one hemisphere is destroyed there i s an immediate division between i t and the remaining hemisphere. Similarly when the corpus callosum is sectioned the two hemispheres are separated. If the brain is normally connected, however, there i s no reason why we should believe that the subject has two minds instead of one. His potential for having two minds does not make i t the case that he does have two minds. Bogen also suggested that because the hemispheres think different-ly, this should count for there being two different minds. There is no reason why this should be so. Mathematical reasoning i s a different type of thought than trying to remember the appropriate word to use in a sentence. Yet both of these types of thought take place in the major hemisphere. We are not at a l l tempted to think that these varieties i n the ways of thinking should count as evidence for more than one mind being associated with the major hemisphere. Different ways of thinking allow the mind to be functionally more complex. It i s not evidence for two minds. Bogen has argued for the functional independence of the hemispheres on the basis of their a b i l i t y to continue operation after the other has been destroyed, and the fact that they are specialized for different 46 functions. This type of argument does not show that humans have two minds. It could be the case, however, that the hemispheres were so independent of each other that the destruction of the one would not affect the operation of the other in any significant way. The integra-tion between the hemispheres would be more on the model of helping the other but not cooperating on a single task. It could be possible to s t i l l consider this type of mind as being one mind instead of two. The oneness-of the mine, however, would be more conclusively proved i f i t could be shown that the two hemispheres suffer i n their functional a b i l i t y when separated, and that when connected the behavior solution to the problem could be seen to arise out of both hemispheres at the same time. The hemispheres would then be seen as two parts of an integrated brain which gave rise to one mind. We w i l l argue that this is the case in the next chapter. We w i l l therefore deny this type of functional independence of the two hemispheres and give a positive account of why we should consider the normal human being to have only one mind. 47 CHAPTER III ONE MIND IN NORMAL HUMANS Introduction Why i s i t that man developed in such a way that he has two hemi-spheres instead of just one? If i t is just that two minds are better than one, then this i s just an accident of nature that leaves man some-what disjointed although the two minds cooperate to the f u l l extent possible. Under this scheme one would have Rembrandt l e f t congratu-lating Rembrandt right for the great job he was doing. Frege right, on the other hand, would be dazzled beyond comprehension by Frege l e f t . Puccetti leaves men disjointed. When, however, one contemplates why this duality of hemispheres should come about in the f i r s t place, one i s not as tempted to jump to the two person conclusion. One expects that an organism w i l l develop in such a way that i t w i l l increase i t s own capacity and not give rise to another except through reproduction. When we ask why an organism developed in the way that i t did we expect to see an intricate functional integration between the parts that con-tribute to the l i f e of the whole organism. One would therefore expect, or at least look for, some functional integration of the two hemispheres that contributes to the overall working of the mind and thereby the man. Interference The evidence that there i s this functional integration is f a i r l y impressive. One type of evidence i s the interference that different kinds of tasks impose on each other. The argument i s that i f different 48 tasks are well lateralized to different areas of the brain, i t should be possible to carry on the two tasks without interference. Experiments to find tasks that did not interfere with one another have so far not been successful. D. E. Broadbent gives several examples of interference. One is between tactual reaction time and acoustic memory for letters. The subjects were to respond by pushing down with their finger tips when stimulated. This reaction i s l i t t l e more than a reflex and response time "shows very l i t t l e increase... as the number of possible stimuli i s increased..."''" (i.e., the number of fingers one can expect to push). The subjects were stimulated once every five seconds and were given a letter of the alphabet in the same time period. Every minute at least one letter would occur twice. At the end of the minute the subject would have to report which letter had been most frequent. One task was therefore verbal and highly specialized. The other was tactual and almost on the level of reflex action. Yet the tasks interfered with each other. The memory for speech was even affected by the number of fingers being stimulated even though the number of possible responses did not affect reaction time when only tactual response was being tested. At the same time the reaction time for the fingers was increased when i t was combined with the memory task. This "was true for the l e f t 2 hand considered alone." Thus even when two different hemispheres were involved along with two very different tasks, these tasks s t i l l inter-fered with each other. Similar results have been found with tasks l i k e music and speech. Another type of experiment also resulted in interference between two tasks. A number of lights were used so that both the right and l e f t 49 visual f i e l d had two possible stimuli. The l e f t hand was to respond to l e f t visual f i e l d stimuli and the right hand responded to stimuli on the right. Since there were two possible responses on each side, the patient was instructed to raise his index finger for one stimulus and his middle finger for the other. The two sides were parallel so that the index finger would respond to the same kind of light on both sides. Which index finger was raised was governed by which side the light was flashed to. The patient was then told which side he would have to respond to f i r s t . The second side would have to be responded to shortly after the f i r s t and after a few t r i a l s the patient could even anticipate when the second stimulus would come. He would not, however, know which light would be flashed. Even given a l l these advantages "there was a substan-t i a l interference between the two tasks i f the second stimulus arrived before the f i r s t response had been made." Thus, even though the stimulus and reaction on each side are fed to and controlled by one hemisphere; i f the hemisphere that reacts f i r s t has not finished i t s reaction the second hemisphere finds i t s e l f at a disadvantage in react-ing. Its reaction time would be different i f the f i r s t hemisphere had finished i t s response. Thus the two tasks interfere with each other even though one would i n i t i a l l y expect that the two tasks are done by different hemispheres. There were some other interesting results in the above experiment. If the f i r s t hand responded with the index finger, then the reaction of the second hand was slower i f i t had to react with the middle finger and vice versa. One f i e l d , therefore, gave a bias to the other f i e l d . It seems that the two hemispheres are working together on the problem 50 instead of separately. The interference is similar to what we would expect i f both reactions used the same decision making center. One possible response to the argument from interference could be that although there are two centers for consciousness, one interferes with the other through the commissure linkage when a task is being performed. Both sides, therefore, get a glut of information and are interfered with in their own tasks. This argument is not plausible though. In these experiments the subject was consciously trying not to l e t the two tasks interfere. One can select the information that one w i l l attend to. For instance, as I have been typing, the fridge has been rattling less than three meters from me. Yet i t i s only as I thought of this i l l u s t r a t i o n that I began to notice this noise and l e t i t interfere with my thought. Generally I block out this unwanted stimulus and proceed with my regular tasks. Interference, therefore, does give evidence for an integration of the mechanisms between the hemispheres and other areas of the brain. In the previous chapter evidence was cited that what side of the environment stimulus came from might be more important than which hemi-sphere did the responding. In this experiment the reaction time to the stimulus was affected by which side of the visual f i e l d the hand was responding to instead of which hand was doing the responding. It was as i f the brain conceptually worked out how It was to react to i t s environment and ignored which hemisphere or which side of the body was reacting to the stimulus. As long as the response was on the side that the visual stimulus came from, either hand responded faster than when the visual stimulus was on the other side. Hemispheres did not work on 51 their own or faster when they could work on their own. Instead i t seems as i f both hemispheres are integrated together for the task and the side that responds is governed by other considerations than the fact that i t i s doing the action. The picture i s more one of integration than coop-eration between the hemispheres. Two Hemispheres Working on One Task B. Milner cites another type of evidence for the integration of the two hemispheres. The evidence comes from patients who suffer many of the epileptic problems that the brain-bisected patients suffered from. Thus these patients have a f a i r amount of brain damage although their corpus callosum is intact. These patients served as a control group. It was found that even the most proficient of the brain bisected patients could not begin to match the control group in tactual recog-nition of complex perceptual material. Milner concludes that either "the separation of the two hemispheres reduces their (i.e., the hemi-spheres') functional efficiency or that the l e f t hemisphere normally participates in tasks of this kind..."^ The fact that the hemispheres do not work as well separately as they do together seems to indicate that they need each other to adequately do their job. Impairment has also been noticed with short term memory and even with s t r i c t l y verbal tasks. Thus the hemispheres may not be as specialized as was f i r s t thought. There seems to be a trend i n the literature that emphasizes the cooperation of the hemispheres on a single task rather than a radical functional lateralization. This i s true of speech. 52 Rasmusen speculates that "the richer the speech the greater part of the brain that i s involved..."^ He believes that this i s one of the problems with localizing speech to one area. Speaking uses a variety of informational processing operations. There i s no reason why they should a l l come from the major hemisphere. Liberman suggests that the major hemisphere "may be specialized to deal with grammatical coding, a conversion of information that distinguishes language from other perceptual and cognitive processes." He sees language as restructuring information to be used i n long term memory. When listening to a lecture one does not remember the exact sentences much less the exact sequence of sounds and pauses. Language capacity transforms the latter into a form that makes i t appropriate for long term storage and at the same time takes the non-grammatical cognitive processes and transforms i t into something appropriate for vocal transmission. The language centers, therefore, can be seen as being between the non-linguistic cognitive centers and the linguistic intake and output centers. While some of this process may be restricted to the major hemi«-sphere i t i s not necessary that a l l i s . Both hemispheres are capable of intake processing and there i s some evidence that the right ear distinguishes vowels better than the l e f t , while the l e f t i s superior on consonants. This evidence is not conclusive and depends on how the experiment i s set up, but there is no reason to suppose that hearing and decoding does not involve the two hemispheres working together i n an integral way. As for output the speech center must draw from the non-linguistic areas for the information to be spoken about. The coding and decoding 53 that i s necessary might be restricted to the major hemisphere but the rest of what i s necessary for speech need not be. Sperry and Zaidel find that cerebral commissurotomy impairs tasks that are s t r i c t l y verbal so we can presume that the two hemispheres participate to-gether in speech functions.