The suffix effect: How many positions are involved?

Transcription

1 Memry & Cgnitin 1980, Vl. 8(3), The suffix effect: Hw many psitins are invlved? RANDALL W. ENGLE University fsuth Carlina, Clumbia, Suth Carlina Three experiments tested the effect f the availability f the last item n the recall perfrmance fr earlier list items in a stimulus suffix paradigm. A decrement due t the suffix ccurred fr preterminal psitins even when the last item was made available. This preterminal suffix effect was fund t be mre extensive in a cnditin in which subjects were free t recall the end items first than in a cnditin in which subjects were frced t recall in a strict left-t-right fashin. When a redundant speech sund is appended t the end f an auditrily presented list, recall perfrmance is impaired fr thse items at the end f the list when cmpared with lists fllwed either by n sund r by a nnspeech sund such as a tne r buzz. This phenmenn is called the suffix effect, and it is imprtant because f the argument by Crwder and Mrtn (1969) that the effect is a reflectin f the cntributin f the auditry sensry memry r echic memry t recall in the nnsuffix cntrl cnditin. In fact, inferences abut echic memry have been drawn almst exclusively frm experiments using the suffix prcedure (Crwder, 1972, 1975). The suffix effect is mst prnunced fr the last serial psitin in the list, but it is frequently bserved fr the three r fur terminal psitins. Crwder (1978) has argued that the decrement in perfrmance fr nly the last item shuld be cnsidered imprtant t therizing abut echic memry. But, as he pints ut (see Crwder, 1978, Ftnte 4), there are few data regarding this issue. If, indeed, the suffix effect is a reflectin f the cntributin f echic memry t recall f auditrily presented lists, then hw far the suffix effect extends int the list and whether the decrement fr preterminal psitins is als a reflectin f echic memry are nntrivial questins. The purpse f this paper is t address this issue f the cause f suffix effect decrements fr psitins immediately prir t the last ne. Tw hyptheses cme t mind as explanatins fr what I will call the preterminal suffix effect. One is that, indeed, the preterminal items als benefit frm the lingering echic trace and that the suffix acts as a mask fr the echic infrmatin persisting fr these items as well as fr the terminal psitins. This hypthesis des nt view the preterminal suffix effect as qualitatively different frm the effect f the suffix n recall f the last item. The difference wuld be ne f degree, with the preterminal items simply having less f an echic trace than the terminal item. This hypthesis has been viewed as bjectinable because it des nt fit well with estimates f the duratin f the echic memry. A5 Crwder (1978) pints ut, estimating the duratin f the echic trace has been a particularly sticky prblem, but attempts using a delayed suffix suggest abut 1-2 sec as a reasnable appraisal (Crwder, 1978). If this figure is accurate, then preterminal suffix effects shuld nt be bserved with presentatin rates as slw as 2 r 4 sec/item. Since such preterminal suffix effects are fund with rates this slw (Watkins & Watkins, in press), this suggests either that this hypthesis is wrng r that echic infrmatin persists fr lnger than the 1- t 2-sec estimate. An alternative hypthesis is that in the nnsuffix cnditin, the last item is the nly ne fr which there is an echic trace available t aid recall. The recall f this last item might serve as a retrieval cue fr recall f ther items, particularly thse items immediately prir t the terminal ne. It wuld be assumed that the suffix masks echic infrmatin fr nly the last item, but with this item n lnger available, it culd nt serve as a retrieval cue fr the preterminal items. This view, which I will call the lst retrieval cue hypthesis, predicts that, if we resupply the last item, the preterminal suffix effects shuld disappear. This is the predictin tested in the three experiments reprted here. EXPERIMENT 1 This research was supprted in part by Grant HD frm the Natinal Institute f O1.ild Health and Human Develpment. I wish t thank Lydia Wilsn Neely and David Stagg fr help with data cllectin and analysis. Parts f Experiment 3 were suggested by an apprpriately cautius annymus reviewer. Requests fr reprints shuld be sent t Randall Engle, Department f Psychlgy, University f Suth Carlina, Clumbia, Suth Carlina This experiment was prmpted by the predictin f the lst retrieval cue hypthesis that prviding the subject with the last item prir t recall wuld eliminate preterminal suffix effects. Methd Subjects. Thirty students frm elementary psychlgy Cpyright 1980 Psychnmic Sciety, Inc X/80/ $00.85/0

