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Psychopathy and semantic processing Jutai, Jeffrey William 1980

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PSYCHOPATHY AND SEMANTIC PROCESSING by JEFFREY WILLIAM JUTAI B.Sc, The Univ e r s i t y of Toronto, 1978 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES (Department of Psychology) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA November 1980 0 J e f f r e y William J u t a i , 1980 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of Brit ish Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Psychology The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 D a t e November 17, 1980 - i i -ABSTRACT The performance of psychopathic (n=16) and nonpsychopathic (n=ll) right-handed male criminals was compared on tasks r e q u i r i n g the verbal semantic processing of f o u r - l e t t e r concrete nouns presented t a c h i s t o s c o p i c a l l y to e i t h e r the l e f t or the r i g h t v i s u a l h a l f - f i e l d . Subjects processed s t i m u l i at a s u p e r f i c i a l l e v e l (Simple Recognition), and at deeper l e v e l s (Lower-order and Higher-order Categorization conditions). "Yes/No" responses were made manually by t r i g g e r i n g microswitches. Responding hand ( l e f t or r i g h t ) was counterbalanced across conditions. Dependent measures were reaction time (RT) and error rate (ER), and were analysed separately as a function of group, processing l e v e l , responding hand, and v i s u a l h a l f - f i e l d of presentation. The groups did not d i f f e r with respect to the pattern of RT r e s u l t s . S t a t i s t i c a l l y s i g n i f i c a n t group differences did emerge i n the ER r e s u l t s however, with psychopaths making fewer errors than nonpsychopaths i n the categorization conditions. These findings are discussed i n the context of current neuropsychological models of verbal semantic function and psychopathy. - i i i -TABLE OF CONTENTS Abstract i i L i s t of Tables v L i s t of Figures v i i Acknowledgements v i i i I. Introduction 1 I I . The neuropsychology of psychopathy: Current status 4 I I I . Behaviour and memory: Frontal and temporo-limbic contributions A. Frontal cortex 9 B. Temporo-limbic tissues ....... 10 IV. Semantic dementia: A neuropsychological theory ' .... A. Brown's model of neural organization 14 B. Semantic aphasia and semantic dementia 17 V. A tachistoscopic i n v e s t i g a t i o n of semantic dementia A. A note on hemispheric s p e c i a l i z a t i o n 25 B. The l o g i c of a tachistoscopic approach 28 VI. Method A. Subjects • 36 B. Materials 37 C. Apparatus 38 D. Procedure 39 - i v -VII. Results and Discussion 41 A. Reaction time (RT) 42 • . 1. Levels of processing 44 2. Psychopathy 62 B. Error rate (ER) 62 1. Levels of processing 63 2. Psychopathy .... 74 C. Reaction time and error rate: Joint considerations 75 Reference notes 79 References 79 Appendix I Tachistoscopic performance score sheets .............. 89 -v-LIST OF TABLES Table 1. Cleckley's speech disorder and personality disorder continua 20. Table 2. Mean re a c t i o n times and standard deviations 43. Table 3. Analysis of variance f o r reaction times 45. Table 4. Correlations between reaction time and error rate 47. Table 5. Test of simple main e f f e c t s f o r reaction times f o r v i s u a l h a l f - f i e l d f actor at the Simple Recognition l e v e l 48. Table 6. Test of simple main e f f e c t s f o r reaction times f o r v i s u a l h a l f - f i e l d f a c t o r at the Higher-order Categorization l e v e l .... 49. Table 7. Test of simple main e f f e c t s f o r reaction times f o r v i s u a l h a l f - f i e l d factor at the Lower-order Categorization -l e v e l 50. Table 8. Mean error rates and standard deviations 64. Table 9. Analysis of variance f o r error rates 65. Table 10. Test of the Group x Hand i n t e r a c t i o n f o r error rates at the Simple Recognition l e v e l 68. Table 11. Test of the Group x Hand i n t e r a c t i o n f o r error rates at the Higher-order Categorization l e v e l 69. Table 12. Test of the Group x Hand i n t e r a c t i o n f o r error rates at the Lower-order Categorization l e v e l 70. Table 13. Test of simple main e f f e c t s f o r error rates for the v i s u a l h a l f - f i e l d f a c t o r i n the r i g h t hand 71. - v i -Table 14. Test of simple main e f f e c t s f o r error rates f o r the v i s u a l h a l f - f i e l d f a c t o r i n the l e f t hand 72. - v i i -LIST OF FIGURES Figure 1. Brown's l e v e l s of b r a i n organization and language disorders .... 22. Figure 2. Levels of cognition i n personality and aphasia 24. Figure 3. A p a r t i a l map of long-term semantic memory as described i n the C o l l i n s and Q u i l l i a n model .31. Figure 4. Mean reaction times (across groups) as a function of processing l e v e l and v i s u a l h a l f - f i e l d of presentation . 51. Figure 5a. The operation of the semantic hierarchy within the l e f t hemisphere 58. Figure 5b. Hemispheric processing operations under conditions of v i s u a l h a l f - f i e l d of presentation and categorization l e v e l . 60. Figure 6. Error rates as a function of group, responding hand, and processing l e v e l 66. Figure 7. Error rates (across groups) as a function of v i s u a l h a l f - f i e l d of presentation and responding hand ......... 67. Figure 8. The most e f f i c i e n t hemispheric processing and response i n i t i a t i o n operations for the non-psychopathic and psychopathic groups i n the Lower-order and Higher-order semantic categorization conditions 76. - v i i i -ACKNOWLEDGEMENTS I would l i k e to thank my committee members, Dr. A. R. Hakstian and Dr. J . C. Y u i l l e f o r t h e i r advice and for constructive c r i t i c i s m s of e a r l i e r d r a f t s of t h i s t h e s i s . I g r a t e f u l l y acknowledge the e f f o r t s of Janice F r a z e l l e and Brent McNeil, who ass i s t e d i n the se l e c t i o n and te s t i n g of subjects. Special thanks are extended to my supervisor, Dr. R. D. Hare, for h i s i n s i g h t s , encouragement, and patience. -1-I. Introduction Psychopathy is undoubtedly one of the most complex and puzzling psychological "disorders". The generally accepted clinical profile of the psychopath, as outlined by Cleckley (1976), consists of the following: superficial charm and good intelligence; absence of delusions and other signs of irrational thinking; absence of "nervousness" or psychoneurotic manifestations; unreliability; untruthfulness and insincerity; lack of remorse or shame; inadequately motivated anti-social behaviour; poor judgment and failure to learn by experience; pathologic egocentricity and incapacity for love; general poverty in major affective reactions; specific loss of insight; unresponsiveness in general interpersonal relations; fantastic and uninviting behaviour with drink and sometimes without; suicide threats rarely carried out; sex l i f e impersonal, tri v i a l , and poorly integrated; failure to follow any l i f e plan. The mixture of both positive (e.g., the first three) and negative characteristics indicates that psychopathy does not represent a simple mental disturbance (Hare, 1970). The neuropsychology of psychopathy is poorly understood at present. In general, research has not yielded consistent support for hypotheses of clinically significant cortical dysfunction in psychopaths. Hypo-theses of this type typically follow observations that lesions of certain neuroanatomical structures result in the appearance of symptoms which seem quite similar to some of those typically ascribed to the psychopath (Elliott, 1978; Schalling, 1978a). The basic problem with this "cortical dysfunction" approach is that the core psychopathic symptoms (Cleckley, 1976) demonstrate -2-quantitative and qualitative differences from those typically reported for cortical damage (Elliott, 1978). Neural "impairment" in psychopathy, if i t exists, is probably more subtle than that which standard neuropsycho-logical tests are designed to reveal. The "cortical dysfunction" logic does not provide an adequate theoretical framework for research in this area. Its symptom-oriented, inductive nature belies a disjoint and superficial appreciation of the basic psychopathic syndrome. In devoting attention to the neural bases of individual symptoms, and in assuming cortical disruption at this level, the collective neuropsychological significance of the psychopathic symptom constellation has been largely ignored. This constellation, described by Cleckley (1976), is the basis of recent work on the formulation of diagnostic criteria for psychopathy. From a l i s t of the personality traits, behaviours, indicants and counterindicants which form the basis of a reliable global clinical assessment of psychopathy, Hare (1980) assembled a 22-item psychopathy checklist. A principal components analysis of the checklist produced five factors which can be summarized as follows: 1) impulsive, unstable life-style; 2) self-centeredness, callousness, and lack of empathy; 3) superficial interpersonal relationships; 4) chronic anitsocial behaviour; 5) inadequately motivated criminal acts. A similar analysis was performed on the scores of prison inmates on Cleckley's (1976) sixteen criteria for psychopathy, and five factors were extracted. A canonical correlation between factors derived from the checklist items and the Cleckley criteria revealed an excellent f i t between the two sets of factors. Hare's efforts emphasize the multi-dimensional nature of psychopathy, and demonstrate that the essential -3-ingredients of the c l i n i c i a n ' s conception of the symptom c o n s t e l l a t i o n can be captured n i c e l y i n an objective, operationally defined assessment procedure. Cleckley (1976) argues that the psychopath wears a "mask of sanity", imitating normal behaviour remarkably w e l l . Consequently, any dysfunction must be subtle and deep-seated, and not r e a d i l y recognized i n the con-s i d e r a t i o n of i n d i v i d u a l symptoms. He suggests that the core psychopathic symptoms are a l l rooted i n some ce n t r a l personality disorder. The con-s t e l l a t i o n as a whole indicates a condition he l a b e l s as, "semantic dementia", marked by, ". . . a s e l e c t i v e defect or elimination which prevents important components of normal experience from being integrated into the whole human reac t i o n . . ."(P. 410). Despite i t s importance i n Cleckley's i n f l u e n t i a l t h e o r e t i c a l scheme, the concept of semantic dementia has received scant experimental a t t e n t i o n . To what extent i s o r g a n i c i t y implied i n semantic dementia? Is semantic dysfunction a unitary phenomenon? What type of experimental manipulations might be expected to be s e n s i t i v e to semantic disruption? Researchers generally have f a i l e d to note the relevance of Cleckley's (1976) "peripheral vs. c e n t r a l " dimension of personality disorders to the neuropsychological i n v e s t i g a t i o n of psychopathy. It i s my i n t e n t i o n to present groundwork for neuropsychological study based upon the hypothesis that some form of "semantic dementia" underlies the widely accepted c l i n i c a l p i c t u r e of the psychopath. My approach w i l l , f i r s t l y , involve a b r i e f review of current neuropsycho-l o g i c a l research i n psychopathy. This w i l l be followed by a more d e t a i l e d d i s c u s s i o n of s p e c i f i c neuroanatomical structures considered to be c r u c i a l -4-to the support of both semantic c a p a b i l i t y and performance. Then w i l l come an elaboration of the theory proper - l a r g e l y a synthesis of schemes developed by Brown (1977) and Cleckley (1976). F i n a l l y , I w i l l r e l a t e the r a t i o n a l e behind, and the d e s c r i p t i o n of, a tachistoscopic experiment designed to begin the systematic i n v e s t i g a t i o n of semantic dementia. I I . The neuropsychology of psychopathy: Current status The most popular neuropsychological explanation of psychopathy seems to be that of f r o n t a l lobe pathology. A sizeable amount of animal and human research has documented the following e f f e c t s of p r e f r o n t a l and f r o n t a l damage; impulsiveness, defective goal-oriented behaviour, diminished a f f e c t , impairments of s e l e c t i v e a t t ention, f a i l u r e to learn from past experience, lack of fore s i g h t and planning ( E l l i o t t , 1978; Sch a l l i n g , 1978a). These symptoms bear a s t r i k i n g resemblance to part of the psychopathic symptom c o n s t e l l a t i o n as described by Cleckley (1976), an observation which has encouraged the recent use of neuropsychological te s t i n g procedures on psychopaths (see Sch a l l i n g , 1978a, 1978b). Schalling and her colleagues found that psychopaths, l i k e f r o n t a l lobotomy patients (see, eg., Meier and Story, 1967), obtain higher Q-scores on the Porteus maze test than do non-psychopaths (Schalling, 1978a). Also, i t seems that more impulsive-psychopathic subjects report a greater rate of change i n the Necker cube, a r e v e r s i b l e f i g u r e s e n s i t i v e to b i l a t e r a l f r o n t a l l e s i o n , than do l e s s impulsive-psycho-pathic subjects (Schalling, 1978a). The Porteus findings are somewhat co n t r o v e r s i a l as they have not been r e p l i c a t e d by some other investigators -5-(Sutker, Moan, and Swanson, 1972; Hare and Jutai, (Note 1)). There are however, as Elliott (1978) reports, important differences to consider between the frontal patient and the psychopath. For example, the psychopath tends toward episodicity rather than consistency in his abnormal behaviour. Also, there is no obvious impairment of memory in psychopathy (see Hare, Frazelle, Bus, and Jutai, 1980). In fact, the long-term memory of psychopaths has been reported as being superior to that of non-psychopaths (Sherman, 1957). Furthermore, unlike the frontal patient, the psychopath often displays unusual s k i l l in the arts of persuasion and ingratiation. Other notable differences exist. Cleckley (1976) characterizes the psychopath as possessing a specific loss of insight, in the sense of realistic evaluation of self and circumstances. It is unlikely that the psychopath behaves inappropriately because of an inability to act upon the dictates of a sound evaluative system. Rather, his verbal dexterity and good intelligence permit excellent mimicry of insight despite grossly defective evaluative capabilities. According to Konow and Pribram (1970), neuropsychological research strongly supports