^ Evidence from Hemispheric Specialization The last section argued that there are a range of ac t i v i t i e s that should be explained by assuming that both hemispheres were at work on the one task. The two hemispheres are therefore integrated and work as one. They are not functionally independent of one another. At the same time i t seems obvious that the hemispheres do have specialized functions. Bogen attempted to use this fact as evidence that there were two different minds at work. Sperry uses i t as evidence for the exact opposite result. While at f i r s t blush one might be tempted to think of the callosum as just a link between the two hemispheres that harmonized them and duplicated information in each, this i s not the plausible way of approaching the issue. To Sperry i t seems more probable, "especially with each hemisphere processing i t s input i n fundamentally different ways, that callosal excitation serves to span g and unite a single unified process with parts in each hemisphere." Given these differing approaches to the tasks presented, the two hemisphere development of the human brain begins to make sense. Both these ways of thinking are extremely important in the day to day con-cerns of the human being. He heeds to recognize his friends as well as speak and reason with them. The two hemispheres can be seen as two functional areas that help him i n a wide variety of tasks. Some of 54 these tasks require the integrated use of both hemispheres while some are more the product of one. There i s no reason at a l l , however to dissociate oneself from one of the hemispheres. One's a b i l i t y to rec-ognize a friend is as much one's a b i l i t y as one's a b i l i t y to do inter-mediate logic. Two hemispheres give one more functional capacity than one would otherwise have had. This location of functions in the minor hemisphere can be seen in the same light as functional location within a single hemisphere. In a sense the mind can be seen as a set of various functions that compose the whole. Members of this set would include audio capacity, visual capacity, tactual capacity and the li k e , along with capacities that combined a number of areas such as speech and logic. By adding the capacity of the minor hemisphere one i s not adding another mind, but rather augmenting the membership of the set which is the mind. Thus the second hemisphere is seen as just giving the mind additional functional capacity. The whole mind i s working in unity together. The mind could be seen as the organization of a l l these different functional areas. Our mind is complex enough that i t can think i n different ways. Adding another hemisphere can be seen as just adding another area to the brain that w i l l add further functions. It i s to the mind's advantage to have such specialization of hemi-spheres. The brain has a great pl a s t i c i t y so that i t can adapt to internal disorders. Such adaptations, however, usually impair some of the other functions of the brain. For instance, i f a child has exten-sive damage to i t s major hemisphere at a very early age, speech w i l l develop in the other hemisphere. The brain is able to make such wide 55 use of i t s various areas. The problem, though, is that the child w i l l suffer the loss of other functional a b i l i t i e s that i t otherwise would have had. The minor hemisphere can learn to speak, but i t w i l l suffer a loss to i t s normal functional a b i l i t i e s . The same result is found i n people who have been born without a corpus callosum. One such patient was a 19 year old college sophomore. Her marks were average and she scored 111-112 on the verbal part of the Wechsler Adult Intelligence Scale, which i s above normal. Amytal tests showed that she had developed language capacity in both hemispheres and she also showed none of the usual symptoms of the split-brain patients. Yet, "she was found to be selectively subnormal on a variety of percep-9 tuomotor, spatial, nonverbal reasoning tasks..." Both hemispheres were capable of language, but, i t seems plausible to suppose, language capa-city i n the minor hemisphere crowded out some of the normal capacities. What we can make of a l l this i s that the brain i s organized in such a way so as to maximize i t s capacities. If i t enhances the brain's cap-acity to have two areas for memory, one that approaches the data d i f f e r -ently from the other, there i s every reason for the brain to organize i t s e l f l i k e this. The two hemispheres represent different areas of the same brain. They contribute different capacities to the whole brain, but they are united into a whole mind in the normal human. The evidence for a single mind in the normal man, therefore, comes from evidence that shows that for some actions the entire brain i s i n -tegrated for the task. At the same time, the different functional cap-acities of the two hemispheres can be seen to be complementary and add-ing to the whole rather than being merely redundant. The human mind is capable of this type of unification. Normal humans, therefore, have one mind instead of two. .56 CHAPTER IV ARGUMENTS FOR ONE MIND IN BRAIN BISECTED PATIENTS Introduction J. C. Eccles i s inclined to agree with Puccetti and Bogen that what is the case with the brain bisected patient is also the case for normal humans. According to both of them commissurotomy does not change anything fundamental about the number of minds one can be said to have. With this agreement behind them, their views diverge radi-cally. Puccetti and Bogen believe that we a l l have two minds, while Eccles believes that we a l l have onemind that i s associated with the major hemisphere. For Eccles the minor hemisphere i s l i k e a computer that performs a wide range of brain functions, but never gives rise to consciousness. Instead i t i s the servant of the major hemisphere and performs a great deal of unconscious work for i t . He speculates, how-ever, that consciousness only arises after the major hemisphere has gained the information.^ When the minor hemisphere is separated from the major i t retains this i n a b i l i t y to become conscious. Thus the brain bisected patient only has one mind associated with the l e f t hemisphere and one unconscious, but complex, computer l i k e hemisphere. Unconscious Behavior Since the minor hemisphere gives rise to a large amount of sophis-ticated behavior, Eccles attempts to show that this type of behavior does not need to be explained by consciousness in that hemisphere. To make this plausible he refers to experiments where conscious experience 57 is a r t i f i c i a l l y induced. The object of the experiment is to determine the minimum amount of stimulation that i s necessary before the patient reports a conscious experience. Therefore, during brain surgery the patient i s l e f t conscious and the exposed brain i s submitted to e l e c t r i -cal stimulation. It was found that i t could take up to half a second for the patient to respond to the stimulus. Eccles concludes that at the threshold levels "there is opportunity for a great elaboration of neuronal activity in complex spatio-temporal patterns during the incu-bation period of a conscious experience..." This also shows that "measurements of reaction time cannot be used as a measure of the time 3 required for elaboration of a conscious experience." Thus Eccles believes that i t is possible for a great deal of sensory input to be processed and even to be reacted to, before the subject ever becomes conscious of the input. The experiment shows that sensory stimulation need not give rise to consciousness, nor need we suppose that the reaction stimulus is a conscious action. Aside from such experiments, Eccles suggests an example of what i s to count as an elaborate case of unconscious behavior. A doctor who is supposedly in an 'automatic' state diagnosed a patient. Later he remembers nothing of the experience. Such an action is highly complex and i f unconscious is a good example of the type of unconscious be-havior that Eccles wishes to show i s possible. D. M. MacKay gives another example of extended and complex uncon-scious behavior."* While involved in a discussion i n his bedroom, MacKay had intended to change his shirt. Instead, at the end of the conversation, he found that he had put on his pajama top instead of a 58 shirt. He comments that the "common sense description (of the event) i s that I had l e f t some of my learned routines to run because I was attending to something else."^ The action was done without conscious thought. There seems to be a great deal of other brain activity that is not conscious. Problem solving i s often done in the subconscious. One may not know the solution to a logical puzzle or a similar problem and then suddenly at a time when the problem is not being thought about the mind becomes aware of the solution. The same thing can happen when someone i s trying i n vain to remember something. After the event the memory suddenly comes easily. In both these cases i t would seem that a computer was unconsciously working on the problem. When the solution was f i n a l l y reached, the information was then relayed to the conscious self. Eccles can argue, therefore, that the brain i s capable of a great deal of unconscious behavior. It could be that consciousness is not necessary to explain the behavior of the minor hemisphere. If Eccles has been successful i n showing that the minor hemisphere's behavior does not need to be explained by consciousness, he has succeeded in meeting one possible objection to his position. At the same time i t counts as a positive argument since consciousness can be dismissed as an unnecessary hypothesis using Occam's razor. It can be argued that i t i s always best to postulate the least amount of consciousness necessary to explain the phenomena. 59 The Unity of Consciousness Eccles now considers some further arguments that are intended to give positive evidence that the minor hemisphere really i s unconscious. The f i r s t argument can go under the t i t l e of 'the unity of conscious-ness'. What he has in mind by this term i s the fact that the 'play of experience appears to be, as i t were, a l l on the stage before one single conscious se l f . . . " ^ No matter how diverse the mental situation gets this 'single s e l f remains conscious and claims the experience as i t s own. For instance, when the brain i s subjected to hallucinatory drugs a l l the diverse experiences are reported to have been experienced by the one sel f . The case i s similar after extensive brain surgery. What remains of the patient's mental capacities a l l belong to the one self. Even when the conscious experience i s a r t i f i c i a l l y induced, the patient reports the experience as his own. There i s no mental diplopia within our conscious experience. If there i s mental activity i t comes to a 'single conscious s e l f . Eccles applies this point to the brain bisection case by asserting that the unity "of conscious experience i s retained at the expense of a loss of a l l the experience that would be expected to be associated with the a c t i v i t i e s of the minor hemisphere." Since these patients do retain their unity of consciousness, according to Eccles, i t could not be that the minor hemisphere i s also conscious. This iv-ould count as a case of mental diplopia. There would be two spheres of consciousness in the mind and thus the play of experience would be on a stage for two selves. This type of diplopia i s not reported nor is i t found i n other cases of brain operations. 60 Eccles Is Impressed by the fact that the major hemisphere does not seem to even acknowledge the existence of the minor hemisphere. If cued by the minor hemisphere i t remains ignorant of the fact that i t has been cued. It knows that i t received the information, but is not aware that the minor hemisphere was the source of information. Thus, to Eccles, i t seems that the minor hemisphere has been dropped from the conscious experience of the person. Mental unity has been salvaged but only at the expense of minor hemisphere input. We supposedly know that there i s no conscious activity in the minor hemisphere because the person does not report any such activity. Epistomological Considerations Another reason why Eccles does not believe that the minor hemi-sphere i s conscious, stems from epistomological considerations concern-ing the problem of whether there are other minds. Eccles i s aware of the extremely complex behavior that the minor hemisphere i s capable of. He knows that i t i s capable of responding to commands and can recognize and identify complex objects. Yet he does not believe that this sort of behavior i s sufficient evidence for postulating a mind for the hemi-sphere. In the absence of lin g u i s t i c behavior, Eccles believes that "we must be agnostic (about minds), just as with the question of con-9 sciousness in animals." Linguistic behavior i s , therefore, the only evidence that he w i l l accept as relevant to the question of whether a being is conscious. He not only puts the minor hemisphere on the same mental level as the animals, but he denies conscious experience to both, due to the lack of appropriate evidence. 61 Eccles Is very impressed with the communicating capacity of l i n -guistic behavior. He believes that i t i s this feature of linguistic behavior that keeps his position from slipping into solipsism and from being an arbitrary behavioral criterion for another mind. His assertion is that one comes to know of other minds when one comes to communicate with them. By interpreting their words one comes to see that the being is trying to communicate with oneself. Part of what i s communicated is that the other mind is conscious.^ Accordingly Eccles claims that solipsism i s untenable because other minds can communicate that they have mental states. From this, Eccles concludes that since the brain bisected patient's l e f t hemisphere does not communicate, that i t is not conscious. Therefore, these patients only have one mind. Objections to Eccles Another Look at Unconscious Behavior Eccles' position is untenable. It i s , of course, logically pos-sible. Philosophers have believed for some time that i t would be pos-sible for a being to exhibit a l l the behavior that humans exhibit and s t i l l not be conscious. It could also be that animals l i k e dogs are very complex machines that are programmed to yelp when stepped on with-out the accompanying mental state of pain being experienced. It is logically possible that even the major hemispheres of these patients are not conscious. The fact that the position is possible is not at stake. The plaus i b i l i t y of the position, however, is at stake. Eccles gave examples of unconscious behavior to give his position some i n i t i a l p l a u s i b i l i t y . His examples f a l l short of this objective 62 for several reasons. F i r s t of a l l , the experiment that he cites as evidence that stimulation of the senses does not necessarily give rise to conscious experience, does not also show that one can react to a stimulus before being conscious of i t . It may be true that i t takes a while for the stimulus at low threshold levels to give rise to con-sciousness, but that fact does not speak to the question of whether complex behavior could be unconscious. Thus the experiment does not prove the point that he wishes i t to prove. Another problem with this experiment i s that at most i t only counts as evidence for isolated cases of unconscious behavior. At most i t would apply to a reaction to a flash or to another type of response action. It does not give any plausi b i l i t y at a l l to the argument that a brain can perform a wide degree of integrated behavior, respond to tests, keep appointments and the lik e and s t i l l remain unconscious. Eccles needs illustrations of sustained behavioral output that s t i l l are thought to be unconscious. His i l l u s t r a t i o n of the doctor diagnosing a patient i n an 'auto-matic' state i s an example of what is thought to be sustained unconscious behavior. Unfortunately, i t i s even less plausible than the experiment above. Presumably the doctor's diagnosis w i l l require a good deal of lin g u i s t i c behavior. Eccles, however, counts such behavior as evidence for consciousness. Therefore, the doctor was conscious during the time that he was held to be exhibiting unconscious behavior. The fact that he could not remember the event later i s irrelevant. Eccles does not wish to assert that amnesiacs were unconscious before they came to suffer from amnesia. His i l l u s t r a t i o n , therefore, f a i l s completely. 