Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Interference and coding processes in verbal and visual short-term memory Ternes, Willi 1973

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1973_A1 T47_7.pdf [ 4.86MB ]
Metadata
JSON: 831-1.0101030.json
JSON-LD: 831-1.0101030-ld.json
RDF/XML (Pretty): 831-1.0101030-rdf.xml
RDF/JSON: 831-1.0101030-rdf.json
Turtle: 831-1.0101030-turtle.txt
N-Triples: 831-1.0101030-rdf-ntriples.txt
Original Record: 831-1.0101030-source.json
Full Text
831-1.0101030-fulltext.txt
Citation
831-1.0101030.ris

Full Text

INTERFERENCE AND CODING PROCESSES IN VERBAL AND VISUAL SHORT-TERM MEMORY by WILLI TERNES B.A., U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1969 M.A., U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in t h e Department of Psychology  We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1973  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r  an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the  L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e  and study.  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department or by h i s r e p r e s e n t a t i v e s .  I t i s understood t h a t copying or p u b l i c a t i o n  of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my written  permission.  Psychology Department o f The U n i v e r s i t y o f B r i t i s h Vancouver 8, Canada  D a t e  July 2 0 1 9 7 3  Columbia  ABSTRACT A d e t a i l e d e v a l u a t i o n of short-term  v e r b a l and v i s u a l  coding  e f f i c i e n c y as a f u n c t i o n of Interpolated a c t i v i t i e s , varying along t h e d i m e n s i o n s o f a t t e n t i o n and s i m i l a r i t y , was undertaken i n t h i s The  research.  r e s u l t s show t h a t r e t e n t i o n l o s s e s due t o a t t e n t i o n demand changes a r e  comparable In v e r b a l and v i s u a l c o d i n g of t h e Interpolated a c t i v i t y . t h e same m o d a l i t y task.  Retention  Is involved  c o n d i t i o n s , regardless of the modality  In a d d i t i o n , r e t e n t i o n l o s s e s a r e l a r g e r when i n processing  t h e s t i m u l u s and I n t e r p o l a t e d  losses a r e Interpreted as demonstrating a c l e a r separa-  t i o n o f short-term  l o s s e s due t o :  a ) a t t e n t i o n d i v e r s i o n ; and b) d i r e c t  Interference, with a t t e n t i o n d i v e r s i o n accounting total  retention losses.  Information  for a larger part of  The d a t a f u r t h e r s u g g e s t t h a t t h e maintenance o f  In v e r b a l and v i s u a l STS r e l i e s t o a l a r g e e x t e n t on t h e  a v a i l a b i l i t y o f t h e common c e n t r a l p r o c e s s i n g s p e c i f i c coding  processes determining  for a given stimulus  situation.  capacity, with  t h e most a p p r o p r i a t e  modality  c o d i n g mode  ii  T A B L E OF CONTENTS  ABSTRACT  .  I  T A B L E OF CONTENTS  II  L I S T OF APPENDIX  I TABLES  L I S T OF APPENDIX  II  LIST  Ill  TABLES  Iv  OF FIGURES  .  ACKNOWLEDGEMENT GENERAL  vt  INTRODUCTION  EXPERIMENT  I  -  •  Introduction  39  Method Results EXPERIMENT  II  -  42 and D i s c u s s i o n  47  Introduction  55  Method Results DISCUSSION  -  EXPERIMENT  III  v  EXPERIMENTS -  56 and D i s c u s s i o n . I and  .  57  I I  61  Introduction  67  Method Results  70 and D i s c u s s i o n  72  GENERAL DISCUSSION  •  •  •  83  SUMMARY  •  •  •  97  REFERENCES  99  APPENDIX  I  -  T A B L E S OF MEANS  105  APPENDIX  II  -  ANOVA T A B L E S  HI  iii  L I S T OF APPENDIX  Table  I.  Recall  Table  2,  Mean In  Table  3.  4.  Values  5.  Visual  and  II  106  Coding Groups  Verbal  Coding Groups  Ml  108 of  Verbal  Mean P e r c e n t a g e Experiments  I  107  Mean P e r c e n t a g e s and  Experiments  TABLES  III  for  Experiment  Visual Table  for  Experiment  Mean R e c a l l in  Table  Scores for  I  of  I and  Correct  Stimuli Correct II  Recall  In  for  Experiment  Recall  III  109  tn 110  iv  LIST OF APPENDIX II Table I.  TABLES  ANOVA for Correct Reproductions In Experiment I  Table 2.  112  Newman-Keuls Test f o r Treatment E f f e c t s for Correct Reproductions in Experiment I  113  Table 3.  ANOVA for d' Scores in Experiment I  114  Table 4.  Newman-Keuls Test for d* Scores in Experiment I  Table 5.  115  ANOVA for Recall Scores in Experiment II  Table 6.  116  Newman-Keuls Test for Treatment Effect in Experiment II  Table 7.  117  ANOVA for Correct Reproductions of Visual Patterns in Experiment III  Table 8.  118  ANOVA for d ' Scores of Visual Pattern Reproductions In Experiment III  Table 9 .  ANOVA for Verbal Recall Errors In Experiment III  Table 10.  119  ...  120  Analysis of Simple Effects f o r AB Interaction of Verbal Recall Errors in Experiment i l l  121  V  L I S T OF FIGURES F i g u r e I . Mean S c o r e s f o r C o r r e c t R e p r o d u c t i o n s o f V i s u a l P a t t e r n s In E x p e r i m e n t I F i g u r e 2.  48  Mean d' S c o r e s f o r V i s u a l C o d i n g in Experiment I  F i g u r e 3.  Mean C o r r e c t R e c a l l  49 Scores  i n E x p e r i m e n t II F i g u r e 4.  58  Mean V a l u e s o f C o r r e c t R e p r o d u c t i o n s o f V i s u a l P a t t e r n s i n Experiment I I I  F i g u r e 5.  Mean V a l u e s o f V e r b a l R e c a l l  ••••  75  Scores  in Experiment I I I F i g u r e 7.  74  Mean d' S c o r e s f o r V i s u a l C o d i n g In E x p e r i m e n t Ml  F i g u r e 6.  .,  76  Percentage Values f o r Correct Recall i n E x p e r i m e n t s I and II  86  vi  ACKNOWLEDGEMENT I would  l i k e t o e x p r e s s my a p p r e c i a t i o n f o r the h e l p f u l  comments  and s u g g e s t i o n s of D r s . Ray C o r t e e n , Dennis F o t h , Ron M a r t e n i u k , and John Y u i l l e i n the w r i t i n g of t h i s p a p e r .  I am e s p e c i a l l y  indebted  t o D r . John Y u i l l e f o r h i s c o n t i n u o u s s u p p o r t which made t h i s possible.  research  I GENERAL INTRODUCTION The e m p i r i c a l and t h e o r e t i c a l I s s u e s e v a l u a t e d I n t h i s I n t r o d u c t i o n c e n t e r a r o u n d t w o a s p e c t s o f t h e c u r r e n t s t a t e o f knowledge a b o u t human memory.  In t h e I n i t i a l t o p i c , r e s e a r c h e v i d e n c e and t h e o r e t i c a l p o s i t i o n s  are d i s c u s s e d which a r e d i r e c t l y concerned  with problems Inherent In t h e  a r g u m e n t s u n d e r l y i n g t h e c o n c e p t u a l i z a t i o n o f memory a s e i t h e r a u n i t a r y o r a dichotomous system.  Within t h e context o f t h i s d i s c u s s i o n t h e emphasis  i s p l a c e d o n r e s e a r c h I n v e s t i g a t i n g s h o r t - t e r m memory (STM) p r o c e s s e s .  Issues  c o n c e r n e d w i t h s e n s o r y memory (SM) and l o n g - t e r m memory (LTM) a r e o n l y p e r i p h e r a l l y I n t r o d u c e d t o p r o v i d e an o v e r a l l framework f o r a g e n e r a l model o f memory.  With r e s p e c t t o t h e arguments p e r t a i n i n g t o a u n i t a r y versus  d i c h o t o m o u s memory, I . e . , t h e need t o p o s t u l a t e q u a l i t a t i v e l y s i m i l a r o r q u a l i t a t i v e l y d i f f e r e n t p r o c e s s e s f o r STM and LTM, two a r g u m e n t s a r e forwarded.  F i r s t , r e s e a r c h d a t a o b t a i n e d i n s t a n d a r d STM and LTM p a r a d i g m s  a r e r e v i e w e d , and t h e c h a r a c t e r i s t i c f e a t u r e s o b s e r v e d a s a f u n c t i o n o f t h e d i f f e r e n t p a r a d i g m s a r e u t i l i z e d i n s u p p o r t o f a d i c h o t o m o u s memory  system.  S e c o n d , STM r e s e a r c h d e m o n s t r a t i n g o t h e r t h a n s h o r t - t e r m p r o c e s s i n g c h a r a c t e r i s t i c s a r e e v a l u a t e d w i t h r e s p e c t t o t h e n a t u r e o f t h e STM p a r a d i g m s u s e d , and t h e s p e c i f i c p a r a m e t r i c c o n s i d e r a t i o n s employed i n s u c h I t I s argued  experiments.  i n l i g h t o f t h i s e v a l u a t i o n t h a t a s t r i c t adherence t o para-  m e t r i c c o n s i d e r a t i o n s o f t h e s t a n d a r d STM p a r a d i g m p r o v i d e s an i n t e r p r e t a t i o n o f STM d a t a c o n s i s t e n t l y i n s u p p o r t o f a d i c h o t o m o u s memory  system.  Once I t i s t e n t a t i v e l y a c c e p t e d t h a t q u a l i t a t i v e l y d i f f e r e n t a r e i n v o l v e d i n STM and LTM s i t u a t i o n s , t h e s e c o n d  processes  issue i s introduced  w h i c h p r o v i d e s t h e g e n e r a l framework f o r t h i s r e s e a r c h .  Of m a j o r c o n c e r n  In t h i s t o p i c I s t h e d e t a i l e d e v a l u a t i o n o f s h o r t - t e r m p r o c e s s e s .  Evidence  Is o u t l i n e d which supports t h e e x i s t e n c e o f q u a l i t a t i v e l y d i f f e r e n t coding  2  p r o c e s s e s i n STM e x p e r i m e n t s , I . e . , r e v i e w of t h e l i t e r a t u r e  v e r b a l and v i s u a l c o d i n g .  i t f u r t h e r becomes a p p a r e n t t h a t  In t h e  information  about v e r b a l s h o r t - t e r m p r o c e s s e s i s more c o m p l e t e than i n f o r m a t i o n visual processes.  D e s p i t e the i n c o m p l e t e I n f o r m a t i o n ,  however,  about  there  appears t o be s u f f i c i e n t e v i d e n c e t o p o s t u l a t e s e p a r a t e v e r b a l and visual short-term processes. theoretical  As a r e s u l t of t h i s r e v i e w t h e  following  q u e s t i o n i s posed as t h e b a s i s of t h i s r e s e a r c h :  e x t e n t a r e v e r b a l and v i s u a l s h o r t - t e r m c o d i n g p r o c e s s e s o r independent from each o t h e r ? Investigate t h i s theoretical  problem makes use of a f a c t o r i a l  s t i m u l u s c o d i n g s i t u a t i o n s ; b) I n t e r p o l a t e d  activities differing  activities differing  of t a s k demands w i t h i n each m o d a l i t y o f t h e d i m e n s i o n of t a s k d i f f i c u l t y ,  interpreted  i.e.,  with  verbal versus  with respect to  difficulty  interpolated a c t i v i t y .  The  i n terms of a t t e n t i o n demands,  Is Introduced t o e v a l u a t e the e f f e c t s of t h e c e n t r a l i n v e r b a l and v i s u a l c o d i n g .  combination  a) v e r b a l and v i s u a l  r e s p e c t t o t h e m o d a l i t y of the I n t e r f e r e n c e t a s k , Interpolated  inter-related  The e m p i r i c a l approach proposed t o  of t h r e e major d i m e n s i o n s of t h e STM p a r a d i g m :  v i s u a l ; and c )  t o what  V e r b a l and v i s u a l  p r o c e s s i n g component  Interpolated  t a s k s are  Introduced t o f u r t h e r e x p l o r e the n a t u r e of the c o d i n g p r o c e s s e s f o r each s t i m u l u s c o d i n g s i t u a t i o n . Evidence f o r STM C u r r e n t approaches t o human memory i n c o r p o r a t e a r a t h e r  widely  a c c e p t e d framework of s e v e r a l b a s i c p r o c e s s e s and mechanisms which a r e c o n s i d e r e d as n e c e s s a r y a s p e c t s of an adequate memory m o d e l . d i s t i n c t i v e d i f f e r e n c e s can be d e t e c t e d among approaches of t h e o r i s t s , t h e r e appears t o be a t  Though various  l e a s t a g e n e r a l agreement t o  postulate  3  separate memory systems for STM and LTM functions.  C e r t a i n l y , research  u t i l i z i n g the operational d i s t i n c t i o n s underlying STM end LTM has generated consistent evidence supporting the concept of a dichotomous human memory. The need to d i s t i n g u i s h between memory processes along a loosely defined temporal continuum had already been realized by William James (1890).  James proposed a dichotomous memory system based on speculations  about d i f f e r e n t i a l  attentional  demands underlying what he c a l l e d primary  and secondary memory processes.  Within t h i s system, primary memory  processes were said to be involved when information was recalled which had not yet l e f t consciousness, i . e . ,  which had been attended to continuously.  Recall of information which had been absent from consciousness for some time,  In c o n t r a s t , r e l i e d on secondary memory processes.  The nature of  the r e c a l l process provided a further d i s t i n c t i o n between the two systems. The stored information in primary memory, for Instance, was readily available for r e c a l l , while recall from secondary memory required active search and r e t r i e v a l  processes.  model of William James  Common elements between the descriptive  and current models appear unmistakable.  Isolated  instances supporting his ideas for a dichotomous memory appeared in the following decades in the work of Wundt and Ebblnghaus on memory span capacity ( c f ^ K l n t s c h , 1970).  However, i t was not u n t i l these d e s c r i p t i v e  notions could be investigated by the operational d i s t i n c t i o n s Introduced by Brown (1958) and Peterson and Peterson (1959) that the current trend in memory research f u l l y emerged. The current operational d i s t i n c t i o n s between STM and LTM include the following major considerations of basic experimental manipulations.  Experi-  ments investigating memory after s i n g l e , brief stimulus presentations, with  4  retention  intervals of up to 15-30 seconds, are usually considered as  displaying STM processes.  In contrast, experiments using repeated  long stimulus presentations and retention  trials,  Intervals ranging as long as  hours, or weeks, are defined as LTM research.  Research based on t h i s  operational d i s t i n c t i o n has In turn generated r e s u l t s which suggest qualitatively STM.  d i f f e r e n t underlying mechanisms and processes in LTM and  Long-term memory c h a r a c t e r i s t i c s include, among others, an unlimited  storage capacity, indefinite retention of stored information, and elaborate coding, storage, and r e t r i e v a l mechanisms.  In contrast, the basic  c h a r a c t e r i s t i c s proposed for STM include a limited storage capacity, a coding mechanism which r e l i e s predominantly on verbal-acoustic features of the stimulus m a t e r i a l , and an active rehearsal mechanism. Evidence for d i s t i n c t STM c h a r a c t e r i s t i c s has been obtained in a variety of experimental manipulations.  An outline of supportive evidence  for these c h a r a c t e r i s t i c s presents a rather convincing picture for the verbal acoustic interpretation  of STM.  Research demonstrating factors  not included in a verbal acoustic STM framework, such as nonverbal or semantic f a c t o r s , is excluded from the discussion at t h i s time, and w i l l be added at a later point. Storage capacity, as already mentioned, has been investigated by Ebblnghaus and Wundt around the turn of the century and found to be around six items (Kintsch, 1970). Miller  Similar results were obtained by  (1956)' who found the immediate memory span to be seven items, plus  or minus two, whether employing d i g i t s , l e t t e r s or words.  Further  evidence for a limited STM capacity can be extracted from a comparison of t r i a d (Murdock,  1963) and 12 item (Glanzer and C u n i t z , 1966) free r e c a l l .  5  STM c h a r a c t e r i s t i c s were obtained in the t r i a d study but appeared only for the last few items in the free recall task.  In other words, only the  last few items had been recalled from STM, while the e a r l i e r either  lost from STM or recalled from LTM.  items were  A s l i g h t l y different conceptua-  l i z a t i o n of storage capacity is suggested by Atkinson and S h i f f r l n who treat the limited storage capacity in terms of a rehearsal i.e.,  the capacity of the rehearsal mechanism.  the rehearsal buffer reorganizational  (1968),  buffer,  The size or capacity of  in t h i s model is in turn determined by input and  factors of a given experimental  situation.  In other  words, the evidence for a limited or fixed STM capacity appears to be rather c o n s i s t e n t , and, furthermore, would have to be expected simply in light of the temporal defines of the STM paradigm. The second important feature of STM centers around the predominantly verbal-acoustic e f f e c t s obtained In STM experiments.  Probably the  first  indication of t h i s c h a r a c t e r i s t i c was reported by Sperling (I960, 1963), who postulated an "auditory information stage" in immediate memory as a result of observing a large number of auditory confusion errors with t a c h i s t o s c o p i c a l l y presented s t i m u l i . from a theoretical  The Implication of t h i s finding  viewpoint appears rather  important since i t suggests  that coding in short-term recall r e l i e s strongly on auditory-acoustic features of the stimulus material. to coding e f f e c t s importance.  These findings are quite in contrast  in LTM, where semantic c h a r a c t e r i s t i c s are of more  A more detailed evaluation of verba I-acoustic e f f e c t s  in  STM was subsequently derived from a basic paradigm which investigates types of error scores when a c o u s t i c a l l y similar or d i s s i m i l a r items are used as stimulus material.  The generally consistent findings in t h i s  6  experimental  situation can be summarized by the following conclusions:  a) substitution errors tend to be  acoustically  confusing Items; and  b) the error score Is higher with a c o u s t i c a l l y s i m i l a r than d i s s i m i l a r lists.  These detrimental  e f f e c t s of acoustic s i m i l a r i t y were consistently  demonstrated under a variety of changes In experimental manipulations. For instance, acoustic interference e f f e c t s appeared when using strings of consonants, whether the letters were a u d i t o r a l l y presented and embedded in noise (Conrad, 1964) or presented v i s u a l l y (Wickelgren, 1965).  Further-  more, the acoustic s i m i l a r i t y effect was also obtained with words, homophones, in a recall task (Wickelgren, 1966).  i.e.,  (Kintsch and Buschke, 1969) or In a recognition Thus, the consistency of these results strongly  supports the proposition that coding in STM r e l i e s largely on verbal acoustic properties of the stimulus, in contrast to LTM. The t h i r d c r i t i c a l aspect of STM is the rehearsal mechanism, a concept c l o s e l y tied to memory capacity on the one side and v e r b a l acoustic coding on the other s i d e .  Evidence for the functional significance  of the rehearsal mechanism derives from comparing two experimental operations, i.e.,  rehearsal versus  interval  interference  In an STM task.  a c t i v i t i e s during the retention...  Murdock (1963) found recall of t r i a d s and  trigrams to decrease to a probability of .08 a f t e r 15 to 18 seconds of verbal interference. retention  In contrast, if rehearsal  i n t e r v a l , r e c a l l for l e t t e r s , words and sentences has been shown  to increase over a ten second delay interval 1966).  is allowed during the  (Crawford, Hunt, and Grahame,  The f a c l l i t a t i v e e f f e c t s of rehearsal, in contrast to verbal  Interference, have been further substantiated with verbal material recall and recognition (Ternes and Y u i l l e , 1972).  Furthermore, by  in  7  combining the two operations within a single experimental  setting,  recall  can be e f f e c t i v e l y manipulated by introducing repetition  (HeI Iyer,  1962)  or rehearsal  (Stonner and Muenziger, 1969)  ference task during the retention  before the onset of the  inter-  interval.  The current d i s t i n c t i o n between STM and LTM i s , however, not only based on behavioral data.  Neurological evidence has also contributed a  convincing argument for a dichotomous memory.  In f a c t , t h e o r i s t s such  as Atkinson and S h i f f r i n (1968) consider the e f f e c t s of hippocampal lesions as the most convincing demonstration of a dichotomy in the memory system.  Milner (1968), for instance, found that patients with hippo-  campal lesions appeared to display normal immediate memory functions as tested by d i g i t span and dichotic listening tasks.  At the same time,  there appeared to be no loss of preoperative Iy acquired s k i l l s .  However,  the patients appeared incapable of adding new information to the long term s t o r e .  Buschke (1968) confirmed these findings using a missing scan  procedure on patients with b i l a t e r a l  hippocampal lesions.  He concluded  from his r e s u l t s that the patients suffered from a I e a r n i n g d e f i c l t , displayed normal immediate memory functions.  but  Also in support of these  results is a later study of Baddeleyand Warrington (1970) with amnesic patients.  In e f f e c t , the implications of the neurological evidence is  quite consistent with a dichotomous memory model.  Since STM functions  as well as preoperative LTM information appear to be normal, while no new information can be added to LTM, the notion of some type of memory compartmentalization appears quite f e a s i b l e . In summary, data from two widely divergent research approaches, such as behavioral and neurological research, present consistent evidence for  8  the concept of a dichotomous memory. has to be q u a l i f i e d by additional clusion.  However, t h i s i n i t i a l  Interpretation  research data contradicting t h i s con-  For instance, there has also been data questioning the consistency  of the above reported neurological findings (Robbins and Meyer,  1970).  Since neurological evidence is based on only isolated research examples, however,  i t appears premature at t h i s time to consider the unitary versus  dichotomous controversy f u l l y resolved on the basis of t h i s line of research.  In a d d i t i o n , the dichotomous interpretation  has also come  under attack by researchers stressing the e f f e c t s of semantic factors in behavioral argument  research of STM functions ( e . g . , Wickens, 1970).  in t h i s context  is the following:  The  if semantic f a c t o r s ,  i.e.,  LTM c h a r a c t e r i s t i c s , play an important role in STM functions, there is no need to postulate separate memory systems. Behavioral data of t h i s nature point out a c r u c i a l the interpretation  issue underlying  of general STM research within the context of the  unitary versus dichotomous memory controversy.  As stated at the beginning of  t h i s introduction, there are two interdependent  factors underlying the  general concepts of STM and LTM.  On the one hand, there are  d e f i n i t i o n s describing the s p e c i f i c experimental memory is t e s t e d ,  i.e.,  there are q u a l i t a t i v e l y  STM versus LTM paradigms.  operational  situations under which On the other hand,  d i s t i n c t c h a r a c t e r i s t i c s ascribed to memory  mechanisms and processes which are operative as a result of the s p e c i f i c experimental  paradigms, i . e . ,  STM versus LTM c h a r a c t e r i s t i c s .  In  light  of the number of variables involved, and the rather vaguely defined boundaries of parametric values of these variables in the two operationally d i s t i n c t paradigms, the interpretation  of a given experiment  In terms of  9  the usually obtained c h a r a c t e r i s t i c processes of the paradigm is not always unequivocal.  