a dissociation between "utilization" and "evaluation" of environmental input. Frontal lesions primarily disturb the former, while the latter has functional substrates in more posterior brain areas (Pribram, 1969). Luria (1966) had suggested that frontal lesion-induced disruptions stem from damaged response regulatory mechanisms. Recent work elaborates upon these notions, allocating response regulation to certain frontal areas and evaluation to limbic (especially, hippocampal) tissues (Iverson, 1976; Numan, 1978). - 6 -A key feature of the psychopath's eva luat ive process i s i t s emotional poverty . The v e r b a l accompaniments of h i s " s o u l - s e a r c h i n g " in a c l i n i c a l interv iew possess no a f f e c t i v e c o n v i c t i o n , and are o f ten communicated i n a l i g h t - h e a r t e d , s u p e r f i c i a l l y humourous manner (C leck ley , 1976). A comparison of t h i s observat ion with the emotional r e a c t i o n of aphasic pat ients to t h e i r i l l n e s s i s i l l u m i n a t i n g . Aphasics whose d i s a b i l i t y has resu l ted from f r o n t a l l e s i o n u s u a l l y demonstrate acute awareness of t h e i r cond i t ion and are t y p i c a l l y depressed (Geschwind, 1974), whi le temporal l e s i o n - i n d u c e d aphasics in f requent l y d i s p l a y i n s i g h t into t h e i r i l l n e s s and are o f ten euphoric (Brown, 1977; Geschwind, 1974) . Geschwind (1974) suggests that temporal l e s i o n in these pat ients might a l so sever temporo- l imbic connections thereby impair ing arousa l of emotional responses to the d i s o r d e r . This severance might a l s o d is rupt v e r b a l l ea rn ing and so f r u s t r a t e r e h a b i l i t a t o r y e f f o r t s . In a s i m i l a r manner, the f a i l u r e of behaviour m o d i f i c a t i o n approaches to the treatment of psychopathy, and the d e f i c i e n c i e s i n learn ing shown by psychopaths in c e r t a i n experimental s i t u a t i o n s (Hare, 1970, 1978; Suedfeld and Landon, 1978) might i n d i c a t e l imb ic d i s r u p t i o n , i n v o l v i n g , i n p a r t i c u l a r , l i m b i c substrates of punishment (see Fowles, 1979). Gascon and G i l l e s (1973) descr ibed the case of a twenty -s ix year o ld woman with complete, but s e l e c t i v e l imb ic lobe damage. The p a t i e n t ' s behavioural aberrat ions included d e n i a l of i l l n e s s , inappropr iate j o c u l a r i t y , negat iv ism, h y p e r a c t i v i t y , short a t t e n t i o n span, and d i s t r a c t a b i l i t y . Gascon and G i l l e s l a b e l l e d the syndrome, " l i m b i c dementia" , -7-... .to emphasize that, although on superficial examination she may have appeared demented in the usual sense, the functions primarily lost were not those cognitive functions usually associated with 'intelligence', usually measured by psychometric tests, and often based on language, but those which imprint an affective quality, thereby giving meaning, to daily survival interactions with the environment and imprinting them into memory. Moreover, the neuropathological lesions were not those of the usual cortical dementias, but were confined essentially to hemispheral structures within the limbic system, (p. 429). There"is very l i t t l e mention in the literature of the effects of frontal lesions on naturally occurring social interactions in man. This is unfortunate since these interactions represent situations of particular importance in the study of the subtleties of psychopathic social behaviour (Rime, Bouvy, Leborgne, and Rouillon, 1978). However, one recent study has described frontal patients as "social isolates", with marked impairment in desire and ability to form social relation-ships (Deutsch, Kling, and Stelkis, 1979). This description contrasts sharply with the friendly attitude, extraordinary poise, and easy social graces which usually dominate one's clinical impression of the psychopath (Cleckley, 1976). Furthermore, the paralinguistic and proxemic behaviours of the frontal patients of Deutsch et al. (1979) did not appear to share the intrusive, reactive character of psychopathic performance in inter-personal situations as observed by Rime et al. (1978). In general, it seems that pathology of the frontal lobes is insufficient (or even in-appropriate) to account for some of the core features of psychopathy. A major difficulty exists in the interpretation of frontal lobe research with humans. Elliott (1978) has noted the inconsistency of -8-frontal lobotomy effects on human personality. The main problem stems from the great variability reported in lesion sites. In particular, most posterior ablations involve limbic structures as well as frontal cortex, promoting a mixture of cognitive and affective symptoms. Thus, the label "frontal" means different things to different researchers. The problem is somewhat unavoidable since the vast majority of human subjects are clinical patients - victims of accident or disease. Another interesting neuropsychological approach to psychopathy is Flor-Henry's (1976) suggestion that lateralized (i.e., dominant hemisphere) frontal/temporal dysfunction may foster psychopathic symptomatology. Flor-Henry provides no direct evidence to substantiate his hypothesis, and available physiological data do not entirely support such a notion (Hare, 1978, 1979). Hare (1979) tested the hypothesis as i t would apply to verbal tachistoscopic recognition (i.e. it would predict impaired right visual field relative to left visual field recognition) using well defined groups of psychopaths and non-psychopathic controls (see Hare and Cox, 1978; Hare, 1980), and reported nothing unusual about the performance of psychopaths. Also, the Porteus maze test, on which the psychopathic subjects of Schalling (1978a) obtained high scores, has been found to be more sensitive to right rather than to left frontal insult (Meier and Story, 1967). While there is l i t t l e evidence in the current literature to implicate lateralized hemispheric dysfunction in psychopathy, most of this research has been unfocused theoretically. The psychopath is not just impulsive, or incorrigible, or cold; he is a l l of these at once, and more. A theoretical framework faithful to the integral, clinical picture of the psychopath is necessary to guide neuropsychological investigation. -9-At this point, a more detailed specification of relevant neuroanatomy w i l l be presented. The limbic system and possible fronto-limbic con-nections, in particular, merit attention. III. Behaviour and memory: Frontal and temporo-limbic contributions A. Frontal cortex Stanley and Jaynes (1949) proposed a "cortical act-inhibition" theory of frontal lobe function. They suggested that frontal ablation-induced learning deficits were due to impaired performance, rather than to an inability to inhibit previously learned response sequences. Sub-sequent work has resulted in the elaboration of this position. Frontal areas have been described as being heavily involved in the ut i l i z a t i o n of feedback relevant to the consequences of behaviour (Luria, 1966; Numan, 1978). Nauta (1971) proposed that frontal areas are central participants in behavioural anticipation and in the overall course and temporal st a b i l i t y of complex goal-oriented behaviours. A distinction has been made between orbital and dorsolateral frontal influences on behaviour. Selective damage to the former area disturbs emotionality and autonomic regulation, while dorsolateral insult disrupts actual response modulation (Girgis, 1971; Numan, 1978). Milner (1964) attributed the poor performance in memory tasks of frontal-lesioned human subjects, not only to poor memory, but also to an inability to maintain concentration on current stimuli and to suppress the memory of prior stimuli (see also Butters, Samuels, Goodglass, and Brody, 1970; Perret, 1974). She concluded that good performance on these tasks requires the functional integrity of both lower frontal -10-and temporal areas. Milner (1970, 1971) has also reported research which found that patients with left frontal lesions demonstrated excellent recognition memory for familiar stimuli, but were very poor at judging when these stimuli had appeared. Iverson (1976) suggests that the frontal lobe in humans plays a sophisticated role in the memory storage process, namely, the coding of order in time. In a recent review of contemporary animal (especially primate) research, Numan (1978) conduced that the frontal association cortex was not directly involved in general memory processes. He points out that current work favours a response modulation explanation of frontal function. Impairments are described in terms of inefficient utilization of feedback, and the dorsolateral area in particular is implicated. Human research generally places memory (particularly semantic memory) systems in a more posterior locus (eg., Warrington, 1975). Ojemann (1978) described evidence which indicates that the posterior frontal lobe, adjacent to the anterior language area of the brain, houses the retrieval mechanism of short-term verbal memory in man. In summary, the frontal lobe appears to be an executor, rather than a container or a generator of mnestic processes, directing the coding, retrieval, and utilization"of stored information. B. Temporo-limbic tissues Douglas and Pribram (1966) suggested that the hippocampus and amygdala were jointly involved in the learning process, with the amygdala recording stimulus meaningfulness and the hippocampus evaluating response strategies (see also Numan, 1978), strengthening correct and weakening incorrect responses to stimuli. The two structures comprise an hypothesis-- l i -test ing or strategy-searching mechanism selectively impaired by limbic lesion (Iverson, 1976). The hippocampus also appears to play a crucial role in the fixing of attention to relevant stimuli, and in behavioural habituation (Iverson, 1976). Hippocampal-lesioned animals seem less distractable in goal-directed activity, and often show slower rates of habituation than controls (Jarrard, 1973). Kimble (1968) interpreted the habituation findings as evidence of response disinhibition. While rat studies seem to support such a notion, the simple loss of response control is not easily ascribed to the deficits observed in hippocampal-lesioned monkeys (Iverson, 1976). The hippocampus also appears to exert considerable influence on general activity. Jarrard (1973) reports that, in situations requiring goal-oriented behaviour, lesloned animals often display greater activity than controls, especially in cases where the lesion is extensive and bilateral. Furthermore, he has observed a selective effect on reactivity to auditory or photic stimuli, with lesions resulting in increases only when stimulation is intense. In interpreting the literature, species differences constitute an important consideration. It seems that the rat, unlike the monkey, has poorly developed frontal cortex, disconnected from limbic structures (Nauta, 1964; Numan, 1978). In the rat, it is limbic rather than frontal damage that results in classical frontal-like effects (Numan, 1978). Nauta (1964) suggested that frontal association cortex is the neocortical extension of limbic mechanisms. Numan (1978) contends that the hippocampus forms a significant -12-functional and structural link between frontal and limbic mechanism. Once again, dorsolateral and orbital frontal cortex can be separately treated. From the analysis of fiber distributions in monkeys, it appears that the former is closely related to the hippocampus, while the latter is closely tied to the amygdala and temporal lobe (Nauta, 1964). A review of the literature leaves l i t t l e to doubt the existence of a fundamental relationship between temporal structures and memory (see, eg., Fedio and Van Buren, 1974; Hagberg, 1978; Milner, 1967, 1968, 1970). Verbal memory is selectively impaired by left (i.e., where the left is dominant) temporal damage (Iverson, 1976),'with the degree of impairment related to the extent of limbic lesion (Omaya and Fedio, 1972). Semantic memory and semantic retrieval appear to be particularly vulnerable to temporal lobe damage (Coughlan and Warrington, 1978). The left anterior temporal area is especially important (Fedio and Van Buren, 1974; Hagberg, 1978), and seems to be heavily involved in the registration and/or storage of verbal information (Fedio and Van Buren, 1974; Iverson, 1976). Right anterior temporal lobe damage disrupts the recognition and retention of nonverbal material (Milner, 1967, 1968, 1970). Fedio and Van Buren (1974) suggest that in the left posterior temporo-parietal area of the brain may be located a common mechanism for the retrieval of information from both long- and short-term memory. However, their opinion is not shared by a l l researchers. Ojemann (1978), for example, contends that short-term verbal memory storage, rather than retrieval, is supported by posterior temporal structures. It may be more reasonable to look elsewhere in the brain for the executor of retrieval processes. As was mentioned earlier (Section III. A.), -13-Ojemann (1978) offers the posterior frontal lobe as a likely candidate. Hagberg (1978) points out that recognition memory tests require a planned, serial activity (i.e., an active search for the right answer) within a given space of time coupled with differential judgment, as well as mnestic ability. The former type of activity, as earlier noted (Section III. A.), seems to be quite dependent upon frontal regions, while mnestic ability (i.e., encoding and storage) per-se remains the province of temporo-limbic areas. An impressive amount of research indicates that the integrity of limbic (especially hippocampal) tissues is essential to normal memory processes (eg., Brion, 1969; Isaacson, 1975; Iverson, 1976; Milner, 1967, 1970; Numan, 1978; Ojemann, 1978; Stepien and Sierpinski, 1964). Korsakoff's syndrome is always accompanied by bilateral limbic lesion (Brion, 1969) , and its associated memory defects are equally reproducible by bilateral hippocampal resection (Barbizet and Cany, 1969). Milner (1972; 1978) suggests that bilateral hippocampal lesion might disturb the consolidation process required for proper transition of information from the short- to the long-term store. McLardy (1970) proposed that the hippocampus and anterior lateral temporal cortex support a recent memory system, with immediate access to a long-term store. Kinsbourne and Wood (1975) have hypothesized that subcortical and limbic system (and not cortical) structures are the most deeply involved in memory processing, especially in the retrieval- of information. In