63 MacKay's personal i l l u s t r a t i o n of unconsciously putting on his pajama shirt i s perhaps the best i l l u s t r a t i o n of sustained unconscious behavior. The force of the i l l u s t r a t i o n could be weakened by insisting that MacKay was aware of putting on something l i k e a shirt. He was, therefore, aware of some of his actions since he had consciously intend-ed to put something on. On the other hand, he does seem to be unaware of the texture of the garment, i t s shape and other such details. He i s so caught up with other activities that in a sense he is doing this activity without expl i c i t l y thinking about i t . In a sense, then, i t could be considered unconscious activity. The problem with this i l l u s t r a t i o n i s that the behavior exhibited i s not extensive enough. Presumably MacKay is able to put on a shirt unconsciously, but that i s no reason to believe that he can carry out extensive tests without being conscious of the fact. The i l l u s t r a t i o n does not show that behavior as complex as that exhibited by the minor hemisphere i s capable of being performed by a human being while uncon-scious of the activity. The same objection applies to unconscious activities such as suddenly remembering or suddenly solving a problem. That sort of unconscious phenomenon is normal in the human race. The phenomenon is not so complex that i t suggests that the minor hemisphere might operate unconsciously. Eccles' discussion of unconscious activity, therefore, does not lend enough pla u s i b i l i t y to his thesis that the minor hemisphere i s unconscious. The Unity of Consciousness It i s not clear that Eccles is right when he asserts that no matter how diverse the mental phenomena become there is no mental diplopia. 64 Cases of s p l i t personality and extreme dissociation could count against this claim. On the other hand, a l l that Eccles needs to assert i s that in the case of brain bisected patients this sort of question about dip-lopia does not arise. This objection i s , therefore, only a minor one. A much more serious objection to Eccles 1 argument i s that i t seems to miss the point of those who believe that these patients have two minds are making. They are asserting that the patients have two minds and not one. If there are two minds, then each of these minds should have i t s own unity of consciousness. Since the two minds are separated, they do not have f i r s t hand knowledge of the other mind. The type of diplopia where the mind asserted consciousness of conscious experience that was not i t s own would be a puzzling situation. This i s not, how-ever, the type of position that Eccles i s trying to deny. He is trying to deny that there are two conscious but separated spheres of mental activity in these patients. Given that position, one would not expect mental diplopia to arise. The major hemisphere can remain conscious and maintain i t s unity of consciousness at the great loss of the input from the minor hemisphere. The minor hemisphere, however, should also be able to remain conscious and maintain a unity of consciousness at the great loss of major hemispheric input. It seems that Eccles believes that since there was one conscious entity before the operation, only this entity could preserve i t s unity of consciousness. This, however, is just to deny that minds can be s p l i t . Eccles has not produced any argument to that effect. If the mind has been s p l i t by the operation, then one hemisphere preserves the unity of consciousness with what is l e f t of i t s separated a b i l i t i e s . 65 In a similar way the other hemisphere would preserve mental unity with the functions l e f t to i t . Therefore, Eccles' argument from the unity of consciousness presents no problem to theorists who wish to assert that brain bisected patients have two minds. Eccles' Epistomological Grounds For Postulating Conscious States Eccles' approach to the other minds problem is not very plausible. He wishes to make linguistic behavior the only acceptable criterion for postulating another mind of a being. Language i s of course the most sophisticated form of behavior that man i s capable of and we do commu-nicate with language. Even i f this i s granted, however, lin g u i s t i c behavior i s s t i l l only behavior. Our only evidence for other minds comes from behavior. If one takes the other minds problem seriously one "should take seriously the question of whether there i s anything mental going on behind what a speaker says to us...""^ Linguistic behavior is just another type of behavior that we must evaluate and interpret. One's assertions of consciousness could be just an instinc-tive reaction. A l l communication is carried out through behavior of which language is just a type. Communication and meaning are not mag-ic a l l y in the words. They are interpreted l i k e any other behavior. Eccles could modify his position by asserting that even though ling u i s t i c behavior i s not on a special communicating level apart from a l l other behavior, i t i s s t i l l the only good criterion of other minds due to the complexity of the behavior. For example, there are animals that are capable of simple swimming behavior. Their swimming action can be explained by their simple nervous system. No one i s tempted to 66 think that the animal is conscious. As one moves up the scale of com-plexity in animals, i t becomes more and more plausible that the more complex animals are conscious. Somewhere along the line, one w i l l attribute consciousness to a l l animals that are above the line. At the same time there w i l l be a line marking off those l i v i n g things that one would not believe are conscious. There may be a large range of animals that we are agnostic about, so there need not be a sharp dis-tinction between conscious l i v i n g things and unconscious liv i n g things. Eccles' line i s , of course, very sharp. If an animal can speak i t is 12 conscious, otherwise i t i s not. One i s inclined to think that Eccles has placed the dividing line between conscious entities and non-conscious entities too high. He seems to believe that consciousness i s necessary for statements lik e 'I am conscious' but not for other complex behavior. Yet i f one i s to start with one's own conscious experience, as Eccles suggests is the only appropriate way, one i s aware of conscious experience at a much more primitive level than that exhibited by linguistic behavior. The feeling of pain and pleasure do not require l i n g u i s t i c a b i l i t y to be f e l t or expressed. One can have plenty of evidence that a being is i n pain, enjoying i t s e l f , or disgusted without i t reporting the state of i t s mind. The minor hemisphere i s f u l l y capable of exhibiting this type of behavior and this should count as evidence that i t i s conscious. Linguistic a b i l i t y i s necessary for certain conscious experiences but i t is not necessary for a l l . There is no reason why everyone must t e l l me that he i s in pain before I w i l l believe him. 67 Eccles seems to be in grave danger of solipsism. He refuses to accept a great range of sophisticated evidence because he does not be-lieve that i t is sufficient for postulating a mind of the being exhibi-ting the behavior. If one can be so skeptical after such a wide range of sophisticated behavior has been displayed, i t is hard to see how the addition of linguistic behavior will help. If the violent motions and howls of a dog undergoing an operation without anesthetic did not con-vince one that the dog was in pain, the addition of the dog calmly stating what mental states he was in would not help. If one can remain skeptical through the Initial behavior, i t should not be too great a leap to remain skeptical of conscious states after the linguistic be-havior . Eccles' position fails, therefore, because we have excellent evi-dence that animals like dogs are conscious. The minor hemisphere is capable of displaying behavior a good deal more sophisticated than the higher animals. In the words os Sperry, " i t is our own interpretation based on a large number and variety of nonverbal tests, that the minor hemisphere is indeed a conscious system in its own right, perceiving, thinking, remembering, reasoning, willing, and emoting, a l l at a char-13 acteristically human level..." It is, therefore, untenable to hold that the minor hemisphere is like an unconscious computer. The range of its behavioral sophistication is just too high to make that plausible. 68 CHAPTER V AN ATTEMPT TO MEDIATE BETWEEN PUCCETTI AND ECCLES Introduction L. W. Dewitt agrees with our argument against Eccles. He believes that Eccles has been too extreme i n assessing the a b i l i t i e s of the mi-nor hemisphere. Dewitt feels forced to"grant the impressive cognitive a b i l i t i e s of the minor hemisphere ( i t simply won't do to say that i t i s unconscious)."^" At the same time he i s impressed with Eccles' posi-tion in that i t shows the great disparity that language makes between the two hemispheres. Dewitt therefore attributes consciousness to the minor hemisphere, but denies that i t i s on a par with the major hemi-sphere. He believes that Eccles i s right when he de-emphasizes the importance of the minor hemisphere. Dewitt identifies what he believes to be the difference by insisting that the major hemisphere meets the conditions for personhood but the minor hemisphere does not. Dewitt sees his paper as a mediation between Eccles and Puccetti since he agrees with Puccetti that what is the case in brain bisected patients i s also true of the normal brain. He believes that personhood in the normal human is invested in the major hemisphere while the minor hemisphere does not qualify, but i s a mind that helps the person in the major hemisphere. Thus, he believes that the normal person has two minds, one of which is not very important. 69 Humans and Personhood Dewitt i s a b l e to make h i s t h e s i s p l a u s i b l e because the n o t i o n of personhood i s not co-extensive w i t h the n o t i o n of being a human. For example, most science f i c t i o n depends on some encounter w i t h a non-human being that i s a l s o thought to be a person. I f the n o t i o n of personhood would not a l l o w f o r t h i s expansion of personhood o u t s i d e the realm of the human race, s c i e n c e f i c t i o n would l o s e a good deal of i t s p l a u s i b i l i t y . Another example of a non-human being that i s thought to be a person comes from t r a d i t i o n a l C h r i s t i a n theology. God i s thought to be a person and yet i s not thought to be human at a l l . P l a u s i b l e examples of humans who are not thought to be persons are more d i f f i c u l t to f i n d . The problem i s not f i n d i n g s u i t a b l e candidates but w i t h convincing other humans that they are not persons. The exam-pl e s t h a t are most p l a u s i b l e are the 'human vegetables', the s e v e r e l y insane whose only c a p a c i t y i s to enjoy the s a t i s f a c t i o n of t h e i r b o d i l y a p p e t i t e s , and babies who have not yet developed beyond a p r i m i t i v e s t a t e . We do not b e l i e v e t h a t animals which manifest the same c a p a c i -t i e s as these beings are persons and yet we do not want to be hasty and d i v e s t the humans described above of personhood. They do not seem, however, to pass the u s u a l self-awareness t e s t s that d i s t i n g u i s h per-sons from the non-human animals. We w i l l r e t u r n to self-awareness l a t e r . The reason that we do not wish to d i v e s t these marginal persons of t h e i r personhood i s that we have strong emotional t i e s to beings of our own s p e c i e s . We remember the human vegetable and the insane person as they used to be. To d i v e s t them of personhood now would take too great 70 of an emotional leap from how we used to feel about them. The babe i n arms i s also thought of as a person due to the great potential for personhood that i t possesses. By ascribing personhood to the baby we are not thinking of i t s present state but of the being that i t w i l l become. Another reason that we do not wish to judge these cases i s the legal and moral problems that could arise. One does not know where to draw the border between personhood and non-personhood. Take the example of the baby. At what point does i t become a person? When i t learns to talk? But then how much vocabulary must i t have before i t i s considered a person? The line at which the distinction could be made i s not clear. Similar examples can be presented for the human vegetables and insane. When is a human body beyond the point of recovering some of i t s mental faculties? When i s the insane human so insane that he i s not a person? These questions do not have clear answers. The moral and legal questions arise since we tend to treat non-persons differently than persons. We eat non-human animals, experiment 2 on them and slaughter unwanted pets. Peter Singer believes that this is immoral. He believes that there should be some equality of rights among animals. The only relevant criterion for treating a being d i f f e r -ently i s i t s ina b i l i t y to suffer. Since dogs, cows and rats are capable of suffering, he believes that such treatment of them is immoral. Singer i s right that the capacity to suffer i s a relevant issue i n how we treat animals. Some cruel experiments and the torture of animals are immoral. Personhood, however, is also a relevant consideration i n our treatment of animals. One should not torture a cow, but i t i s not 71 clear that the cow suffers extensively from being butchered. It does not contemplate the evils of death or the benefits of a long l i f e . I t i s , therefore, not