For example, in a s e r i a l recall task,  standard LTM paradigm, the recency e f f e c t processes.  In other words, i t  is interpreted  i.e.,  a  in terms of STM  is possible to obtain STM c h a r a c t e r i s t i c s ,  in addition to LTM c h a r a c t e r i s t i c s , in a standard LTM paradigm.  A  similar argument can be made for results obtained in STM experiments. Given, for instance, an STM experiment which r e f l e c t s data contrary to the standard STM c h a r a c t e r i s t i c s , such as semantic coding e f f e c t s , two types of interpretations are possible:  a) STM contains other than  standard STM c h a r a c t e r i s t i c s ; or b) the given experiment tested other than STM processes.  While both interpretations  j u s t i f i e d , there is a certain c i r c u l a r i t y  appear to be equally  in the interpretation of STM  data wtth respect to the unitary versus dichotomous controversy.  With  a predisposition towards a unitary model, a researcher may argue that evidence for LTM c h a r a c t e r i s t i c s obtained in STM experiments the need to postulate separate memory systems.  eliminate  Conversely, with a pre-  disposition towards a dichotomous system, a researcher  uiay  argue that LTM  c h a r a c t e r i s t i c s obtained in STM experiments merely provide examples showing that LTM processes may occur under c e r t a ' n experimental an STM paradigm.  conditions within  In a subsequent part of the introduction t h i s writer  w i l l argue that the c i r c u l a r i t y of both positions may be resolved by a s t r i c t adherence to parametric considerations of the STM paradigm. Theoretical Conceptualizations of STM Based on the above types of experimental models have been proposed. next.  evidence several memory  Examples of these models w i l l be outlined  While some of these models contain descriptions of other aspects  10  of memory, i . e . ,  sensory memory and LTM, only STM functions of the models  w i l l be considered in t h i s context. w i l l be mentioned only If  Sensory memory and LTM functions  relevant to the discussion of p a r t i c u l a r STM  processes. One of the e a r l i e r memory models was developed by Waugh and Norman (1965, 1968), who proposed a simple quantitative method to separate longterm and short-term functions.  B r i e f l y , t h e i r aim was to obtain a  s t a t i s t i c a l estimate of memory performance in a probe-procedure and then apply t h i s estimate to the data of a series of published free-recalI and paired associate studies.  The success in predicting STM functions in  these two standard long-term memory paradigms led them to postulate two d i s t i n c t memory processes, primary and secondary memory, in the line of William James (1890).  In t h i s model, primary memory was hypothesized  to contain a limited storage capacity in which retention was attributed to overt or  covert rehearsal.  Rehearsal was explained in terms of  attention and was attributed a dual role in primary processing: a) re-entering items into primary memory; and b) transferring items into secondary memory.  Loss of information from primary memory was described  in terms of input and output interference, such that input Interference was determined by the number of Items presented during the  retention  Interval and output interference by the number of items recalled before the c r i t i c a l t e s t  item.  In e f f e c t , a basic framework for STM was  established displaying the limited storage capacity, as well as the rehearsal and interference functions which applied to processes observed in an STM task.  At the same time, the model succeeded in separating  STM and LTM processes in standard LTM paradigms.  11  Neisser (1967) proposed separate visual and auditory  temporary  memory systems, stressing the functional s i g n i f i c a n c e of these systems as transitory types of memory processes lying between the perception of an item on one side and the active memory on the other.  Within the  temporal defines of the standard STM paradigm, i . e . , 15 to 30 seconds, Neisser distinguished between echoic memory and the active verbal memory.  Echoic memory in t h i s system can be considered as analogous to  sensory memory.  The active verbal memory, in contrast, appears to describe  what i s usually called STM.  In other words, with respect to the concept  of primary memory, as proposed by Waugh and Norman, Neisser subdivides the concept into two parts.  The f i r s t part is explained in terms of  attention and the second part described in terms of the three STM c h a r a c t e r i s t i c s , i . e . , predominantly acoustic coding, the importance of the rehearsal mechanisms, and limited memory capacity.  In e f f e c t , Neisser  incorporates STM c h a r a c t e r i s t i c s into a d i s t i n c t system within a broader model of human memory. While these two models show a certain amount of agreement on the general conceptualization of STM functions, several models opposing t h i s general framework have also emerged.  Based on a d i f f e r e n t  line of  research methodology, Laughery (1972) proposed a computer simulation model of STM. By rejecting the notion of item displacement in STM, and making use of decay as well as rehearsal functions, Laughery proposes an STM model of unlimited storage capacity.  However, the model js r e s t r i c t e d  to one s p e c i f i c task and a total of only 36 input Items.  In light of  these r e s t r i c t i o n s , the a p p l i c a b i l i t y of t h i s model f o r human memory at t h i s time suffers from crucial shortcomings, though o p t i m i s t i c predictions  12  with an extension of tasks and Input Items are o f f e r e d . A complete rejection of the dichotomous memory hypothesis has recently been expressed by Murdock (1972).  While he admits that short-  term e f f e c t s must be explained by any memory model, he proposed that t h i s could be accomplished using a f i n i t e - s t a t e decision model.  However,  Murdock's approach appears to be more applicable In evaluating STM functions in f r e e - r e c a l l and pal red-associate learning, than in the investigation of processes observed in standard STM research.  Furthermore, his main objec-  t i o n "why such modal models ( i . e . , two store models) must be wrong is that in a very general sense they are incompatible with what we know about grammatical utterances" ( p . 9 1 ) .  While It w i l l c e r t a i n l y be necessary to  interpret STM processes within a broader f i e l d of cognitive processes, an attempt already made by Neisser (1967), the lack of knowledge about both problems make an integration at t h i s stage rather premature.  Murdock's  evaluation then appears to be more of an exposition of problems Inherent in a dichotomous memory, than a convincing argument for a unitary memory system. Probably the most f r u i t f u l current model using the concept of separate memory systems has been developed by Atkinson and S h i f f r i n (1968).  Sub-  divided into the sensory memory (SM), short-term store (STS), and long-term store (LTS), the model presents a comprehensive account of memory research within a single theoretical  framework.  For instance, an attempt is made  to d i s t i n g u i s h between structural features and control processes within each subsystem.  The basic invariant memory mechanisms, such as the  rehearsal buffer, are defined as structural features, and s i t u a t i o n s p e c i f i c task requirements, such as Instructional  s e t , are considered as  13  control processes.  Though the potential usefulness of these concepts Is  undeniable, the lack and d i f f i c u l t y of experimental v a l i d a t i o n make these additions to memory models s t i l l  highly t e n t a t i v e .  Furthermore, a clear  d i s t i n c t i o n Is made in t h i s model between STM and STS, a d i s t i n c t i o n based on the operational versus the theoretical aspects in memory experiments.  Hence, the term STM applies to the operational d e f i n i t i o n of the  experimental s i t u a t i o n , and STS pertains to mechanisms and processes which may be displayed In an STM experiment.  In light of t h i s d i s t i n c t i o n ,  it  becomes possible to treat the results of an STM task in terms of STS and LTS functions, depending on the c h a r a c t e r i s t i c features obtained in the given experiment.  Within t h i s general framework, Atkinson and S h i f f r i n  incorporated the previously mentioned STM c h a r a c t e r i s t i c s , i . e . , capacity, verbal-acoustic coding, and a rehearsal mechanism. within t h i s system are described In the following way. I s presented, a u d i t o r a l l y or v i s u a l l y , it  limited  STS processes  When a stimulus  is registered in the sensory  memory and immediately coded in a verbal-acoustic form and maintained in the rehearsal buffer.  From there i t  is transferred to LTS, where organizational  and semantic features of the stimulus are stored.  The rehearsal  buffer,  therefore, has the dual role of maintaining items in STS, as well as some undetermined transfer function in moving information to LTS. the rehearsal buffer can be lost by displacement if the  Items in  information  exceeds the buffer capacity, and can also be lost if attention  is  diverted from the rehearsal process by an interpolated a c t i v i t y . the a v a i l a b i l i t y of a given amount of Information in STS Is by the rehearsal process and reduced:  Thus,  facilitated  a) by an information overload;  and b) by an interruption of the rehearsal process by attention  diverting  14  activities. The d i v e r s i t y of these memory models creates an interesting question as to the j u s t i f i c a t i o n of the different theoretical various researchers.  positions taken by  In other words, how is i t possible that from the  broad f i e l d of STM research different theoretical conceptualizations of short-term processes emerge. particular experimental  Probably an obvious reason l i e s in the  paradigm which is preferred as the research tool  for investigations of these processes.  For instance, In free r e c a l l and  PA learning (Murdock, 1972), different aspects of short-term processing might be investigated than by the probe or d i s t r a c t o r technique (Atkinson and S h l f f r i n , 1968).  However, if one considers the latter as  a more refined research tool to investigate short-term processes, contradictory r e s u l t s can also be obtained which, in t u r n , j u s t i f y theoretical  positions.  different  In the following discussion, a detailed evaluation  of the standard STM paradigm (Peterson and Peterson, 1959) w i l l be undertaken in order to expose several sources within the experimental  situation  which underlie contradictory results and subsequently iead to the d i v e r s i t y of theoretical p o s i t i o n s . Variations on a Theme by Peterson and Peterson In the standard Peterson and Peterson paradigm (1959) the following sequence of events occurs. a retention  A brief stimulus is presented, followed by  interval during which S_may be required to perform an  additional task.  F i n a l l y , a memory test of the stimulus is made.  Within t h i s experimental  setting there are three major factors contribu-  ting to the results and interpretation of a given experiment.  First,  the stimulus presentation contains a series of variables which a f f e c t  15  response p r o b a b i l i t y :  a) the c h a r a c t e r i s t i c s of the stimulus material;  b) the modality of presentation; c) the duration of presentation; and d) the information load. interval.  The second major factor l i e s In the  The basic e f f e c t s in t h i s category are due t o :  retention  a) duration  of the retention i n t e r v a l ; and b) the type of interpolated a c t i v i t y be performed by S_. response measure.  The third source of response v a r i a b i l i t y Different  to  l i e s in the  response patterns can be obtained as a  function of the response demands, e . g . , recall versus recognition, and the temporal constrains of the response task. f a c t o r s , and t h e i r  Examples of each of these  interactions, w i l l be considered next in an attempt  to evaluate t h e i r relationship to theoretical  interpretations of STM  experiments. It should be noted that basic s i m i l a r i t i e s can be identified  between  operational variables in the Peterson and Peterson task and other paradigms Investigating  STM processes.  For example, response trends generated by  the manipulation of the stimulus duration variable in a Peterson and Peterson task are not unlike the e f f e c t s obtained due to changes In the presentation rate in an STM s e r i a l recall experiment.  Therefore, con-  clusions can in many instances be generalized to problems inherent  in  other paradigms used to investigate STM functions. I  The Stimulus Condition  a)  Stimulus Material Some of the examples of the e f f e c t s of the stimulus material  dimension have already been mentioned.  Differential  a c o u s t i c a l l y s i m i l a r and d i s s i m i l a r material  error scores with  have been i n f l u e n t i a l  in  16  considering STS as a predominantly verbal acoustic memory system (Atkinson and S h i f f r i n , 1968).  However, when words are contrasted with  pictures in an STM task (Ternes and Y u i l l e ,  1972) evidence is obtained  which cannot be Interpreted within a verbal STS framework.  In f a c t , a  considerable amount of data has accumulated supporting the existence of a visual, i.e.,  non-verbal, STS.  This evidence has been obtained under  a variety of experimental t a s k s , such as Tversky's (1968) demonstration of visual and verbal coding preferences a f t e r a one second retention interval and a demonstration of visual coding e f f e c t s by Parks, Parkinson, and KrolI (1971) after a 25 second retention i n t e r v a l .  Research of t h i s  nature does not detract from the general assumption that a verbal acoustic memory system e x i s t s .  Rather, i t suggests that another type of coding  can be demonstrated within the confines of an STM framework. about the necessary additions are, however, s t i l l  Details  controversial.  While  a visual STS currently receives a great amount of a t t e n t i o n , evidence for kinesthetic STM (Posner, 1967) also has to be considered. b)  Presentation Modality The method of presentation of the stimulus m a t e r i a l ,  i.e.,  auditory  or v i s u a l , has been shown to r e s u l t in similar or d i f f e r e n t response patterns, depending on the experimental s i t u a t i o n under study.  Error  scores for a c o u s t i c a l l y s i m i l a r and d i s s i m i l a r consonants display a consistent trend whether obtained under auditory presentation (Conrad, 1964) or visual presentation (Wickelgren, 1965).  Murdock (1972) in con-  t r a s t , reports a consistent auditory over visual superiority in STM when employing the free recall paradigm.  Furthermore, response differences  can be obtained with visual presentations if the visual presentation  17  consists of either verbal or p i c t o r i a l material of familar objects (Ternes and Y u i l l e , 1972) or face drawings (Tversky, 1969).  Thus, the  inter-  action between presentation modality and other task variables again generates contradictory r e s u l t s , providing evidence for verbal as well as non-verbal coding in STM experiments. c)  Stimulus Duration Apart from peripheral problems pertaining to c e i l i n g or f l o o r e f f e c t s  as determined by the duration of a stimulus presentation, the major theoretical  problem inherent in t h i s discussion pertains to the type of  coding processes which can occur under given stimulus durations.  Paivio  and Czapo (1969), f o r instance, have demonstrated that the presentation time for a word or picture has to be reduced to around 200 m seconds in order to prevent cross-modality coding, that i s , in order to reduce verbal coding of pictures and visual coding of words. In a d d i t i o n , q u a l i t a t i v e l y d i f f e r e n t types of verbal coding processes can be identified with verbal material duration dimension.  due to changes in the stimulus  The focal point of the argument here pertains to  the question of whether acoustic as well as semantic types of coding occur in STS.  Baddeley (1964) has c l e a r l y demonstrated q u a l i t a t i v e l y  different  coding processes within the s t r i c t confines of the operational manipulations of the STM and LTM paradigm.  He concludes that verbal coding in  STM r e l i e s predominantly on acoustic features of the stimulus, whereas coding in LTM r e l i e s predominantly on semantic features of the stimulus information.  However, semantic coding in STM experiments has also been  reported ( e . g . , Dale and Gregory, 1966; Wickens, 1971; Wickens and Eckler, 1968).  Evidence of t h i s nature shows that there can be l i t t l e argument  18  that semantic e f f e c t s can be obtained in an STM experiment.  However,  within the s t r i c t confines of the STM paradigm, semantic e f f e c t s can quite readily be attributed to the parametric considerations of a given experimental s i t u a t i o n .  In a comprehensive review of t h i s problem, Shulman  (1971) concludes that semantic coding can be demonstrated in STM t a s k s , i f S_ is given s u f f i c i e n t time to make use of other than acoustic coding processes.  For example, if the stimulus duration in a verbal coding  STM experiment is changed from a minimum to a maximum within the vague defines of the STM paradigm, the parametric changes can lead to r e s u l t s supporting acoustic as well as semantic coding.  While the basic paradigm  can be considered in terms of STM, the theoretical evaluation of processes underlying the results can be interpreted  in terms of STS and LTS processes.  That i s , with a minimum stimulus duration, the predominant coding mode should be a c o u s t i c , and the e f f e c t s can be interpreted functions.  With a maximum stimulus duration, the possible influence of  LTS processes cannot be ignored. under t h i s c o n d i t i o n , the actual acknowledged. denied.  in terms of STS  If  semantic coding e f f e c t s do occur  involvement of LTS processes must be  However, the c i r c u l a r i t y of this argument cannot be  After a l l , a researcher with a predisposition towards a unitary  memory model can equally argue that there is no need to postulate a dichotomous system since s i m i l a r coding c h a r a c t e r i s t i c s can be obtained in LTM as well as STM experiments. one important issue:  The latter p o s i t i o n , though, ignores  parametric changes in the experimental paradigm  lead to quantitative as well as q u a l i t a t i v e changes in the experimental results. attributed  Semantic coding effects in STM, therefore, can be largely to LTS involvement as a function of parametric changes in the  19  STM paradigm. In summary, changes in stimulus duration can lead to cross-modality coding in a comparison of verbal and visual material, thereby influencing the argument of verbal versus visual STS. changes with verbal material processes, i . e . ,  Furthermore, stimulus duration  can lead to q u a l i t a t i v e l y d i f f e r e n t coding  acoustic versus semantic.  Unless parametric values of  the STM paradigm are c a r e f u l l y considered, the c l e a r d i s t i n c t i o n between coding processes In STS and LTS with respect to acoustic and semantic coding is diminished. are instrumental  However, if  it  is admitted that parametric changes  in generating not only quantitative  but also q u a l i t a t i v e  differences, a conceptualization of STS and LTS in terms of acoustic and semantic coding is supported. d)  Memory Load Changes in memory load are ultimately  memory capacity ( M i l l e r ,  1956).  It  free recall w i l l generate d i f f e r e n t intervals than triad recall  r e s t r i c t e d by the  immediate  is therefore not surprising that 12 item response patterns over retention  (Glanzer,  1972).  of the immediate memory capacity, d i f f e r e n t i a l  Even within the defines response patterns are  observed between single item, t r i a d , and trigram recall  (Murdock, 1963).  In a d d i t i o n , with a constant information load d i f f e r e n t i a l  response  patterns can be obtained as a function of the type of stimulus presentat i o n and the presentation times per Item.  Paivio and Czapo (1969)  demonstrated t h i s effect by presenting either words or pictures of familar objects at two d i f f e r e n t  presentation rates.  constant information load, d i f f e r e n t i a l  Hence, given a  results can be obtained by changing  20  other relevant dimensions of the experimental task.  In other words, if  the  information load across experiments is not comparable, d i f f e r e n t i a ! response patterns can be expected in STM research.  As long as interactions of  various c r u c i a l variables with memory load are not c l a r i f i e d , contradictory conceptualization of STS c h a r a c t e r i s t i c s can be expected. II  Retention  a)  Duration  Interval  The length of the retention retrieve the response. interval  interval may affect the store S_ uses to  For instance, if a r e l a t i v e l y  is employed, It  "long" rehearsal  becomes impossible to a t t r i b u t e the response level  to a s p e c i f i c retention mechanism, i . e . ,  STS or LTS.  postulated processes involved i l l u s t r a t e s t h i s point.  A description of the F i r s t , it  is assumed  that the information enters the verbal rehearsal buffer, where i t temporarily stored and a v a i l a b l e for r e t r i e v a l .  is  Second, there is an unknown  transfer function between the buffer and LTS, such that a f t e r a "long" rehearsal  interval  the stimulus information may be either s t i l l  buffer or already in LTS.  in the  With respect to the previously mentioned issue  regarding acoustic versus semantic coding in STM, i t should not be d i f f i c u l t to obtain evidence for semantic coding if the information has been retrieved from LTS (Shulman, 1971). obtained after a r e l a t i v e l y interpreted  In e f f e c t , the interpretation of responses long retention  interval cannot be confidently  in terms of STS processes alone.  c h a r a c t e r i s t i c s might be attributed  Consequently, other than STS  to STM, unless parametric considerations  are c a r e f u l l y evaluated. A similar problem e x i s t s on the other end of the duration continuum  21  with regard to very short retention i n t e r v a l s .  Ternes and Y u i l l e (1972,  1973) have found that in a six item recognition sequence the f i r s t recognition item, i f presented immediately after the stimulus, decreases the recognition level of the subsequent items in the sequence.  This observa-  tion is not unlike the masking e f f e c t obtained in sensory memory experiments.  Thus, by changing the duration of the retention interval  STM experiment, the results can be e f f e c t i v e l y  in an  influenced at both ends  of the continuum by factors inherent in sensory memory or LTS. b)  Type of Interpolated A c t i v i t y Since t h i s p a r t i c u l a r problem will be discussed in more detail  In  the next s e c t i o n , only a general statement concerning the d i v e r s i t y of results due to interpolated a c t i v i t y effects w i l l be presented at t h i s point.  