the dominant hemisphere, verbal recent (i.e., short-term) memory processes, including both learning and retention, are dependent upon the hippocampus (Ojemann, 1978; Stepien and Sierpinski, 1964). There is -14-some evidence that right (non-dominant) hippocampal insult disrupts visuo-spatial short-term memory (Ojemann, 1978) . The hippocampus has also been described as the memory mechanism of the response regulation system (Numan, 1978). In this context its duties involve the coding of sensory input and response to input and laying down a record of the correlation between the two (Iverson, 1976). As i t is generally accepted that the properties of human motor memory differ from those of verbal memory (Milner, 1972), it is interesting to note the critical participation of the hippocampus in both of two qualitatively dissimilar memory systems (Iverson, 1976). In summary, the temporo-limbic tissues seem to be directly involved in attention and memory processing, and in the evaluation of behavioural response strategies. It is important to note the distinction made between frontal (planned, serial, regulatory) and temporo-limbic (mnestic, evaluative) functions because of the implications i t has for the con-current analysis of reaction time and error rate data in tachistoscopic memory paradigms (see section V. B.). IV. Semantic dementia: A neuropsychological theory A. Brown's model of neural organization Brown (1978, 1977, 1976) has recently proposed a model which maps linguistic disorders onto levels of phylogenic and ontogenic brain organization. The model involves a cognitive hierarchy of "limbic-presentational", "cortical-representational", and "asymmetric-symbolic" stages. The first two stages are phylogenic, corresponding roughly to the "paleomammalian" and "neomammalian" components of McLean's (1972) -15-tri-partite model. The last level is a maturational achievement. Active structures at the limbic-presentational level include familiar constituents of the limbic lobe (i.e. hippocampus, anterior thalamus, cingulate gyrus, hypothalamus, and associated interconnections), orbito-frontal, pyriform and possibly insular cortex, and some sub-cortical participants (e.g., amygdala, septial nuclei, dorsomedial thalamus). In cognitive terms, this stage is marked by a fundamental semantic processing of a l l emerging thought. At this level, objects are not perceived as fully exteriorized, but rather are incorporated by the organism. The rudiments of semantic operations are evident here as affects accompany a l l object perceptions and responses, giving environmental interaction a highly subjective flavour. Semantic develop-ment, then, originates as a true empathy^ ", as an indistinction of object from self. The functional integrity of paleomammalian tissues is crucial in cognitive phylogeny for the grasping of meaning, and in particular, for the optimal development of affective self - object bonds. Neomammalian cortex is a phylogenic latecomer, emergent in the higher mammalian species. Anatomical constituents are the frontal and parietal "integration" cortices which surround primary sensory regions. Both areas have comparable thalamic, and medial and lateral limbic con-nections, and cortico-cortical connections. The hallmark of cognition at the cortical-representational stage is object awareness - objects are Cf. Ax's (1962) related discussion of limbic involvement in the "inappropriateness of affect" or "impairment of empathy" in schizophrenia. -16-externalized and divorced from the self. Differential affective states develop with this new perceptual capacity. Says Brown (1977), "the object and its affective component are like arborizations of the affect-laden image that precedes them" (pp.20-21). The self, too, is seen as an object. At the asymmetric-symbolic level, core differentiation in frontal and temporo-parietal cortex produces new functional zones. According to Brown, asymmetry in the form of lateralization, or cerebral dominance, represents the extension of phylogenic encephalization into ontogeny, and is a response to size restrictions on cortical expansion. At this level, action is volitional, or consciously guided. Language develops to articulate the mind, as objects had formerly described the environment. Language further permits the awareness of the self as a subject in the awareness of the object. Furthermore, as Brown (1977) suggests, "awareness is a type of affect", since cognition develops as a, "unitary arborization of affect, awareness, and language together into a new inner or private space" (p. 23). Brown's is not a static "sandwich" or "layer cake" model, but one of growth in the organic sense. New structures not only develop out of predecessors, they make new structures of progenitor substances as is required to nurture emergent abstract representation. The realization of a new performance level will affect cognition at preceding stages . . . in the forward development of cog-nition, structure acts as medium for a transformation and is not irrevocably bound to function. As in evolution or embryo-genesis, cognition does not advance as an elaboration of the previous endstage. Each new level is not simply a continuation but as a differentiation of an earlier, less specialized stage. (1977; pp.23-24) -17-Th is premise is important in the construction of a framework within which Cleckley's (1976) concept of semantic dementia can be represented in actual neural organization. I will propose that Cleckley's (1976) dementia - aphasia analysis can proceed beyond the level of analogy provided it is accepted that, as Brown (1977) contends, "language is not 'added on' to prelinguistic cognition, but rather in its development recapitulates a l l of the preceding stages" (p.24). B. Semantic aphasia and semantic dementia The semantic aphasic patient has been described as possessing the following: a lack of recognition of the f u l l significance of words and phrases apart from their verbal meaning; an inability to anticipate the final result of an action; a failure to synthesize perceived details into a general conception; only a partial insight into his malaise; a tendency toward logorrhea and euphoria; a general absence of hallucination and paranoia (Brown, 1977, 1972; Chapey and Lubinski, 1979; Green and Boiler, 1974; Schuell, Jenkins, and Jimenez-Pabon, 1964; Von Stockert, 1972; Wepman, 1972; Zurif, Green, Caramazza, and Goodenough, 1976). According to Cleckley (1976), the psychopath possesses a "semantic dementia" - he is incapable of finding meaning in l i f e . The symptom constellation includes: poor judgment; failure to learn by experience; specific loss of insight; superficial charm; good intelligence; and absence of delusions and other signs of irrational thinking. As he repeatedly points out in his book, Cleckley (1976) is describing a gross personality disorder with a marked absence of superficial sympto-matology (in the sense of clinical deficits). The psychopath is said to -18-be quite adept at the technical conveyance of linguistic and intellectual competence, while completely lacking in adequate motivation and any sense of value. The power of this "mask of sanity" was recently displayed in a study by Hare et al. (1980). Prison inmates were divided into three groups on the basis of highly reliable assessments of psychopathy, and a comprehensive battery of primary ability tests (the CAB) was administered. No significant differences were reported between the high-, medium-, and low-psychopathy groups on any of the eighteen measures. There was nothing in the pattern of test results for the high-psychopathy group indicative of any obvious intellectual or linguistic impairment.. Cleckley (1976) proposes an analogy between speech disorders and disorders of personality in order to illustrate the centrality of the psychopathic condition. In his scheme, both kinds of disorder are arranged along a continuum bounded by endpoints representing periphery and centrality. An injured tongue constitutes a def ect in the distal organ of vocal speech - a peripheral speech impairment. One of the most central of such problems is represented in the semantic aphasia produced by a lesion in language area neocortex, a problem which is often well disguised by the integrity of more superficial structures. In the personality domain, delirium is an obvious, peripheral, manifestation of psychosis. In psychopathy, "psychosis" is deep-set, well-concealed by adept mechanical reproduction of appropriate behaviour. Cleckley's analogy is presented in Table 1. To the extent that he develops i t , Cleckley's analogy is interesting but vague. Several questions come to mind. Are linguistic disorders intended to be thought of as independent of those of personality (hence, -19-parallel continua)? How similar are the semantic components of aphasia and dementia? Can substrates of the personality analogues be located in the brain? The answers to these questions require a more detailed examination of the neuropsychology of both disorders. Brown (1977) has interpreted clinical and neurological aspects of language disorders within his aforementioned model of neural organization. The various aphasias1 tend to be restricted to certain cortical areas, namely, limbic cortex (semantic aphasia), generalized (temporo-parietal) cortex (nominal aphasia), and specialized (dominant posterior-superior temporal gyrus and supramarginal gyrus) cortex (phonemic aphasia). These anatomic structures support the limbic-presentational, cortical-represent-ational, and asymmetric-symbolic levels, respectively, in Brown's (1977) cognitive hierarchy. The process involved in any given act of language production proceeds through these structural levels in an invariant sequence. First, there is semantic encoding (limbic stage), followed by word selection (generalized stage), terminating in phonemic realization (specialized stage). The disorders which can affect these aspects of linguistic production are not by nature nested within each other, but are quite independent. Thus, a disruption at the limbic level which may result in semantic aphasia will not necessarily alter the technical capabilities of the generalized and specialized structures. To put i t I do not include here the nonfluent aphasias. These action, speech (as opposed to perceptual, linguistic (fluent)) aphasias are discussed in detail by Brown (1977). The two classes of aphasias are organized in parallel within the cognitive hierarchy. Table 1 PERIPHERAL <•? Speech and personality continua. (adapted from Cleckley, 1976) — > SOMEWHAT PERIPHERAL < > CENTRAL Speech Disorders Injured tongue Anatomic defect in distal organ of vocal speech DYSARTHRIA" ~TW APHAS1AT Severed hypo-glossal nerves Anatomic lesion Lesion of motor cortex or pyramidal tract less distal but dysfunc-Verbal aphasia tion s t i l l circumscribed to vocal produc-j tion Syntactic aphasia Lesions in quadri-lateral space of Marie Nominal aphasia Lesion atj or about angular gyrus Semantic aphasia Lesion at or about supra-marginal gyrus (only physiologic mechanisms for speech impaired) (physiologic mechanisms for speech and writing entirely unimpaired) Personality Disorders Delirium Psychosis immediately abvious Hebephrenic schizophrenia Paranoid schizophrenia Paranoid psychosis and paranoia vera =5f Psychosis less obvious, better preserved func-tion tending to obscure i t ; although less obvious, disorder not less severe Masked schizophrenia Psychosis not demon-strable, but outer aspects of personality show some apparently minor deviation The psychopath Abnormality not technically demonstrable; maximally con-cealed by outer surface of intact function; manifested only in behaviour; may, however, be extremely severe -21-another way, a disability in semantic encoding, as occurs in semantic aphasia, need not coincide with difficulty in directly naming objects, as in nominal aphasia, but rather will likely manifest itself in in-appropriate (but not inarticulate) labelling (see Figure 1). Grober, Perecman, Kellar, and Brown (1980) examined the semantic categorization of pictures and words in anterior (generalized neocortex; Broca's area) and posterior (limbic cortex; Wernicke's area) aphasics. The performance of posterior aphasics was significantly worse than that of anterior aphasics and control patients. Anterior aphasics did not differ from controls. Posterior (limbic cortical) pathology appeared to disrupt semantic processing. Semenza, Denes, Lucchese, and Bisiacchi (1980) studies the comprehension of class (superordinate) and thematic (spatial/temporal contiguity) relationships in Broca's area aphasics, Wernicke's aphasics, and control patients. Broca's aphasics had difficulty with thematic relationships, while Wernicke's patients performed particularly poorly on judgments of class inclusion. Both groups did not differ from controls on the other test in each case. This recent research suggests that semantic aphasia manifests itself independently of peripheral semantic retrieval mechanisms and of spatial-/temporal-contiguity-processing capabilities. Semantic disorders, Brown (1977) observes, tend to occur with bilateral temporal lobe''" pathology. This appears to be especially true ^ This does not necessarily refer to true temporal neocortex, but instead, to, "cortical representatives of limbic structures" (Brown, 1977). Gascon and Gilles (1973) refer to these tissues as "hemispheral structures within the limbic system". They include posterior orbital, insular, and anterior and medial temporal lobe areas. I CM CM I Disorders of language production correspond with evolutionary and maturational l e v e l s of brain organization. Focal Neocortex Generalized Neocortex Limbic Cortex Structu a l l e v e l S p e c i a l i z e d Neocortex L e f t f o c a l l e s i o n t Generalized Neocortex P a r t i a l or p e r i p h e r a l l e s i o n of speech zone on l e f t side T Limbic Cortex B i l a t e r a l or u n i l a t e r a l l e s i o n Posterior (fluent) aphasia Phonemic aphasia Nominal aphasia Semantic aphasia Figure 1. Levels of b r a i n organization and language disorders. (adapted from Brown, 1977) for younger patients. In general, the likelihood of bilateral lesion increases with the depth of the disorder in the cognitive hierarchy. Unilateral (i.e. dominant hemisphere) lesion more often fosters more superficial problems. Returning to Cleckley's speech/personality disorder analogy, we see that when basic neural organization is interfaced with the speech and personality disorder continuum, a strict parallelism of the two dimensions breaks down. Both Cleckley's "central" personality and Brown's deep aphasic disorders are examples of fundamental