clear that butchering i t i s immoral. It i s , how-ever, usually thought that a person may only be k i l l e d i f the situation is clearly one of self-defense or the li k e . If the humans considered above were thought to be non-persons a wide variety of treatments could be legitimatized. Some kinds of experiments on the insane might be ju s t i f i a b l e . Euthanasia in regard to healthy children and the like could be suggested with more plaus i b i l i t y . We, however, do not want to make such decisions. The practice of treating these humans as non-persons i s too open to abuse. The temptation would be to start abusing the rights of borderline cases or to arb i t r a r i l y classify one's enemies in the non-person camp. It is easier to treat a l l humans as persons even though some of them may not be persons f u l l y developed. Dewitt, of course, i s not suggesting that we treat minor hemispheres as non-persons. He i s suggesting that they probably f a l l into the same category as the baby that has not developed into a f u l l person. Thus, according to Dewitt, there i s a great deal of difference between the major hemisphere and the minor hemisphere. Both are conscious minds. One, however, i s f u l l y a person while the other would only be considered for personhood due to i t s a f f i n i t y with the human species. Dewitt's Criterion of Personhood Dewitt contends with many that self-awareness i s the major c r i t e r -ion of personhood. He also contends that " i t i s the presence of lan-guage which allows self-awareness to appear."3 There is some plausi-b i l i t y to this claim. Behaviorally, language i s the chief attribute 72 that distinguishes us from the rest of the animals. This should at least make i t prima facie plausible that language w i l l be the capacity that allows humans to rise above the animals and become self-aware. Language i s used to help us abstract our thought from ourselves, reason logically, and perform other abstract thinking functions. Dewitt be-lieves that language is necessary for the contemplation of death and such contemplation is a prime example of being self-aware. Since, according to Dewitt, language i s necessary for self-awareness, which i s the criterion of personhood, the minor hemisphere which lacks language cannot be self-aware. Therefore, i t i s not a person. Dewitt does not analyze the type of self-awareness that i s dis-cussed above. He mentions i t and then moves on to consider what he thinks of as a more subsidiary self-awareness. This self-awareness does not require linguistic capacity to make i t s e l f manifest. Chimpanzees are capable of this rudimentary self-awareness, but Dewitt does not believe the minor hemisphere i s . Thus, i f he is successful he would have shown an even deeper disparity between the hemispheres than just the fact that one is not sufficiently capacitated to count as a person. The evidence that counts for a type of self-awareness that chimps are capable of and minor hemispheres are not is taken from a study of 4 chimps by Gallup. Gallup experimented by putting mirrors i n the same room as chimps. At f i r s t the chimps started to treat the image in the mirror as another chimp. When subjected to the same test a monkey never learned that this image was a mirror image of i t s e l f . After some time, however, the chimp started to treat the mirror image of himself d i f f e r -ently than another chimp. He would groom himself and give other evidence 73 t h a t h e b e l i e v e d t h a t t h e image was o f h i m s e l f . G a l l u p a n d D e w i t t c o u n t t h i s a s e v i d e n c e f o r some d e g r e e o f s e l f - a w a r e n e s s i n t h e c h i m p . D e w i t t t h e n t r i e s t o l i n k t h i s t y p e o f s e l f - a w a r e n e s s w i t h t h e c a p a c i t y f o r l a n g u a g e . He i s v e r y i m p r e s s e d t h a t t h e same s p e c i e s t h a t was a b l e to i d e n t i f y i t s e l f i n t h e m i r r o r was a l s o a b l e t o l e a r n s i m p l e n o n - v e r b a l l a n g u a g e s u s i n g p l a s t i c b l o c k s . E x p e r i m e n t e r s , o n t h e o t h e r h a n d , h a v e h a d no s u c c e s s w i t h t e a c h i n g m o n k e y s , o r o t h e r a n i m a l s who f a i l e d t h e m i r r o r t e s t , a n y s y m b o l i c n o n - v e r b a l l a n g u a g e . To D e w i t t t h i s l e n d s " c o r r o b o r a t i n g s u p p o r t t o t h e c o n j e c t u r e t h a t l a n g u a g e i s e s s e n t i a l f o r s e l f - a w a r e n e s s . " D e w i t t r e a l i z e s t h a t t h i s i s o n l y c o r r o b o r a t i n g e v i d e n c e . I t c o u l d b e a c o i n c i d e n c e t h a t t h e s e two c a p a -c i t i e s h a p p e n e d t o a r i s e i n t h e same a n i m a l . D e w i t t , h o w e v e r , s h o u l d b e m o r e c a u t i o u s i n how h e p r e s e n t s h i s a r g u m e n t . He i n s i s t s t h a t t h i s i s e v i d e n c e t h a t l a n g u a g e i s e s s e n t i a l f o r s e l f - a w a r e n e s s when a l l t h e e x p e r i m e n t shows i s t h a t a n i m a l s c a p a b l e o f s e l f - a w a r e n e s s a r e p e r h a p s a l s o c a p a b l e o f l e a r n i n g some k i n d o f l a n g u a g e . T h e c h i m p s d i d n o t n e e d l a n g u a g e t o r e c o g n i z e t h e m s e l v e s a n d n o t e v e r y chimp t h a t d i d , a l s o h a p p e n e d t o know a l a n g u a g e . D e w i t t m u s t r e s t h i s p o i n t o n t h e c a p a c i t y o f t h e c h i m p f o r b o t h f u n c t i o n s . T h e F a i l u r e o f D e w i t t ' s P r o g r a m D e w i t t ' s p r o g r a m was t o show t h a t a l t h o u g h t h e m i n o r h e m i s p h e r e was c o n s c i o u s , i t f a i l e d t o p a s s t h e c r i t e r i o n f o r p e r s o n h o o d s i n c e i t was n o t c a p a b l e o f s e l f - a w a r e n e s s . By a l l o w i n g c h i m p s , h o w e v e r , t o p o s s e s s t h e n e c e s s a r y l e v e l o f s e l f - a w a r e n e s s f o r p e r s o n h o o d D e w i t t u n d e r m i n e s h i s o v e r a l l p r o g r a m . He l o w e r s h i s c r i t e r i o n enough t h a t , c o n t r a r y to what h e t h i n k s , t h e m i n o r h e m i s p h e r e i s e a s i l y a b l e t o p a s s t h e t e s t . Thus t h e d i s c r e p a n c y b e t w e e n t h e h e m i s p h e r e s i s n o t p r o v e n . 74 Dewitt does not believe that the minor hemisphere is capable of recognizing i t s own face in a mirror. The evidence for this i s non-existent. As was seen i n the f i r s t chapter, the minor hemisphere i s much better equipped to pass this test than the major hemisphere. If there were any doubt about f a i l i n g this test, one would put odds on the major hemisphere f a i l i n g before the minor hemisphere would. Dewitt might i n s i s t that although the minor hemisphere is very good at recog-nizing faces, that does not mean that i t would be able to recognize i t s own face as i t s own. The tests, of course, have not been done on this, so i t i s hard to say how one should respond. There i s , however, no reason to doubt that he could also identify himself i f shown a picture of himself. The minor hemisphere can also display a good deal more language s k i l l than the chimps w i l l ever be able to demonstrate. For one thing, human beings "where a l l language functions i n both hemispheres have been destroyed by cerebrovascular accident, symbolic functions can be re-learned far more quickly and easily than chimpanzees can learn them, 'using the same plastic cut-outs'."^ If this i s the test, then the minor hemisphere has a much greater capacity than the chimps whom Dewitt thought to be self-aware. Thus, Dewitt's program f a i l s since he lowers the criterion of personhood low enough for the minor hemisphere to easily pass the test. Dewitt did not need to discuss the 'self-awareness' i n chimps. He could have continued on his original program of showing that the minor hemisphere was lacking in important respects that barred i t from 75 being considered a person. Personhood would just require;a more ad-vanced form of self-awareness than that shown by the chimpanzees. Thus, his original program could s t i l l show some promise. Self-Awareness and the Minor Hemisphere Dewitt is following the vast majority of philosophers when he accepts self-awareness as the major criterion of personhood. There are of course different views as to what kind of self-awareness i s necessary or what i t i s about self-awareness that makes i t necessary for person-hood. Nonetheless, there is generally a consensus that self-awareness i s the major criterion for personhood. It i s not so clear, however, why we should agree with Dewitt that language is necessary for self-awareness to arise. As was admitted earlier language i s extremely important in human affairs. Much of what we are able to do would be impossible without i t . Yet there does not seem to be any compelling reason to believe that l i n g u i s t i c a b i l i t y i s necessary for self-awareness to develop in a being. There may be an epistemological problem in how we would discover that the being was self-aware to a degree greater than the chimpanzee mirror experiments. This, however, should not lead us to conclude that l i n g u i s t i c capacity is necessary for self-awareness to exist. Gardner t e l l s of a case that evades the epistemological problem. A patient of his awakended one morning thinking that a l l was normal. To his horror, however, he discovered that he could not speak to his wife. His 'words' had no meaning that he or his wife could understand. Yet, he was aware of himself and horrified at the tragedy that had 76 overtaken him. A f t e r some time the patient recovered and was able to r e l a t e what h i s f e e l i n g s were during t h i s time of l i n g u i s t i c i n a b i l i t y . ^ Such self-awareness i s t y p i c a l l y human and one can imagine himself taking the same stance i n the predicament. He was aware of himself and h i s incapacity. I t seems somewhat a r b i t r a r y to deprive the above human of h i s per-sonhood merely because he cannot speak or understand. He i s reac t i n g exactly how we would expect a self-aware person to react. His s i t u a t i o n , however, i s very s i m i l a r to the case of patients who have had t h e i r major hemisphere removed. The biggest d i f f e r e n c e between the above case and the minor hemisphere's case, i s the minor hemisphere's greater ' l i n g u i s t i c capacity. Apart from the witness of those working c l o s e l y 8 with these patients that t h e i r actions are t y p i c a l l y human, there i s the f a c t that they seem aware that they have l o s t a good deal of capa-c i t y . This i s e s p e c i a l l y seen when the patient i s being tested f o r l i n g u i s t i c capacity. He w i l l grope f o r words with l i t t l e success but i f there i s any success and he i s capable of some p r i m i t i v e s o r t of communication he shows obvious signs of being very pleased. His beha-v i o r i s best described as one struggling with a problem and r e a l i z i n g 9 that i t i s a struggle followed by great r e l i e f when he succeeds. This presupposes self-awareness. I f a patient who only has one hemi-sphere i s capable of t h i s s o r t of self-awareness there i s no reason why we should b e l i e v e that the minor hemisphere of commissurotomy patients should not have the capacity f o r self-awareness. 77 > Language in the Minor Hemisphere Both Dewitt and Eccles f a i l for the further reason that they do not take the language capacity of the minor hemisphere seriously. As was seen in our f i r s t chapter the language capacity of the minor hemisphere is f a i r l y extensive. They can produce a few words verbally and with great d i f f i c u l t y can write simple nouns. On the intake level, however, they are capable of a great deal of comprehension. If Eccles wishes the minor hemisphere to assert that i t i s conscious, the examiner can ask i t to nod i t s head i f i t is conscious. Dewitt could ask the appro-priate questions to determine the level of self-awareness. For instance, Smith reports a patient with only a minor hemisphere that was being tested for color recognition. After a few failures Smith "carefully 9 explained that this was a test to see i f he could recognize colours... The patient nodded that he understood and proceeded to correctly pick out the right colors. Such an understanding pre-supposes a great deal of self-awareness. Thus even i f linguistic capacity is necessary for self-awareness, the minor hemisphere should have enough capacity for self-awareness to arise. Dewitt's program therefore f a i l s because he both underestimates the li n g u i s t i c capacity of the minor hemisphere and he falsely believes that linguistic capacity is necessary for self-awareness. .78 CHAPTER VI FURTHER ATTEMPTS TO SEE SPLIT-BRAIN PATIENTS AS HAVING ONE MIND Eccles denies that severing the corpus callosum results i n two minds i n one body because the minor hemisphere i s not conscious. There-fore the person's one mind is being cut off from a computer l i k e brain but not from a conscious sphere within i t s own head. Robinson also denies that this s p l i t results in a person having two minds but his reasons for this position are an attack on the interpretation of the experimental results. His basic strategy i s to find counter examples to the results that make i t so plausible that these patients have s p l i t minds. Counter Examples The f i r s t counter example that Robinson gives is called 'backward masking'. In this experiment the subject's reaction time to a brief flash i s tested. Once the reaction time has been established, a second flash of greater intensity and duration follows closely. When this happens the subject only reports seeing the last flash. Yet, the sub-ject w i l l respond as quickly to the f i r s t flash that he now cannot report, as he did when he could report seeing a flash. Robinson sug-gests that "the observer has the a b i l i t y to respond as quickly to a flash he f a i l s to see as to one he does." ^ Robinson claims that this is the same type of experimental phenom-enon that led some to believe that the brain-bisected person had a 79 s p l i t mind. In Robinson's words the patient seemed to both know and not to know at the same time. Here the subject reacts as fast to a stimulus that he is verbally unable to report as to one that he can report. In this case, however, the hypothesis of two minds in one body is not plausible. The same hemisphere could be used throughout the experiment, so one could not have one hemisphere knowing and the other not knowing what was going on. There i s no reason at a l l to think that two minds are involved here. Yet, i f the arguments for the split-brain patients having two minds are valid, backward masking, according to Robinson, i s evidence for two minds in these patients. It i s obvious, however, that backward masking is just one of the interesting results that one obtains i n special cases with the one human mind. Robinson therefore wonders why we should not approach the results of split-brain experiments in the same way? Robinson sees a similar situation arising from another class of experiments. In these experiments an observer i s b r i e f l y exposed to a matrix of letters. Normally the observer can correctly report five to nine of the sixteen or so items. If, however, a cuing ring i s projected over one of the unreported matrix positions, the observer can then report the correct letter. Therefore, "the observer simultaneously 'knows' and does not 'know' that the letter i n question was part of the 2 array." No one i n this case, however, wishes to postulate two minds of the observer to deal with the phenomenon. The above counter examples deal with normal people but, according to Robinson, similar results to the split-brain behavior can be found in brain damaged patients who s t i l l have corpus callosums intact. 