Rehearsal a c t i v i t y during the retention interval  has been shown  to increase, decrease, or result in no change with respect to an immediate memory t e s t , depending on the type of material  and type of  performance measure of the p a r t i c u l a r experimental s i t u a t i o n 1968; Posner, 1967; Ternes and Y u i l l e , 1972). activity  Similar'y,  (Milner,  interpolated  e f f e c t s defined as interference conditions interact with material  and response task to produce either the response measure (Glanzer,  increases, decreases, or no changes in  1972; Kintsch, 1970).  In a d d i t i o n ,  polated task e f f e c t s are influenced by the s i m i l a r i t y of the  interpolated  a c t i v i t y to the stimulus material and by the d i f f i c u l t y of the activity.  Differential  inter-  interpolated  results of t h i s nature therefore have to be  evaluated in light of the s p e c i f i c experimental manipulations introduced in a given experiment, in order to obtain some type of consistent pattern of interpolated a c t i v i t y e f f e c t s ,  22  I 11  Response Measures In addition to quantitative  response changes due to temporal con-  s t r a i n t s on the response task, q u a l i t a t i v e l y  different  said to underlie recall and recognition performance. and retrieval  responses are In r e c a l l , storage  processes are involved, and recognition is considered as  a purer estimate of storage (Kintsch, 1970; Murdock, 1972).  Again,  examples of contradictory response patterns due to response measures can be found by a comparison of Murdock (1972) and previously reported results investigating acoustic s i m i l a r i t y e f f e c t s (Baddeley, 1966).  Murdock reports a higher response level  1964; Wickelgren,  in recognition experiments,  while Baddeley as well as Wickelgren find an equally strong acoustic similarity effect  in both r e c a l l and recognition experiments.  Further-  more, in a series of experiments contrasting these two response measures, Ternes and Y u i l l e (1972) found evidence for d i f f e r e n t i a l recognition and recall conditions.  coding under  Words as well as pictures were shown  to be coded verbally in free r e c a l l , whereas pictures were coded v i s u a l l y in the recognition task.  In e f f e c t ,  qualitatively  coding strategies can be obtained depending on task demands.  different Changes  in task demands therefore may contribute some information to the issue of verbal versus non-verbal c h a r a c t e r i s t i c s in STS.  It should be noted  though that response differences in t h i s context are not concerned with immediate response l e v e l s , but with response trends over  retention  i ntervaIs. To summarize the impact of these examples with respect to theoretical arguments concerning the notion of STM, several tentative statements can  23  be made regarding two d i s t i n c t questions:  a) does the evidence favour  a dichotomous or a unitary memory modei; and b) to what extent can nonverbal processes be identified With respect to the f i r s t  in an STM experiment? issue, i . e . ,  unitary versus dichotomous  memory systems, i t has been shown that changes in a series of variables of the STM paradigm may lead to contradictory conclusions about t h i s issue.  Apart from quantitative differences in the information load  between STS and LTS, as well as the postulated existence of a rehearsal mechanism, the c r u c i a l factor d i f f e r e n t i a t i n g  the two systems is the  q u a l i t a t i v e l y d i f f e r e n t coding system attributed to each.  Unless STS and  LTS are c l e a r l y d i f f e r e n t i a t e d along the acoustic versus semantic coding dimension, the need to postulate q u a l i t a t i v e l y d i f f e r e n t memory systems is greatly reduced. STM research pertaining to the dichotomous versus unitary question generates two possible viewpoints.  The p a r t i c u l a r preference of one over  the other in t h i s case seems to be largely determined by the researcher's emphasis on a s t r i c t adherence to parametric considerations of the STM-LTM paradigms. effects.  After a l l , there are STM experiments reporting semantic coding However, if these STM experiments are evaluated in light of  STM parametric considerations, i t becomes evident that changes, such as in stimulus duration and retention  i n t e r v a l , constitute experimental  sources leading to LTS involvement in STM experiments.  In other words,  i t cannot be denied that semantic coding can occur in STM, however, these e f f e c t s can be attributed  to LTS functions.  S i m i l a r l y , acoustic coding  can be demonstrated in LTM experiments, which would detract l i t t l e from  24  the importance of the predominantly semantic e f f e c t s in LTS.  In light of  the contradictory results which can be obtained due to changes in the basic paradigms, t h i s writer prefers the conceptualization of STS and LTS in terms of q u a l i t a t i v e l y  d i s t i n c t coding c h a r a c t e r i s t i c s , thereby  adhering to the idea of a dichotomous memory system. If the assumptions underlying a dichotomous memory system can be accepted, the s p e c i f i c c h a r a c t e r i s t i c s underlying STS can be evaluated. The conceptualization of a verbal STS has been proposed in detail by Atkinson and S h i f f r i n  (1968).  Even in t h i s model the addition of a  visual STS has been acknowledged, depending on c l a r i f i c a t i o n by future research.  Since then, STS research evaluating crucial v a r i a b l e s , such  as presentation mode, stimulus material, and response demands, provides strong evidence for the existence of visual processes in STS.  A clarifi-  cation of s p e c i f i c c h a r a c t e r i s t i c s of the visual system in STS is s t i l l outstandi ng. In light of this discussion of experimental  variables in the STM  task, two d e f i n i t e conclusions can be drawn about the current state of knowledge regarding memory models.  F i r s t , contradictory results can be  obtained within the general STM research area, which can be attributed to parametric changes and interactions of c r i t i c a l basic STM paradigm.  As a result of these contradictory f i n d i n g s , it can  be expected that opposing theoretical it  dimensions of the  positions will emerge.  Second,  is apparent that s u f f i c i e n t evidence is available which points out the  incompleteness of each STM model, especially with respect to the evidence for non-verbal processes.  25  The second conclusion Is of importance in the context of t h i s paper. If a visual STS can be postulated on the basis of current information,  it  is of importance to e s t a b l i s h : a) to what extent t h i s visual STS is independent from verbal STS; b) what i t s c h a r a c t e r i s t i c features are; and c) what, i f any, common elements can be identified between the visual and verbal STS.  A detailed evaluation of research data with respect to these  theoretical questions will follow  In order to create the framework of  the problem to be investigated in t h i s research project. The Problem As noted above, the possible existence of other than verbal coding processes in STS was acknowledged by Atkinson and S h i f f r i n (1968), but was at that time only considered as a possible extension of the model to be c l a r i f i e d by further research.  Since that time, convincing examples  of visual coding processes in STM experiments have been demonstrated in a variety of experimental  situations.  Information from t h i s type of research  can be divided into two basic aspects:  a) visual coding for  immediate  response conditions; and b) investigations of visual coding over shortterm retention i n t e r v a l s .  The emphasis in the latter case centers on the  rehearsal functions of visual coding, and e f f e c t s of various  interpolated  a c t i v i t i e s on visual coding. Visual coding for immediate response conditions has been demonstrated by researchers such as Posner (1969) and Tversky (1969).  For instance,  in a l e t t e r matching task, reaction time was shown to be faster when judgements are based on physical rather than naming properties of the comparison s t i m u l i , if the two letters were separated by an interval of  26  less than one second (Posner, Boles, Eichelman, and T a y l o r , 1969).  In  the same experiment, however, i t was also shown that the superiority of a physical match disappears when the interstimuI us interval to two or more seconds.  In a similar experimental  is expanded  s e t t i n g , Tversky (1969)  investigated verbal and visual coding processes by using schematic faces and their well  learned nonsense names as comparison s t i m u l i .  In each  block of t r i a l s , Ss were presented with either word or picture s t i m u l i , followed a f t e r one second by the comparison stimuli of either  presentation  mode.  words or  The presentation mode of the comparison s t i m u l i , i . e . ,  p i c t u r e s , within each block of t r i a l s  wss always presented in a ratio  of eight to one, such that in a given block of t r i a l s , S_could always build up expectations regarding the most frequently occurring presentation mode.  The results of t h i s experimental setting showed that reaction  times for same-different judgements, regardless of the presentation mode of the f i r s t stimulus within each block, were always faster for the most frequently occurring presentation mode of the second stimulus. verbal material  Thus,  was shown to be coded verbally as well as v i s u a l l y , and  p i c t o r i a l material  was shown to be coded v i s u a l l y as well as v e r b a l l y ,  depending on S_'s expectations of the most frequent mode. Experiments of t h i s nature present consistent data which cannot be interpreted  in terms of a verbal STS.  In a d d i t i o n , recent evidence from  neurological Iy oriented research supports the idea of d i s t i n c t verbal and visual aspects in short-term processes.  The theoretical  framework  for t h i s type of research is based on the general assumption of hemispheric asymmetry in the context described by theorists such as Lenneberg  27  (1967).  That Is,  language processes predominantly involve the  left  hemisphere, whereas non-verbal or spatial processing is evident in the right hemisphere.  Assuming l e f t hemispheric dominance of speech and  language functions, and assuming right hemispheric dominance of non-verbal processes, i t can be expected that verbal and visual stimulus material presented in a matching task to the right or l e f t visual f i e l d should result in reaction time patterns showing a relationship between the presentation mode of the stimulus and the respective hemispheric dominance. Geffen, Bradshaw,and Wallace (1971)  confirmed these expectations.  stimuli resulted in faster reaction times when processed in the  Verbal  left  language hemisphere, and conversely, non-verbal s t i m u l i , such as faces, were processed faster in the right spatial hemisphere.  Additional  support for hemispheric asymmetry has been obtained in a memory scanning task (Klatzky,  1970; Klatzky and Atkinson, 1971).  Both experiments agree  on the general findings that test stimuli requiring spatial matching are processed faster by the right hemisphere and t e s t stimuli using verbal processing are processed faster by the l e f t hemisphere. gation of t h i s problem (Geffen, Bradshaw, and Nettleton,  A further  investi-  1972) points out  that reaction time differences must be Interpreted in terms of hemispheric asymmetry as well as interhemispheric transfer of  information.  It should also be pointed out that in the experiments reported, the evidence for l e f t hemispheric dominance is always more pronounced.  In-  complete as t h i s line of research may be, i t contributes a strong argument for verbal and visual processing in STM functions. In light of these research examples, the existence of d i s t i n c t visual  28  and verbal coding processes for immediate response conditions in STM experiments is consistently supported.  If verbal and visual short-term  processes are postulated in immediate response conditions, i t becomes of further  interest to evaluate the functional c h a r a c t e r i s t i c s of these  coding processes within the total temporal range of the STM paradigm. In order to determine c h a r a c t e r i s t i c features of the verbal STS, the e f f e c t s of rehearsal and interference conditions on verbally coded material were evaluated over short-term retention i n t e r v a l s .  Conversely, character-  i s t i c features of the visual STS should be obtained in an evaluation of similar interpolated a c t i v i t i e s on v i s u a l l y coded material.  The basic  aim of t h i s evaluation is to determine what types of common properties as well as d i s t i n c t differences can be identified  in the verbal and visual  coding system. With respect to rehearsal effects in visual STS, two contradictory research findings are to be reported at t h i s time.  On the one s i d e , there  is evidence that u n f i l l e d retention intervals lead to an improvement in recognition of faces (Milner, response (Posner, 1967).  1968) and accuracy of a visual location  Furthermore, Cohen and Granstrom (1970) show  recognition of p i c t o r i a l material to be higher a f t e r retention  intervals  f i l l e d with rehearsal a c t i v i t y compared with visual interpolated  activity.  In contrast to the f a c i l i t a t i v e e f f e c t s of rehearsal on v i s u a l l y coded material, Ternes and Y u i l l e (1972) did not obtain performance differences of v i s u a l l y coded material  a f t e r rehearsal or verbal  interference.  The  lack of an e f f i c i e n t rehearsal mechanism in visual STM has also been demonstrated by Potter and Williams (1970).  29  The basic question posed in these experiments centers on whether visual  information can be maintained over STM intervals without any  retention  losses, or even improvements in retention as has been shown in  verbal STS.  The assessment of t h i s question i s , however, not easy.  There are two possible evaluation methods available in this case.  One,  the rehearsal effect can be assessed with respect to the immediate r e c a l l or recognition l e v e l .  Two, rehearsal e f f e c t s can be assessed with respect  to interference conditions using the same retention  interval.  In the  f i r s t case, the assessment of the rehearsal e f f e c t can be d i s t o r t e d , since responding at zero delay has been shown to be a possible interference cond i t i o n in i t s e l f  (Ternes and Y u i l l e , 1972).  Therefore, the response level  obtained at zero delay does not always constitute an accurate reference level  in the evaluation of the rehearsal  effect.  In the second type of assessment, the problem of cross-modality encoding appears as a c r u c i a l f a c t o r .  As already mentioned in the context  of verbal STS, cross-modality coding can be reduced by a reduction in stimulus presentation time (Paivio and Czapo, 1969).  In other words,  unless cross modality coding is reduced, i t becomes necessary to distinguish between recognition of visual material and recognition r e f l e c t i n g predominantly visual coding.  That i s , if visual material  is presented for a  long duration, correct recognition of the information might be due to a combination of visual and verbal coding.  With a long duration for  stimulus presentation, a f a c i l i t a t i v e e f f e c t would have to be expected simply on the basis of the verbal rehearsal e f f e c t .  With respect to t h i s  operational r e s t r i c t i o n , only the Potter and Williams (1970) as well as  30  the Ternes and Y u i l l e (1972) experiments qualify as investigating visual coding e f f e c t s ,  it  is therefore not surprising to note the  different  conclusions drawn about the visual rehearsal mechanism by the latter two experiments in contrast t o M i l n e r  (1968) and Posner (1967).  Though within  t h i s context the arguments favour a rejection of the rehearsal mechanisms in visual STS, the evidence appears by no means conclusive at t h i s stage. Since the e f f e c t s of cross-modality coding have been shown to underly  contradictory conclusions about the existence of a visual rehearsal  mechanism, s i m i l a r problems can be expected in assessing effects when v i s u a l , p i c t o r i a l material  is used.  interference  Hence, unless i t can  be established that cross-modality coding of visual material detrimental  is reduced,  effects due to interference conditions have to be expected,  and can be interpreted  in terms of the f a m i l i a r  loss in verbal STS.  Interference e f f e c t s in the visual STS have been investigated within a theoretical  framework highly compatible with the neurological data  pertaining to hemispheric asymmetry. is processed in the l e f t ,  That i s , if a given verbal stimulus  language hemisphere, storage of this stimulus  is more affected when the interpolated a c t i v i t y requires verbal processing, i.e.,  processing by the l e f t hemisphere, than if the interpolated  requires processing by the r i g h t , v i s u a l - s p a t i a l hemisphere.  activity  A similar  prediction about stimulus processing can be made about the right hemisphere.  In other words, the notion of modality s p e c i f i c interference  e f f e c t s is in agreement with the present knowledge about hemispheric asymmetry.  Though research investigating t h i s p a r t i c u l a r aspect of  modality s p e c i f i c interference has not been reported, general STM research  31  investigating the problem supports t h i s proposition.  It should be noted  though, that differences in modality s p e c i f i c interference should be r e l a t i v e l y small.  Gel I en et al_. (1972) have already demonstrated the  existence of interhemispheric t r a n s f e r , even if the stimulus presentation is r e s t r i c t e d to the l e f t or right visual f i e l d .  Subsequently, an even  larger amount of transfer of information between visual and verbal processes can be expected if the stimulus is presented to both visual f i e l d s , i.e.,  to the language and spatial hemispheres simultaneously. Research Investigating the problem of modality s p e c i f i c interference  effects within the behavioral research framework generates rather consistent support for t h i s proposition.  Margrain (1967), for instance, reports  a stronger interference e f f e c t for r e c a l l of v i s u a l l y presented words following written than verbal  interpolated a c t i v i t y .  Furthermore, in an auditory  shadowing task r e c a l l suffered more for a u d i t o r i a l l y than for v i s u a l l y presented l e t t e r s ,  but only a f t e r a 25 second retention interval  Potter, Parkinson, Bieber,and Johnson, 1970). paradigm (Parks, Parkinson,and K r o l l ,  (Kroll,  In an expansion of t h i s  1971), recall performance for v i s u a l l y  presented letters was shown to be superior to a u d i t o r i a l l y presented after auditory shadowing.  letters  Posner (1969), in summarizing some of his own  research, establishes a type of hierarchy of interference factors of the visual code. a c t i v i t y may,  The • introduction of a single auditory d i g i t as interpolated or may not,  have an e f f e c t , depending on the amount of  practice S_ has with the experimental  situation.  Adding visual d i g i t s as  an interpolated a c t i v i t y has a s i g n i f i c a n t detrimental e f f e c t on the visual code.  The concept of hierarchial  interference conditions has also been  32  demonstrated with nonverbal material case with simple stimulus f i g u r e s . loss of p i c t o r i a l material  (Cohen and Granstrom, 1970), in t h i s Apart from showing a larger recognition  due to visual rather than verbal  interpolated  a c t i v i t y , Cohen and Granstrom obtained an increase in recognition losses with a corresponding increase in the task demands of the visual polated a c t i v i t y .  Further support for a selective loss of  by means of visual and verbal by den Heyer and Barrett  interpolated a c t i v i t y  inter-  information  has been reported  (1971) in an experiment where information regard-  ing the identity or position of  letters  in a matrix had to be r e c a l l e d .  In summary, i t appears that despite the p o s s i b i l i t y of  different  degrees of cross-modality encoding, which might be underlying the abovementioned visual coding examples, there appears to be consistent evidence for some type of s p e c i f i c as well as general  interference e f f e c t s .  example of s p e c i f i c interference can be observed in the visual effect on visual coding. in contrast, appear  An  interference  Auditory interference e f f e c t s on visual coding,  to be an example of a more general type of  inter-  ference. In the theoretical  interpretation  of interference e f f e c t s  in STS,  two dimensions w i l l be considered in t h i s context as independent factors contributing to the  losses in STS.  expressed in terms of s i m i l a r i t y 1969), the other attentional Shiffrin,  One of these factors has been variously  (Bernbach, 1969; Glanzer, 1972; Laughery,  in terms of task d i f f i c u l t y , or generally,  demands of the interpolated a c t i v i t y 1968; Glanzer, 1972; Kintsch, 1970).  appear to be instrumental  in retention  (cf.  in terms of  Atkinson and  Both of these dimensions  losses in verbal and visual STS.  33  The concept of s i m i l a r i t y as an interference factor has already been demonstrated by t h e o r i s t s such as Baddeley (1964) and Wickelgren (1966) by showing a c o u s t i c a l l y similar material  to be more detrimental  STS than a c o u s t i c a l l y d i s s i m i l a r material. defined s i m i l a r i t y  to verbal  Glanzer and Cunitz (1966)  in terms of formal s i m i l a r i t y between the stimulus  material and the verbal material of the interpolated a c t i v i t y .  However,  they found that s i m i l a r i t y , as defined by formal properties of the material, was not a c r i t i c a l dimension in short-term losses.  Yet in the same experi-  ment Glanzer and Cunitz obtained a larger performance decrease over shortterm retention  intervals when the interpolated a c t i v i t y required process-  ing of mathematical problems.  In other words, processing words during  the maintenance of word stimuli mathematical problems.  in STS is more damaging than processing  Thus, if s i m i l a r i t y  is defined in terms of the  degree of s i m i l a r i t y between the processes required to maintain informat i o n In STS and the processes required to perform the interpolated a c t i v i t i e s , the dimension of s i m i l a r i t y can account for research findings as diverse as modality s p e c i f i c interference e f f e c t s as well as acoustic similarity effects.  