semantic dysfunction. If psychopathy is neuro-structurally supported, then a synthesis of Brown's and Cleckley's formulations would suggest the localization of substrates bilaterally, within temporo-limbic cortex where, similarly, the germ of semantic aphasia would reside. The basic idea is that the semantic capabilities are centrally, deeply, determined (see Gainotti and Lemmo, 1976). The manifestation of semantic disorder as either aphasia or psychopathy is a function of the relative integrity of the entire transformational pathways leading up through the cortical levels to respective peripheral endpoints (see Figure 2). Although temporo-limbic cortical dysfunction of some kind could be expected in both of these disorders, there is no reason to expect that aphasia and dementia must be coincident. The dysfunction occurs primarily in the interaction between the limbic-presentational and cortical-representational levels. Thus, semantic aphasia may appear in a non-psychopathic personality as a result of defective linguistic semantic transition only. Semantic dementia may represent mal-transition through other, nonlinguistic, behavioural (especially social) Personality (Cleckley) Aphasia (Brown) Peripheral/Superficial Central/Deep A " ^ m ™ « * - Symbolic B - Cortical - Representational C = Limbic - Presentational Figure 2. Levels ot cognition in personality and aphasia. (adapted from Brown, 1977, and Cleckley, 1976) -25-areas of the cortical-representational level (it is acknowledged, of course, that at present these areas are less delineated than their linguistic counterparts). In summary, the key assumption of this aphasia/dementia synthesis model is that any existing neuro-structural and/or neuro-functional correlates of psychopathy are centrally and bilaterally located. The model allows for some important predictions: 1) owing to the depth and bilaterality of the semantic disorders, instruments designed to measure virtually any gross, superficial or lateralized aspect of cognitive function will be inadequate in identifying the psychopath; 2) a device designed to assess linguistic semantic competence might identify the psychopath only if i t taps functions at the limbic-present-ational level, where the distance is minimal between "linguistic" and "psychopathic" semantic pathways leading upward to cortical representation. V. A tachistoscopic investigation of semantic dementia A. A note on hemispheric specialization One of the most extensively documented (and criticized; White, 1969, 1972) findings in neuropsychology is that the dominant hemisphere excels at verbal processing, while visuo-spatial processing is more efficiently handled by the non-dominant hemisphere. Recent research has suggested exceptions to this general rule, and has contributed to the description of "specialized" functions in greater detail. Of particular importance to this paper are studies which have in some way attempted to specify and distinguish mnestic and linguistic aspects of hemispheric speciali-zation. -26-Ojemann and Whitaker (1978) report a high degree of interindividual variability in language localization in the brain, however, when the left hemisphere is dominant, language and verbal memory are its general responsibility. In cases presenting this typical dominance arrangement, these authors contend that a blanket characterization of the right hemisphere as language deficient may not be entirely appropriate since research seems to indicate an absence only of functions required for naming, which is an expressive, late stage in verbal production (Brown, 1977; Thatcher and John, 1977). Hardyck, Tzeng, and Wang (1978) suggest that lateralization of memory rather than of language per se may explain the results of most tachistoscopic studies. Verbal memory, and, visuospatial and pattern memory, they claim, may be highly lateralized in the left and right hemispheres respectively. As an explanatory alternative to lateralization of mnestic and linguistic functions, i t is possible that the hemispheres differ in the degree of relative efficiency with which they process certain types of information (Springer, 1977). Moscovitch (1976) has considered this issue of the "performance" versus the "competence" of the right hemisphere. It is his opinion that the right hemisphere possesses a poorer short-term verbal memory than the left, but some verbal mnestic capacity nonetheless. He describes work by Zaidel which has demonstrated that the right hemisphere, " . . . can comprehend not only abstract words, but also a variety of syntactic structures . . . and semantically abstract references" (p.592) (see also Day, 1977; Hecaen, 1978). Leiber (1976), however, reports quite the opposite (i.e., exclusive left hemisphere word-appreciation capacity) and does not favour the possibility of mere quantitative hemispheric differences. Bevilacqua, Capitani, Luzzatti, and Spinnler (1979) have shown that the memory processing of stimuli projected to the right hemi-sphere is at least as efficient as that projected to the left when sufficiently long retention intervals are permitted. This may have implications for results such as those of Martin (1978). She investigated the recall of tachistoscopically-presented words as a function of a requirement to process the words "physically" (i.e., count the number of syllables) versus "semantically" (indicate category membership). She found the left hemisphere to excel in physical processing of words, while neither hemisphere was superior at semantic processing. It is possible that the retention level used differentially influenced recall at the two levels of processing. Caramazza, Gordon, Zurif, and De Luca (1976) present evidence that verbal reasoning can be impaired by right hemisphere lesion, and suggest that some type of right hemispherically-formed imagery may be required at an important stage in verbal problem solving (see also, Seamon and Gazzaniga, 1973). The main conclusion to be drawn from this sampling of recent research is that, while the relative linguistic prowess of the left hemisphere is not in doubt, the neuropsychology of verbal coding is poorly understood. As Iverson (1976) points out, the conditions under which a stimulus is transformed from a visual perceptual event to a word lack adequate description. -28-B. The logic of a tachistoscopic approach A neuropsychological investigation of verbal mnestic processes in the psychopath is a reasonable way to initiate the experimental analysis of semantic dementia. The basic questions here are, "can a central semantic abnormality be detected in linguistic semantic function, and, if so, at what level or depth of the latter, and implicating which relevant neuroanatomical structures?". One of the most influential theoretical developments in the area of verbal memory in recent years has been the "levels of processing" framework of Craik and Lockhart (1972). It posits that the increased depth to which stimuli are processed is associated with increased retention of information about these stimuli. "Depth" is equated with movement from physical to semantic analysis. While this framework has generated a good deal of research (see Craik and Tulving, 1975; Peterson, 1977), its neuropsychological significance has not been adequately considered. Memory models in general tend to interface rather poorly with neuropsychological data. In a recent review, Erickson and Scott (1977) report that, A sampling of the literature reveals that we do not possess a coherent understanding of memory functioning from a psychological or neuropsychological point of view. Psychological models of memory have proliferated during the past decade, but each model poses as many problems as i t purports to solve . . . conventional discriminations that lend a certain order to experi-ments in this area represent a quasi-precision imposed by experimental procedures and do not reflect an accurate portrayal of the structure of memory . . . (p.1130) -29-Th e issue of hemispheric specialization for different levels of processing has only lately been addressed. The results of two tachistoscopic experiments performed by Martin (1978) indicated that the recall of words presented to the left hemisphere under conditions requiring physical processing was superior to that of words shown to the right. Semantic processing of words, however, did not appear to be significantly lateralized. These findings have implications for the previously discussed contention of Brown (1977) that semantic capabilities are deeply and bilaterally located (limbic-presentational), whereas physical word processing is accomplished at a more superficial, lateralized level (asymmetric-symbolic). The tachistoscopic examina-tion of verbal processing depth would seem to hold promise then as a technique in the study of semantic dementia. Martin's (1978) particular procedures are not well-suited to the goals of this study, nor for that matter do they really permit generali-zation of her results beyond a discussion of physical versus semantic encoding effects on retention. For example, a demonstration of a difference in recall as a function of left or right visual field presentation does not necessarily imply a difference in hemispheric processing of stimuli, i f we take the term "processing" to denote operations leading up to and including the storage of stimulus information. The observed difference might be due to retrieval effects operating independently of relative hemispheric processing abilities - effects likely associated with particular response requirements (eg., vocal or written recall, as was used by Martin). Also, recall, as a dependent measure may not be sensitive enough to discern hemispheric differences -30-on more complex tasks. On a trial-by-trial (word-by-word) basis, recall is usually measured in binomial fashion - that is, a word either is or is not correctly recalled. If hemispheric differences existed with respect to the amount of time devoted to processing at the time of stimulus presentation, recall could not be expected to adequately assess these. The experiment to be described in this paper utilizes a procedure similar to that originally used by Landauer and Freedman (1968) . These researchers were interested in retrieval from long-term memory as a function of semantic category size. Subjects were shown single words and were required to indicate (manual response), as quickly as possible, whether or not the words belonged to familiar semantic categories. Reaction times were found to be longer for large categories than for small ones. Collins and Quillian (1970) were able to replicate these results only when the categories were nested (i.e., the smaller categories were subsets of the larger ones). They interpreted this finding within the framework of their (1969, 1970, 1973) model of semantic memory. The structure of semantic memory is envisioned as a network of inter-related concepts denoted by English words. Individual concepts and their properties constitute the nodes of this network. In the process of retrieval, the structure is entered and a search for connections between concepts ensues. The structure is hierarchically organized with retrieval time a function of both the number of, and distance between, concepts (see Figure 3). As an example, the model predicts that the decision as to THING GERBIL Figure 3. A p a r t i a l map of long-term semantic memory. (adapted from C o l l i n s and Q u i l l i a n , 1970) whether or not the word "GERBIL" is an exemplar of the category "RODENT" requires less time than deciding if "GERBIL" is or is not an "ANIMAL". This is presumably because, as illustrated in Figure 3, the "semantic distance" separating "GERBIL" and "RODENT" is smaller than that between "GERBIL" and "ANIMAL". Furthermore, i t is assumed that the path from "GERBIL" to "ANIMAL" invariably passes through "RODENT". The important points to note about a l l of this research and theory as far as this paper is concerned are: 1) with the Collins and Quillian model, we can conceive of processing depth not only in terms of physical/semantic dichotomies, but also in relation to different organizational levels within semantic memory, with each accessible only via semantic elaboration at sub-levels; 2) reaction time appears to be a sensitive index of retrieval from processing depths. In the present study (see Procedure), subjects are required to process the same verbal stimuli at three different "levels". In one condition, they merely decide (manual response) whether or not test words match pre-trial cue words. The remaining two conditions demand semantic judgments about test stimuli. In one, subjects indicate i f a test stimulus can be classified as a "LIVING THING" or not. In the other, they must judge whether or not a test word is an exemplar of a smaller semantic category (eg., "BIRD", "VEHICLE"). Performance is assessed on different tasks with identical stimulus and response features but with different cognitive processing requirements. An attempt is thus made not to confound sensory-motor and cognitive aspects of the memory task. The semantic processing is examined as a function of visual -33-half-field of presentation (left and right) and responding hand. The dependent measures are reaction time (RT) and error rate (ER). Manual, rather than vocal responses are used since the latter may be governed exclusively by the left hemisphere (Gazzaniga and Hillyard, 1971; Levy and Trevarthen, 1976; Sperry, 1968). The mere requirement of a verbal response may produce a right visual half-field advantage in reaction time. The present study permits the right hemisphere to display whatever linguistic abilities it may have by compelling it to respond on half of the trials. Error rate is included for several reasons. It was the dependent variable in the studies which first reported hemispheric speciality in tachistoscopic recognition (eg., Bryden and Rainey, 1963; Mishkin and Forgays, 1952). It has also been a popular measure in recent research. Hare (1979), for example, found no difference between psychopathic and non-psychopathic criminals on visual half-field error rate performance in a noun recognition tachistoscope task. (Hare suggested, however, that important group differences might emerge in tasks requiring a degree of semantic processing greater than that of mere noun recognition. This notion was directly tested in the present study.) Some studies in which both reaction time and error rate were recorded found significant visual field differences with one measure but not with the other (see, eg., Springer, 1977; Tsao, Feustal, and Soseos, 1979). This raises the question of differential sensitivity of these variables, with