80 Robinson refers to cases where patients recognize objects held in the hand but are not able to identify the same object when i t is seen visually. Such visual agnosias "are common in the neurological l i t e r a -3 ture and there are auditory and tac t i l e agnosias as well." These patients do not have two minds yet the results of these experiments, according to Robinson, are similar to the cerebral commissurotomy patients. Robinson could also appeal to the phenomenon concerning the con-scious and subconscious self. As long as information remains within the subconscious i t is not available to the conscious self. At the same time i t i s believed that the subconscious self influences our decisions and actions. The patient is not able to report the informa-tion in the subconscious, yet the subconscious is able to demonstrate the informational content that i t possesses. This is not as strong a counter example as those lis t e d above because there is some tendency to reify the subconscious self and the conscious self thus admitting two minds or selves in one body. It is also possible to explain the phenomena without postulating 4 two rei f i e d minds. H. Fingarette explains the defense mechanisms of the subconscious by asserting that some information was never explic-i t l y made conscious due to the threatening nature of the information. It i s not that the patient i s not conscious of the information, but that he does not consciously allow himself to reflect on i t and make i t part of the explicit knowledge that he retains. Thus i n one sense he has the information but i n another he does not have i t , since his defense mechanisms refuse to make i t conscious. Yet i t is only one 81 mind that i s doing a l l of this and not two. It seems therefore that i t is possible to explain this phenomenon without postulating two minds. Commissurotomy Symptoms as an Instance of a Larger Agnosias Class Robinson's argument i s that since i t i s possible i n these other cases for us to accept the phenomena and s t i l l the singularity of the mind we should also be able to accept the singularity of the ' s p l i t -brain' patient's mind. The results of experiments with split-brain patients are not unique and therefore should not require a unique solution. Robinson tends to treat the cerebral commissurotomy symptoms as. just another instance of a genre of agnosias which are usually associ-ated with left-hemisphere disturbances. If one i s to identify a human being with respect to genius and species one can assert that the human being i s the sort of an organism which reacts in a certain way to back-ward masking, who can be cued i n a certain way and "who behaves in a 5 predictable way i f he happens to have his corpus callosum s p l i t . " One expects some symptoms to arise when the brain has been operated on. In the case of cerebral commissurotomy certain symptoms arise that show that a kind of agnosias has developed. Robinson does not think this should be surprising nor should i t be treated differently than agnosias that arise from different kinds of brain damage. If we are to treat i t differently there must be something significantly different about the symptoms that require this. Otherwise the phenomenon is not so unusual. An observer's reports are "not always a reliable measure of what he knows or has perceived."^ 82 The Split-Mind Thesis Defended To count as appropriate counter examples, Robinson's examples must at least be similar enough to the general type of symptoms the s p l i t -brain patient exhibits. Otherwise one could dismiss Robinson's examples because there i s something special and new about the cerebral commissur-otomy symptoms. Yet this does seem to be the case. The most s i g n i f i -cant difference i s that the cerebral commissurotomy patient's symptoms are not a simple case of just knowing information and not knowing the same information at the same time. Yet, a l l of Robinson's examples seem to depend on some sort of knowing and not knowing formula. The evidence for two minds in the brain bisection case is good because of the lack of integration between the hemispheres. This lack of inte-gration does not just show i t s e l f i n one area or i n very special circum-stances. Instead, i t is spread throughout the patient's experience. Robinson's knowing and not knowing formula is just too simple to describe what i s going on with these patients. Robinson acquired this formula from Puccetti but Puccetti i s probably wrong in stating his case in these terms. At the same time, however, Robinson should have realized that the case was not as simple as he represented i t . This should also be obvious from Puccetti 1s work. Even i f Robinson's knowing and not knowing formula was adequate however, his counter examples are s t i l l not relevant to the brain b i -section cases. Take backward masking as an example. The knowing and not knowing in this case can be explained in a way that i s an inappro-priate explanation for cerebral commissurotomy symptoms. One possible 83 explanation of the backward masking results i s that the mind i n con-junction with the eyes is not very fast at distinguishing short time spaces between flashes. If one i s given a series of flashes close enough together, the mind w i l l report the flashes as one continuous light. It may be that the mind consciously sees the f i r s t flash and responds appropriately but is unable to distinguish i t from the second. In other words, i t would be seeing a flash that was longer than the second flash alone. The mind here would just be ignorant of the time gap between the flashes but not of the flashes to which i t responds. This would not, of course, be a case of knowing and not knowing, so backward masking could not count against the split-mind interpretation. A different problem arises with the cuing experiment. For one thing the subject does not know and not know at the same time. At f i r s t he cannot remember the letter and later he recalls i t . At one time he did not know the right answer and later he did. This could not possibly count as evidence for two minds at one time. It seems to/be a case that can f a i r l y easily be described along the lines of forgetting and remem-bering. We a l l know that there are times when we have forgotten infor-mation and some chance incident helps us to re c a l l i t . The cuing in this case just assists our mind to r e c a l l something from i t s memory banks. It may be that this information was never e x p l i c i t l y recognized but most of our sensory intake i s in the same situation. Yet, there i s no problem in recalling i t given the proper motivation and stimulation. The commissurotomy symptoms, however, are different. The patient gives evidence that he is both expl i c i t l y conscious of the stimulus and at the same time cannot report any knowledge of the stimulus. This i s 84 nothing l i k e a memory problem. One of the minds has not temporarily lost some information for r e c a l l . The major hemisphere seems to be incapable of retrieving the information even after the correct answer has been indicated by the minor hemisphere. The symptoms with the cuing ring and the brain bisection cases are significantly different and require a different interpretation. Robinson referred to cases of agnosias in the belief that this phenomenon was similar to the brain bisection phenomenon. This, how-ever, does not seem to be clear. Visual and tactual agnosias occur because of some learning deficiency. Cerebral commissurotomy patients show no such deficiency. Cases of visual-tactual agnosias have arisen among patients who have passed most of their lives in near blindness due to congenital cataracts. After their sight has been restored they often experience severe visual problems. Some never get beyond the a b i l i t y to d i s t i n -guish brightness and color. Others, "over a period of months and even years, develop the a b i l i t y to identify simple geometric figures..."^ The patients above did not have lenses in their eyes and vision was affected by jerky movements of the eyeballs. The effect of these defects is hard to estimate. Therefore experiments were done on normal chimpanzees. Riesen t e l l s of two chimps that were l e f t in a dark room for sixteen months after birth. After this, one was put on rationed light for another f i v e months and the other for another seventeen months. The f i r s t chimp, after many months, began to recognize objects normally. The latter chimp improved slightly when f i r s t put into a normal situation but after this "he actually lost ground in visual 85 responsiveness, u n t i l even reflex activity began to die away."" It seems, therefore, that i f the chimp is to be able to correlate his visual experience with his tactual experience he w i l l have to experience the two together. If he lacks this for too long a period he w i l l lose the a b i l i t y to learn to correlate the two senses. As has been seen i n the previous paragraph there i s evidence that humans react i n much the same way. The mind therefore has to learn how to correlate the senses. If a patient has not learned to correlate the two senses because of some defect or lost the ab i l i t y because of some accident, this i s explainable on grounds that the mechanisms or learned a b i l i t y for such a correlation are absent. One i s not tempted to postulate two minds because one knows that the problem i s the lack of a certain kind of s k i l l , instead of a duplicity in the mind. The case after cerebral commissurotomy i s such that one side of the body can correlate tactual and visual stimuli with no agnosias but there i s an agnosias between the two sides. The major hemisphere cannot visually identify informa-tion that the minor hemisphere received tactually and vice versa. The problem is therefore considerably more complicated than with the case that Robinson gives. The cerebral commissurotomy symptoms cannot be explained as the loss of some learned a b i l i t y . The a b i l i t y i s s t i l l there but there is no cross communication between the hemisphere for either hemisphere to act on either tactually or visually. That i s , one hemisphere cannot even identify tactually what the other hemisphere can. Robinson's counter example does not f i t . The problem with the counter example using the conscious self and the unconscious self is that the counter example collapses i f one is 86 allowed to reify the subconscious. On the other hand i f i n explaining the phenomena one shows how the subconscious i s really one with the conscious self one reduces the sense in which the patient knows and does not know the same information. It i s easier to understand how one mind can both know something and yet not have 'spelled i t out' so that i t i s explicit knowledge, than to explain how the cerebral commissur-otomy patient f a i l s to be able to verbally identify something held i n the non-dominant hand. In the f i r s t case the problem with speaking about the information is just a case of never allowing the information to r i s e to an explicit level. In the second, the patient is trying to raise the information to an explicit level. This i s generally very simple when the object is being held in the hand. Yet, the patient i s not able to do this with the dominant side of the body while the non-dominant side i s able to show evidence of raising this information to an explicit level. The latter seems to be a case of two minds while, i f one explains the subconscious self as Fingaretti does, only one mind is needed to explain the phenomena. The counter examples that were used are therefore not conclusive against the split-mind theory. Robinson has tried to treat cerebral commissurotomy sumptoms as just a class of symptoms that normally happen. It may be true that the human being is such that he just behaves in a certain way after his corpus callosum has been sectioned. He is just that type of organism. The question, however, i s whether he i s that type of organism that is capable of having i t s mind s p l i t with the sectioning of the corpus callosum. That could be seen as an identifying mark also. The types of agnosias Robinson has cited are significantly different than the 87 type displayed after cerebral commissurotomy. Symptoms in a l l these agnosias are normal for the type of brain damage that has been done in each case. The question i s whether some type of damage results i n two minds. It seems that some agnosias symptoms do not require a two mind interpretation while cerebral commissurotomy symptoms do. The observ-er's reports of what he knows and perceives are not always a reliable measure of what he knows. Sometimes the lack of a verbal report does not count as evidence for two minds. In the case of cerebral commissur-otomy, however, input and output seem to be restricted to the two d i f -ferent hemispheres. The tasks are simple and the s k i l l has not been lost. The lack of verbal reports from happenings on the non-dominant side of the body seem to be a case of the dominant hemisphere being cut off from the minor hemisphere rather than some of the special explana-tions that are needed to explain some of the other tactual-visual agnosias. Robinson therefore has failed in his attempt to treat cere-bral commissurotomy symptoms as just another type of symptom that one mind can be presumed to manifest. 