In summary, if short-term processing of the stimulus  information and processing of the interpolated a c t i v i t y require the activation of similar c r i t i c a l coding mechanisms  a tendency of increasing  stimulus losses can be expected. The other dimension, i . e . , task d i f f i c u l t y , as an e f f e c t i v e visual  has been demonstrated  interference variable with verbal (Posner, 1965) and  (Cohen and Granstrom, 1970) material.  be divided into e f f e c t s due to the d i f f i c u l t y  Although t h i s dimension can in performing a given task  34  and the e f f e c t s due to the amount of information to be processed in a given time (Glanzer, 1972), the theoretical  interpretation of STS losses  due to these manipulations in both cases can be made in terms of  attention  demands of the interpolated a c t i v i t y (Atkinson and S h i f f r i n , 1968; Posner, 1968).  The general assumption here seems to be that any a c t i v i t y during  the retention interval w i l l take up a given amount of central processing capacity.  As a r e s u l t , the central processing capacity w i l l be divided  between maintaining short-term information and performing the activity.  As the attentional  interpolated  demands of the interpolated a c t i v i t y are  increased, a larger part of central processing w i l l be diverted from maintaining stimulus information and, subsequently, greater STS losses can be expected.  In general, while the e f f e c t s of attention demands of  the interpolated a c t i v i t y have been well substantiated in verbal STS (Glanzer, 1972; Kintsch, 1970), only isolated examples investigating visual STS have been reported (Posner, 1969; Cohen and Granstrom, 1970). However, the response trends obtained In changes in attention demands appear to be consistent across the verbal and visual STS. It should be noted that within the context of t h i s research, the terms task d i f f i c u l t y , a t t e n t i o n , and central processing, are e s s e n t i a l l y describing the same basic phenomena on d i f f e r e n t operational and theoretical levels ( e . g . , Atkinson and S h i f f r i n , 1968). a task i s , the more attention  That i s , the more d i f f i c u l t  is required to perform the task properly.  The amount of attention u t i l i z e d  in the performance of a task In turn  describes the amount of central processing diverted from the t o t a l central processing capacity.  35  A conceptual framework for the s i m i l a r i t y and attention components of a given Interpolated a c t i v i t y may be construed in the following way. On the one hand, there are retention  losses due to the s i m i l a r i t y of  processes required to perform the interpolated a c t i v i t y and the processes required to store the stimulus information. are retention  On the other hand, there  losses due to the diversion of the central processing  capacity by the attention demands required to perform the interpolated activity.  The relationship of these two components of a given Inter-  polated a c t i v i t y appears, to some extent, to be a d d i t i v e .  For instance,  the attention demands in learning an a c o u s t i c a l l y similar versus an a c o u s t i c a l l y d i s s i m i l a r l i s t appears to be constant, yet the s i m i l a r i t y component in the f i r s t paradigm generates a larger error rate.  Further-  more, the visual interference condition in the experiment by Cohen and Granstrom (1970) is constant across verbal and visual coding conditions, yet leads to a greater retention  loss in visual coding conditions. The  additive nature of these two components therefore seem tentatively supported by research examples and should be pursued further. In light of t h i s overview, several tentative statements can be made with respect to common and d i s t i n c t c h a r a c t e r i s t i c s of verbal and visual processes in STM experiments.  The existence of visual coding processes  in STM has already been s u f f i c i e n t l y demonstrated.  Though the r e l a t i v e  e f f i c i e n c y of the visual and verbal coding system cannot be d i r e c t l y investigated experimentally,  in light of the inherent differences in the  stimulus s i t u a t i o n , the general assumption that STS is a predominantly verbal system and probably a more e f f i c i e n t system, w i l l be adhered to in t h i s paper.  36  Research investigating rehearsal e f f e c t s on visual coding have generated an equally unsatisfactory p i c t u r e .  Supportive evidence as well  as data rejecting the existence of a visual rehearsal mechanism have been reported.  Although a conclusion about the visual rehearsal mechanism  cannot be made, the contradictory findings in visual STS, in contrast to the consistent f a c i l i t a t i v e e f f e c t s in verbal STS, suggest that the d i f f e r e n t degrees of e f f i c i e n c i e s of the rehearsal processes can be considered as d i f f e r e n t i a t i n g  c h a r a c t e r i s t i c s of the two systems.  Interpolated a c t i v i t y e f f e c t s , on the other hand, appear to be not unlike those obtained in the verbal STS. demands of the interpolated a c t i v i t y  initially  Increases in attention  lead to corresponding retention  losses of v i s u a l l y coded material, a general trend consistently demonstrated in verbal STS.  Furthermore, the dimension of s i m i l a r i t y , as defined in  t h i s discussion, applies equally well to verbally and v i s u a l l y coded information.  However, because s i m i l a r i t y e f f e c t s appear to be operat-  ing in both systems, a convincing argument for d i s t i n c t verbal and visual STS can be made.  If visual interference a c t i v i t y  is more detrimental  to visual coding, q u a l i t a t i v e l y d i f f e r e n t coding processes must be involved in the storage of verbal and visual  information.  In summary, q u a l i t a t i v e l y d i f f e r e n t coding processes for verbal and visual STS can be inferred from the modality s p e c i f i c interference e f f e c t s underlying the s i m i l a r i t y dimension.  The d i f f e r e n t i a l  e f f i c i e n c y of the  rehearsal mechanism between verbal and visual coding suggests an additional distinguishing c h a r a c t e r i s t i c between the two systems. attention demands on retention  The e f f e c t s of  losses c l e a r l y point towards a common  37  c h a r a c t e r i s t i c underlying verbal and visual STS. Given that common and d i s t i n c t c h a r a c t e r i s t i c s in the verbal and visual system can be i d e n t i f i e d ,  i t becomes of interest to evaluate the  extent of independence or interdependence of the two systems within the STS framework. of retention  This theoretical  issue can be investigated in a comparison  losses of verbal and visual coding situations requiring  performance of interpolated a c t i v i t i e s varying in the dimension of s i m i l a r i t y and attention demands. conditions do not d i f f e r  If  response patterns in both coding  in light of changes in both s i m i l a r i t y and  attention demands of the interpolated task, the notion of separate systems for verbal and visual STS could be rejected.  Conversely, i f  changes along both dimensions of the interpolated task would generate differential  response patterns in verbal and visual coding, the need to  postulate two q u a l i t a t i v e l y d i s t i n c t memory systems would be quite apparent.  The other a l t e r n a t i v e ,  generates a d i f f e r e n t i a l  effect,  i.e.,  only one of the dimensions  should r e s u l t in a conceptual framework  specifying the type and degree of interrelationship between the two postulated systems. It  Is the general purpose of the present series of experiments to  generate verbal and visual interpolated tasks with d i f f e r e n t degrees of attention demands in each modality, and to observe the e f f e c t s of these interference conditions in experimental situations requiring verbal or visual coding. If the conceptual framework proposed in t h i s discussion accurately describes the processes  in visual and verbal STS, the following general  38  trend of results should be obtained.  Cross-modality interference e f f e c t s  should be less pronounced than same modality interference e f f e c t s .  Hence,  verbal interference e f f e c t s should be more damaging to the verbal code than to the visual code.  Conversely, visual interpolated a c t i v i t y should  be more damaging to the visual than verbal code.  Furthermore, Inter-  polated a c t i v i t i e s with high attention demands should lead to a greater retention  loss than interpolated a c t i v i t i e s with low attention demands.  This should occur whether processing the stimulus and the a c t i v i t y requires the same or d i f f e r e n t modalities.  interpolated  A general response  pattern of t h i s nature would support the following theoretical points: a) verbal and visual STS rely on q u a l i t a t i v e l y different coding processes; b) both systems rely equally on attention demands in maintaining information in STS; and c) retention losses in verbal and visual STS are an additive function of the attention and s i m i l a r i t y components inherent in the given interpolated a c t i v i t y .  39  EXPERIMENT I I introduction The f i r s t experiment was designed to evaluate the e f f e c t s of  inter-  polated a c t i v i t i e s varying on the dimensions of s i m i l a r i t y and attention demands in an experimental  setting requiring visual coding.  The  initial  problem to be resolved was in the selection of the stimulus situation which could be interpreted mentioned in the general situations which f a l l  in terms of visual coding requirements.  As  introduction, there are several stimulus  into t h i s category, among them:  pictures of objects,  drawings of schematic faces, and letters or d i g i t s placed on a spatial matrix.  Since i t  is d i f f i c u l t to completely eliminate possible influences  of verbal coding e f f e c t s in each one of these conditions, the final choice of the stimulus situation rested with a visual pattern previously used by Schnore and Partington (1967) in an investigation of visual d e f i c i t s in i n s t i t u t i o n a l i z e d populations.  The p a r t i c u l a r stimulus  display consisted of a 4 x 4 matrix of black and white squares, where the pattern generated by the s p e c i f i c arrangement of black squares had to be retained for subsequent reproduction. pattern of t h i s nature  The advantage in using a  lies in the absence of any verbal cues under a  short presentation duration.  The interpretation of the results in terms  of visual coding therefore appeared quite j u s t i f i e d . The selection of appropriate interpolated a c t i v i t e s varying along the s i m i l a r i t y and attention dimensions appeared more d i f f i c u l t and was largely determined in a series of p i l o t research.  Since the damaging  effect of counting backwards by threes from a three d i g i t number had  40  been substantiated  in previous experiments ( e . g . , Peterson and Peterson,  1959), t h i s p a r t i c u l a r task was chosen and defined in terms of a verbal interference task with high attention  demands.  With the intent of keeping  the modality s p e c i f i c task demands constant and decreasing the  attention  demands, counting forwards by one from the number one was chosen and defined as constituting a verbal  interference task with low attention  demands. The selection of appropriate visual interpolated a c t i v i t i e s , contrast, turned into a more elusive project.  Posner (1969) had already  demonstrated that a visual matrix presented during the retention has no damaging e f f e c t s on visual coding.  in  interval  This appears not too s u r p r i s i n g ,  if one considers the amount and type of processing which might be required in looking at a given matrix d i s p l a y . requiring a substantial for the basic visual  Therefore, a task had to be generated  increase in visual processing.  The final choice  interference condition consisted of a visual  similar to the stimulus d i s p l a y .  pattern,  The visual pattern contained six black  squares which continuously changed at a rate of eight successive movements per second of two of the black squares.  The visual  effects  obtained in t h i s manipulation can be described as a constantly changing black pattern on a white background.  The next step in the p i l o t research  was to create conditions d i f f e r i n g with respect to attention demands required to process t h i s visual different  degrees of attention  information.  It was assumed that  demands could be obtained by varying the  s p e c i f i c instructions about the nature of the visual interpolated Three types of instructions were i n i t i a l l y  tested:  one,  task.  "look at the  41  moving pattern, but let i t not disturb you in the retention of the stimulus"; two, "there will be a moving pattern", with no s p e c i f i c instructions about the visual display; three, "concentrate on the moving pattern and follow i t with your eyes". two instructions did not d i f f e r , with respect to the third  Since the results under the  but were s i g n i f i c a n t l y less  i n s t r u c t i o n , the f i r s t and t h i r d  conditions were selected and defined in terms of visual  first  interfering  instruction  interference  conditions with low and high attention demands. One additional problem had to be resolved, which is inherent In the nature of a visual interference task.  The issue here centers around the  experimenter's lack of control and evaluation of the subject's task performance required by the interpolated task.  Contrary to the verbal  interference c o n d i t i o n , where t h i s type of assessment is readily available in S/s verbalization of the number sequence, any visual Interference this built  in performance t e s t .  In other words, a visual  lacks  Interference  condition with an observable performance task had to be obtatned.  Since  i t was important to avoid the involvement of a verbal component as a performance check of the visual interference task, a visual-motor task was chosen to meet the above mentioned requirements. consisted of the presentation of a  4x4  This condition  matrix of squares with  successive changes in the black-white r a t i o of the d i s p l a y . the r a t i o changes were accompanied by pattern changes.  In a d d i t i o n ,  The subject's  task in t h i s condition was to adjust a lever in accordance with the black and white ratio changes which had to be abstracted from the accompanying pattern changes.  This Interference  condition was defined  42  In  terms In  of  very  order  high  to  evaluate  response measures any  attention  interpolated  for  the  zero  demanding  effects  delay,  activity,  were  of  and  also  for  non-verbal these a  or  interpolated  retention  required  visual  interference.  activities,  interval  as a d d i t i o n a l  without  reference  points. With this the  respect  experiment,  attention should the  several  theoretical  issues  projections  c o u l d be made a b o u t  basis of  However, the  the  task  nature,  with  in  visual  component  attention  during the  comparable.  could  visual  similarity  obtained  in  interference similarity  of  the  this  were  the  response pattern  of  low  task Two,  that  on  higher  Interference.  and  the  materialize  visual  degree  or  interamount  was p o s s i b l e , a n d assumed t o  similarity  verbal  be o f  effect  however,  obtained  requiring  in  a common  should only  verbal  modalities  effects  coding.  verbal  effect the  resolved  S T S , h i g h and  visual  relationship,  i n an e x p e r i m e n t  the  be p r e d i c t e d  than  effects  be  interference  S i n c e no a s s e s s m e n t o f  s p e c i f i c p r e d i c t i o n s about  a comparison of  coding  levels of it  to  demands a r e  specific  c o n d i t i o n s of  A clarification  that  and  w h i c h were  attention  response  about  demands and  if  each modality  should occur  demands a c r o s s  be made.  expected  verbal  similarity  low  are  One,  differential  prediction  attention  additive  ment  the  losses  attention  not  in  h i g h and  polated  since  underlying  conditions within  result  retention  of  the  proposed m a n i p u l a t i o n s .  characteristic  if  to  in  could this  an  could be experi-  coding.  METHOD  Subjects One  and  Design  h u n d r e d and  five  volunteers  between  the  ages of  seventeen  and  43  twenty-two from the Introductory Psychology subject pool participated in the experiment and were randomly assigned to one of seven groups, except to keep the male-female ratio constant per group. individually tested.  A l l subjects were  The seven groups consisted of the following  conditions: Group I:  immediate recall (IMM).  The remaining groups were tested after a ten second retention  interval  with the following interpolated a c t i v i t i e s : Group II:  rehearsal, no interpolated a c t i v i t y (REH);  Group III:  verbal  Group IV:  verbal interference, high attention (HVER);  Group V:  visual interference, low attention  Group VI:  visual interference, high attention  Group VII:  visual-motor interference  interference, low attention (LVER);  (LVIS); (HVIS);  (VM).  Material The stimulus material consisted of 4 x 4 matrices containing eight black and eight white squares (Schnore and Partington, 1967).  The  stimulus configuration to be remembered for subsequent reproduction was the p a r t i c u l a r pattern the eight black squares created in each matrix. Across the series of test t r i a l s the patterns were randomly generated with the r e s t r i c t i o n that each c e l l of the matrix was equally often f i l l e d with a black square.  After randomly generating the t e s t s t i m u l i ,  several changes had to be undertaken, according to the above mentioned r e s t r i c t i o n , since several of the random patterns appeared as more cohesive or meaningful patterns than others.  The f i n a l set of random, meaningless  44  patterns was then tested across a series of stimulus durations to obtain a recall  level at zero delay meeting two c r i t e r i a :  a) verbal coding  should be reduced; and b) a response level should be obtained which would permit possible increases or decreases due to interpolated a c t i v i t y A stimulus duration of 1.75  effects.  seconds was selected as an optimal value meet-  ing the above c r i t e r i a . Four d i f f e r e n t  sets of test t r i a l s ,  including a start s i g n ,  retention  i n t e r v a l , and recall cue, were filmed on standard eight mm f i l m with a single frame advance camera.  The four test t r i a l s and t h e i r corresponding  conditions were as follows: Film I contained the stimulus display immediately followed by the recall cue and was used for the immediate recall condition. Film II  contained a retention  interval  which darkened out the screen  for ten seconds between the stimulus and recall cue.  This set was used  for the rehearsal group as well as for the low and high attention  verbal  interference group. In film III, retention  a ten second film s t r i p was inserted during the  interval  the screen.  displaying a continuously changing black pattern on  This condition contained a pattern of six black squares  continuously changing position at a rate of eight times per second throughout the ten second retention low and high attention visual  interval.  This film was used for  interference groups.  Film IV was used for the visual-motor interference group. second interval  The ten  displayed continuous changes in the r a t i o of black and  white squares In the d i s p l a y , as well as pattern changes for each black  45  and white r a t i o .  More s p e c i f i c a l l y , there were f i v e  white r a t i o s , ranging from a l l  black, three-quarters  one-quarter black, to no black, i . e . ,  a l l white.  levels of black and black, half  black,  Ratio changes occurred  once every second with an accompanying pattern change for a given  ratio  level a f t e r .5 seconds. Apparatus The films containing the material a Kodak Instamatic movie projector.  of the test t r i a l s were shown on In a d d i t i o n , Ss in Group VII  had to  operate a lever along a seven inch continuum with end points marked black and white.  The lever mechanism was connected to some inoperative  equipment to give the impression that an accurate measure for the  test lever  response was obtained. Procedure The experimental  procedure for the seven groups was identical with  respect to the stimulus and response requirements.  For instance, the  immediate recall group was told that each t r i a l would begin with a s t a r t s i g n , followed immediately by a 4 x 4 matrix of black and white squares presented for 1.75  seconds.  Subjects were instructed to retain  the  s p e c i f i c pattern formed by the black squares, which had to be reproduced when the r e c a l l cue appeared on the screen. with 4 x 4  matrices.  A scoring sheet was provided  The stimulus pattern was to be reproduced by placing  an X into the corresponding c e l l s on the scoring sheet for each black square on the stimulus d i s p l a y .  For the remaining six groups, the  following  instructional changes had to be introduced regarding the nature of the interpolated  activity.  46  Group II:  (Rehearsal condition)  "Following the stimulus presentation  there w i l l be ten seconds during which you are to rehearse the stimulus pattern and then reproduce i t when the r e c a l l cue is g i v e n . " Group III:  (Low a t t e n t i o n , verbal  interference condition)  "Follow-  ing the stimulus presentation, start counting forward by one, as soon as I c a l l out ' o n e ' , u n t i l the recall cue appears on the screen." Group IV:  (High attention, verbal interference condition)  "You  will be given a three d i g i t number immediately following the stimulus presentation, and you are to count backwards by threes  from t h i s number  until the r e c a l l cue appears." Group V:  (Low a t t e n t i o n , visual interference condition)  "The  stimulus w i l l be followed by a continuously changing black pattern. Look at the changing pattern, yet try not to be disturbed by i t retaining the stimulus pattern. Group VI:  in  However, do not close your e y e s . "  (High attention, visual interference condition)  "The  stimulus will be followed by a continuously changing black pattern.  Con-  centrate on t h i s changing pattern and follow It with your eyes." Group VII:  (Visual and motor interference condition)  "The stimulus  w i l l be followed by a continuously changing matrix with changes in pattern and black and white ratios of the d i s p l a y .  Adjust the lever as  fast as possible along the black-white continuum in accordance with your perceptions of the r a t i o changes." Each S_ received 15 t r i a l s , of which only the last ten t r i a l s were considered as t e s t t r i a l s .  The f i r s t f i v e t r i a l s were discarded in  order to obtain a stable performance level free from d i s t o r t i o n s such  47  as practice e f f e c t s and proactive  interference.  The following temporal sequence was maintained throughout each condition.  The subject was told the t r i a l would s t a r t , at which time  the projector was a c t i v a t e d .  