special relevance to reports in the literature of equal visual field accuracy (White, 1972). -34-Springer (1977) suggests that reaction time might be the more sensitive variable to hemispheric differences in both tachistoscopic and dichotic listening tasks. Her argument rests on evidence that reaction time has revealed asymmetries where error rate has not. It must be appreciated, however, that the exact relationships between lateralized processes and each of these measures have yet to be elaborated. Given that any tachistoscopic recognition task usually involves a conglomerate of perceptual and mnestic operations (Hochberg, 1971), it is entirely possible that differential sensitivity exists more with respect to one or more of these aspects of brain processing rather than to lateralization per se. As was pointed out earlier in this paper (Section III. B.), most recognition memory tests include both planned/serial and mnestic functions. Speed of recognition (reaction time) might be more sensitive to temporal characteristics of retrieval, while accuracy might reflect more the integrity of and accessibility to stored information. For example, Grober et al. (1980), in a study described earlier (Section IV. B.), found that although both latency and accuracy measures were recorded, the accuracy score was the more sensitive index of anterior and posterior (semantic) aphasic group differences in semantic processing. Likewise, the Semenza et al. (1980) results (see Section IV. B.) were derived from analyses of performance errors. Earlier in this paper (Section III.), evidence was discussed which favoured the assignment (albeit, crude) of utilization and evaluation operations to frontal and temporo-limbic areas respectively. The inclusion of both speed and accuracy as measures in the tachistoscopic design can -35-thus be expected to enhance the informative potential of this under-taking. In any event, i t clearly is important that both variables take part in research of this kind, and that some attempt be made to consider their joint significance. A final reason for the concurrent analysis of these two measures is to assess any speed-accuracy tradeoff which might occur as a result of changes in the relative emphasis on speed and accuracy across conditions. It is well-established, for example, that when subject instructions emphasize extreme speed, fast reaction times are obtained at the cost of low accuracy (Pachella, 1974). The opposite tradeoff takes place when extreme accuracy is stressed. Thus, as long as speed and accuracy either do not correlate, or correlate positively within a condition, i t is fairly safe to assume that a tradeoff is not in effect. A serious interpretive problem would arise, however, if reaction time and error rate were each to show significant visual field asymmetry but in opposite directions. The teasing out of true lateralized effects would be rendered extremely difficult by a situation which would not permit one to rule out the possibility that obtained response latency differences were due to speed-accuracy tradeoff. The present study was designed to test the following hypotheses: 1) that psychopathic subjects differ . from nonpsychopaths on aspects of verbal semantic processing which are unrelated to the lateralization of stimulus input, which would suggest that psychopathic behaviour cannot be traced to lateralized neurological dysfunction; 2) that these group differences increase with "depth" of semantic processing, which would point to central, rather than peripheral neurological correlates of -36-psychopathy. VI. Method' A. Subjects Two experienced investigators rated each of 62 white male inmates of a Canadian federal medium security penitentiary located in British Columbia a few months before the start of the study. The rating pro-cedure, based upon Cleckley's (1976) conception of psychopathy (see Hare and Cox, 1978; Hare, 1979), produced highly reliable assessments. The interrater reliability of the 7-point scale ratings was .92. From this larger pool, 33 men volunteered to serve as subjects in the experiment. Twenty-seven were strongly right-handed (as determined by a score of +3 on three handedness questionnaire items) and used a non-inverted writing position (see Hare, 1979, for details). The remaining group of 6 men displayed the following range of scores: +2 (n=l); +1 (n=2); -3 (n=3). The 27 right-handers were divided into two groups on the basis of the combined psychopathy ratings given by the two raters (i.e., each subject could now have a score between 2 and 14). The mean rating for a l l 27 subjects was 9.52. The cut-off rating for group membership was 9. "Low" ratings of psychopathy were those below 9, while "High" ratings were those greater than 9. Group P (h=16) consisted of inmates with "High" psychopathy ratings (mean = 11.81, range = 10-14). Group NP (h=ll) contained subjects with "Low" ratings (mean = 6.18, range = 3-8). Because of the small N involved in this study the data from a l l 27 subjects were included in the analyses. As a result, the group separation on the basis of global ratings was not as wide as it could have been. The mean ages of the men in groupsP and NP were 28.8 (SD = 5.5) -37-and 28.4 (SD = 6.6) years respectively. There were no group differences in years of education (mean = 9.6, SD = 2.2). Estimates of the I.Q.s of these subjects were not obtained, however, previous research with similar populations employing a variety of intelligence measures has not yielded consistent psychopath versus non-psychopath intellectual differences (Hare, 1979; Hare et al., 1980). All subjects were interviewed regarding eyesight and had passed a vision test requiring verbal identification of a few tachistoscopically-presented words (see Appendix 1). B. Materials On each 4 x 6 in. white index card a four-letter word was printed vertically (White, 1972) with Letraset to the right or the left of a central fixation point. A numeral from 1 to 9 occupied the fixation point of each card. The distance between the inner edge of the word and the point of fixation subtended a visual angle of 1.5 degrees. The words selected were exemplars of the following four categories included in the Battig and Montague (1969) category norms: Four-footed animal; Weapon; Bird; Vehicle. The per category mean ranks (R) (see Battig and Montague, 1969) of the chosen exemplars were 6.26 (SD = 0.35; mean norm R = 7.49), 4.89 (SD = 0.63; mean norm R = 4.64), 5.13 (SD = 0.62; mean norm R = 5.05), and 4.22 (SD = 1.41; mean norm R = 5.15), respectively. The Battig and Montague norms have figured prominently in semantic memory research (Herman, Chaffin, and Corbett, 1973; Landauer and Meyer, 1972). Two prime considerations dictated the particular choice of categories: 1) maximal intra- and comparable inter-category -38-range of frequency of four-letter exemplars; 2) suitability for categori-zation into "LIVING THING" versus "NON-LIVING THING" superordinates. Two additional types of stimuli were constructed. Blank cards (fixation digit only)(White, 1972) and four-letter expletives, both for use as checks on compliance with instructions, received infrequent but balanced visual field presentation within and between stimulus sets (see Procedure). Four different stimulus sets, each consisting of two subsets of sixteen pseudo-randomly ordered stimuli, were constructed. Each was used (counterbalanced) in the three experimental conditions (see Procedure for details). The stimulus order and score sheets are presented in Appendix 1. C. Apparatus Stimuli were presented in a two-field Cambridge tachistoscope. The 2 luminance of each field was kept constant at 13.85 cd/m . In the absence of test stimuli, the center of the preexposure field was always occupied by a fixation dot. Each stimulus presentation followed 1 second after a verbal "Ready" signal given by one of the experimenters. Stimulus duration was 80 msec, well below saccadic supralatency exposure (Alpern, 1971; White, 1972). It triggered an electronic timer which was stopped the instant that S depressed either of two microswitches, located on either side of the left or right hand thumb, to indicate a "Yes" or "No" response. Responding hand was counterbalanced within each stimulus set, along with thumb movement (flexion/extension). S's hand was placed, palm down and comfortably cupped, on a 1 inch thick 12 x 12 in. piece of wood adjacent the tachistoscope. The thumb -39-was placed between two wide Velcro strips glued to the wood. Two small box-shaped microswitches, with a bit of Velcro adhering to each, were then positioned on either side of the thumb and adjusted such that they could be triggered by minimal thumb extension or flexion. The switches were wired to a panel housing a red and a green light, each labelled either "Yes" or "No". These labels matched two which appeared on the wooden board, one above each microswitch. Both the light panel and timer were in f u l l view of another experimenter who recorded the choices made and the response latencies. Neither piece of equipment was visible to S. An air conditioner set on "low" fan speed and "comfort" temperature setting located in the experimental room provided a steady audible background hum. The ambient sound pressure level in the room with the conditioner on measured 52 db. D. Procedure One experimenter manipulated the stimulus materials and provided the "Ready" signals, while another sat out of S's view and recorded response choices and reaction times. Both experimenters were male. On every tr i a l in the session, S was required to do two ' things in the following order: 1) respond to the stimulus as quickly and as accurately as possible by depressing an appropriate microswitch with the thumb, without saying anything aloud; 2) when signalled by E (immediately following timer registration of reaction time), report first the fixation digit and then the stimulus word. The importance of central fixation and of the reporting of the digits was stressed. The red and green light panel was monitored to ensure that S's switch res-ponses matched intended choices as indicated by verbal report. -40-Three conditions were presented to each S (order was counterbalanced across Ss). In each condition, Ss received 32 trials in a l l , 16 per hand. In each set of 16, there were 12 word trials (i.e., each of 6 different category norm words presented in both the left and right visual fields), 2 expletive trials (1 expletive in both fields), and 2 blank card trials. In the Lower-order Categorization (LC) condition, S was shown a cue word printed in large ( l x l inch) block letters and centered on a 6 x 4 in. white card placed upright beside the tachistoscope. The word was the name of one of the four categories (FOUR-FOOTED ANIMAL, BIRD, VEHICLE, WEAPON) and was punctuated with a question mark. S was instructed to study the cue as he would be required to indicate ("Yes" or "No" switch) whether or not each subsequently tachistoscopically-presented stimulus was a member of the cued category. A few seconds elapsed while S studied the cue whereupon he looked into the tachistoscope at the fixation dot and awaited the "Ready" signal from E. The stimulus word set (2 sets of 16 each; one set per hand) presented to S was appropriate to the cue category word, and was constructed such that there were 6 possible correct "Yes" responses (3 different exemplars, each in both visual fields) and 10 correct "No" responses (3 different exemplars of the other 3 categories and 1 expletive, each in both visual fields, plus 2 blanks). The Higher-order Categorization (HC) condition was identical to the LC- condition except that the cue shown to S before the first t r i a l consisted of the label, "LIVING THING?". S's task was to indicate whether or not each stimulus represented an animate object. One of the four different sets of 32 stimuli (16 per hand) was presented. Each of -41-the 16 stimuli subsets was designed such that there were 8 possible correct "Yes" and "No" responses (each stimulus appearing once in both visual fields). In the Simple Recognition (SR) condition, each t r i a l began with E showing S a cue word. S was required to indicate whether or not the cue matched the to-be-presented stimulus. The cues in each stimulus subset were the category exemplars of that subset randomly ordered with the restriction that there be 8 possible correct "Yes" (4 different words, each in both visual fields) and 8 "No" responses. Prior to the actual start of each condition, S was given a few practise trials. The practise format is depicted on the first page of Appendix 1. Trials in which S failed to respond by depressing a microswitch were repeated at the end of the subset, unknown to S. These were seldom more than one or two in number. The entire experiment was completed in approximately one hour. VII. Results and Discussion Separate analyses of variance were performed on reaction time (RT) and error rate (ER) data. Scorable trials were those on which S had centrally fixated (i.e., accurately reported the fixation digit) and on which S had correctly recalled the stimulus word immediately after registering (manual response) his "Yes/No" decision. The mean percentage -42-of scorable trials for the nonpsychopathic (NP) and psychopathic (P) groups was 67.8 and 78.2, respectively. A two-tailed t-test (Hays, 1973) on these percentages failed to reach significance at the .05 level (t = 1.97, p<.10). RT and ER results will be considered separately to avoid giving the reader any impression that these are interchangeable measures of cognitive processing. Although many researchers appear to make this assumption, it has not been justified in the published literature (Posner, 1978). A. Reaction time (RT) Mean RTs were calculated for each subject as a function of level of semantic processing, responding hand, and visual half-field, only for those scorable trials on which S made a correct "Yes/No" decision. Group means of these means are presented in Table 2. These mean RTs tend to be higher overall than those obtained from college students in categorization time research reported in the memory literature (eg., Conrad, 1972).1 Although RT slowing is a salient behavioural feature of brain disease (Hamsher and Benton, 1977) , this aspect of the data cannot be properly discussed until normative data are available on other, non-criminal, male groups for these tasks. Some preliminary data obtained with non-criminal male subjects does suggest that criminals as a group may be slower than "normals". However, this may be a quantitative difference only, as the pattern of RTs across processing levels and visual half-fields appears to be similar to that of the