88 CHAPTER VII AN UNRESOLVABLE PROBLEM Introduction T. Nagel i s not satisfied with any of the positions taken i n regard to the brain bisected patients. He feels the force of the argu-ments that would lead one to postulate one mind for these patients and yet he feels the force of the arguments that postulate two. He also does not see how any plausible middle ground could be reached. He therefore categorizes these patients "midway between ordinary persons with intact brains...and pairs of individuals...""'" His point i s not that these patients have a highly unusual number of minds, but that the question of how many minds they have i s unresolvable. Nagel, for reasons similar to our own, discounts theories lik e Eccles' that ascribe l i t t l e or no consciousness to the minor hemisphere. He does, however, take the two mind theory of Sperry seriously. He also believes that a theory ascribing one mind to these patients would have some i n i t i a l p l a u s i b i l i t y . Since both of these theories break down, he also seriously considers a third alternative that normally postulates one mind of the patient except when the patient i s under-going tests. During the tests, according to this theory, the patient has two minds. Although Nagel finds these theories plausible i n i t i a l l y , he i s not satisfied with any of them. But i f none are satisfactory, then what position are we to take? This puzzle, according to Nagel, i s unresolvable. 89 The Problem With the Positions Nagel believes that the position postulating two minds and the position postulating one mind must be discussed together. The " d i f f i -culty about each of them l i e s in the impossibility of deciding among 2 them." Nagel finds that each of these positions i s plausible. The positions are, however, inconsistant with each other. Therefore an argument that counts for one position counts against the other. Thus both positions have plausible arguments that count for and against them. Nagel, therefore, does not know how to decide which position to take. The arguments that give the two mind position plaus i b i l i t y were seen in our f i r s t chapter. Each hemisphere seems to give rise to i t s own set of beliefs, actions, and sense data. A l l the functional areas of each hemisphere are correlated to the other areas of that hemisphere in the normal ways. Yet the two hemispheres seem to be cut off from one another. When cuing is interfered with, the hemispheres are re-duced to guessing at what stimulus was received by the other side of the body. It seems very plausible that two minds are at work. The problem with the two mind theory, however, also counts as rea-son to believe that the patients only have one mind. Normally these patients act l i k e any other person. It was years before doctors could identify any symptoms related to the severed callosum. These patients are capable of a great number of tasks that require the cooperation of both hemispheres. They can swim, walk, button their shirt and the li k e . It i s , obvious therefore, that the two hemispheres can pool their 3 information "to yield integrated behavioral control." They act l i k e 9 0 one person in these tasks, not li k e two people who are trying to do a task together. Friends of these patients find i t very natural to treat these patients as single individuals. One possible objection to the position stated i n the last para-graph i s that the pooling of information is not done in the normal way. If this pooling of information i s explained by a model similar to the model of the pooling of information for the working of a two man saw, we would'*'not think that the two hemispheres were integrated into one mind. The fact, however, that the integration i s not carried out by the usual channels does not settle the question in favour of the two mind hypothesis. Nagel finds i t strange "to suggest that we are not i n a position to ascribe a l l those experiences to the same person, just be-4 cause of some peculiarities about how the integration i s achieved." There is no reason why we should leave the one mind theory, then, just because the hemispheres pool the information in an unusual way. The problem with the one mind theory arises in the experimental situation. If we postulate one mind for these patients, then we must also be able to describe the experimental situation with that one mind. That i s not easy to do. Nagel suggests one theory that might be thought to help with this problem. There is one mind i n this theory, but two preconscious control systems that are independent of each other. The mind would then temporally alternate between the hemispheres during the test situation. This explanation, according to Nagel, "would be i n t e l -l i g i b l e , though mysterious." Nagel sees, however, that the explanation is not tenable since the mind i s capable of two simultaneously incom-patible tasks, one in each hemisphere. There i s not a lack of inter-91 action on the preconscious level, but in the "domain of visual experi-ence and conscious intention..."^ Thus the one mind theory cannot be saved by postulating a dual control with the mind switching back and forth between them. There seem to be two incompatible conscious experi-ences going on at the same time. A mind switching between control systems w i l l not explain this phenomenon. The problem of deciding between the one mind and two mind theory gives some i n i t i a l attraction to the theory that postulates one mind during normal situations and two during test situations. The evidence that the patients have one mind comes when the patient i s i n his normal environment and the evidence that the patient has two minds comes when the patient i s being tested. The theory that calls for one mind i n the normal situation and two minds during testings seems to allow for the best of both the one mind and two mind theories. If i t was plausible, we could decide what we wanted to say about these patients. Nagel has several problems with this suggestion. " F i r s t , i t i s entirely ad hoc; i t proposes to explain one change in terms of another without suggesting any explanation of the second."^ Nagel does not see how the experiments could change the situation so as to produce two minds i n the patient. There is certainly no change in the anatomy of the patient. But i f the experiment does not change anything about the patient, how can i t create another mind or s p l i t the existing one? There does not seem to be any explanation of how the experiment does this, so the postulation that i t does produce two minds i s ad hoc. According to Nagel, the suggestion i s illegitimately pulled in to ex-plain some phenomena but there i s no explanation of how i t accomplishes that change of behavior. 92 Nagel is also bothered by the fact that he thinks that the experi-ment would cause a mind to be popping in and out of existence. This i s not furthering the accusation of being ad hoc, but i t accuses the position of being so unusual that i t cannot claim any p l a u s i b i l i t y . A mind popping in and out of existence i n these patients would be such an implausible result that any theory holding i t could not succeed. It seems puzzling why Nagel should think that this would be a con-sequence of the position being discussed. When he f i r s t described the position he suggested that perhaps "the single mind splits in two and reconvenes after the experiment i s over." If he took this suggestion seriously there should be no problem of a mind suddenly being created and then suddenly dropping from existence. There are two minds in the experimental stage because the mind has been s p l i t into two. There is only one mind after the experiment because the two minds fused to be-come one. There is no mysterious mind suddenly appearing out of no-where. Nagel i s wrong therefore, i n suggesting that this i s a problem for this position. Nagel has a more serious objection to the position that spli t s the mind only during the experiments. The problem is that during the experiment "the individual i s functioning largely as i f he were a single 9 individual..." The position under discussion would have us think that the patient has two minds during the experiment, yet that does not seem to be clear. The patient attempts to carry out the experiment as one person. He follows the instructions as one person and the instructions are directed to one person. If told to pick something up with his l e f t hand, he proceeds to do so just as he would in a normal situation. 93 Except i n rare cases the l e f t hand does not obey the command outside the conscious control of the l e f t hemisphere. The l e f t hemisphere i n other words is not surprised that the hand responds to the command. In this situation the "two halves of his brain cooperate completely except in regard to those very special inputs that reach them separately and d i f f e r e n t l y . " ^ Thus there is evidence for both one mind and two minds during the experimental situation. Nagel cannot decide which evidence i s conclusive so he i s l e f t with the same problem he had before he considered the position. According to Nagel, the position that postu-lates a mind spl i t t i n g during the experiment i s , therefore, of no help. Thus Nagel i s not able to decide how many minds these patients have. Mental Unity Nagel finds i t very puzzling that we should not be able to decide how many minds these patients have. He concludes that this shows that "significant mental activity does not require the existence of a single mental s u b j e c t . T h i s i s an extremely puzzling conclusion to have to come to. Usually when we think about someone else's mental states, we tend to construe these states on a model similar to our own mental states. According to Nagel, however, the "fundamental problem i n trying to understand" the split-brain "cases in mentalistic terms i s that we take ourselves as paradigms of psychological unity, and are then unable 12 to project ourselves into their mental lives, either once or twice." Thus, according to Nagel, our problem with counting the number of minds in these patients leads to a fundamental d i f f i c u l t y i n understanding them. We shall return to this later. 94 Nagel suggests that another problem is that we could subtly be 13 "ignoring the possibility that our own unity may be nothing absolute." What he seems to have in mind is that our mental unity only consists of an integration of the various functions of the mind. This, however, is seen to erode the notion of a numerically single subject. Nagel be-lieves that "either this subject contains the mental l i f e , in which case i t i s complex and i t s unity must be accounted for i n terms of the uni-fied operation of i t s components and functions, or else i t i s an exten-sionless point, i n which case i t explains nothing.""^ The mind in the latter disjunct would be united. Nagel does not say why he thinks the single extensionless point explains nothing, but i t does seem to be the case that such a conception of our unity i s of l i t t l e value. At best i t i s mysterious how the functional areas of the brain could be related to such a point. Thus such an account of what i s necessary for a mind to be considered one mind would force us to reconsider whether or not we were single people. The mind conceived of as an integration of functions is also seen to lose i t s singularity. The conglomeration speaks with one mouth and thinks of i t s e l f as one, but i t is complex and therefore, according to Nagel, not clearly one. Nagel is therefore tempted to think that i f we are to count minds, then the mind must somehow be one in a different sense than just.an integration of functional areas. He i s tempted by the extentionless point conception of unity yet he sees that this w i l l not explain our minds. He is therefore suspicious of the unity and countability of our minds. 