After one second, a Start sign appeared,  followed by a .25 second blank Interval before the stimulus d i s p l a y . stimulus was presented for 1.75 seconds, and was Immediately the r e c a l l cue in Group I, remaining groups.  The  followed by  or the ten second interpolated a c t i v i t y  in the  For the delay groups, the r e c a l l cue appeared after  the ten second interval at which time the projector was turned o f f . Subjects were given 20 seconds to reproduce the stimulus pattern.  A short rest  period was given between t r i a l s for an inter-stimulus interval of 60 seconds. RESULTS AND DISCUSSION Responses were i n i t i a l l y  scored with respect to the number of  correct squares reproduced per stimulus pattern.  The mean recall values  for the ten t e s t t r i a l s are plotted in Figure I for a l l seven conditions. In a d d i t i o n , the total number of correct and incorrect scores per subject were converted into d ' scores, a correction factor for guessing (Kintsch, 1970).  Figure 2 shows the mean d  1  values for a l l  response trends in the two d i f f e r e n t  seven groups.  The  response measures appeared to be in  close agreement across the seven conditions (Appendix I, by indicating a r e l a t i v e absence of d i f f e r e n t i a l  Table I),  guessing rates.  thereThe  general trend in both figures showed a rather stable response level for the immediate and rehearsal conditions, as well as the low attention groups of both verbal and visual interference.  Pronounced retention  losses were  48  VERBAL 0-DELAY  FIG. 1  VISUAL  MOTOR  10 SECOND DELAY  Mean scorea f o r correct reproductions of v i s u a l patterns i n Exp I . 0  '  49  3  _  to  w « o o to  IMM  REH  LOW  HIGH  VERBAL 0-Delay  LOW HIGH VISUAL  10 SECOND DELAY  FIG. 2 Mean d' scores for visual coding in Exp I. 0  VISUALMOTOR  50  displayed by the high attention verbal condition and the visua I-motor condition, with intermediate  losses due to high attention visual  inter-  ference. Analyses of variance were performed with the data of both response measures (Appendix I, cant treatment e f f e c t ,  Tables I and 3).  Both measures revealed a s i g n i f i -  F(6,98)=26.67; p<.01, for number of correct scores,  and F(6,98)=20.74; p<.0l, for d' scores.  Post hoc tests by the Newman-  Keuls method produced the following s i g n i f i c a n t comparisons in both response measures (Appendix II,  Tables 2 and 4).  There was no s i g n i f i c a n t  difference between the immediate recall and the rehearsal groups.  Both  groups in t u r n , did not d i f f e r from the low attention groups of verbal and visual interference.  High attention verbal  interference,  in contrast,  showed a s i g n i f i c a n t difference with respect to every other c o n d i t i o n , a l l p ' s < . 0 l , except in the d' analysis where a smaller difference was obtained with respect to the high attention visual c o n d i t i o n , p<.05.  The  high attention visual c o n d i t i o n , in t u r n , revealed a greater difference with respect to the rehearsal group, p<.01, than with respect to the immediate r e c a l l condition as well as both low attention conditions in verbal and visual interference, a l l p's<.05.  On the other hand, the  visual motor group showed a s i g n i f i c a n t l y greater retention comparison with every other condition, a l l  p's<.0l.  The interpretation of these data within the theoretical suggests several tentative  loss in  framework  statements regarding evidence for s i m i l a r i t y  and attention components underlying retention  losses due to  interpolated  a c t i v i t i e s , yet provides l i t t l e c l a r i f i c a t i o n with respect to the nature  51  or effectiveness of the visual rehearsal mechanism. The problems inherent  in the assessment of rehearsal e f f e c t s have  already been mentioned in the general  introduction.  They include e f f e c t s  of cross-modality coding of the stimulus as well as the problem of establishing a v a l i d reference point for the assessment of the rehearsal effect.  Cross-modality coding e f f e c t s appear to be negligible in  of the absence of verbal cues inherent presentation time of the stimulus.  light  in the stimulus pattern and  As a v a l i d reference point, the  immediate recall group seems to provide the most appropriate comparison. There is no difference between immediate r e c a l l and recall after a ten second retention  interval  with no interpolated a c t i v i t y .  the rehearsal mechanism does neither f a c i l i t a t e  Stating that  nor lead to an appreciable  loss in retention does l i t t l e in c l a r i f y i n g the nature of the postulated visual rehearsal mechanism, however, e s p e c i a l l y since i t becomes doubtful whether the immediate recall group is indeed a v a l i d reference point for zero delay coding e f f i c i e n c y . has been shown to be an e f f e c t i v e Yuille,  1972).  After a l l , responding at zero delay interference condition (Ternes and  The nature of the response task may even be construed as  containing a certain interference component leading to the low retention  level  in t h i s condition.  For instance, Margrain (1967),  among others, has shown that a written interpolated a c t i v i t y an interference e f f e c t  in STM.  relatively  constitutes  In t h i s experiment, Ss have to reproduce  the stimulus pattern by putting X ' s onto a response sheet, a task which required up to twenty seconds.  It  Is not unreasonable to suspect that  the v i s u a l l y coded stimulus pattern might undergo some changes during the  52  time it takes to complete the reconstruction of the pattern on the response sheet.  The same argument can be made for the rehearsal group.  since sensory memory e f f e c t s at zero delay cannot be ruled out,  However, differential  coding losses due to the task demands of the response task are quite  likely  to occur between immediate recall and r e c a l l after a ten second retention interval.  Therefore, an evaluation of rehearsal e f f e c t s should not be  made based on these data.  On the other hand, the rehearsal group does  appear as a v a l i d reference point in evaluating interpolated a c t i v i t y e f f e c t s , since possible interference e f f e c t s due to the response task demands should be constant for a l l groups having a ten second retention i ntervaI. Although the response patterns generated by the Interpolated a c t i v i t i e s appear at certain points to be unexpected, it should be noted that a subsequent experiment using a three second stimulus duration e s s e n t i a l l y replicated the response trend, thereby at least substantiating the consistency of the Interpolated a c t i v i t y e f f e c t s in t h i s visual stimulus situation.  Despite the consistency of the response trends, the  interpre-  tation of these results within the proposed theoretical framework evaluating s i m i l a r i t y and attention components appears at times ambiguous; tentative statements can s t i l l  Several  be made to summarize the theoretical  imp Iications. First,  interpolated a c t i v i t i e s d i f f e r i n g in t h e i r degree of  attention  demands for each modality s p e c i f i c interference task display consistent increases in reproduction losses corresponding to increases in attention demands.  This Is true for verbal interference where counting forwards  53  by ones and counting backwards by threes d i f f e r e n t i a l l y level.  A smaller difference  a f f e c t the r e c a l l  is obtained in visual Interference between  low and high attention groups, yet,  in conjunction with the visual-motor  group, the response trend due to attention demands is comparable in visual and verbal conditions. Second, retention  losses due to the postulated s i m i l a r i t y component  are more d i f f i c u l t to i s o l a t e . visual and verbal  interference for the respective low attention groups.  Furthermore, there  is a difference between the high attention groups of  both modalities, yet, higher retention  There are no response differences between  it  loss.  is the verbal  interference which leads to a  In other words, there  that visual interference  is more detrimental  is no apparent than verbal  indication  interference on  visual coding. To i l l u s t r a t e  t h i s problem, response differences in the two verbal  interference conditions can be considered as a function of the increased central processing demands required to count backwards, since the modality s p e c i f i c task component, i . e . ,  the verbal production of the number  sequence, is r e l a t i v e l y constant across both groups. retention  Hence, there  is no  loss due to the modality s p e c i f i c task component in the verbal  Interference c o n d i t i o n , i . e . ,  there is no s i m i l a r i t y e f f e c t .  same conclusion can be drawn about the visual  However, the  interference groups, since  the modality s p e c i f i c component in the low attention group does not lead to a s i g n i f i c a n t retention  loss.  Subsequently, the retention  loss of the  high attention visual group can be interpreted again in terms of due to attention demands.  losses  The visual-motor e f f e c t s then appear as a mere  54  extension of the attention demand continuum. i l a r i t y component, i . e . ,  Thus, the postulated sim-  visual interference should be more detrimental  to visual coding than the e f f e c t s of verbal  interference, does not emerge  in t h i s experiment. However, since the amount of attention demands required to perform interpolated a c t i v i t i e s  in both modalities is unknown, the  arbitrarily  defined low and high attention groups across modalities cannot be expected to be comparable on t h i s dimension,  in e f f e c t , while several  alternative  interpretations of s i m i l a r i t y and attention e f f e c t s can be forwarded, a detailed evaluation of these e f f e c t s has to await a comparison of response trends in Experiment I with those obtained in an experimental requiring verbal coding.  setting  The rationale underlying t h i s expectation  centers around the following argument.  If a comparable response trend  is observed in verbal coding conditions, an Interpretation of e f f e c t s can be made in terms of attention demands alone.  interference  If a d i f f e r e n t i a l  response pattern emerges, other than attention components must be incorporated in rhe interpretation of re-i*?ntion losses.  55  EXPERIMENT I I Introduction Experiment II  was designed to evaluate the e f f e c t s of the  interpolated  a c t i v i t i e s used in Experiment I in a stimulus situation requiring predominantly verbal coding.  The theoretical value of t h i s experiment was:  a) in providing additional data to evaluate the postulated s i m i l a r i t y and attention components of the interpolated a c t i v i t i e s ; and b) In providing Information about the interrelationship or independence of the verbal and visual systems in STS. The p a r t i c u l a r paradigm selected for t h i s experiment consisted of the presentation of three words per t e s t t r i a l ,  in other words, a stimulus  situation which has been frequently used in previous experiments i n v e s t i gating verbal STM function ( e . g . , Murdock, 1963; Peterson and Peterson, 1959).  The advantage of using t h i s method l i e s in the well established  response pattern obtained at zero delay as well as after intervals f i l l e d with verbal  interference,  i.e.,  retention  counting backwards by  threes. Depending on the theoretical  assumptions which are adhered to with  respect to s i m i l a r i t y and attention components of the interpolated  activity,  the following predictions can be made about the expected r e s u l t s .  If  retention  losses due to the interpolated a c t i v i t i e s are assumed to be an  additive function of the s i m i l a r i t y and attention component of the ference task, a d i f f e r e n t  inter-  response pattern should be obtained in t h i s  experiment in comparison to Experiment I.  More s p e c i f i c a l l y , verbal  ference conditions should lead to a larger retention  inter-  loss with respect to  56  visual Interference conditions, r e l a t i v e to the response pattern obtained in visual coding conditions.  On the other hand, if the postulated  similarity  e f f e c t s are non-existent, and losses In a given interpolated a c t i v i t y cond i t i o n are a d i r e c t function of the amount of central processing required to perform the interpolated task, an identical  response pattern should  be obtained in t h i s experiment as found in Experiment I.  Regardless of  the response pattern obtained, the results should lead to some informat i o n c l a r i f y i n g the extent to which the postulated s i m i l a r i t y and attention components can be considered as crucial factors underlying losses during interpolated  retention  activities. METHOD  One hundred and f i v e Ss from the same subject pool participated t h i s experiment.  Fifteen S_s were randomly assigned to each of seven groups  except to maintain an equal male-female r a t i o . individually. I,  in  Subjects were again tested  The general procedure was identical to that in Experiment  except for the stimulus display and the response task.  The stimulus  display consisted of a consecutive presentation of three words, each word presented for 5/16 second, with no inter-item  interval.  The  Individual  stimulus items consisted of one and two s y l l a b l e concrete nouns with high frequency r a t i n g , selected from a standard l i s t of rated words (Paivio, Y u i l l e and Madigan, 1968).  It should be noted that a l l  stimulus words  had been previously used in an STM task (Ternes and Y u i l l e ,  1972).  Further-  more, Ss were given response sheets and instructions for a standard written recalI  test.  To b r i e f l y summarize the general procedure,  the seven groups differed  57  with respect to Experiment I only In the type of stimulus material and stimulus duration, as well as the subsequent r e c a l l task. experimental one:  factors remained constant with respect to Experiment the material  for the Interpolated a c t i v i t i e s ,  ing s t a r t and recall two:  The following  includ-  signs;  temporal parameters of interpolated a c t i v i t i e s and trial  I:  inter-  intervals;  three:  Instructions with respect to Interpolated a c t i v i t i e s ;  four:  the number of practice and test  five:  general apparatus, e . g . , film presentation.  trials;  RESULTS AND DISCUSSION The mean numbers of words correctly recalled were tabulated for the last ten t r i a l s and are shown in Figure 3.  An almost perfect recall  score  was obtained for the immediate recall and rehearsal groups ( e . g . , Murdock, 1963).  At the same time, both visual interference conditions displayed a  s i m i l a r l y high response l e v e l .  The verbal  interference conditions, in  contrast, showed a decrease in word r e c a l l , with a substantial drop between the low and high attention  conditions.  The visual-motor group  also showed a decrease in r e c a l l , yet, unlike in Experiment I,  the v i s u a l -  motor group was not the most damaging interference condition (Appendix Table  I,  I). An analysis of variance was performed on recall scores which revealed  a s i g n i f i c a n t treatment e f f e c t , 5).  F(6,98)=93.65; p<.OI.  (Appendix II,  Post hoc tests by the Newman-Keuls method were used to further  s p e c i f i c comparisons between individual conditions (Appendix II,  Table clarify  Table 6).  58  1  FIG. 3«  Mean correct recall scores in Exp II» e  59  These comparisons generated the following recall trend across conditions. There was no s i g n i f i c a n t difference between the immediate recall and rehearsal group.  Both, in t u r n , did not d i f f e r  attention groups of visual  interference.  from the low and high  In contrast, both verbal  inter-  ference conditions as well as the visual-motor condition showed a decrease with respect to the rehearsal condition, and revealed s i g n i f i cant differences with respect to each other, a l l The results show a d e f i n i t e c e i l i n g effect  p's<.OI. for the immediate r e c a l l ,  rehearsal, and low and high attention groups of visual effect,  recall appears to be almost e r r o r l e s s for a l l  ever, there  is a highly s i g n i f i c a n t d i f f e r e n t i a t i o n  three groups.  interference. four groups.  In How-  between the remaining  B r i e f l y , recall differences due to attention demands  appear in both modality s p e c i f i c tasks.  As central processing demands  are increased from counting forwards to counting backwards, corresponding recall  losses can be observed between the two verbal  ditions as in Experiment I.  Interference con-  Though a similar retention  loss is not  obtained between the low and high attention groups in visual  interference,  a comparable trend emerges along the attention continuum In the visual modality,  if the visual-motor condition is considered as an additional  level of visual interference with very high attention demands. more, since in the detrimental  low attention groups verbal  than visual interference, there  loss can be attributed condition.  interference  Further-  is more  is some indication that t h i s  to the s i m i l a r i t y component inherent  in the verbal  However, t h i s is not necessarily the case since i t could be  argued that counting forward contains a larger attention component than  60  merely looking at a continuously changing visual pattern.  In other words,  the assessn.ant of s i m i l a r i t y and attention components in Experiment contains similar problems as in Experiment  I.  It appears therefore  II that  as long as attention components cannot be specified across modalities of the interpolated task, s i m i l a r i t y effects within experiments cannot be clearly  isolated.  A detailed comparison of response trends across  Experiments I and II between s i m i l a r i t y  are expected to c l a r i f y the s p e c i f i c relationship  and attention components underlying retention  due to Interpolated a c t i v i t i e s .  losses  61  DISCUSSION EXPERIMENTS I and  II  The general purpose of the two experiments was to evaluate the extent to which the postulated s i m i l a r i t y and attention components of  interpolated  a c t i v i t i e s can be shown as the c r u c i a l factors underlying retention in STM tasks.  The conclusions drawn from an evaluation of  losses  retention  losses were in turn expected to provide information regarding the nature of verbal and visual STS. With respect to the f i r s t  issue, i . e . ,  s i m i l a r i t y and attention  components, several conclusions can be drawn from the results of the two experiments.  Both experiments attest to the importance of  demands underlying losses of information in STS.  As a larger proportion  of central processing is required in the performance of the a c t i v i t y , a larger retention loss can be observed.  attention  interpolated  This trend appears in  experimental situations requiring either verbal (Experiment II)  or visual  (Experiment I) coding and is true for interpolated a c t i v i t i e s in the verbal and visual modality.-  In a d d i t i o n , the d i f f e r e n t i a l  response  trends across experiments c l e a r l y point out that attention demands are not s u f f i c i e n t to explain retention  losses.  Results of t h i s nature  suggest the need to postulate other than attention components in the interpretation of retention  losses in STS.  There are three s p e c i f i c  comparisons of interpolated a c t i v i t y e f f e c t s across experiments which support the existence of the s i m i l a r i t y component as an important  inter-  ference factor i n STS. One, the low attention verbal  interference condition has no s i g n i f l -  62  cant e f f e c t on visual coding (Experiment I), recall  yet produces a s i g n i f i c a n t  loss in verbal coding (Experiment II).  If the  'nterpolated  a c t i v i t y for t h i s condition is evaluated in terms of s i m i l a r i t y and attention components, Experiment I shows that counting forward by ones contains an i n s i g n i f i c a n t s i m i l a r i t y e f f e c t as well as an i n s i g n i f i c a n t attention component. condition.  After a l l , visual coding does not decrease in t h i s  The same interpolated a c t i v i t y , however, leads to a loss in  verbal r e c a l l .  Since i t  is safe to assume that attention demands inherent  in counting forwards remain constant across the two experiments, recall losses in Experiment II  must be attributed to the s i m i l a r i t y  effect.  In other words, the modality s p e c i f i c task component in the counting task does not affect the visual code, yet interferes with r e c a l l of verbal material. Two, the low attention visual groups do not lead to retention in either coding conditions.  losses  In other words, the e f f e c t s of the s i m i l a r i t y  and attention components of the interpolated a c t i v i t y do not add up to generate a s i g n i f i c a n t re'tention loss.  However., the high attention  v i s u a l ' c o n d i t i o n d i f f e r e n t i a l l y affects the two coding conditions. retention  l o s s . f o r t h i s interference condition was i n i t i a l l y  in Experiment I in terms of attention demands. is c o r r e c t , a similar retention  If t h i s  interpreted  interpretation  loss due to the identical attention demand  component would have to be expected in Experiment II, case.  The  yet t h i s is not.the  Consequently, i t can be argued that the retention  loss in Experi-  ment I must be due to the simiIarity component inherent in t h i s experimental s i t u a t i o n , where visual processing is required in retaining the  63  stimulus information and in performing the interpolated task.  The same  visual processing component of the interpolated a c t i v i t y does not i n t e r fere with verbal coding.  This evidence for modality s p e c i f i c  interference  further confirms the postulated existence of the s i m i l a r i t y component as an important factor  in STS losses.  Three, a comparison of the r e l a t i v e effects of the high attention verbal groups and the visual-motor groups across both experiments provides further support for the additive hypothesis of retention s i m i l a r i t y and attention components.  losses due to  Again, if retention  losses are  due to attention demands alone, the visual-motor condition should lead to greater r e c a l l  losses than the high attention verbal group in the  results of Experiment  II,  as was observed in Experiment  I.  However, the  order of increasing losses due to these conditions is c l e a r l y reversed in Experiment II. it  Despite the lack of a d i r e c t s t a t i s t i c a l  is apparent that counting backwards is the most damaging  comparison, interference  condition In verbal coding, and the.visual-motor group leads to the retention  loss In visual coding.  largest  Honce, the attention, component by i t s e l f  is i n s u f f i c i e n t to explain the retention  losses in t h i s comparison.  