inmates. It should be mentioned here that the reliability of the RT estimates obtained in this study is probably not an issue. Hamsher and Benton (1977) report Spearman-Brown (corrected split-half) reliability coefficients on the order of .90 for both brain-damaged and control subjects on a two-choice RT task with as few as six trials. Furthermore, reliability was unrelated to the particular measure of central tendency chosen (mean, median, reciprocal, log). -43-TABLE 2 Mean reaction times (sec.) and standard deviations (parentheses) SR LC HC Group Hand LVF RVF LVF RVF LVF RVF NP L 1.255 (.465) 1.313 (.431) 2.137 (.940) 1.931 (.740) 1.791 (.552) 1.894 (.712) R 1.252 (.375) 1.348 (.444) 1.917 (.850) 1.922 (.519) 1.784 (.737) 1.920 (.961) P L 1.242 (.343) 1.362 (.332) 1.741 (.481) 1.526 (.330) 1.635 (.458) 1.713 (.475) R 1.176 (.342) 1.244 (.390) 1.760 (.455) 1.601 (.344) 1.607 (.487) 1.952 (.858) SR = Simple Recognition LC = Lower-order Categorization HC = Higher-order Categorization LVF = RVF = Left Visual Field Right Visual Field -44-Reaction time distributions for each group in each experimental condition tended to be positively skewed (i.e., in favour of faster RTs). Prior to analysis of variance, assumptions regarding homogeneity of variance and independence of errors were tested. F tests for homo-geneity of covariance matrices (Winer, 1971) were made between groups at each level of semantic processing. None reached satistical signi-ficance at the .05 probability level. F tests of compound symmetry (Winer, 1971) were computed, one for each error term in the analysis of variance for which there was more than one degree of freedom for a repeated measure factor. None of these reached significance at the .05 level. A 5-way (Subjects x Groups x Levels x Hand x Field) analysis of variance (Table 3.) revealed a main effect of Level (F(2,50) = 26.82, p<.00005) and an interaction of Level with (visual half-) Field (F(2,50) = 5.04, p =.0101) (see descriptions below). There were no statistically significant effects involving Groups (NP vs. P). While error rates differed across various combinations of group, hand, level, and field, i t is unlikely that a speed-accuracy trade-off produced the RT differences. Correlations between RT and ER in the condition combinations tended to be either negligible or positive, for each of the NP and P groups.^  (Table 4.). 1. Levels of processing Simple tests of main effects (Kirk, 1968) assessed visual half-field effects of semantic level. The Field effect for the Simple Recognition (SR) level was not significant (F(l,25) = 2.22, p> .05) Table 5.) The effect for the Higher-order Categorization (HC) level Table 3 Analysis of variance for reaction times Source df Group 1 Subj. w. Groups 25 Level 2 Group x Level 2 Level x Subj. w. Groups 50 Hand 1 Group x Hand 1 Hand x Subj. w. Groups 25 Level x Hand 2 Group x Level x Hand 2 Level x Hand x Subj . w. Groups 50 F i e l d 1 Group x F i e l d 1 F i e l d x Subj. w. Groups 25 Level x F i e l d 2 Group x Level x F i e l d 2 Level x F i e l d x Subj. w. Groups 50 Hand x F i e l d 1 Group x Hand x F i e l d 1 Hand x F i e l d x Subj. w. Groups 25 Level x Hand x F i e l d 2 Group x Level x Hand x F i e l d 2 Level x Hand x F i e l d x Subj. w. Groups 50 SS MS F 1.97399 1.97399 1.00 0.3272 49.41061 1.97642 19.43550 9.71775 26.82 0.0000 1.10954 0.55477 1.53 0.2263 18.11715 0.36234 0.00179 0.00179 0.01 0.9309 0.04860 0.04860 0.21 0.6521 5.83507 0.23340 0.15137 0.07569 0.60 0.5552 0.25691 0.12845 1.01 0.3713 6.35545 0.12711 0.09957 0.09957 1.28 0.2687 0.00112 0.00112 0.01 0.9054 1.94501 0.07780 1.33969 0.66985 5.04 0.0101 0.10496 0.05248 0.40 0.6757 6.64144 0.13283 0.16761 0.16761 2.89 0.1016 0.00004 0.00004 0.00 0.9785 1.45025 0.05801 0.09801 0.04900 0.76 0.4733 0.14229 0.07115 1.10 0.3399 3.22624 0.06452 -46-was significant (F(l,25) = 5.27, p<.05) in favour of the left visual half-field (Table 6.). For the Lower-order Categorization (LC) level the effect was also significant (F(l,25) = 4.36, p<.05), but in favour of the right half-field (Table 7.). The results of these tests are depicted in Figure 4. The double dissociation (Teuber, 1960) between LC and RVF superiority on the one hand, and HC and LVF superiority on the other, indicates that this specialization pattern cannot be explained on the basis of general hemispheric intellectual abilities. The SR results do not support an hypothesis of right visual half-field (RVF) superiority for the recognition of verbal stimuli, per se. The left and right hemispheres appear to be equally adept at processing the range of concrete nouns chosen from the Battig and Montague (1969) norms. The finding is not too surprising. Day (1977, Experiment I) reports similar results with four- and five-letter nouns selected from the Paivio, Yuille, and Madigan (1968) l i s t . It would be difficult to argue that the right hemisphere ability displayed here is due to per-ceptual-feature, and not so much to linguistic, processing of stimuli. The RT data are based upon trails meeting the criteria of central pre-exposural fixation, correct decision, and correct post-exposural verbal recall. Thus, it is fairly safe to say that subjects treated the stimuli as linguistic units and did not make judgments solely on the basis of ini t i a l orthographic features or overall perceptual form. The overall pattern of RT results indicates that cerebral asymmetry of function is amplified with depth of semantic analysis. Unlike the SR condition, both LC and HC conditions demonstrate reliable and approximately equal visual half-field differences (albeit in opposite directions). This does not support Martin's (1978) thesis that lower-level (physical) rather -47-Table 4 Correlations between reaction time (sec.) and error rate Condition Level F i e l d Hand r_ L L .0274 SR R .1062 R L .0874 R .2566 L L .2941 LC R -.0365 R L .4923 ** R .2264 L L .4718 * HC R .1716 R L .0108 R .2290 * p .05 ** p .01 - 4 8 -Table 5 Test of simple main e f f e c t s f o r r e a c t i o n times for v i s u a l h a l f - f i e l d at Simple Recognit ion (SR) l e v e l Source df SS MS F i e l d 1 0.18857 0.18857 2.22 0.1486 F i e l d x Subj . w. Groups 25 2.12197 0.08488 - 4 9 -Table 6 Test of s imple main e f f e c t s f o r r e a c t i o n t imes f o r v i s u a l h a l f - f i e l d a t H i g h e r - o r d e r C a t e g o r i z a t i o n (HC) l e v e l Source df SS MS F i e l d 1 0.71393 0.71393 5.27 0.0304 F i e l d x S u b j . w. Groups 25 3.38969 0.13559 -50-Table 7 Test of simple main effects for reaction times for visual half-field at Lower-order Categorization (LC) level Source df SS MS F P Field 1 0.53676 0.53576 4.36 0.0470 Field x Subj. w. Groups 25 3.07478 0.12299 - 5 1 -LEVEL SR LC HC to o CD co cu E a o •«—• o ra cu ra cu L R L R Visual Half-Field Figure 4 Mean reaction times across groups as function of processing level and visual half-field of presentation -52-than h i g h e r - l e v e l (semantic) processing of words produces a l e f t hemisphere advantage. It i s , however, i n l i n e with regional cerebral blood flow (rCBF) research (Wood, Taylor, Penny, and Stump, 1980) i n which rCBF i s s i g n i f i c a n t l y l a t e r a l i z e d during semantic categorization, but not i n a recognition memory word task. The magnitude of the RT differences between the SR and the two categorization conditions i n the present study suggests the greater cognitive processing requirements of the l a t t e r since a l l of the tasks had common sensory-motor demands. The l a t e r a l i t y patterns obtained i n the HC and LC conditions are unique. The RVF s u p e r i o r i t y i n LC should not be s u r p r i s i n g . Given a r e l i a b l e l a t e r a l i t y e f f e c t i n a verbal task, the published l i t e r a t u r e would not lead one to expect i t to be of any other form. However, Day (1977, Experiments I, II) was unable to produce t h i s e f f e c t i n a s i m i l a r task requiring superordinate c l a s s i f i c a t i o n of concrete nouns ( i e . , there was no s t a t i s t i c a l l y s i g n i f i c a n t v i s u a l h a l f - f i e l d d i f f e r e n c e ) . 1 The concrete categories he chose to use were "Animals", "Clothing", "Furniture", and "Food." These were not selected from a l i s t of superordinates for which published norms (e.g., B a t t i g and Montague, 1969) are a v a i l a b l e , consequently i t i s d i f f i c u l t to determine the e f f e c t of category choice on the v i s u a l f i e l d r e s u l t s . Reaction time, for example, might well be expected to c o r r e l a t e p o s i t i v e l y with category s i z e . Furthermore, the reader i s not t o l d the degree to which the noun s t i m u l i were exemplary of t h e i r respective superordinates. Thus, Day's r e s u l t s are not e a s i l y compared with those for the LC condition i n the present 1 Day did obtain RVF s u p e r i o r i t y when abstract nouns were s i m i l a r l y c l a s s i f i e d , although methodological problems (which he c i t e s ) tend to obscure the concrete vs. abstract d i s t i n c t i o n . -53-experiment. The C o l l i n s and Q u i l l i a n (1969, 1970, 1973) model of semantic memory would predict RT to be an increasing function of the semantic judgment process at successively higher l e v e l s within a memory hierarchy. This i s p r e c i s e l y the r e s u l t which obtains across SR, LC, and HC conditions for the r i g h t v i s u a l h a l f - f i e l d , but not for the l e f t (Figure 4.). In other words, the l e f t hemisphere seems quite capable of processing words within a semantic memory hierarchy of the C o l l i n s and Q u i l l i a n v a r i e t y . In the t y p i c a l i n vestigations of t h i s h i e r a r c h i c a l model, r e l i a b l e r e s u l t s have emerged when reaction time to f u l l v i s u a l - f i e l d s t i m u l i i s measured using v o i c e - or r i g h t hand-activated switches (e.g., C o l l i n s and Q u i l l i a n , 1970; Freedman and Loftus, 1971; Loftus and Freedman, 1972; Loftus and Suppes, 1972). The a v a i l a b l e evidence suggests that both response modes are under the pre-dominant or exclusive c o n t r o l of the l e f t hemisphere (Berlucchi, 1978; Gazzaniga and H i l l y a r d , 1971; Levy and Trevarthen, 1976; Sperry, 1968; White and Kinsbourne, 1980). The pro-portion of right-handers i n the general population i s on the order of 90%, therefore i t i s s t a t i s t i c a l l y probable that the vast majority of subjects i n the memory studies were right-handed, possessing the t y p i c a l pattern of left-hemisphere l i n g u i s t i c dominance. The RVF r e s u l t s of the present study thus constitute a d i s t i l l e d version of those used to support the h i e r a r c h i c a l models, deriving as they do from right-handed subjects under conditions of exclusive left-hemisphere stimulation. This might also explain the greater RT d i f f e r e n c e between LC- and HC-type conditions obtained here than reported i n the memory l i t e r a t u r e . The C o l l i n s and Q u i l l i a n (1971) experiment i s a p a r t i c u l a r l y i n t e r e s t i n g -54-example. A l l subjects were required to use the r i g h t hand to indicate p o s i t i v e category membership decisions and the l e f t hand to s i g n i f y negative instances. S t a t i s t i c a l l y s i g n i f i c a n t r e s u l t s i n favour of the semantic hierarchy i n t e r p r e t a t i o n emerged only for p o s i t i v e instance data ( i . e . , right-hand responses). Negative instance data (left-hand responses) did not conform. The c o n f l i c t i n g motor and/or cognitive processing p r e d i l e c t i o n s of the contralateral:, 1 . r i g h t hemisphere may well have contributed to the l e f t hand's "misbehaviour". Right v i s u a l h a l f - f i e l d performance can be described within the C o l l i n s and Q u i l l i a n framework, but what about the LVF re s u l t s ? Why should r e a c t i o n times i n the LVF be fas t e r i n the HC than i n the LC condition - a r e s u l t opposite to that predicted by the h i e r a r c h i c a l model? In f a c t , why should a supposed verbally-disadvantaged hemisphere display any preference at a l l ? The l i t e r a t u r e supports two types of explanation. The f i r s t assumes that regardless of the v i s u a l h a l f - f i e l d of verbal stimulus presentation, a l l semantic categorization takes place i n the l e f t hemisphere. Nouns a r r i v i n g i n i t i a l l y i n the l e f t hemisphere are processed up the semantic hierarchy. Those f i r s t reaching the ri g h t hemisphere must access the semantic system of the l e f t , but are then processed i n a r a d i c a l l y d i f f e r e n t manner. A second approach to the problem de-emphasizes interhemispheric co-operation during c a t e g o r i -zation and po s i t s instead f u n c t i o n a l l y d i s t i n c t semantic memory hierarchies i n the r i g h t and l e f t hemispheres. This l a t t e r p o s s i b i l i t y w i l l be examined f i r s t . Warrington (1975) studied semantic memory i n three patients with v i s u a l agnosia. Her findings lent support to a h i e r a r c h i c a l memory organization i n -55-these subjects, but one quite different from the Collins and Quillian version. Warrington cites the following as an example of the semantic behaviour of her subjects. A normal subject would respond more quickly to the question, "Is a duck a bird?", than to, "Is a duck an animal?". However, the agnosic patient has less difficulty with the latter question. Warrington uses this as evidence in support of a developmental model of semantic differentiation wherein broad concepts are gradually differentiated. For example, "mallard" would be first discerned as a "living thing" then, later, as an "animal", then "bird", and then "duck", rather than the usual (Collins and Quillian) formulation of "mallard", to "duck", to "bird", to "animal", then to "living thing". This kind of process has been described in children by Clark (1973) . Warrington suggests that developmental patterns of visual differentia-tion and the heavy reliance on this sensory mode of experience are reflected in analogous semantic growth. The net result may be the co-existence in the brain of functionally distinct and modality-specific meaning systems, one primarily verbal, the other visual. Although Warrington does not specify a structural distinction, the left and right hemispheres, respectively, might qualify. Of her three subjects, two displayed neurological signs of left hemisphere abnormality, while in the third damage could not be localized. The visual semantic organi-zation which surfaced in