95 Counting Complex Entities Nagel believes that there is something unusual about counting minds i f the minds are thought to be complex integrations of different functions. Somehow this raises questions about whether there i s one or two or some uncountable number of minds. To be countable in a straight-forward way Nagel would require minds to be simple extentionless points. Because we are not such points, Nagel questions our own mental unity and the sense i n which we could be said to have one mind even i f a l l the brain connections were normal* Nagel w i l l have to explain himself further i f his puzzlement i s to have any force. We have no problem counting other complex entities. Human bodies are complex entities with various functions that become integrated through the muscles, bones and sinews. Yet we have no prob-lem thinking that one body i s before us instead of some uncountable number of bodies. The set of functions working together i s as easily counted as the individual functions. If the mind is a set of different functional areas working i n close cooperation as one entity, why should we question the unity of the mind? Nagel i s impressed that the mind's functional system speaks i n the f i r s t person through the one mouth. It would seem that the integration of the functions then has become one. The fact that there are many functions combined in the task should not cause us to question that only one mind is at work,here. Minds are complex entities, but that should not hinder one from being able to count them. Problems with Counting Jonathan Bennett disagrees with Nagel that taking ourselves as the paradigm of psychological unity somehow distorts our understanding of 96 the split-brain patient just because we cannot project ourselves into the patient either once or twice. Bennett claims that taking ourselves as the paradigm does not distort our view of the patient. These "charges are no more appropriate here than they would be i f I were confronted by a self-sufficient organic configuration (not involving mentality) which I could not acceptably classify either as a single organism or as a colony."'''"' What Bennett has i n mind is that sometimes our notion of what i t is that counts for one thing is not so a l l encom-passing that i t can accommodate a l l possible situations. Therefore, there can come times when we are faced with genuine counting problems. This is not because we have somehow distorted our view of the entity we are trying to count. Instead i t arises because we understand what the entity i s l i k e and find that our notion of what one of that kind of thing i s , does not cover this situation. Thus i t is a counting problem and not an understanding problem. Nagel seems to be asserting that the problem arises because we cannot imagine being one of the split-brain patients. We cannot project ourselves into their mental lives either once or twice. But these patients have a conception, identical with our own, of a single unified mind. Any problem we would have, they would have too. The patient cannot imagine being both hemispheres at once, but Nagel does not require that. What he finds puzzling for us to imagine i s two hemispheres that are partly integrated. The patient, however, does not experience the partial integration. He experiences mental phenomena that lead us to think that his hemispheres are only partially integrated. For i n -stance, with his l e f t hemisphere he experiences what usually comes to 9 7 the l e f t hemisphere plus some of what usually takes the cooperation of the right hemisphere. Yet he finds that he i s cut off from certain right hemisphere stimuli. The right hemisphere, on the other hand, experiences the stimuli that the l e f t misses along with a l l that the l e f t experiences of the right hemisphere. It also experiences some of the l e f t hemisphere that i s integrated with, but is cut off from cer-tain l e f t hemisphere stimuli. Neither hemisphere taken by i t s e l f causes any conceptual problems. The problems arise when both hemispheres must be taken at once. Then i t seems that the mind i s integrated and yet i t i s not integrated. There seem to be two minds and yet there only seems to be one. This however, i s a problem of counting and not neces-sarily of imagining what i s going on. An i l l u s t r a t i o n w i l l help to explain the situation better. If one had two computers with different capacities, they could be joined to form one machine which would possess the combined capacities of the two mach-ines. Imagine that the computers were slowly integrated so that half way through the integration some of their capacities were joined and others were not. During this time in the integration of the two machines, i t would not be clear i f there was one machine or two. This would not be because we could not describe the situation, but because our notion of what one computer was would not cover the situation where some capa-cit i e s were integrated and others were not. The situation seems to be similar with the minds of the split-brain patients. Severing the corpus callosum has involved the mind in some sort of a s p l i t . Before the s p l i t the two hemispheres formed one mind^ Now some of the capacities of the hemispheres are s p l i t from each other 98 while at the same time some seem to be integrated. The situation can be described, but i t i s hard to do any counting. Our notion of what one mind i s does not cover such situations. The number of minds in these patients i s therefore uncountable, but that i s not because the situation cannot be described due to some distortion caused by taking ourselves as the paradigm of mental unity. Reworking the Position that Asserts Two Minds only During the Tests Up to now we have assumed that Nagel i s right that there is a prob-lem with counting how many minds these patients have. It seems possible, however, to rework one of the positions that Nagel rejected so that i t w i l l meet the objections that he had against i t . The position that can be reworked and defended is the one that asserts that the split-brain patients have one mind normally but two minds during the test situation. One of Nagel's own suggestions is helpful in meeting the objections that he brings up against this position. This suggestion comes in the discussion of the amazing behavioral integration of these patients. Nagel suggests that there i s no doubt that the information from both hemispheres i s somehow being pooled to accomplish this integration. He suggests that "although this i s not accomplished by the usual methods, i t i s not clear that this settles the question against assigning the 16 integrative functions to a single mind." The unusual connection that Nagel must have i n mind i s the amazing cuing a b i l i t y of the hemispheres that was described i n chapter one. If this 'connection' between the hemispheres is what is integrating the hemispheres this w i l l go a long way to meeting Nagel's objections to the position. 99 Nagel i s right in asserting that an unusual connection being i n -volved does not settle the question against mental unity. One can think of a number of unusual connections that would suffice for mental integration. For instance, i f an a r t i f i c i a l corpus callosum could be created and connected in such a way that i t would function just as a normal corpus callosum and yet stop the spread of epilepsy between the hemisphere, mental integration would not be threatened. It would matter l i t t l e whether the a r t i f i c i a l callosum worked through e l e c t r i c a l means, radio signals or mechanical stimuli as long as the resulting mind was functionally equivalent to the normal connected mind. The functional capacity would not even have to be equivalent to the normal mind, but should approximate a minimally united mind. How the integration i s accomplished i s not important. What i s important i s the degree of integration that the connection allows. There i s , however, a prima facie objection to thinking that cuing is integrating the hemispheres. Cuing normally takes place between two minds and i s not thought to integrate those minds. For instance, two men can operate a two man saw with a great deal of s k i l l . Such performance requires a l o t of practice and i s successful only because a host of unconscious cues are passed between the men. The men come to know what the other w i l l do without the other consciously communicating the information. Yet no one is tempted to think that the two men's minds are even starting to integrate. 17 Another example of such cuing i s found i n Tolstoy's War and Peace. Natasha and Pierre are conversing. Their conversation does not follow logical lines. If i t did i t would be a sure sign that something was 100 amiss i n their communication. They know each other so well that they do not have to say what they f e e l . A word or gesture w i l l express the whole thought. This sort of cuing can be seen i n more mundane marriages. One's partner's mood can be told without any verbal communication. The thought i s not consciously communicated by the sender nor need i t be consciously received by the recipient. Instead i t i s communicated un-consciously. Yet i t i s only i n a highly figurative sense that the two could be said to be of one mind on that issue. Part of the problem with the above objection to cuing i s that cuing between a husband and wife and two men on a saw i s not extensive enough to count as integrating what would otherwise be thought of as two minds into one. The situation could be different i f the husband's and wife's cuing was extensive enough to work for most or a l l of their thoughts. It i s d i f f i c u l t to know just what we would want to say about their minds in that case. The two hemispheres, on the other hand, are capable of performing at a very high level with l i t t l e or no learning involved. Two minds would have a great deal of d i f f i c u l t y in matching their per-formance through normal cuing. Imagine how long i t would take two people to learn to type rapidly i f each controlled one hand. A similar problem would arise for buttoming a shirt, walking or a host of other s k i l l s the split-brain patient continues to do with ease. Therefore the type of cuing that did not count as integration was not nearly as inclu-sive as that displayed by these patients. There i s a bigger difference between hemispheric cuing and husband and wife cuing. When the husband cues his wife, his wife received the message second hand. That i s , the message is no different than i f her 101 husband had told her. When the husband experiences pain he can t e l l his wife that he is in pain or she just perceive i t through the cues that he gives her. At no time, however, w i l l she experience her hus-band's pain. It would seem that the case i s different between the hemispheres. For one thing they do not seem to be aware of each other's existence. When the l e f t hemisphere comes to know what i s being held in the l e f t hand i t believes that i t gained that information f i r s t hand. When the patient moves his l e f t hand the>left hemisphere does not be-lieve someone else is moving the hand except i n very rare cases. Simi-l a r l y i f the l e f t hemisphere reports a flash i n the l e f t visual f i e l d , i t believes that i t actually experienced that flash. The cuing i n the hemispheres, therefore, has a more integrating effect than i n the hus-band and wife example. The cuing between husband and wife i s more along the lines of communication. The one has information about the other. Cuing in the hemispheres results in f i r s t hand information and 18 has an integrating effect. The split-brain patient is therefore able to pool the information of his two hemispheres to perform a wide range of act i v i t i e s that re-quire joint action from both hemispheres. Each hemisphere i s capable of insuring that the other hemisphere gains the relevant information. This capacity for transferring information increases with time in the patients with the least amount of brain damage. At the same time the patient i s never aware that two conscious spheres are at work. The information i s transferred but is received as f i r s t hand knowledge. The information of the hemispheres i s pooled, but the pooling results 102 in one integrated mind and not two conscious spheres sharing their information. The cuing takes the place of the sectioned corpus callo-sum. The hemispheres in the normal situation are therefore intact. They can perform a wide range of a c t i v i t i e s , but with none of the d i f -f i c u l t i e s one would expect i f the activity were performed by two minds cuing one another. The split-brain patient therefore only has one mind during his normal everyday l i f e . But, then, what happens in the tests? During these tests the patient suddenly no longer displays the integration that he usually displays. How can a mere test destroy the integration of the hemi-spheres i f the non-integration is not there already? Usually the test-ing situation is thought to show that although the patient appears to be integrated, in fact he i s not. This, however, is no longer clear. Taking seriously Nagel's suggestion that unusual connections are func-tioning, changes the whole picture. The tests are designed to overcome the hemisphere's a b i l i t y to cue each other in to the relevant informa-tion. Thus, what the test does i s to disconnect the unusual connection that allowed the hemispheres to integrate. The test causes the d i s i n -tegration between the hemispheres and the end of the test results i n a reintegration of the hemispheres into one mind. Thus the tests can no longer be thought to just show a lack of integration between the hemi-spheres. It would appear that the tests themselves cause the lack of integration. This interpretation of the testing situation should help us to meet one of Nagel's criticisms of the position that asserts that the tests cause two minds in the patient. His f i r s t cirticism was that the 103 position was ad hoc. He suggested that " i t proposes to explain one change in terms of another without suggesting any explanation of the 19 second." The experiment did not change anything internally within the patient so how could i t s p l i t the mind? The answer, of course, i s that the experiment has changed something. It i s not an internal change, but the change is relevant i n causing the symptoms. If the corpus c a l -losum of a normal brain was s p l i t and then rewired, there would be an anatomical change that would cause a temporary lack of integration be-tween tested hemispheres. Now, instead of an anatomical change, the experiment does something equivalent to the split-brain patient. The experiment causes the usual links of this patient to be ineffective. The patient's hemispheres are therefore s p l i t during the testing time. This i s not ad hoc. Instead i t rests on a theory of how the patient is integrating and explains that the experiments devise ingenious ways to stop the integration. If successful, the experiment i s expected to stop the integration between the hemispheres of the patient. This position is therefore not ad hoc. The position postulates exactly what we would expect of hemispheres integrating through cuing. Nagel's other problem with only ascribing two minds to the patient during the test i s that the patient did not give clear evidence of a definite s p l i t . Part of the patient's actions were integrated while part were not. Certain behavior required an interpretation of two minds while other behavior required that the patient only had one mind. Unfortunately for the position, both types of behavior were manifested at the same time. The patient could not be said to have one mind before the experiment and two during. Therefore, the position was thought to have failed. 