In light of the results of both experiments,  i t should be noted  that the s p e c i f i c labels supplied to the d i f f e r e n t Interference conditions with respect to attention demands can be rather misleading at t h i s For instance, the low attention visual  time.  interference condition should not  any more be considered as a comparison condition for the low attention verbal  interference condition.  In f a c t , the results strongly  indicate  that the high attention visual condition and the visual motor condition  64  are  the  r e s p e c t i v e comparison groups f o r  low a n d h i g h a t t e n t i o n  verbal  i nterference, In  summary, a c o m p a r i s o n o f  clearly  points out  underlying across and t h e  the  to  The  verbal  for  g r o u p s , as well  coding,  interpretation  of  interference  of  be j u s t i f i e d ,  this  since  retention effects  the  coding than losses  losses  low a t t e n t i o n  verbal  reversed order  e x i s t e n c e of  additional in  all  of  to  of  in terms  verbal of  than  in  terms  above mentioned verbal  interference  of  other  factor  the  a p p e a r s more d e t r i m e n t a l  visual  experiments  and v i s u a l - m o t o r g r o u p s  and c o n v e r s e l y , v i s u a l  loss of  both  retention  as the  verbal  interpretation  interference  retention  coding  leads to  coding.  In  both general  a  effect,  and  becomes a p l a u s i b l e c o n c e p t u a l i z a t i o n o f  processes. The  interpretation  attention with  The d i f f e r e n t i a l  high attention  appears t o  visual  specific STS  STS.  coding experiments  visual  due t o  losses.  instances  larger  in  across  demands c o n s t i t u t e m e r e l y o n e c o m p o n e n t  coding c o n d i t i o n s , strongly suggests the  similarity  than  and v e r b a l  losses  attention of  losses  high a t t e n t i o n  retention across  that attention  retention  visual  response trends  components, in  respect to  visual  systems.  appear  to  retention comparable attention  the  losses  In  retention demands o f  retention  turn,  losses  in terms of  contains several  c o n c e p t u a l i z a t i o n of  First,  be g e n e r a l  of  attention  similarity  important  STS i n t e r m s  verbal  and  processing  a n d c a n be c o n s i d e r e d a s a common f a c t o r  underlying  losses the  and v i s u a l in  coding.  This  of  implications  central  verbal  demands i n t e r m s  of  and  i s demonstrated  b o t h c o d i n g s y s t e m s due t o  interpolated  activity,  changes  r e g a r d l e s s of  the  by  in modality  65  of the interference task.  Second, if the maintenance of the stimulus  information and the performance of the interpolated a c t i v i t y  require  q u a l i t a t i v e l y s i m i l a r processes, a larger retention loss is obtained than if d i f f e r e n t processes are required in the performance of the two tasks. If  i t can be postulated that the attention and s i m i l a r i t y components  are important factors underlying retention  losses, i t becomes of  interest  to consider to what extent these two factors are Involved In the maintenance of information in STS.  For example, i t may be argued that reten-  tion losses over STM intervals should not occur in an experimental setting u t i l i z i n g a retention interval which contains no attention and no s i m i l a r i t y component. are the following:  The basic questions posed in t h i s example  a) does the absence of the attention and s i m i l a r i t y  components during the retention  interval  describe the optimal  level of  STS functioning; b) can t h i s state of optimal functioning be described in terms of processes underlying these two components? questions could be answered in the a f f i r m a t i v e ,  If these two  i t could be postulated  that the maintenance of information in STS r e l i e s on the  availability  of the central processing capacity in conjunction with modality s p e c i f i c coding processes.  In experiments investigating verbal and visual functions  in STM, common factors underlying the observations could then be considered as defining c r i t e r i a for STS processes.  Conversely, modality  s p e c i f i c factors which might be observed can be considered as defining c r i t e r i a for separate verbal and visual systems in STS.  A detailed  evaluation of t h i s conceptualization, however, has to await the c l a r i f i c a -  \  66  tlon of one assumption which has been consistently made so f a r . The conceptual framework proposed has been based on data considering the visual-motor group as a visual interference condition requiring r e l a t i v e l y high attention demands.  While t h i s Interpretation might be  appropriate in so far as the visual-motor task does not contain a verbal component, the unexpectedly high retention  losses in both experiments  warrant a more detailed evaluation of the visual-motor task. can be argued that the motor component, i . e . ,  Though i t  one lever movement per  second, does not constitute a s i g n i f i c a n t interference component, and has been shown that looking at a changing pattern, visual group In Experiments I and II, it  i.e.,  it  low attention  does not lead to retention  losses,  Is not c l e a r what s p e c i f i c aspect or combination of performance demands  generate t h i s pronounced retention becomes, therefore, of further components, i . e . , retention  attention,  loss in both coding conditions.  It  interest to Investigate what s p e c i f i c  s i m i l a r i t y , or motor, might be underlying  losses of the v I sua I r-motor task.  67  EXPERIMENT I I I Introduction The purpose of t h i s experiment was to evaluate the r e l a t i v e cont r i b u t i o n s of separate components of the visual-motor Interference task to the retention  losses obtained in Experiments I and II.  postulated e a r l i e r that retention  losses were an additive function of  the s i m i l a r i t y and attention components of the given activity.  It was  interpolated  However, the presence of the motor task in t h i s  a c t i v i t y appeared as a possible confounding factor in the of retention  losses.  Interpolated interpretation  The e f f e c t s of the motor task as a potential  inter-  ference component in STM research had already been demonstrated by Posner (Posner, 1969; Posner and Konick, 1967).  Two dimensions had been  identified as possible sources of interference:  a) response compati-  b i l i t y ; and b) the d i f f i c u l t y of the motor task.  The relationship between  these two components of the motor task and the concept of attention as defined in t h i s research appeared unmistakable.  Motor task  difficulty  seemed to be related to the general concept of task d i f f i c u l t y .  Response  c o m p a t i b i l i t y , on the other hand, also appeared to be related to central processing requirements.  For instance, if the task input consists of  discrete changes and a continuous motor adjustment is required, more central processing is required than i f the input and motor task are in discrete u n i t s .  A close evaluation of the experimental  requirements  inherent in the visual-motor condition resulted in the following tentative conclusions about motor task d i f f i c u l t y and response c o m p a t i b i l i t y . The motor task in both experiments consisted of lever adjustments  68  .5  t o a v i s u a l p r e s e n t a t i o n which d i s p l a y e d p a t t e r n changes every and b l a c k - w h i t e black-white  r a t i o changes once per second.  ratio levels.  I t should  There were f i v e  seconds,  distinct  be noted here t h a t , s i n c e p a t t e r n  changes c o u l d n o t be produced f o r t h e a l l b l a c k and a l l w h i t e  levels, a  s i n g l e w h i t e o r b l a c k square was i n t r o d u c e d r e s p e c t i v e l y as a s i m u l a t i o n o f p a t t e r n changes f o r t h e s e two l e v e l s .  In e f f e c t , S_ had t o  a b s t r a c t t h e r a t i o changes from t h e p a t t e r n changes and a d j u s t t h e l e v e r accordingly.  Although  a response measure was not o b t a i n e d on t h e motor  performance, t h e t a s k appeared t o be v e r y d i f f i c u l t .  In f a c t , t h e t a s k  appeared t o be i m p o s s i b l e t o e x e c u t e w i t h any degree of a c c u r a c y , as i n d i c a t e d byS_s' p o s t e x p e r i m e n t a l  reports.  Thus, i t was s a f e t o p l a c e  t h i s t a s k a t t h e extreme end o f t h e motor t a s k d i f f i c u l t y d i m e n s i o n .  An  e v a l u a t i o n o f t h e response c o m p a t i b i l i t y dimension suggested t h a t t h e experimental  c o n d i t i o n s were indeed  not h i g h l y c o m p a t i b l e ,  r e s p e c t t o one c r u c i a l a s p e c t o f t h e t a s k . visual  at least with  That i s , changes of d i s t i n c t  l e v e l s had t o be t r a n s l a t e d i n t o c o n t i n u o u s  motor a d j u s t m e n t s .  In summary t h e n , t h e v i s u a l - m o t o r t a s k c o u l d be c o n s i d e r e d as c o n t a i n i n g a high  l e v e l o f motor t a s k d i f f i c u I t y as we 11 as a low l e v e l  o f response c o m p a t i b i l i t y . Hence, i n o r d e r t o e v a l u a t e p o s s i b l e r e t e n t i o n l o s s e s due t o t h e s e two components o f t h e motor t a s k , an i n t e r f e r e n c e c o n d i t i o n c o n t a i n i n g a s m a l l e r motor t a s k d i f f i c u l t y component as w e l l as a l a r g e r response c o m p a t i b i l i t y component had t o be c r e a t e d f o r an e f f e c t i v e comparison c o n d i t i o n .  P i l o t work i n d i c a t e d t h a t  a response a p p a r a t u s c o n t a i n i n g f i v e m i c r o s w i t c h e s  placed  i n a semi-  c i r c u l a r arrangement, t o f i t t h e c u r v a t u r e o f t h e hand, might c o n s t i t u t e  69  a less d i f f i c u l t and more compatible response c o n d i t i o n .  In t h i s condition,  Ss would have to press one of the buttons in accordance with one of the five  levels of black-white r a t i o s . Assuming that a comparison between adjusting a lever and pressing a  button could, at least to some extent, evaluate retention  losses related  to the s p e c i f i c motor component of the interpolated a c t i v i t y ,  i t also  became necessary to evaluate to what extent the visual input of the polated task was responsible for retention  losses.  inter-  If an appropriate  analogue of the visual input information could be found in the verbal modality, the s i m i l a r i t y component could be further evaluated.  However,  a d i r e c t translation of the visual information into verbal components appeared impossible.  Although there were f i v e d i f f e r e n t  could be e a s i l y translated into f i v e d i f f e r e n t  ratios  which  numbers presented auditor-  ial l y , an attempt to find an analogue for the superimposed pattern changes resulted in a rather f u t i l e search. visual  The f i n a l verbal analogue of the  information to be processed during the interpolated  activity  consisted of the auditory presentation of a number sequence from one to f i v e , where one represented black and f i v e represented white.  The taped  number system corresponded to the appropriate r a t i o changes in the visual condition.  Apart from number changes which occurred once per second,  each number was repeated once at .5 second in an attempt to create an analogue of pattern changes of the visual presentation.  The obvious  shortcoming of t h i s auditory analogue was, of course, the absence of a comparable d i s t o r t i o n of information which was obtained in the visual presentation by the accompanying pattern changes.  It should be noted here  70  that the shortcomings of this auditory analogue contain potentially serious implications with respect to the interpretation of r e s u l t s .  For  example, any response differences between verbal and visual presentations of the interpolated condition  would have to be considered in terms of  modality s p e c i f i c e f f e c t s as well as corresponding changes in task demand requi rements. In order to obtain more information about the nature of  retention  losses obtained in the visual-motor condition of Experiments I and  II,  a f a c t o r i a l combination of both response demands and both presentation modalities of the interpolated task, tested under visual or verbal coding conditions, was considered as an appropriate assessment.  Because of the  exploratory nature of t h i s experiment, s p e c i f i c predictions were not made.  Regardless of the r e s u l t s , though, i t was expected that the data  should provide some information to isolate s i m i l a r i t y , a t t e n t i o n , and motor components underlying retention  losses of the visual-motor task.  METHOD Subjects and Design Eighty Ss from second year undergraduate Psychology courses participated  in t h i s experiment.  Except to keep male-female r a t i o s constant,  ^s were randomly assigned to one of eight groups for individual t e s t i n g . Four groups received visual patterns and the other four groups received word s t i m u l i , as in Experiments I and II.  Each stimulus condition was  tested under four d i f f e r e n t types of interpolated a c t i v i t i e s , consisting of a f a c t o r i a l combination of the two motor tasks and the two presentation modalities of the interpolated a c t i v i t y .  In e f f e c t ,  for each stimulus  71  condition, two groups received the visual presentation of the  interpolated  a c t i v i t y and had to respond either by adjusting a lever or by pressing a button.  S i m i l a r l y , two groups in each stimulus condition received the  auditory analogue of the interpolated a c t i v i t y and responded with one of the two motor tasks. Material The stimulus m a t e r i a l ,  i.e.,  words from Experiments I and II, verbal coding conditions.  the visual patterns and sets of  were again used for the visual and  In a d d i t i o n , the visual pattern sequence  used in the visual-motor conditions in Experiments I and II a l l conditions tested with visual presentation of the activity.  three  was used for  interpolated  For the groups receiving an auditory presentation of the  interpolated a c t i v i t y , a number sequence, representing the corresponding black-white r a t i o changes of the visual presentation, was recorded and presented on a tape recorder.  The auditory presentation consisted of  a recording of the numbers one to f i v e , arranged in accordance with the r a t i o changes.  The numbers were presented at a rate of one per second,  with each number repeated once after .5 second. Apparatus The stimulus material presented on f i l m . activity,  and the visual interpolated a c t i v i t y were  For the auditory presentation of the  the screen was darkened out during the retention  interpolated i n t e r v a l , and  a tape recorder was activated to present the number sequence.  The  apparatus for the response task of the interpolated a c t i v i t y consisted of either a lever arrangement  labelled "black to white" or "one to f i v e "  72  for the visual or auditory presentation of the interpolated  activity  respectively, or consisted of a f i v e button arrangement with similar labels.  The response apparatus in each condition was hooked up to an  elaborate set of  inoperative test equipment, to give the impression  that accurate measurements were being obtained on the performance of the interpolated  activity.  Procedure The general procedure was unchanged from the previous experiments. In f a c t , the visual-motor conditions requiring lever adjustments were e s s e n t i a l l y r e p l i c a t i o n s of the visual-motor groups in Experiments I and II.  The remaining groups differed only with respect to the s p e c i f i c  task demands of the interpolated a c t i v i t y .  For instance, the v i s u a l -  motor group requiring button press responses received the visual presentat i o n of the interpolated a c t i v i t y and was instructed to press the corresponding buttons labelled from a l l  black to a l l white.  The auditory  interpolated a c t i v i t y groups, in turn, received the taped number sequence during the retention  interval  and had to either adjust the lever  labelled  one to f i v e , or press the corresponding buttons in the other group.  These  four interpolated a c t i v i t y conditions were tested under both visual and verbal stimulus conditions.  The response task to the stimulus material  consisted, as in Experiments I and II,  of either the reproduction of the  stimulus pattern or written recall of the verbal  stimuli.  RESULTS AND DISCUSSION Since the dependent measures obtained in the visual and verbal stimulus conditions d i f f e r e d , the data were analyzed as two separate  73  experiments.  Responses f o r the v i s u a l  Experiment  recorded w i t h r e s p e c t  well the  I,  measures  interference indicated  auditorially  a  conditions. larger  presented  due t o t h e two m o t o r both  interpolated  tasks  modality  of the interpolated  cant modality  lever  effect  correct  I,  for visually  2).  Table  II,  T a b l e s 7 a n d 8).  condition, visual  versus button.  In o t h e r  Was  words,  with  factors:  interpolated  activity  than  to the retention  differences  a)  F(I,36)=I0.80; p<.OI,  for d ' scores  effect  the auditory of v i s u a l l y  (Appendix  with changes in  r e g a r d l e s s o f t h e motor t a s k ,  was more d e t r i m e n t a l  for  A 2 x 2 analysis of  condition,  no s i g n i f i c a n t  presentation  both  v e r s u s a u d i t o r y ; and  F(I,36)=8.95; p<.OI,  There  than  in  B o t h a n a l y s e s showed a s i g n i f i -  of the interpolated  r e s p o n s e s , and  tasks.  loss  response trend  r e s p o n s e m e a s u r e s was p e r f o r m e d  for  motor  responses as  c o n d i t i o n s , with only minor  (Appendix  with  response t a s k ,  The general  retention  variance  b)  t o t h e number o f c o r r e c t  as in  F i g u r e s 4 a n d 5 show t h e r e s p e c t i v e mean v a l u e s f o r  as d ' scores. four  stimulus c o n d i t i o n s were,  the visual  presentation presented  of the  stimulus  information. T h e mean in Appendix trend  across  decrease  I,  recall Table  scores 3,  between  A t t h e same t i m e t h e r e at  least  of  variance  There  and r e v e a l e d  interpolated  in recall  f o r the visual  f o r the verbal  a similar,  conditions. auditory  s t i m u l u s c o n d i t i o n s a r e shown y e t more a m b i g u o u s r e s p o n s e  There appeared  and v i s u a l  interpolated  a p p e a r e d t o be a d i f f e r e n c e interpolated  supports t h i s  initial  general  conditions.  between m o t o r  conditions (Figure  impression  was a . s i g n i f i c a n t m a i n e f f e c t  t o be a  (Appendix  due t o m o d a l i t y ,  6). II,  tasks,  An a n a l y s i s Table  9).  F(1,36)=I7.30; p<.01,  75  2.0  1.5. CO  w « o o to  1.0  .5  BUTTON LEVER  0„0  -o5  JL  VISUAL  AUDITORY  PRESENTATION MODALITY OF INTERPOLATED ACTIVITY \  \ '  FIG. 5 Mean d« scores for visual coding in Exp III, 0  \  \  PRESENTATION MODALITY OF INTERPOLATED ACTIVITY i  FIG. 6  Mean v a l u e s o f v e r b a l r e c a l l s c o r e s i n Exp. I I I .  77  and no differences due to the motor tasks.  However, the  interaction  between modality and motor task was also s i g n i f i c a n t , F(I,36)=4.08; p<.05.  An analysis of simple e f f e c t s c l a r i f i e d the nature of t h i s  action (Appendix II,  Table 10).  There was a greater retention  inter-  loss for  visual than auditory presentations of the interpolated a c t i v i t y with button press responses, F(I,36)=19.09; p<.0l, than with the lever response, F(I,36)=2.28; p<.05.  In a d d i t i o n , there was a corresponding difference  between motor responses to visual presentations, F(I,36)=6.93; p<.05. In other words, there was no difference between response levels for both auditory groups and the lever adjustment group in the visual presentation. However, a greater recall  loss was obtained when the interpolated  activity  consisted of pressing the corresponding buttons to visual changes during the retention  interval.  An interpretation of these data within the theoretical  framework  proposed generates the following tentative conclusions about s i m i l a r i t y , attention, and motor components underlying retention  losses.  The s t a t i s t i c a l analysis for both coding conditions shows a s i g n i f i cant main e f f e c t for interference modality. interpolated a c t i v i t y  Visual input during the  leads to a larger retention  loss than verbal  While t h i s response trend in the visual coding condition  initially  suggests that a s i m i l a r i t y component is underlying retention visual  interference  Is more detrimental  interference, a s i m i l a r main e f f e c t dicts this  input.  losses,  i.e.,  to visual coding than verbal  in the verbal coding condition contra-  interpretation.  Thus, as already mentioned in the introduction to this experiment,  78  response differences between visual and auditory presentations of the interpolated a c t i v i t y must be considered in light of modality changes as well as inherent changes in the attention demands.  The recall differences  in the verbal coding condition cannot be interpreted  in terms of a main  effect for s i m i l a r i t y , since the visual presentation leads to the greatest retention  loss.  Retention losses must therefore be considered as a  function of d i f f e r e n t i a l  attention demands between modalities.  This  suggests that a motor response to v i s u a l l y presented black and white r a t i o changes, which have to be abstracted from pattern changes, contains an inherently higher central processing component than a response to a number sequence. S t i l l , there are two s p e c i f i c aspects of the data which suggest response differences due to the s i m i l a r i t y component.  F i r s t , the response  differences between auditory and visual presentations are greater  relatively  in the visual than verbal coding condition (Appendix I,  Table  4).  The larger percentage losses in visual coding could be an indicator of an additional retention is no verbal r e c a l l  loss due to the s i m i l a r i t y e f f e c t .  Second, there  loss between modalities in the motor task requiring  adjustments, whereas the respective comparison in visual coding shows a significant difference.  However, an interpretation of these aspects of  the data-in terms of s i m i l a r i t y appears not j u s t i f i e d , since the data c l e a r l y point out that a t t e n t i o n ,  s i m i l a r i t y , and motor components do not  e x i s t in i s o l a t i o n , but display a complex interaction between stimulus coding and the total  interpolated a c t i v i t y demands.  is a r e l a t i v e l y strong indication for retention  In other words, there  losses due to  attention  79  demands which appears to be overshadowing any clear e f f e c t s due to s i m i larity. The evaluation so f a r , however, ignores the third postulated ference component, i . e . ,  inter-  the motor task, which appears to be equally  ambiguous in i t s interpretation.  