the performance of these patients may well have been that of the intact right hemisphere, as this type of organi-zation is precisely that observed in the left visual half-field per-formance of the inmate subjects in the present study. In other words, localized left-hemispheric damage and tachistoscopic left half-field -56-presentation may, under these circumstances, be similarly exposing the unique semantic system of the right hemisphere. This is relevant to the thesis that the dominant (left) hemisphere normally inhibits the expression of nondominant (right) hemisphere semantic competence (Moscovitch, 1976a, 1976b). It suggests that right hemispheric "illiteracy" may be largely an artefact of testing procedures. That the right hemisphere possesses a rich lexicon and is capable of participating in sophisticated semantic analysis, are propositions for which supporting evidence has been steadily accumulating in recent years (Hecaen, 1978; Zaidel, 1978a, 1978b). As was previously mentioned, the second type of explanation relegates a l l semantic analyses to the left hemisphere, regardless of visual half-field of stimulus presentation. Caplan, Holmes and Marshall (1974) studied the tachistoscopic half-field recognition of three syntactic classes of words with "-er" endings: "pure" unambiguous nouns (i.e., no verb pro-perties), e.g., "river," "lawyer"; verb-derived agentive nouns, e.g., "worker", "teacher"; and, category-ambiguous words like "order" or "murder" which can be used as nouns or verbs. A most interesting finding was that category-ambiguous words were better recognized than unambiguous nouns in the LVF but not in the RVF. This result appeared to Caplan et al. to indicate that in i t i a l right hemisphere presentation facilitates the syntactic analysis of complex items as compared to those which are syntactically simpler. They proposed a mechanism whereby the left hemisphere linguistic system is somehow operated in parallel to determine syntactic class when information arrives trans-callosally from -57-the r i g h t hemisphere. Information i n i t i a l l y received by the l e f t hemisphere i s processed i n s e r i e s beginning with the searching of noun stores. Figures 5a and 5b i l l u s t r a t e how t h i s i n s e r i e s / i n p a r a l l e l , RVF-/LVF-presentation d i s t i n c t i o n may help describe the LC and HC r e s u l t s obtained i n the present study. Figure 5a schematizes the operation i n the l e f t hemisphere of. the type of semantic hierarchy displayed i n Figure 4. A stimulus noun i n i t i a l l y received by t h i s hemisphere i s matched against i t s represent-a t i v e i n a noun store comprising the base of the network. In the SR condition, the noun store representative was primed j u s t p r i o r to the a r r i v a l of the stimulus word. This would be expected to have f a c i l i t a t e d the match/mismatch decision process. If categorization were required, as i n the LC condition, the representative of the cued category i n a higher-l e v e l , category store i s primed. It i s then determined whether or not a s u i t a b l e semantic t i e l i n k s the noun store representative to the appropriate element of the category store - an examination of the stimulus' status as exemplar of the cued category. If higher c a t e g o r i -zation were demanded, as in the HC condition, an element of an even higher l e v e l category store i s primed and a pathway traced from the noun store through intermediate category stores up to the desired l e v e l . The dots between the stores pictured i n Figure 5a i n d i c a t e that there may well be intervening l e v e l s i n the hierarchy other than those three which were chosen f o r t h i s experiment. When an element of a category store i s primed (by cueing), a p a r t i c u l a r semantic hierarchy i s selected out of a l l those which may possibly e x i s t . The primed element i s a s o l i t a r y endpoint. At each descending l e v e l there are increasing numbers -58-Higher - Order Category Store Lower - Order Category Store Rc 1 _ 4 4 I A 4 Rc Noun Store Rs co o Q_ co co CD o o < o CD sz CO-CO E CD CD RvF Presentation Figure 5a Operation of semantic hierarchy within the left hemisphere (S = stimulus noun, Rs = noun store representative, Rc = cued category representative) (see text for explanation). -59-of elements until the exemplar level (noun store) at which there exists the maximum number of units in the selected network. The key feature of Figure 5a is its depiction of the left-hemisphere semantic system as operating in a strictly sequential fashion. Beside each store in the figure is a gap representing a port of access for the right hemisphere to the semantic network of the left. These parallel accesses are pre-sumably via the cerebral commissures in the brain. When a stimulus noun initially enters the right hemisphere, trans-callosal signalling activates a search for a primed representative in the left hemisphere noun store to determine match or mismatch. If cate-gorization is required the right hemisphere selectively samples the hierarchy of the left at the appropriate semantic level, bypassing intermediate levels. This might be accomplished by a process wherein the right hemisphere does not trace a semantic pathway but rather compares attributes of the primed noun and category store elements, in a search for a common feature (or features) which would indicate a suitable semantic kinship. 1 At higher semantic levels stores will contain fewer elements thus making it progressively easier for the right hemisphere to locate the primed category element to compare with the exemplar. Figure 5b illustrates the use (post hoc) of this model for the four combinations of visual half-field presentation and categorization level (LC vs. HC) data obtained in this study. Attribute theories of human memory are certainly not new. The most in-fluential is probably that of Bower (1967, 1972). -60-Lower - Order Categorization Left Hemisphere HC LC J RVF Lett Hemisphere HC 1 LC Right Hemisphere faster than Right Hemisphere Left Hemisphere Right Hemisphere Left Hemisphere Right Hemisphere faster than HC LC _ "fa RVF Higher - Order Categorization Figure 5b Hemispheric processing operations under conditions of visual half - field presentation ( LVF or RVF ) and categorization level (LC = Lower-Order, HC = Higher-Order) (see text for explanation). -61-With RVF presentation,reaction times are fas t e r under LC than under HC conditions since the l a t t e r requires processing further up the semantic hierarchy through intermediate l e v e l s . With LVF presentation, RTs are fas t e r under HC than under LC conditions since i n the former there are fewer elements f or the r i g h t hemisphere to sample and compare with a t t r i b u t e s of the stimulus. In the HC condition RTs should favour the LVF since the category store required i s sampled d i r e c t l y , bypassing intermediate l e v e l s through which l e f t hemisphere processing must proceed. In the LC condition the required l e v e l of categorization i s so close to the exemplar l e v e l i n the hierarchy as to render s e r i a l processing more e f f i c i e n t than the t r a n s c a l l o s a l p a r a l l e l approach of the r i g h t hemi-sphere. The RT data from the present study seem to be adequately described i n t h i s scheme. The absence, too, of a s t a t i s t i c a l l y s i g n i -f i c a n t F i e l d x Hand i n t e r a c t i o n tends to support r i g h t - t o - l e f t hemisphere communication in each of the LC and HC conditions. Within each condition the amount by which RTs favour one v i s u a l h a l f - f i e l d does not s i g n i f i c a n t l y d i f f e r as a function of the hemisphere which i n i t i a t e s the response ( i . e . , as a function of hand). This implies that the l i n g u i s t i c a n a l y s i s i s taking place i n one hemisphere (the l e f t ) only, n e c e s s i t a t i n g communication i n cases of LVF presentation (see Day, 1977, and Moscovitch, 1973, for d e t a i l e d d i s c u s s i o n s ) . However, i t i s u n l i k e l y that t h i s c r o s s - t a l k involves a simple t r a n s f e r of words from r i g h t to l e f t hemisphere with LVF presentation. There i s no l o g i c a l reason why the neural represent-ations of i d e n t i c a l concrete nouns should be degraded under LC conditions and not under HC conditions by the transfer unless the r i g h t hemisphere had f i r s t processed them to some degree (see E l l i s and Sheperd, 1974; -62-Hines, 1976, f o r si m i l a r arguments). Obviously research i s needed to determine i f indeed the l e f t hemi-sphere enjoys a monopoly on verbal semantic a n a l y s i s . 2. Psychopathy The reaction times of psychopathic subjects did not d i f f e r s i g n i -f i c a n t l y from those of nonpsychopathic subjects i n any of the experimental conditions. The pattern of F i e l d x Level performance for both groups was very s i m i l a r (Table 2). The RT r e s u l t s suggest that psychopathic criminals cannot be distinguished from nonpsychopaths on the basis of l a t e r a l i z e d aspects of verbal semantic processing such as speed of recognition and r e t r i e v a l . B. Error r a t e (ER) Errors consisted of f a i l u r e s to decide c o r r e c t l y whether or not stimulus words were matches (SR condition) or category exemplars (LC and HC con d i t i o n s ) . Error rate d i s t r i b u t i o n s f o r each group i n each experimental condition tended to be p o s i t i v e l y skewed ( i . e . , i n favour of smaller error r a t e s ) . P r i o r to analysis of variance, assumptions regarding homogeneity of variance and independence of errors were tested. F t e s t s for homogeneity of covariance matrices (Winer, 1971) were made between groups at each l e v e l of semantic processing. A s i g n i f i c a n t F value was obtained f o r the test made at the HC l e v e l (F(10,2154) =2.06, p <.03). 1 F tes t s of compound symmetry (Winer, 1971) 1 A l l subsequently reported analyses were also performed on transformed (ar c s i n , and square-root) ER values to approach normality and because these transformations produced homogeneous covariance matrices. The r e s u l t s did not d i f f e r from those obtained from the analyses of raw ER data, thus, untransformed r e s u l t s are described to f a c i l i t a t e i n t e r p r e t a t i o n . -63-were computed, one for each error term i n the analysis of variance for which there was more than one degree of freedom for a repeated measure f a c t o r . None of these reached s i g n i f i c a n c e at the .05 l e v e l . Error rates ( i n percentages) were subjected to a 5-way (Subjects x Groups x Levels x Hand x F i e l d ) analysis of variance. The group (NP vs. P) values are presented i n Table 8. There were s t a t i s t i c a l l y s i g n i -f i c a n t main e f f e c t s f o r the Group (F(l,25) = 6.25, p<.02) and Level (F(2,50) = 9.75, p<.0005) f a c t o r s . Interactions emerged f o r Level x Group (F(2,50) = 3.90, p<.03), Level x Group x Hand (F(2,50) = 6.38, p<.005), and Hand x F i e l d (F(l,25) = 4.29, p<.05). The ANOVA i s summarized i n Table 9. The r e s u l t s are depicted i n Figures 6 and 7 (see d e s c r i p t i o n s below). The Group x Hand i n t e r a c t i o n was examined at each of the three processing l e v e l s i n separate analyses of variance (Tables 10-12). The i n t e r a c t i o n was s i g n i f i c a n t at the .05 l e v e l for the HC (F(l,25) = 5.76) and LC (F(l,25) = 5.01) l e v e l s only. The F i e l d e f f e c t was examined separately f o r each l e v e l of Hand (Tables 13 and 14). Neither simple main e f f e c t was s i g n i f i c a n t at the .05 p r o b a b i l i t y l e v e l . 1. Levels of processing The absence of s i g n i f i c a n t e f f e c t s f o r v i s u a l h a l f - f i e l d might suggest that ER i s not as s e n s i t i v e as RT to l a t e r a l i z e d aspects of c o r t i c a l processing (see Springer, 1977). Had there been no subject-grouping, processing l e v e l , and responding hand manipulations t h i s may well have been the simple conclusion. However, s t a t i s t i c a l l y s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s involving Group, Level and Hand factors -64-Table 8 Mean error rates (percent) and standard deviations (parentheses) SR LC HC Group Hand LVF RVF LVF RVF LVF RVF NP L 9.700 (11.965) 11.209 (17.398) 21.218 (17.191) 32.118 (24.330) 17.582 (14.984) 21.509 (19.049) R 12.436 (10.964) 11.364 (17.585) 20.755 (16.344) 15.009 (17.560) 36.055 (26.867) 25.764 (22.808) P L 9.588 (17.677) 8.963 (13.318) 13.656 (12.710) 11.669 (12.977) 6.675 (11.555) 15.731 (20.334) R 5.206 (11.727) 6.456 (12.192) 13.338 (15.678) 18.238 (23.222) 9.588 (18.339) 5.631 (8.677) Table 9 Analysis of variance for error rates I Source df SS MS F P Group Subj. w. Groups 1 25 6570.53138 26262.27164 6570.53138 1050.49087 6.25 0.0193 Level Group x Level Level x Subj. w. Groups 2 2 50 4972.77673 1988.06771 12752.31038 2486.38837 994.03385 255.04621 9.75 3.90 0.0003 0.0267 Hand Group x Hand Hand x Subj. w. Groups 1 1 25 0.02640 136.81895 6221.66322 0.02640 136.81895 248.86653 0.00 0.55 0.9919 0.4653 Level x Hand Group x Level x Hand Level x Hand x Subj . w. Groups 2 2 50 628.45890 2402.19814 9411.08387 314.22945 1201.09907 188.22168 1.67 6.38 0.1987 0.0034 F i e l d Group x F i e l d F i e l d x Subj. w. Groups 1 1 25 33.60008 48.10252 4064.83313 33.60008 48.10252 162.59333 0.21 0.30 0.6533 0.5913 Level x F i e l d Group x Level x F i e l d Level x F i e l d x Subj. w. Groups 2 2 50 76.88962 174.30496 10018.80765 38.44481 87.15248 200.37615 0.19 0.43 0.8260 0.6497 Hand x F i e l d Group x Hand x F i e l d Hand x F i e l d x Subj . w. Groups 1 1 25 771.87283 463.01834 4496.86125 771.87283 463.01834 179.87445 4.29 2.57 0.0488 0.1212 Level x Hand x F i e l d Group x Level x Hand x F i e l d Level x Hand x F i e l d x Subj. w. Groups 2 2 50 592.49795 474.20918 11193.34509 296.24897 237.10459 223.86690 1.32 1.06 0.2754 0.3544 -66-NP RH LH RH LH 35r S R H C L C S R H C L C S R H C L C SRHCLC Processing Level Figure 6 Error rates hand (RH, as a function of group (NP.P), responding LH) and processing level (SR, HC, LC). - 6 7 -Right Hand Left Hand CD cr L R L R Visual Half - Field Figure 7 Error rates across group as a function of visual half-field presentation and responding hand. -68-Table 10 Test of Group x Hand interaction for error rates at Simple Recognition (SR) level Source df SS MS Group x Hand 1 155.82069 155.82069 0.83 0.3702 Hand x Subj. w. Groups 25 4678.72206 187.14888 -69-Table 11 Test of Group x Hand interaction for error rates at Higher-order