104 Nagel i s right, but the position only needs a small amendment to avoid this criticism. During the test i t was unclear how many minds the patient had. Instead of insisting that the experimental situation i l l i c i t s two minds from the subject, a l l the position need assert i s that the experimental situation causes a par t i a l s p l i t t i n g of the mind. The mind of the patient would then be i n the same situation as the mind that was partially integrated and partially separated. One does not know how to count the number of minds involved. In fact there does not seem to be a correct answer. We can describe the situation but our notion of what one mind i s , is not broad enough to allow us to count the number of minds present. The position that we are defending, therefore, is that normally the patient has one mind. It i s integrated by cuing and the cuing i s of a kind that would not leave us suspicious that two minds are at work. During the experiments, however, the techniques of the experiments cut these communicating links of the two hemispheres, thereby i l l i c i t i n g the non-integrated behavioral phenomena. The experiments, however, are not successful in stopping a l l the communicating links. The patient i s therefore able to display a good deal of integrated behavior. Since he displays both integrated and non-integrated behavior at the same time, i t i s impossible to decide how many minds the patient has during the testing situation. This, however, i s a problem of counting and not of describing the situation. The patient appears to be partially integrated and partially not integrated. At the end of the test the normal commu-nicating links between the hemispheres start operating as they did be-fore the test. The patient's mind, therefore, is reintegrated at this time. After the test, therefore, he only has one mind. 105 CONCLUSION We have found that the usual positions that postulate one or two minds of cerebral commissurotomy patients are inadequate. Positions that speculate that these patients are a guide to what i s actually the case in normal humans are even more implausible. Nagel was helpful in discussing the plausibility of a one mind versus a two mind theory and vice versa. Since these incompatible positions were both plausible, he showed that there were probably no easy answers as to the number of minds that these patients could be said to have. After rejecting the standard positions we developed a theory of our own. The theory that we defend lacks i n i t i a l p l a u s i b i l i t y . Nagel was very good at pointing this out. This i n i t i a l implausibility, however, was not sustained when we discussed how the hemispheres were integrating after cerebral commissurotomy. It was then shown that our theory ex-plained the different behavioral manifestations that these patients exhibited very well. The patients had given behavioral evidence for one mind in normal situations and for a mind system that was not clearly one or two minds during the tests. Our theory asserts that this be-havioral evidence i s not misleading i n either situation and, therefore, allows us to take the behavioral evidence in a l l situations seriously. We do not have to explain away any behavioral manifestations of these patients. Furthermore, the theory explains why the testing situation makes a difference i n the number of minds that the patient can be said to have. We, therefore, conclude that the cerebral commissurotomy patients have one mind i n normal situations, while the testing situation causes a partial non-integration of the two hemispheres which makes i t impossible to determine how many minds the patient has at that moment. 106 FOOTNOTES CHAPTER I J. E. Bogen and P. J. Vogel, "Cerebral Commissurotomy in Man: Preliminary Case Report," Bulletin of the Los Angeles Neurological Society, 27 (1962), 169-172. R. W. Sperry, "Split-brain Approach to Learning Problems," The Neurosciences: A Study Program, ed. Gardner C. Quarton, Theodore Melnechuk, Francis 0. Schmitt (New York: Rockefeller University Press, 1967), p. 715. 3 M. S. Gazzaniga, J. E. Bogen and R. W. Sperry, "Laterality Effects i n Somesthesis Following Cerebral Commissurotomy in Man," Neuropsychologia, 1 (1963), 209-215. 4 Gazzaniga, Bogen and Sperry, p. 210. 5 J. Levy, R. D. Nebes and R. W. Sperry, "Expressive Language i n the Surgically Separated Minor Hemisphere," Cortex, 7 (1971), 53. 6 M. S. Gazzaniga, "The Split Brain in Man," Scientific American, 183 (1967), rpt. i n Perception: Mechanisms and Models, (San Francisco: W. H. Freeman and Company, 1972), P. 29. 7 Gazzaniga, "The Split Brain i n Man," p. 29. 8 M. S. Gazzaniga, The Bisected Brain (New York: Appleton-Century-Crofts, 1970), pp. 90-92. q H. W. Gordon and R. W. Sperry, "Lateralization of Olfactory Perception i n the Surgically Separated Hemispheres i n Man," Neuropsycho- logia, 7 (1969), 111-120. 107 Gordon and Sperry, p. 116. ^ Gordon and Sperry, p. 116. 12 Gazzaniga, The Bisected Brain, p. 89. 13 Gazzaniga, The Bisected Brain, p. 89. 14 J. Levy, C. Trevarthen and R. W. Sperry, "Perception of Bilateral Chimeric Figures Following Hemispheric Deconnection," Brain, 95 (1972), 61-78. ^ Brenda Milner and Laughlin Tayler, "Right-hemisphere Superiority in Tactile Pattern-recognition After Cerebral Commissurotomy: Evidence for Nonverbal Memory," Neuropsychologia, 10 (1972), 1-15. 1 6 Gazzaniga, "The Split Brain in Man," p./33. Levy, Nebes and Sperry, p. 49-58. 18 Levy, Nebes and Sperry, p. 52. 19 Levy, Nebes and Sperry, pp. 53-54. 20 M. S. Gazzaniga and S. A. Hillyard, "Language and Speech Capacity of the Right Hemisphere," Neuropsychologia, 9 (1971), 273-280. 21 Gazzaniga and Hillyard, p. 274. 22 Gazzaniga, Bisected Brain, p. 106. 23 Gazzaniga, Bisected Brain, p. 92. 24 Gazzaniga, Bogen and Sperry, p. 211. 25 Gazzaniga and Hillyard, pp. 273-280. 26 Gazzaniga and Hillyard, p. 276. CHAPTER II 1 Roland Puccetti, "Brain Bisection and Personal Identity," B r i t i s h Journal for the Philosophy of Science, 24 (1973), 352. 108 2 Roland Puccetti, "A Reply to Professor Margolls," Philosophy of Science, 42 (1975), 281-285. 3 Puccetti, "A Reply," p. 282. J. E. Bogen, "The Other Side of the Brain II: An Appositional Mind," Bulletin of the Los Angeles Neurological Society, 34 (1969), 135-162. 5 Bogen, "The Other Side of the Brain II," p. 151. ^ Donald E. Broadbent, "Division of Function and Integration of Behavior," The Neurosciences: Third Study Program, ed. Francis 0. Schmitt and Frederick G. Worden (Cambridge, Mass.: The MIT Press, 1974), pp. 31-41. 7 Broadbent, p. 37. 8 Roland Puccetti, "Multiple Identity," The Personalist, 54 (1973), 203. 9 Montgomery Furth, "Essence and Individual: Reconstruction of an Aristotelean Metaphysics," mimeographed (1975), section 9. ^ Aristotle, Parts of Animals, 647 b 21. ^ Furth, p. 4 12 K.JJ. Zulch, 0. Creutzfeldt and G.C. Galbraith, ed. , Cerebral Localization (New York: Springer-Verlag, 1975), p. 140. CHAPTER III ^ Broadbent, p. 33. 2 Broadbent, p. 33. 3 Broadbent, P. 35. ^ Brenda Milner, "Hemispheric Specialization: Scope and Limits," 109 The Neurosciences: Third Study Program, ed. Francis 0. Schmitt and Frederick G. Worden (Cambridge, Mass.: The MIT Press, 1974), p. 78. 5 K. J. Zulch, 0. Creutzfeldt and G. C. Galbraith, ed., Cerebral Localization (New York: Springer-Verlag, 1975), p. 310. ^ A. M. Liberman, "The Specialization of the Language Hemisphere," The Neurosciences: Third Study Program, ed. Francis 0. Schmitt and Frederick G. Worden (Cambridge, Mass.: The MIT Press, 1974), p. 54. 7 Milner, p. 78. R. W. Sperry, "Lateral Specialization in the Surgically Separated Hemispheres," The Neurosciences: Third Study Program, ed. Francis 0. Schmitt and Frederick G. Worden (Cambridge, Mass.: The MIT Press, 1974), p. 18. 9 Sperry, "Lateral Specialization," p. 10. CHAPTER IV John Eccles, The Brain and the Unity of Conscious Experience (Cambridge: Cambridge University Press, 1965), p. 34. 2 Eccles, Brain and Unity of Consciousness, p. 20. 3 Eccles, Brain and Unity of Consciousness, p. 21. 4 Eccles, Brain and Unity of Consciousness, pp. 34-34. John Eccles, ed., Brain and Conscious Experience (New York: Springer-Verlag, 1966), p. 312. ^ Eccles, ed., Brain and Conscious Experience, p. 312. 7 Eccles, Brain and Unity of Consciousness, p. 25. Eccles, Brain and Unity of Consciousness, p. 34. 9 Eccles, Brain and Unity of Consciousness, p,,34. ^ Eccles, Brain and Unity of Consciousness, pp. 33-34. 110 • L 1 Jonathan B e n n e t t , " C l a s s N o t e s , " mimeographed (1974-1975) , p. 77. 12 E c c l e s at t imes t a l k s as i f he i s a g n o s t i c about menta l s t a t e s i n n o n - l i n g u i s t i c a n i m a l s . At other t imes he wishes to a s s e r t that such b e i n g s , minor hemispheres i n c l u d e d , j u s t do not have any menta l s t a t e s . 13 S p e r r y , " L a t e r a l S p e c i a l i z a t i o n , " p. 1 1 . CHAPTER V ^ L a r r y D e w i t t , "Consc iousness , M i n d , and the S e l f : The I m p l i c a -t i o n s of the S p l i t - B r a i n S t u d i e s , " B r i t i s h J o u r n a l f o r the Ph i losophy of S c i e n c e , 26 (1975) , 4 5 . 2 P e t e r S i n g e r , " A l l An imals a re E q u a l , " P h i l o s o p h i c Exchange, 1 , No. 5 (1974) , r p t . i n An imal R i g h t s and Human O b l i g a t i o n s , ed . Tom Regan a n d , P e t e r S inger (Englewood C l i f f s , N. J . : P r e n t i c e - H a l l , 1976) , pp. 148 -162 . 3 D e w i t t , p. 43 . 4 G. G. G a l l u p , " I t ' s Done With M i r r o r s : Chimps and S e l f - C o n c e p t , Psychology Today, 4 , No. 10 (1971) , 5 8 - 6 1 . ^ D e w i t t , p. 44. Rowland P u c c e t t i , "The Mute S e l f : A R e a c t i o n to D e w i t t ' s A l t e r -n a t i v e Account of the S p l i t - b r a i n D a t a , " B r i t i s h J o u r n a l f o r the P h i l o s o p h y of S c i e n c e , 27 (1976) , 67. 7 Howard Garner , The Shat te red M i n d : The Person A f t e r B r a i n Damage (New Y o r k : A l f r e d A. Knopf , 1975) , p. 402. S p e r r y , " L a t e r a l S p e c i a l i z a t i o n , " p. 11 . 9 J . E. Bogen, "The Dark S ide of the B r a i n , " l e c t u r e g i v e n at Da lhous ie U n i v e r s i t y (May 2 8 , 1974) , quoted by R. P u c c e t t i , "The Mute S e l f , " p. 70. I l l 1 0 A. Smith, "Speech and Other Functions after Left (Dominant) Hemispherectomy," Journal of Neurology, Neurosurgery, Psychiatry, 29 (1966), 469. CHAPTER VI 1 Daniel N. Robinson, "What Sort of Persons are Hemispheres? Another Look at 'Split-brain' Man," British Journal for the Philosophy of Science, 27 (1976), 74. 2 Robinson, p. 74. 3 Robinson, p. 75. 4 Herbert Fingaretti, Self Deception (New York: Humanities Press, 1969). Robinson, p. 76. ^ Robinson, p. 75. 7 Austin H. Riesen, "Arrested Vision," Scientific American, 183 (1950), rpt. i n Perception: Mechanisms and Models, (San Francisco: W. H. Freeman and Company, 1972), p. 359. 8 Riesen, p. 360. CHAPTER VII * Thomas Nagel, "Brain Bisection and the Unity of Consciousness," Synthese, 22 (1971), rpt. i n Personal Identity, ed. John Perry (Los Angeles: University of California Press, 1975), p. 241. 2 Nagel, p. 237. 3 Nagel, p. 238. 4 Nagel, p. 238. 5 Nagel, p. 239. 112 6 Nagel, p. 239. 7 Nagel, p. 240. g Nagel, p. 234. 9 Nagel, p. 240. 1 0 Nagel, p. 240 1 1 Nagel, pp. 241-242. 1 2 Nagel, p. 242. 1 3 Nagel, p. 242. 1 4 Nagel, pp. 242-243. 15 Jonathan Bennet, Kant's Dialectic (Cambridge, Great Britain: Cambridge University Press, 1974), p. 89. 1 6 Nagel, p. 238. "^7 Leo Tolstoy, War and Peace, trans. Alexandra Kropotkin (Garden City, New York: The Literary Guild of America, Inc., 1949). 18 If this account of what cuing is doing between the hemispheres i s accurate, the question can be raised of whether or not 'cuing' is the appropriate word for what i s going on. The integration that i s happening is too extensive and too unlike usual cuing, i n that i t seems to come to the recipient as f i r s t hand knowledge, that the word 'cuing' does not seem to cover i t . Since, however, 'cuing' has come to be used i n this f i e l d of research we w i l l continue, using the term with the understanding that i t has more force than the word normally has in English. Thus i t becomes a technical word. 1 9 Nagel, p. 240 113 BIBLIOGRAPHY Aristotle. Parts of Animals. Bennett, Jonathan. Kant's Dialectic. Cambridge, Great Britain: Cambridge University Press, 1974. Bennett, Jonathan. "Class Notes." Mimeographed, 1974-1975. Bogen, J. E. and Vogel, P. J. "Cerebral Commissurotomy in Man: Preliminary Case Report." Bulletin of the Los Angeles Neurological Society, 27 (1962), 169-172. Bogen, J. E. "The Other Side of the Brain II: An Appositional Mind." Bulletin of the Los Angeles Neurological Society, 34 (1969), 135-162. Bogen, J. E. "The Dark Side of the Brain." Unpublished lecture given at Dalhousie University (May 28, 1974). Quoted in part by R. Puccetti. "The Mute Self: A Reaction to Dewitt's Alternative Account of the Split-brain Data." 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Newv.York: S p r i n g e r - V e r l a g , 1966. F i n g a r e t t i , H e r b e r t . S e l f Decept ion . New Y o r k : Humanit ies P r e s s , 1969. F u r t h , Montgomery. Essence and I n d i v i d u a l : R e c o n s t r u c t i o n of an A r i s t o t e l e a n M e t a p h y s i c s . Mimeographed, 1975. G a l l u p , G. G. " I t ' s Done With M i r r o r s : Chimps and S e l f - C o n c e p t . " Psychology Today, 4 , No. 10 (1971) , 5 8 - 6 1 . Gardner , Howard. The Shat te red M i n d : The Person A f t e r B r a i n Damage. New Y o r k : A l f r e d A. Knopf , 1975. Gazzan iga , M. S . The B i s e c t e d B r a i n . New Y o r k : A p p l e t o n - C e n t u r y -C r o f t s , 1970. Gazzan iga , M. S . 'ilThe S p l i t B r a i n i n M a n . " S c i e n t i f i c Amer ican , 183 ( 1 9 6 7 ) ; £ r p t . i n P e r c e p t i o n : Mechanisms and Models . San F r a n c i s c o : W. H. Freeman and Company,1972, pp . 2 9 - 3 4 . Gazzan iga , M. S . , Bogen, J . 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Quarton, Theodore Melneckuk and Francis 0. Schmitt. New York: Rockefeller University Press, 1967, pp. 714-722. Sperry, R. W. "Lateral Specialization i n the Surgically Separated Hemispheres." The Neurosciences: Third Study Program, eds., Francis 0. Schmitt and Frederick G. Worden. Cambridge, Mass.: The MIT Press, 1974, pp. 5-19. Sperry, R. W. "The Great Cerebral Commissure." Scientific American, 210 (1964), 42-53. 117 Teuber, Hans-Lukas. "Why Two Brains?" The Neurosciences: Third Study Program, eds., Francis 0. Schmitt and Frederick G. Worden. Cambridge, Mass.: The MIT Press, 1974, pp. 71-74. Tolstoy, Leo. War and Peace. Trans. Alexandra Kropotkin. Garden City, N.Y.: The Literary Guild of America, Inc., 1949. K. J. Zulch, 0. Creutzfeldt and G. C. Galbraith, eds., Cerebral Localization. New York: Springer-Verlag, 1975.
UBC Theses and Dissertations
Philosophical issues arising from cerebral commissurotomy Barkman, Dale Ross 1978
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