There is no difference due to the motor  task changes in the visual coding conditions.  In contrast, there is a  small s i g n i f i c a n t drop between lever adjustment and button pressing in the visual interpolated task for verbal coding.  In f a c t , t h i s response  trend is a d e f i n i t e reversal from predictions made on the basis of d i f f i c u l t y and response compatibility dimensions discussed in the  intro-  duction . Information gained in S_'s post experimental  reports suggests several  interesting points which might lead to some c l a r i f i c a t i o n of t h i s problem. Responding to the a u d i t o r i a l l y presented number sequence by either  adjust-  ing a lever or pressing a button appeared to be a task well within the c a p a b i l i t y of each S_, a f t e r a few practice t r i a l s .  This is not too sur-  p r i s i n g , since the task b a s i c a l l y requires one response to a d i s t i n c t number, once per second.  Except for d i f f e r e n t  latencies, the task  could be performed with r e l a t i v e ease in both coding conditions.  In  other words, the motor component did not constitute a s i g n i f i c a n t problem in the performance of the interpolated a c t i v i t y , and retention must be largely attributed  losses  to central processing requirements inherent  in  processing the rapidly presented information. Assuming that a s i m i l a r motor component is involved in responding to visual  information, the increases in retention  losses during visual presenta-  80  tions of the interpolated a c t i v i t y subsequently constitute an increase in central processing required in recognizing and abstracting the  ratio  changes from the total display sequence, in contrast to central ing demands required to respond to number sequences.  The verbal  difference in motor tasks for visual Interpolated material, shows that t h i s is not the case in every comparison. can again be forwarded from Ss' reports.  processrecall  however,  Some c l a r i f i c a t i o n  When responding to the visual  changes with lever adjustments, S_ is responding continuously, whether correctly or i n c o r r e c t l y , since the S_'s hand always remains on the  lever.  In the button press c o n d i t i o n , in contrast, ^ has to make a d i s t i n c t response in order to indicate that a given r a t i o  level has been recognized.  It seemed that the speed of r a t i o changes and the d i f f i c u l t y  in recogniz-  ing and abstracting the r a t i o changes from the pattern changes constitutes a s i t u a t i o n where d i s t i n c t motor responses cannot be made with any great degree of c e r t a i n t y .  In other words, button pressing appears to be a  less compatible response condition in t h i s s i t u a t i o n .  Thus, it  is  possible to expect a larger central processing component to be involved in t h i s motor condition in v i s u a l l y presented Interpolated a c t i v i t i e s . Elusive as t h i s explanation i s , the Immediate question a r i s i n g i s , of course, why does t h i s difference not emerge In visual coding conditions. The answer here Is rather easy to f i n d , though does l i t t l e to c l a r i f y the reason for motor task differences: stimuli  the retention  level for visual  in visual interpolated conditions shows a d e f i n i t e f l o o r e f f e c t .  The percentage of correct reproductions are 22.40$ and 21.84$ for button and lever responses (Appendix I,  Table 4 ) , and d ' scores put the  retention  81  levels in these conditions very near to zero (Appendix I, other words, there is r e a l l y no room for d i f f e r e n t i a l  Table 3).  In  responding at t h i s  response l e v e l . Unsatisfactory, and at times rather subjective, as these explanations might be, the overall evaluation of this experiment in terms of  isolating  c r i t i c a l components of the interference task generates several tentative conclusions:  a) changes in attention demands, though confounded with  presentation modality, constitute a c r i t i c a l  factor in retention  losses;  b) s i m i l a r i t y e f f e c t s do not c l e a r l y emerge in these conditions; and c) the motor task appears as a rather losses.  In e f f e c t ,  retention  i n s i g n i f i c a n t aspect of  retention  losses in visual-motor or verba I-motor  conditions are not due to the motor performance, but instead are due to central processing demands required to process the information  inherent  in the visual or verbal presentation of the interpolated a c t i v i t y .  In  a d d i t i o n , attention and s i m i l a r i t y components in these tasks appear to be confounded and cannot be c l e a r l y separated. In summary, retention  losses due to the postulated s i m i l a r i t y  effect  are largely overshadowed by corresponding changes in central processing demands between auditory and visual presentations.  Furthermore, response  differences due to the motor tasks did not emerge, except for one comparison where the differences could be interpreted processing demands.  in terms of central  Though this experiment did not succeed in c l e a r l y  delineating the effects of attention,  s i m i l a r i t y , and motor components,  i t provides consistent evidence in support of the interpretation of the visual-motor groups in Experiments I and II.  That i s , retention  losses  82  due to the visual-motor condition in the previous experiments can be interpreted  without reference to a s i g n i f i c a n t retention  motor component.  loss due to the  83  GENERAL DISCUSSION The overall aim of t h i s research project was to investigate STS processes, e s p e c i a l l y with respect to the question of verbal and visual systems.  It seemed of p a r t i c u l a r  interest to evaluate to what extent  the two postulated coding systems could be considered as independent or interrelated aspects of STS.  It was reasoned that common and d i s t i n c t  c h a r a c t e r i s t i c s of the verbal and visual STS could be explored by observing the r e l a t i v e coding e f f i c i e n c y in both modes after a series of polated a c t i v i t i e s varying along two dimensions, i . e . ,  inter-  attention and  similarity. The overall r e s u l t s confirm that common and s p e c i f i c retention losses can be obtained employing these experimental manipulations. Retention losses due to changes in attention demands appeared to be comparable in the visual and verbal coding conditions, regardless of the modality of the interpolated a c t i v i t y .  Therefore, attention diversion  can be considered as a common factor underlying retention verbal and visual coding.  losses in  In a d d i t i o n , when the maintenance of the  stimulus information and the performance of the interpolated task required processing of information of the same coding mode, retention losses were larger different modes.  than i f processing of the two tasks involved Retention losses of t h i s nature were interpreted  in  terms of s i m i l a r i t y e f f e c t s . Since common and d i s t i n c t components underlying retention verbal and visual coding can be i d e n t i f i e d ,  losses in  i t was suggested that the  maintenance of information in STS could be described in terms of these  84  two retention in which:  loss components.  That i s , given an experimental condition  a) no attention diversion is introduced, i . e . ,  the total of  the central processing capacity is u t i l i z e d for stimulus coding; and b) in which there is no processing of a d d i t i o n a l , same modality  Informa-  t i o n , a state of optimal short-term processing should be observed.  This  state could then be described as consisting of central processing plus modality s p e c i f i c coding processes. The e f f e c t s of attention diversion underlying retention STM experiments has been discussed in detail and S h i f f r i n (1968).  losses in  by theorists such as Atkinson  In f a c t , t h i s general concept of attention  is  equally applicable to the models of Waugh and Norman (1966) and Neisser (1967), and is also quite in agreement with the concept of attention primary memory used by William James (1896).  in  In James' terms, informa-  tion in primary memory has to be continuously attended to for r e c a l l . Isolated examples of the effects of s i m i l a r i t y ,  in terms of modality  s p e c i f i c interference e f f e c t s , have also been reported ( e . g . , Parks, Parkinson, and K r o l l ,  1971; Posner, 1969).  Furthermore, there have also  been attempts to combine both dimensions into a single experiment. example, Cohen and Granstrom (1969) have investigated visual e f f e c t s with varying degrees of attention demands.  For  interference  However, a detailed  evaluation of s i m i l a r i t y and attention e f f e c t s in both visual and verbal coding conditions within a single experimental paradigm has not yet been available. The importance of the present research, therefore,  l i e s in the i n v e s t i -  gation of attention and s i m i l a r i t y manipulations of both interpolated  85  modalities in both verbal and visual coding conditions. of t h i s research approach l i e s largely in i t s potential  The advantage usefulness in  generating d i r e c t comparisons of attention and s i m i l a r i t y e f f e c t s across interference modalities and coding modes.  Of special interest  comparison is the evaluation of the r e l a t i v e and s i m i l a r i t y e f f e c t s in STS losses.  importance of  in t h i s  attention  If a consistent trend between  these two factors can be established, a more detailed conceptualization of verbal and visual STS can be obtained. similarity  For example, i f attention  e f f e c t s account for a consistently larger retention  or  loss, a  more refined evaluation of the nature of STS processes w i l l be a v a i l a b l e . Indeed, if the responses in Experiments I and II  are converted into  percentages of correct r e c a l l , some indication of the r e l a t i v e  importance  of losses due to attention and s i m i l a r i t y can be extracted from the data (Figure 7).  The following example will  lying t h i s evaluation:  i l l u s t r a t e the rationale under-  a) the rehearsal group in Experiment II  is the  reference point for verbal coding e f f i c i e n c y after the given retention i n t e r v a l ; b) the task of counting backwards in Experiment II  was defined  in terms of an attention component and a s i m i l a r i t y component; c) the task of counting forwards In Experiment II the s i m i l a r i t y component.  was interpreted  in terms of  A comparison of correct r e c a l l percentages  for these three conditions should then lead to an evaluation of  retention  losses which, more or l e s s , can be d i r e c t l y attributed to attention and s i m i l a r i t y components inherent in the verbal  interference in Experiment  I I. Hence, the percentage difference between the rehearsal group and the  86  100 _  EXP. II  90 J EXP. I  80 i-3  o  w  70 .  EH O W « «  60 .  K  o u  r  50 .  w  o  g  Pi  ko  30  1  IMM  0-DELAY  FIG. 7„  BW  1  LOW  HIGH VERBAL  LOW.  HIGH VISUAL  VISUALMOTOR  10 SECOND DELAY  Percentage values f o r correct r e c a l l i n Ezp  0  I and I I  0  87  counting backwards group constitutes the retention bined e f f e c t of attention and s i m i l a r i t y , (Appendix I,  Table 5).  i.e.,  loss due to the com-  97.56$ - 47.33$ = 50.23$  Furthermore, the difference between the rehearsal  group and the counting forwards group should be an estimate of the retention  losses due to the s i m i l a r i t y component alone, i . e . ,  88.00$ = 9.56$.  In other words, retention  losses due to the  97.56$ similarity  component by i t s e l f constitute a loss of 9.56$, whereas retention due to the combined e f f e c t constitute a 50.23$ l o s s .  Thus, by subtracting  percentage losses due to the s i m i l a r i t y component from the total an estimate of retention  Since attention  losses,  losses due to attention demands inherent  counting backwards should be obtained, i . e . ,  losses  in  50.23$ - 9.56$ = 40.67$.  is considered as a common factor in verbal and visual  coding, and since the attention component in counting backwards should be constant across verbal and visual coding conditions, i t would be expected that percentage losses due to counting backwards in Experiment I should be comparable to those attributed counting backwards in Experiment  to the attention component in  II.  Before pursuing t h i s evaluation,  i t should be noted that these per-  centage losses cannot be considered as absolute values in a comparison. F i r s t , since response levels in verbal and visual coding show a difference for the respective rehearsal groups, i . e . ,  97.56$ versus 82.66$, it cannot  be expected that a given percentage loss with respect to one rehearsal level  is comparable to that obtained in the other.  Second, i t must be  admitted that a given percentage loss due t o , for example, a s i m i l a r i t y component might contain other than retention  losses due to the  similarity  88  effect.  Thus, losses due to s i m i l a r i t y and losses due to a t t e n t i o n , as  used in t h i s context, should be considered as merely describing the most predominant  component in a s p e c i f i c comparison.  So far then, i t has been shown in Experiment II component of verbal  interference accounts for a 9.56$ l o s s , and the  attention component accounts for 40.67$ of retention able retention  that the s i m i l a r i t y  losses.  A compar-  loss due to the attention component in counting backwards  should therefore be obtained in the visual coding condition in the difference between the rehearsal and counting backwards group in Experiment I,  i.e.,  82.66$ - 52.66$ = 30.00$.  It can be seen that  retention  losses due to the attention component inherent in counting backwards are larger in verbal than in visual coding. A s i m i l a r evaluation of s i m i l a r i t y and attention components is a v a i l able for visual Interference in Experiment I. groups are:  The analogous comparison  a) the rehearsal group; b) the visual-motor group, d i s p l a y -  ing a s i m i l a r i t y and attention component; c) the high attention visual group, displaying the e f f e c t s of the s i m i l a r i t y component by  itself.  Hence, the percentage difference between the rehearsal and visual-motor group constitutes the retention  loss due to the combined e f f e c t of  attention and s i m i l a r i t y ,  82.66$ - 31.91$ = 51.75$.  i.e.,  Furthermore,  the difference between the rehearsal group and the high attention visual group should be an estimate of retention component alone, i . e . ,  losses due to the  82.66$ - 66.41$ = 16.25$.  similarity  In other words, reten-  tion losses due to the s i m i l a r i t y effect account for 16.25$ whereas losses due to the combined e f f e c t constitutes a 51.75$ retention l o s s .  Subsequently,  89  retention  losses due to the attention component inherent in the v i s u a l -  motor task in Experiment I can be estimated to account for a 35.50$ l o s s , i.e.,  51.75$ -  16.25$ = 35.50$.  Again, if attention  is considered as  a common factor in verbal and visual coding, a comparable percentage loss should be obtained in the visual-motor group in verbal coding. percentage difference in Experiment II  between the rehearsal group and  the visual-motor group is 27.56$, i . e . , other words, retention  The  97.56$ - 70.00$ = 27.56$.  In  losses due to the attention component inherent in  the visual-motor task are larger in visual than verbal coding, yet show a comparable trend to that obtained in the verbal interference evaluation. In a d d i t i o n , an evaluation of retention conditions,  interpreted  losses of  interference  in terms of s i m i l a r i t y , can also be undertaken.  The s p e c i f i c emphasis here centers around modality s p e c i f i c versus cross modality interference e f f e c t s . group in Experiment I  For example, the high attention visual  was interpreted  in terms of  l a r i t y and constituted a 16.15$ retention  loss.  losses due to s i m i -  The identical  condition in verbal coding leads to a 2.00$ retention the s i m i l a r i t y component in Experiment II, group, resulted in a 9.56$ retention  loss.  polated task leads to a 4.65$ retention of a given interpolated a c t i v i t y  i.e.,  Conversely,  low attention verbal  In Experiment I t h i s  loss.  interpreted  loss.  interpolated  Hence, retention  interlosses  in terms of s i m i l a r i t y are  greatly reduced if d i f f e r e n t modalities are involved in stimulus coding and in the performance of the interpolated a c t i v i t y . a clear differentiation  In e f f e c t ,  there  is  between modality s p e c i f i c and cross-modality effects  in both interpolated modalities and t h e i r respective coding conditions.  90  Despite the shortcomings of this evaluation, several consistent trends emerge in t h i s numerical comparison. comparable retention  The f i r s t point l i e s in the highly  loss in both experiments due to the  interpolated  conditions containing both s i m i l a r i t y and attention components. backwards leads to a 50.23$ loss in verbal coding.  The visual-motor  group displays a similar 51.75$ loss in visual coding. of the different results,  it  Counting  However, in  light  s p e c i f i c experimental manipulations underlying these  Is unclear what s i g n i f i c a n c e , if any, t h i s unexpectedly  comparable retention  loss contains.  about coding and retention  Except for unfounded speculations  loss functions, this comparison will be d i s -  carded as a coincidence of no theoretical  value.  Second, there has been a consistent relationship between the estimates of retention  losses due to the attention component in one experiment to  that obtained in the other experiment.  For example, retention  losses  due to the attention component of counting backwards were 10 to \\% higher under verbal coding than under visual coding conditions. 1  retention  Conversely,  losses due to the attention component of the visual motor task  were about 8% higher in visual coding than in verbal coding. comparisons then, the estimates of retention  losses due to the  In both attention  component were higher when the same modality was involved in processing the stimulus and interpolated a c t i v i t y .  The implications of t h i s con-  sistent trend are that, apart from the s i m i l a r i t y and attention component, there must be some type of interactive effect between the modality of the two tasks which constitutes an a d d i t i o n a l , f a c t o r contributing to the total retention  losses.  In light of the data, the nature of the  interaction  91  appears to be such that retention  losses, with a constant attention com-  ponent, are increased in a same modality experimental s i t u a t i o n .  Though  the existence of an interaction between s i m i l a r i t y and attention appears as a reasonable description of these data, a convincing evaluation of t h i s problem would have to be undertaken in an investigation of s p e c i f i c parametric changes in attention and s i m i l a r i t y components in both coding conditions. The t h i r d finding appears less ambiguous, yet at the same time of greater theoretical  importance.  This trend describes the r e l a t i v e  reten-  tion losses of s i m i l a r i t y and attention components in both experiments. The estimates of retention  losses due to s i m i l a r i t y and attention  inherent in visual interpolated a c t i v i t i e s of Experiment I constitutes 16.25$ and 34.60$ respectively.  Conversely, in Experiment II  the s i m i -  l a r i t y component accounts for 9.67$ and the attention component for 40.67$ of retention  losses of the verbal  experiments, retention  interpolated a c t i v i t y .  Hence, in both  losses due to the attention component constitute  by far the greater aspect of t o t a l retention for in terms of s i m i l a r i t y .  losses than those accounted  In other words, manipulations of the  attention continuum generates a larger retention  loss than changes along  the s i m i l a r i t y dimension, at least for the manipulations in t h i s research. The fourth trend  in t h i s evaluation is a complimentary aspect of the  last part and is concerned with the clear d i s t i n c t i o n obtained between modality s p e c i f i c and cross modality a c t i v i t i e s interpreted  e f f e c t s of the two  In terms of s i m i l a r i t y alone.  interpolated  Counting forwards  as well as the high attention visual group c l e a r l y show comparable e f f e c t s  92  across same modality versus d i f f e r e n t modality experimental s i t u a t i o n s . For each interpolated modality, modality s p e c i f i c e f f e c t s are always more pronounced than cross-modality e f f e c t s on the retention of stimulus Information. The last two observations appear of importance in generating a more refined theoretical conceptualization of STS processes. evidence gained about the r e l a t i v e retention  F i r s t , the  losses due to the  attention  and s i m i l a r i t y components can be used to specify the Importance of central processing and s p e c i f i c coding processing components underlying the maintenance of information in STS.  Second, the evidence obtained about the  s i m i l a r i t y and attention component underlying retention provide a clear separation of retention  losses should  losses in terms of  attention  diversion and d i r e c t Interference in STS. The information gained about the r e l a t i v e and attention components In retention  importance of  similarity  losses provides an interesting  expansion of previous conceptualizations of STS processes. already been stated that the two types of retention  It has  losses obtained in  STS could in turn be used to describe the processes involved In the maintenance of information in STS.  If the r e l a t i v e  l a r i t y and attention components in retention an indicator of the r e l a t i v e  importance of the s i m i -  losses can be considered as  importance of central processing and the  s p e c i f i c coding processes in the maintenance of information in STS, the following important addition to the conceptual framework is warranted: maintenance of information In STS r e l i e s to a greater extent on central processing components than on modality s p e c i f i c coding components.  Hence,  93  STS can be conceptualized as consisting largely of the central processing capacity, u t i l i z i n g the most appropriate modality s p e c i f i c coding process for a given stimulus condition.  The theoretical contribution of t h i s  evaluation to the concept of STS therefore appears to be two f o l d .  First,  a common central processing capacity is identified as underlying d i s t i n c t visual and verbal coding systems in STS.  Second, the maintenance of  information in both coding modes r e l i e s largely on the amount of central processing capacity available for verbal or visual coding. Apart from providing a more s p e c i f i c conceptualization of STS processes, the data also contribute new information regarding the general concept of interference in STS.  