Categorization (HC) level Source df SS MS Group x Hand 1 1458.34517 1458.34517 5.76 0.0242 Hand x Subj. w. Groups 25 6335.10479 253.40419 -70-Table 12 Test of Group x Hand interaction for error rates at Lower-order Categorization (LC) level Source df SS MS Group x Hand Hand x Subj. w. Groups 1 25 924.85123 4618.92023 924.85123 5.01 0.0344 184.75681 -71-Table 13 Test of simple main effects for error rates for visual half-field in the right hand Source df SS MS Field Field x Subj. w. Groups 1 25 241.69303 4387.72334 241.69303 1.38 0.2517 175.50893 -72-Table 14 Test of simple main effects for error rates for visual half-field in the left hand Source df SS MS Field 1 563.77988 563.77988 3.38 0.0780 Field x Subj. w. Groups 25 4173.97104 166.95884 did emerge - e f f e c t s which did not surface with the RT measure. Error rate cannot merely be considered a substitute f o r RT. ER appears to be more s e n s i t i v e than RT to aspects of semantic analysis divorced from the cerebral l a t e r a l i z a t i o n of input. This s e n s i t i v i t y w i l l be discussed l a t e r i n t h i s t h e s i s . The absence of a v i s u a l h a l f - f i e l d e f f e c t i n the present study i s inconsistent with the bulk of published research i n the area. The t y p i c a l f i n d i n g i s that of greater recognition accuracy i n the r i g h t v i s u a l f i e l d (see White, 1972, for a review). The t y p i c a l paradigm involves having the subject v e r b a l l y report tachistoscopically-presented verbal s t i m u l i . In recent years, some investigators have dropped verbal report i n favour of having subjects make manual responses. Under such conditions, studies have shown either no v i s u a l h a l f - f i e l d s u p e r i o r i t y (e.g., Day, 1977) or, i n at least one instance, a LVF s u p e r i o r i t y (e.g., Gibson, Dimond, and Gazzaniga, 1972). The main problem with the established ( i . e . , pre-1972) research l i e s i n the use of verbal report which, for reasons discussed e a r l i e r i n t h i s t h e s i s , tends to bias r e s u l t s i n favour of RVF presentation. Another problem i s common to v i r t u a l l y a l l published studies wherein subjects made either vocal or manual "Yes/No" or "Same/Different" judgments about tachistoscopically-presented words. Many investigators f a i l e d to exert c o n t r o l over the q u a l i t y of psycho-l o g i c a l processing t h e i r subjects devoted to s t i m u l i . Consequently, i t i s impossible to determine the degree to which subjects made judgments on the basis of perceptual versus l i n g u i s t i c stimulus features. It s i m i l a r l y becomes impossible to describe the verbal mnestic c a p a c i t i e s of the l e f t and r i g h t hemispheres apart from considerations of t h e i r -74-preferred perceptuo-operational modes. In the present study scorable t r i a l s were those on which S not only c o r r e c t l y judged the stimulus but also c o r r e c t l y r e c a l l e d the stimulus word a f t e r r e g i s t e r i n g h i s d e c i s i o n . The assumption i s that i f S were able from t r i a l to t r i a l to r e c a l l the stimulus qua word ( i . e . , as a l i n g u i s t i c unit) then he had judged i t on a l i n g u i s t i c rather than a purely perceptual basis. V i s u a l h a l f - f i e l d d ifferences within each hand condition were quite small (maximum of 3.5%, f o r the l e f t hand) and were not s t a t i s t i c a l l y s i g n i f i c a n t . Errors appeared to be fewer when responses were made by the hand i p s i l a t e r a l to a given v i s u a l h a l f - f i e l d . Few tachistoscopic studies of t h i s nature have manipulated l a t e r a l stimulus-response connections through the requirement of manual responses (Day, 1977, i s one of these). When t h i s type of i n t e r a c t i o n has been assessed, i t has tended to be of the kind described above (e.g., Umilta, Frost, and Hyman, 1972). 2. Psychopathy The ER r e s u l t s show that psychopathic criminals generally made fewer errors than nonpsychopaths, p a r t i c u l a r l y i n the two categorization conditions, and most notably i n the HC condition. The s i g n i f i c a n t Group x Level x Hand i n t e r a c t i o n presents a complicated p i c t u r e . Except for the r i g h t hand data of the NP group, the patterns of ER performance across the three processing l e v e l s for each hand are q u a l i t a t i v e l y s i m i l a r (Figure 6.). Error rates progressively increase as one moves from the SR to the HC to the LC conditions. In the NP group, the r e l a t i v e ER s i t u a t i o n for LC and HC for the r i g h t hand i s reversed r e l a t i v e to that found i n the -75-remaining situations for Group x Hand combinations. In the LC condition, psychopaths were more accurate with the use of the left hand, non-psychopaths with the right. In the HC condition, psychopaths made fewer errors with the right hand, nonpsychopaths with the left. The ER data suggest that psychopaths do differ significantly from nonpsychopaths on verbal semantic processing tasks. However, as was also indicated by the RT data, the two groups do not differ on lateralized aspects of this processing. C. Reaction time and error rate: Joint considerations The concurrent examination of the RT and ER findings illuminates group differences in what might be called "efficient" modes of semantic processing. In the LC condition, both NP and P groups correctly processed stimuli faster (RT) when i t was initially presented in the right visual half-field (see Figure A.). In this circumstance, however, psychopaths responded accurately more often (ER) with the contralateral (i.e., left) than with the ipsilateral hand (see Figure 6.). The reverse was true for nonpsychopaths. In the HC condition, overall efficiency was maximized when psychopaths initially receive stimuli in the left visual field and respond with the contralateral (i.e., right) hand. Nonpsychopathic efficiency, too, was maximized with LVF presentation, but when accompanied by ipsilateral (i.e., left hand), not contralateral response. Figure 8 depicts the most efficient (i.e., fastest and most accurate) stimulus-processing/response organizations for each group in each categorization condition. There is a consistent pattern within each group regardless of semantic condition. Nonpsychopaths ^ fRVF TvFl *r L -»•>«•) R LC HC Figure 8 Most efficient hemispheric processing (fastest RT) and response initiation (lowest ER) operations for NP and P groups in LC and HC semantic conditions (see text for explanation). were more e f f i c i e n t at semantic processing of t h i s kind when a sin g l e hemisphere both received input and i n i t i a t e d response. Psychopathic e f f i c i e n c y seemed to required that the two hemispheres "share the load", so to speak; that i s , one received the input and the other i n i t i a t e d response. The psychopathic pattern would seem to involve a greater degree of hemispheric co-operation than that of the nonpsychopaths. This f i n d i n g , coupled with the generally superior performance of psychopaths, argues against "functional commissurotomy" or "functional disconnection" explanations of psychopathy (e.g., S c h a l l i n g , 1978b). With respect to the neuropsychological model developed from the formulations of Brown (1978, 1977, 1976) and Cleckley (1976) (see Section IV), the expected fi n d i n g was that, i f differences between psychopaths and nonpsychopaths i n verbal semantic processing existed, these would emerge s i g n i f i c a n t l y only at deeper (or higher) l e v e l s of semantic function. Furthermore, i t was predicted that the psychopathic subjects would not be distinguished from the nonpsychopaths on c e r e b r a l l y - l a t e r a l i z e d aspects of t h i s processing. Insofar as RT and ER can be considered to be s e n s i t i v e indices of independent l a t e r a l i z e d and n o n - l a t e r a l i z e d aspects, r e s p e c t i v e l y , of the semantic a b i l i t i e s examined i n t h i s study (and reasons why they should be have already been c i t e d ) , then the expectations have been met. It i s possible at t h i s time only to speculate about d i f f e r e n t i a l s e n s i t i v i t i e s of RT and ER to anterior (frontal) and posterior (temporo-limbic) l o c i of semantic processing. As was found In recent research with aphasics (e.g., Grober et a l . , 1980), the ER measure i n t h i s study was more s e n s i t i v e than RT to group differences i n performance. Unlike the aphasic -78-research, i t i s not possible to speci f y a semantic "dementia" i n one of the two groups i n t h i s study since i t i s not yet known which group performed q u a l i t a t i v e l y more l i k e the "norm". However, the quantitative group d i f f e r e n c e s ( i n favour of the psychopaths) c a l l into question the use of the term "dementia" to describe the verbal semantic a b i l i t i e s of the psychopath. The present i n v e s t i g a t i o n provides evidence that psychopaths do d i f f e r from nonpsychopaths i n semantic function, but more so with respect to evaluative and response strategies (ER r e s u l t s ) than to l a t e r a l i z e d stimulus encoding and analysis processes (RT r e s u l t s ) . More research i s needed on other aspects of semantic function i n psychopathy. 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Cortex, 12, 183-186, 1976. -89-APPENDIX I Tachistoscopic performance score sheets -90-Score Sheets" Subject Number Handedness Vision Test 1. 2. 3. 4. BASS 3 7 LION 9 HEAD 5 Unilateral (80 msec.) EX. 1 2 3 4 5 6 CART 2 TUNA 8 7 9 BULL 8 9 LAMB CRAB SLED CARP BEAR CHIN IS IT CART SLED LAMB CRAB TUNA BULL Presentation Order Glasses/Contacts 4-F00TED ANIMAL? Yes No Yes No Yes No Yes No Yes No Yes No LIVING THING? Yes .Yes Yes Yes Yes Yes No No No No No No CONT'D -91-Aa Hand Cue 4-Footed Animal? L i v i n g Tiling? Rxn. Time D i g i t Word 1 3 BEAR BEAR Yes No Yes No Yes No 2 CROW 2 AUTO Yes No Yes No Yes No 3 BOMB 7 BOMB Yes No Yes No h Yes No 4 4 "^CROW Yes No Yes No Yes No 5 WOLF 2 WOLF Yes No Yes No Yes No 6 6 DEER DEER Yes No Yes No Yes No 7 4 AUTO AUTO Yes No Yes No Yes No 8 S T 5 BEAR Yes No Yes No 1 Yes No 9 BEAR 9 BOMB Yes No Yes No Yes No 10 2 BOMB DEER Yes No ' Yes No Yes No 11 6 CROW Yes No Yes No Yes No 12 4 WOLF WOLF Yes No Yes No Yes No 13 9 S T AUTO Yes No Yes No Yes 14 DEER 2 DEER Yes No Yes No Yes No 15 6 CROW BEAR Yes No Yes No Yes No 16 AUTO AUTO Yes No Yes No Yes No Ab Hand 1 HAWK 4 LION Yes No Yes No Yes No 2 8 LION BOAT Yes No Yes No Yes No 3 2 MULE Yes No Yes No Yes No 4 7 GOAT GOAT Yes No Yes No Yes No 5 4 CLUB CLUB Yes No Yes No Yes No 6 BOAT 7 HAWK Yes No Yes No Yes No 7 3 F K BOAT Yes No Yes No Yes No 8 LION 5 LION Yes No Yes No Yes No 9 5 MULE CLUB Yes No Yes No Yes No 10 5 HAWK Yes No Yes No Yes No 11 GOAT 4 GOAT Yes No • Yes No Yes No 12 CLUB 6 CLUB Yes No Yes No Yes No 13 2 BOAT BOAT Yes No Yes No Yes No 14 F K 6 LION Yes No Yes No Yes No 15 MULE 3 MULE Yes No Yes No Yes No 16 8 HAWK HAWK Yes No Yes No Yes No -92-Ba Hand Cue Bird? L i v i n g Thing? Rxn. Time D i g i t Word 1 7 TAXI LION Yes No Yes No Yes No 2 CROW 2 CROW Yes No Yes No Yes No 3 S__T 4 DOVE Yes No Yes No Yes No 4 7 LARK LARK Yes No Yes No Yes No 5 WHIP 5 WHIP Yes No Yes No Yes No 6 DOVE 6 TAXI Yes No Yes No Yes No 7 9 LARK Yes No Yes No Yes No 8 6 CROW CROW Yes No Yes No Yes No 9 TAXI 8 TAXI Yes No Yes No Yes No 10 3 S T WHIP Yes No Yes No Yes No 11 LARK 5 LARK Yes No Yes No Yes No 12 6 WHIP CROW Yes No Yes No Yes No 13 8 LION LION Yes No Yes No Yes No 14 2 TAXI Yes No Yes No Yes No 15 3 DOVE DOVE Yes No Yes No Yes No 16 LION 5 WHIP Yes No Yes No Yes No Bb Hand 1 HAWK 4 BEAR Yes No Yes No Yes No 2 2 SWAN R O P E Yes No Yes No Yes No 3 B I K E 5 BIKE Yes No Yes No Yes No 4 6 F K DUCK Yes No Yes No Yes No 5 8 HAWK HAWK Yes No Yes No Yes No 6 3 B I K E ' Yes No Yes No Yes No 7 9 R O P E ROPE Yes No Yes No Yes No 8 DUCK 2 DUCK Yes No Yes No I Yes No 9 F__K 7 f SWAN Yes No Yes No Yes No 10 3 B E A R BEAR Yes No Yes No Yes No ] 1 4 DUCK DUCK Yes No le s No Yes No 12 SWAN 9 SWAN Yes No Yes No Yes No 13 5 BIKi Yes No Yes No Yes No 14 R O P E 4 "HAWK Yes No Yes No Yes No 15 B E A R 9 B E A R Yes No Yes No Yes No 16 2 BIKE SWAN Yes No Yes No Yes No -93-V a Hand L i v i n g Rxn. Cue Vehicle? Thing? Time D i g i t Word i GOAT 4 GOAT Yes No Yes No Yes No 2 S T 8 JEEP Yes No Yes No Yes No 3 2 BIKE BIKE Yes No Yes No Yes No 4 4 AUTO SWAN Yes No Yes No Yes No 5 5 ROCK ROCK Yes No Yes No Yes No 6 9 GOAT Yes No Yes No Yes No 7 AUTO 5 AUTO Yes No Yes No Yes No 8 6 S T BIKE Yes "No~1 Yes No Yes No 9 2 SWAN SWAN Ye3 ~No I Yes No Yes No 10 ROCK 3 JEEP Yes No Yes No Yes No 11 JEEP 4 AUTO Yes No Yes No Yes No 12 8 SWAN Yes No Yes No Yes No 13 7 GOAT GOAT Yes No Yes No Yes No 14 BIKE 5 BIKE Yes No Yes _ _ _ , Yes No 15 3 JEEP AUTO Yes No Yes No Yes No 16 SWAN 9 SWAN Yes No Yes No Yes No Vb Hand 1 2 BOAT DEER Yes No Yes No Yes No 2 LARK 5 LARK Yes No Yes No Yes No 3 7 TAXI TAXI Yes No Yes No Yes No 4 F K 5 BOAT Yes No Yes No Ye3 No 5 PIPE 2 PIPE Yes No Yes No Yes No 6 3 SHIP SHIP Yes No Yes No Yes No 7 7 LARK DEER Yes No Yes No Yes No 8 4 TAXI Yes No Yes No Yes No 9 BOAT 7 BOAT Yes No Yes No Yes No 10 4 F K SHIP Yes No Yes No Yes No 11 3 PIPE PIPE Yes No Yes No Yes No 12 TAXI 8 TAXI Yes No Yes No Yes No 13 DEER 2 LARK Yes No Yes ™ N o i Yes No 14 9 BOAT Yes No Yes . No Yes No 15 SHIP 6 PIPE Yes No Yes No Yes No 16 6 DEER DEER Yes No Yes No Yes No Wa Hand - 9 4 -Cue MULE 1 2 3 4 5 6 7 8 9 10 3.1 12 1 3 14 15 S__T 16 AUTO W H I P ROCK DUCK BOMB 2 BOMB AUTO WHIP S T ROCK DUCK MULE Weapon? Living Thing? Rxn. Time Digit Word GOAT Yes No Yes No Yes No >ROCK Yes No Yes No Yes No WHIP Yes No Yes No Yes No AUTO Yes No Yes No Yes No BOMB Yes No Yes No Yes No ROCK Yes No Yes No Yes No 1 DUCK Yes No Yes No Yes No 1 WHIP Yes No Yes No Yes No Mule Yes No Yes No Yes No BOMB Yes No Yes No Yes No WHIP Yes No Yes No Yes ' No ROCK Yes No Yes No Yes No AUTO Yes No Yes No Yes No MULE Yes No Yes No Yes No DUCK Yes No Yes No Yes No BOMB Yes No Yes No Yes No Wb Hand 1 4 4- DOVE 8 3 5 4 PIPE 2 5 SHIP 6 6 9 7 F K 9 8 WOLF 2 9 7 10 3 11 4 12 CLUB 6 13 5 14 3 15 ROPE 4 16 3 CLUB ROPE DOVE WOLF F K PIPE SHIP CLUB Yes No Yes No Yes No DOVE Yes No Yes No Yes No ROPE Yes No Yes No Yes No WOLF Yes No Yes No Yes No DOVE Yes No Yes No Yes No ROPE Yes No Yes No Yes No SHIP Yes No Yes No Yes No WOLF Yes No Yes No Yes No CLUB Yes No Yea No Yes No DOVE Yes No Yes No Yes No 1 PIPE Yes No Yes No Yes No CLUB Yes No Yes No Yes No SHIP Yes No Yes No Yes No PIPE Yes No Yes No Yes No ROPE Yes No Yes No Yes No WOLF Yes No Yes No Yes No 

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