The issue raised here centers around  a c l a r i f i c a t i o n of the nature of retention diversion and d i r e c t interference.  losses in terms of  attention  For example, in previous verbal STM  experiments using counting backwards as an interpolated a c t i v i t y , typical  interpretation of retention  the  losses was made in terms of rehearsal  prevention ( e . g . , Atkinson and S h l f f r i n , 1968).  To paraphrase Atkinson  and S h l f f r i n , the arithmetic task plays the role of preventing rehearsal and has no d i r e c t interference e f f e c t . coding are terminated when attention The interpretation of retention  That i s , attempts at stimulus  is given to counting backwards.  losses in the present research, however,  c l e a r l y points out that attention diversion constitutes only one s p e c i f i c aspect of retention  losses.  An evaluation of verbal t h i s argument.  interpolated a c t i v i t y e f f e c t s w i l l  It was shown that counting backwards generated  losses which were interpreted  in terms of  illustrate retention  losses due to s i m i l a r i t y and  94  attention  In Experiment II,  Experiment I.  and losses in terms of attention alone in  Thus, the previous interpretation of the task of counting  backwards in terms of attention diversion has to be modified.  That i s ,  there is a component of attention diversion as revealed by the percentage losses in Experiments I and II.  However, if the same modality is involved  in the performance of the interpolated task and in stimulus coding, there is an additional retention  loss based on the s i m i l a r i t y e f f e c t .  losses due to the s i m i l a r i t y component can then be interpreted  Retention in terms  of a d i r e c t interference e f f e c t . This interpretation  is further supported by an evaluation of the  task of counting forwards in Experiments I and II. tation of the results in Experiment II  A previous interpre-  could have been:  counting forwards  prevents rehearsal through attention d i v e r s i o n , therefore, verbal coding is reduced.  The absence of a comparable decrease In visual coding,  however, indicates that an interpretation is inappropriate in t h i s case.  in terms of attention diversion  In other words, verbal r e c a l l  losses are  a function of the s i m i l a r i t y e f f e c t and therefore can be interpreted terms of d i r e c t interference.  A similar evaluation of retention  in  losses  due to visual interpolated a c t i v i t i e s in terms of attention diversion and d i r e c t interference further supports the consistency of t h i s  interpretation.  Thus, two q u a l i t a t i v e l y d i s t i n c t types of retention losses in STS can be i d e n t i f i e d .  On one hand, there are retention losses due to the  s i m i l a r i t y e f f e c t , as defined in t h i s research, which are modality s p e c i f i c and are interpreted  in terms of d i r e c t interference between STS processes.  On the other hand, there are retention  losses due to the attention component,  95  which display comparable e f f e c t s in verbal and visual coding and are preted in terms of attention d i v e r s i o n .  inter-  Thus, t h i s research has succeeded  in providing a more refined evaluation of retention  losses in STS, such  that i t becomes possible to interpret the previously used concept of attention diversion ( e . g . , Atkinson and S h i f f r i n , 1968)  in terms of a  combination of an estimate of attention diversion as well as an estimate of d i r e c t  Interference.  The data of t h i s research might have far reaching implications for future empirical and theoretical evaluations of STS.  To emphasize the  contribution of this research, three s p e c i f i c conclusions have to be considered:  f i r s t , the separation of attention and s i m i l a r i t y  in STS retention  effects  losses; second, the interpretation of STS retention  losses in terms of attention diversion and d i r e c t interference e f f e c t s ; and t h i r d , the conceptualization of STS processes as a function of a predominant central process component and modality s p e c i f i c coding components, in t h i s case, verbal and visual coding components. However, while these refinements of STS processes have been c l e a r l y exposed tn t h i s research, the d i r e c t implications of these findings to current STS issues are d i f f i c u l t to assess.  On one hand, i t would seem  necessary to evaluate a l l previous research in light of the present, more detailed framework of STS processes to substantiate the general a p p l i c a b i l i t y of these conclusions.  On the other hand, the major  interest  generated by these data could probably l i e in the new research directions opened up, or at least suggested by these f i n d i n g s .  For instance, the  concept of s i m i l a r i t y , as defined in t h i s research, has been shown as a  96  crucial factor in STS.  Within t h i s framework i t would also become of  interest to determine if the s i m i l a r i t y e f f e c t  pertains merely to modality  differences, or whether t h i s concept could be generalized to manipulations within a given modality.  For example, could a s i m i l a r i t y e f f e c t be  obtained in the visual modality by contrasting pictures and random patterns in a f a c t o r i a l combination of both types of material  in the  stimulus and interpolated a c t i v i t y ? Of equal interest would be a more detailed evaluation with respect to central processing and s p e c i f i c coding processes in STS. it  is s t i l l  For example,  not clear what s p e c i f i c factors are underlying the r e c a l l  level of words a f t e r an interval of counting backwards.  It has been  stated that attention diversion and d i r e c t interference account for the recall  losses.  However, t h i s statement does not specify why about 50%  of the words are s t i l l  available for recall at t h i s point.  Depending on  the assumptions made in t h i s context, a series of rather unsupported interpretations could be forwarded.  For example, assuming the t o t a l  central processing capacity is used up in the task of counting backwards, then the r e c a l l process  level must be a function of the modality s p e c i f i c coding  in STS.  Conversely, i t can be assumed that counting backwards  requires the use of only a portion of the central processing capacity, or on the other hand, that attention Interpolated and stimulus task.  is constantly s h i f t i n g between the  If t h i s were the case, the f i n a l  recall  level would have to be interpreted with reference to a central processing component. From the above examples, i t can be seen that t h i s research is  97  r a i s i n g a number of r e l a t i v e l y unexplored aspects of STS processes.  In  e f f e c t , apart from the contributions to the present state of knowledge of STS processes, a major importance of these findings probably l i e s in the potential  usefulness in generating new research which can lead to  a more comprehensive conceptualization of STS processes. SUMMARY The purpose of t h i s research centered around an evaluation of STS processes with respect to the s p e c i f i c relationship between verbal and visual coding systems.  In order to evaluate verbal and visual coding  c h a r a c t e r i s t i c s , the respective coding conditions were investigated as a function of a series of Interpolated dimensions:  a c t i v i t i e s d i f f e r i n g along two  a) changes in attention demands; and b) changes in the  modality of the interpolated task.  It was argued that changes in attention  demands, regardless of the modality of the interpolated task, should exert a r e l a t i v e l y constant effect on both coding condtions.  Changes in the  modality of the interpolated task, in t u r n , were expected to generate results exploring differences between modality s p e c i f i c and cross modality types of interference e f f e c t s .  The data supported these projections.  Two separate components of retention  losses were obtained.  One, the  attention component, which Is a function of changes in attention demands, has a comparable e f f e c t on verbal and visual coding.  Losses due to  attention therefore were considered as a common factor in verbal and visual STS.  Two, when the processes of stimulus information and Inter-  polated a c t i v i t y were s i m i l a r , larger retention  losses were observed than  when unrelated processes were Involved in the performance of both tasks.  98  These findings in both modalities were interpreted larity effect.  in terms of the simi-  The s i m i l a r i t y effect, in turn, was interpreted as evidence  for q u a l i t a t i v e l y d i f f e r e n t coding processes in verbal and visual STS. Furthermore, an evaluation of the r e l a t i v e retention losses attributed to attention and s i m i l a r i t y components strongly suggest that changes of the attention component account for a larger percentage of coding losses than those obtained due to the s i m i l a r i t y  effect.  The data suggested the following conceptualization of verbal and visual STS.  Central processing is the most Important aspect underlying  the maintenance of Information visual coding.  in STS and is common to both verbal and  Verbal STS is therefore conceptualized as consisting of  central processing and verbal coding components, and visual STS consists of central processing and visual coding components.  It was postulated  that the maintenance of information in STS r e l i e s to a large extent on the a v a i l a b i l i t y of central processing capacity with the modality s p e c i f i c coding component determining the most appropriate coding mode for a p a r t i c u l a r stimulus s i t u a t i o n . The data were further  Interpreted as providing evidence for two  q u a l i t a t i v e l y d i s t i n c t retention loss components.  Losses due to s i m i -  l a r i t y were Interpreted in terms of d i r e c t interference between processing similar types of material for the stimulus and interpolated a c t i v i t y . Losses due to attention were considered as a more refined estimate of the effects of attention d i v e r s i o n .  Thus, retention  preted in terms of attention diversion  losses previously inter-  can now be interpreted as a function  of an attention diversion component and a d i r e c t Interference component.  99  REFERENCES Atkinson, R. C. and S h i f f r i n , R. M. i t s control processes.  Human memory:  A proposed system and  In K. W. Spence and J . T. Spence ( E d s . ) ,  The Psychology of Learning and Motivation: and Theory, V o l . II, Baddeley, A. D. Nature,  Academic Press, New York, 1968, pp. 89-195.  Semantic and acoustic s i m i l a r i t y 1964, 204.,  Baddeley, A. D.  Advances In Research  in short term memory.  11 16-1 117.  Short-term memory for word sequences as a function of  acoustic, semantic and formal s i m i l a r i t y .  Quarterly Journal of  Experimental Psychology, 1966, JJ3, 362-365. Baddeley, A. D. and Warrington, E. K. long and short-term memory.  Amnesia and the d i s t i n c t i o n between  Journal of Verbal Language and Verbal  Behaviour, 1970, 9_> 176-189. Bernbach, H. A.  Replication processes in human memory and learning.  In  G. H. Bower and J . T. Spence ( E d s . ) , The Psychology of Learning and Motivation:  Advances in Research and Theory, V o l .  Ill,  Academic Press, New York, 1969, pp. 201-240. Brown, J . A.  Some tests of the .decay theory of  immediate memory.  Quarterly Journal of Experimental Psychology, 1958, 1  Buschke, H.  Input-output, short-term storage.  10, 12-21.  Journal of Verbal Learn-  ing and Verbal Behaviour, 1968, 7_, 900-903. Conrad, R.  Acoustic confusion in immediate memory.  B r i t i s h Journal of  Psychology, 1964, 55, 75-84. Cohen, R. L. and Granstrom, K. term visual memory. 1970, 22, 450-457.  Reproduction and recognition in short-  Quarterly Journal of Experimental Psychology,  100  Crawford, J . , Hunt, E. and Grahame, P.  Inverse forgetting  in STM.  Journal of Experimental Psychology, 1966, J_2, 3, 415-422. Dale, H. C. A. and Gregory, M. term memory.  Evidence for semantic coding in short-  Psychonomic Science, 1966, 5_, 75-76.  den Heyer, K. and Barrett,  B.  Selective loss of visual and verbal  t i o n in STM by means of visual and verbal Psychonomic Science, 1971, 25,  interpolated  I nterhemi spheric e f f e c t s on  reaction time to verbal and non-verbal visual s t i m u l i .  N. C.  Hemispheric assymetry:  Verbal and spacial encoding of visual s t i m u l i .  Glanzer, M.  Psychology, 1972,  Journal of  (in press).  Storage mechanisms in r e c a l l .  Spence ( E d s . ) ,  Journal  Psychology, 1971, 87, 415-422.  Geffen, G . , Bradshaw, J . L., and Nettleton,  Experimental  tasks.  100-102.  Geffen, G . , Bradshaw, J . L., and Wallace, G.  of Experimental  informa-  In G. H. Bower and J . T.  The Psychology of Learning and Motivation:  Advances  in Research and Theory, V o l . V, Academic Press, New York,  1972,  pp. 129-193. Glanzer, M. and Cunitz, A.  Two storage mechanisms in free r e c a l l .  Journal  of Verbal Learning and Verbal Behaviour, 1966, 5_, 351-360. H e l l y e r , S.  Frequency of stimulus presentation and short-term  in r e c a l l . James, W. Kintsch, W.  decrement  Journal of Experimental Psychology, 1962, 64,  P r i n c i p l e s of Psychology, Holt, New York,  1890.  Learning, Memory, and Conceptual Processes.  Sons, New York,  650.  John Wiley and  1970.  Kintsch, W. and Buschke, H.  Homophones and synonyms in short-term memory.  Journal of Experimental Psychology, 1969, 80, 403-407.  101  Klatzky, R. L.  Interhemlspheric transfer of t e s t stimulus representation  in memory scanning.  Psychonomic Science, 1970, 2J_, 201-203.  Klatzky, R. L. and Atkinson, R. C.  S p e c i a l i z a t i o n of the cerebral  hemisphere in scanning for information in short-term memory. Perception and Psychophysics, 1971, J_0_, 335-338. K r o l l , N. E. A . , Parks, T . , Parkinson, S. R., Bieber, S. C , and Johnson, A. L.  Short-term memory while shadowing:  of aurally presented l e t t e r s .  Recall of v i s u a l l y and  Journal of Experimental Psychology,  1970, 85, 220-224. Laughery, K. R.  Computer simulation of short-term memory:  decay model.  In G. H. Bower and J . T. Spence ( E d s . ) , The Psychology  of LearnIng and Motivation: Ill,  A component  Advances in Research and Theory, VoI.  Academic Press, New York, 1969, pp. 136-200.  Margrain, S. A.  Short-term memory as a function of input modality.  Quarterly Journal of Experimental Psychology, 1967, M i l l e r , G. A.  The magical number, plus or minus two:  capacity for processing information.  12, 109-114.  Some limits in our  Psychological Review,  1956,  63, 81-97. Milner, B.  Neuropsychological evidence for d i f f e r i n g memory processes.  Abstract for the symposium on short-term and long-term memory. Proceedings of the 18th international Moscow, 1966, Amsterdam: Murdock, B. B . , J r .  congress of Psychology,  North Holland P u b l . ,  Interpolated r e c a l l  1968.  in short-term memory.  of Experimental Psychology, 1963, 66, 525-532.  Journal  102  Murdock, B. B.  Short-term memory.  In G. H. Bower and J . T. Spence ( E d s . ) ,  The Psychology of Learning and Motivation:  Advances in Research  and Theory, V o l . V, Academic Press, New York, 1972, pp. 67-127. Neisser, U.  Cognitive Psychology.  P a i v i o , A. and Czapo, K.  Academic Press, New York,  1967.  Concrete image and verbal memory codes.  JournaI  of Experimental Psychology, 1969, 80, 279-285. Parks, T . , Parkinson, S. R, and KrolI, N. E. term memory:  Visual and auditory  short-  Effects of phonemicaily similar auditory shadow  material during the retention  interval.  Journal of  Experimental  Psychology, 1971, 87, 274-280. Peterson, L. R. and Peterson, M. J . items. Posner, M. I.  Short-term retention of  individual  Journal of Experimental Psychology, 1959, 58,  193-198.  C h a r a c t e r i s t i c s of visual and kinesthetic memory codes.  Journal of ExperimentaI Psychology, 1967, 67_, 103-107. Posner, M. I.  Abstraction and the process of recognition.  In G. H.  Bower and J . T. Spence ( E d s . ) , The Psychology of Learning and Motivation:  Advances in Research and Theory, VoI.  Press, New York, Posner, M. I.  Academic  1969, pp. 44-100.  and Konick, A. F.  kinesthetic  Ill,  information.  Short-term retention of visual and Organisational  Behaviour and Human  Performance, 1966, j_, 71-86. Posner, M. I.,  Boies, S. J . , Eichman, W. H., and Taylor, R. L.  of visual and name codes of single l e t t e r s . Psychology Monograph, 1969, 79, No. I,  Journal of  Part 2.  Retention Experimental  103  Potter, M . C. and Williams, M. I. memory?  Is there an echo box in p i c t o r i a l  Paper presented at the meeting of the Eastern Psycho-  logical Association, A p r i l ,  1970.  Schnore, M. M. and Partington, J . T.  Immediate memory for visual patterns:  Symmetry and amount of information.  Psychonomic Science,  1967,  8, 421-422. Shulman, H. G.  S i m i l a r i t y effects in short-term memory.  Bulletin. Sperling, G.  Psychological  1971, 75_, 399-415.  The information available in brief visual presentations.  Psychology Monographs, I960, _74 (Whole No. 498). Sperling, G.  A model for visual memory tasks.  Human Factors, 1963, 5_,  19-31. Stonners, R. F. and Muenzinger, G. F.  PronouncabiIity  in STM.  Journal  of Experimental Psychology, 1969, 80, 359-363. Ternes, W. and Y u i l l e , J . C.  Words and pictures in an STM task.  Journal  of Experimental Psychology, 1972, 96, 78-86. Ternes, W. and Y u i l l e , J . C.  Additive interference processes in STM.  Journal of Experimental Psychology, 1973, Tversky, B.  (in press).  P i c t o r i a l and verbal encoding in a short-term memory task.  Perception and Psychophysics, 1969, 6, 225-233. Waugh, N. C. and Norman, D. A.  Primary Memory.  Psychological Review,  1965, 72, 89-104. Waugh, N. C. and Norman, D. A. memory.  The measure of Interference in primary  JournaI of Verba I Learning and Verbal Behaviour,  1_, 617-627.  1968,  104  Wickelgren, W. A.  Acoustic s i m i l a r i t y and intrusion errors In short-  term memory.  Journal of Experimental Psychology, 1965,  70,  102-108. Wickelgren, W. A.  Short-term recognition memory for single  and phonemic s i m i l a r i t y of retro-active Journal of Experimental Wickens, D. D. meaning.  Quarterly  Psychology,1966, 181, 55-63.  Encoding categories of words: Psychological Review,  Wickens, D. D. and Eckler, G. R. ing in STM.  interference.  letters  An empirical approach to  1970, 77.,  1-15.  Semantic as opposed to acoustic encod-  Psychonomic Science, 1968, J_2, 63.  105  APPENDIX  I  106  TABLE I  Recall Scores for Experiments I and  0 Delay  -  Correct Reca11 out of 80  II.  10 Sec. Delay  |MM  REH  Verbal Low High  Visual Low High  VisualMotor  63.80  66.13  62.33  42.13  60.80  53.13  25.53  2.14  2.49  2.00  .76  2.12  1.35  -.02  29.47  29.27  26.40  14.20  29.40  28.67  21.00  Q_  B  d' Scores  —  Correct Reca11 out of 30  Q. X LU  TABLE 2  Mean Values for Visual Coding Groups in Experiment III.  Presentation  Modality  Auditory Correct Reca11  Visual d Scores 1  Correct Reca11  d' Scores  Button  39.70  .59  28.00  .12  Lever  36.60  .39  27.30  .02  TABLE 3  Mean Reca11 for Verbal Coding Groups In Experiment  Presentation Modality Auditory  Visual  Button  23.70  15.90  Lever  23.30  20.60  TABLE 4  Mean Percentages of Correct RecaI I for Visual and Verbal Stimuli in Experiment III.  Presentation of Interpolated Task Aud itory  Visual  Stimulus Condition Verbal Visual  Stimulus Condition Verbal Visual  Button  79.00  49.62  53.00  35.00  Lever  77.66  45.75  68.66  34.12  110  TABLE 5  Mean Percentage of Correct Recall in Experiments I and  0 Delay  II.  10 Sec. Delay  JMM  REH  Verbal Low High  Visual Low High  VisualMotor  EXP I  79.75  82.66  77.91  52.66  76.00  66.41  31.91  EXP II  98.23  97.56  88.00  47.33  98.00  95.56  70.00  Ill  APPENDIX I I  112  TABLE I  ANOVA for Correct Reproductions In Experiment I.  Source of Variance  SS  df  MS  F  p  26.67  <.0I  Treatment  17,626.33  6  2,937.72  Exp. Error  10,795.07  98  110.15  Total  28,421.40  104  113  TABLE 2  Newman-Keuls Test for Treatment Effects for Correct Reproductions in Experiment I.  Order Treatment in Order of Position  VM 25.53  Truncated Range Sxq .95 Sxq -99  HVER 42.13  HVIS 53.13  LVIS 60.80  LVER 62.33  IMM 63.80  REH 66.13  2  3  4  5  6  7  7.56  9.07 11.34  9.69 12.15  10.58 12.71  11.07 13.20  11.44 13.52  6  7  9.99  4  2 16.60** 2 3 4 5 6 7  27.60** 11.02**  35.27** 18.67** 7.65*  36.80** 20.20** 9.18* I .53  38.27**  40.60**  21.67** 10.65* 3.00 I .47  24.00** 12.98** 5.33 3.80 2.33  114  TABLE 3  ANOVA f o r d' S c o r e s i n Experiment I .  Source o f Variance  SS  df  MS  Treatment  73.45  6  12.24  Exp. E r r o r  57.82  98  .59  131.27  104  Total  F  P  20.74  <.0I  115  TABLE 4  Newman-Keuls T e s t f o r d' S c o r e s i n Experiment I .  Order Treatment i n Order o f Position  1  VM .98  Truncated Range Sxq .95 Sxq .99  1 1 2 3 4 5 6  2  3  4  HVER 1.76  HVIS 2.35  LVER 3.00  2  3  .53 .70  2 .78**  -  6  7  LVIS 3.12  IMM 3.14  REH 3.49  4  5  6  7  .63 .79  .70 .85  .74 .89  .77 .92  .80 .95  3  4  5  6  7  1.37** .59*  -  2.02** 1.24** .65*  -  5  2.14** 1.36** .77* .12  -  2.16** 1.38** .79* .14 .02  -  2.51** 1.73** 1.14** .49 .37 .35  116  TABLE 5  ANOVA for Recall Scores in Experiment  II  Source of Variance  SS  Treatment  3,056.86  Exp. Error Total  df  MS  F  6  509.47  93.65  533.34  98  5.44  3,590.20  104  p <.0I  117  TABLE 6  Newman-Keuls Test for Treatment Effect in Experiment II.  Order Treatment in Order of Position  1  HVER 15.80  Truncated Range Sxq .95 Sxq .99  2  3  REH .73  6  LVER 3.60  2  3  4  5  6  1.68 2.22  2.01 2.52  2.21 2.70  2.35 2.82  2.46 2.92  6.80**  HVIS 1.33  5  VM 9.00  4  2  2 3 4 5 6 7  4  12.20** 5.40**  14.47** 7.67** 2.27**  LVIS .60  6 15.07** 8.27** 2.87** .60  15.20** 8.40** 3.00** .73 . 13  7  IMM .53  7 2.54 3.00  7 15.27** 8.47** 3.07** .80 .20 .07  118  TABLE 7  ANOVA for Correct Reproductions of Visuai Patterns in Experiment I I I .  Source of Variance  SS  A (Visual v s . Verbal)  1,102.50  B (Lever v s . Button) A x B  df  MS  F  I  1,102.50  10.80  36.10  I  36.10  .35  14.40  I  14.40  .14  Error  3,674.60  36  102.07  Total  4,827.60  39  p <.0I  TABLE 8  ANOVA for d Scores of Visual Pattern Reproductions in Experiment III. f  Source of Variance A (Visual v s . Verbal)  SS  df  MS  1.79  I  1.79  B (Lever v s . Button)  .20  I  .20  A x B  .03  I  .03  Error  7.38  36  .20  Total  9.41  39  120  TABLE 9  ANOVA for Verbal Recall Errors in Experiment III  Source of Variance  SS  df  MS  F  275.63  I  275.63  17.30  B (Lever v s . Button)  46.23  I  46.23  2.90  A x B  65.02  I  65.02  4.08  Error  573.50  36  15.93  Total  960.38  39  A (Visual v s . Verbal)  p <.0I  <.05  121  TABLE 10  Analysis of Simple Effects for AB Interaction of Verbal Recall Errors in Experiment III.  A B B  2  (  (Auditory)  (Visual )  (Button)  6.30  14.10  (Lever)  6.70  9.40  Source  SS  df  MS  A for B  (  304.20  I  304.20  19.09  B  2  36.45  I  36.45  2.28  .80  I  .80  .05  110.45  I  110.45  6.93  573.50  36  15.93  B for A A  (  2  Error Between  .01  .05  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0101030/manifest

Comment

Related Items