2 248 ENGLE curses vlunteered fr curse credit. They were tested in grups ftw t five pergrup in a small classrm. Materials and Prcedure. The lists were nine items in length and were generated frm a randm number table with the cnstraint that n digit culd appear twice in a list. The lists were presented t the subject in three blcks f 18 lists each, and the psitin f digits within lists was cunterbalanced s that, within a blck f 18 lists, each digit appeared twice in each serial psitin. The lists were recrded by a female vice at.8 sec/digit. The three blcks flists each represented a different cnditin in the experiment. The nnsuffix cnditin (NS) was the cntrl cnditin and simply had a SOO-msec tne ccur in synchrny fllwing the last item. The suffix cnditin (S) had the wrd "G" fllw the last digit, again, in synchrny. The cnditin f mst interest had the suffix "G" fllw the last digit, but in this case, the suffix was immediately fllwed by the experimenter's hlding up a white card with the last digit printed n it in bld black ink, This cnditin, S-YLD, was predicted by the lst retrieval cue hypthesis t eliminate the effect f the suffix n preterminal items. The rder f cnditins was cunterbalanced s that each grup f five subjects received ne f the six pssible rders f cnditins. The subjects were tld what t expect at the beginning f each sessin and immediately befre each cnditin was presented. Fr example, prir t the S-YLD lists, the subjects were tld that they wuld hear nine digits and then the wrd "G" and that the last digit they heard wuld be held befre them immediately afterward. They were tld it wuld be visible until the next list was ready t begin and that they shuld always get this number crrect. Recall was written n answer sheets with nine bxes per list, and instructins emphasized that the digits shuld be written in a left-t-right manner with n regressins. Results The recall perfrmance was analyzed using tw different scring prcedures. The all-r-nne prcedure is the ne typically used in suffix effect studies and allwed credit if and nly if the crrect digit was recalled in the crrect serial psitin. The partial credit prcedure was an attempt t give credit fr items recalled, but recalled ut f psitin. This prcedure allwed ne pint t the serial psitin if the crrect digit was recalled in the crrect psitin. If the item frm a given input psitin was recalled ne psitin away frm the crrect ne, the crrect psitin was credited with.75; if the digit was recalled tw psitins away, the crrect psitin was credited with.5; three psitins away, with.25; and fur r mre psitins away, with 0 pints. The tw analyses yielded slightly different F values, but the cnclusins were identical. Fr this reasn, and because it is typical f suffix effect studies, the discussin belw will be f the analysis using the all-r-nne scring. The mean prprtin crrect at each serial psitin fr the three cnditins is shwn in Figure I. While the analysis yielded significant main effects f cnditins [F(2,48)= 20.0, p <.01, MSe =.046] and Serial Psitin [F(8,192) = 57.2, P <.01, MSe =.046], the fmding f mst interest was the Cnditins by Serial Psitin interactin [F(16,384) = 9.4, p<.oi, MSe=.OII]. Differences between cnditins at each serial psitin were analyzed by Tukey HSD tests at the.05 level. These tests revealed significant decrements in perfr.... c :e A Figure 1. Prprtin crrect recall as a functin f input psitin fr the nnsufflx cnditin (NS), suffix cnditin (S), and suffix cnditin with redundant visual presentatin f the last digit (S-YLD). mance fr the standard suffix cnditin at every serial psitin but the first tw; in ther wrds, there was a significant suffix effect fr the fmal seven psitins. The suffix cnditin 'fllwed by visual presentatin f the last digit (S-YLD) resulted in significant decrements fr Psitins 5-8 when cmpared with the nnsuffix cnditin. Obviusly, the S-YLD cnditin did nt eliminate the suffix effect fr preterminal items, as had been predicted by the lst retrieval cue hypthesis. The suffix effect fr Psitins 5-8 was just as marked fr this cnditin as fr the standard suffix cnditin. It is pssible that the decrement in perfrmance fr the preterminal items in the S-YLD cnditin resulted frm a distractin f the subjects, such as shifting their attentin frm listening t the digits t lking at the visual presentatin f the last digit. T rule ut this hypthesis, sme methd was needed that wuld cnstitute a suffix prcedure and keep the last digit available as a retrieval cue, but which wuld nt require a shifting f attentin frm ne mdality t anther. One prcedure that seemed t satisfy these criteria was t simply repeat the last digit as the suffix. Rate f presentatin was als varied in the next experiment t determine whether the preterminal suffix effects bserved in Experiment 1 generalize t faster rates f presentatin. This is a particularly imprtant manipulatin in terms f Crwder and Mrtn's (1969) thery f echic memry. If the echic trace is time dependent, as well as prne t interference frm subsequent speech masks, the extent f the suffix effect ver the end f the list shuld be tied t the rate f presentatin fr the items. Quickly presented lists shuld shw the suffix effect ver mre preterminal

3 SUFFIX EFFECT 249 psitins than shuld slwly presented lists because, fr an item in a given input psitin, less time passes between the presentatin f that item and the cue fr recall with fast presentatin than fr an equivalent item with slw presentatin. If the lst retrieval cue explanatin is valid, then making the last item available either visually r by making the suffix be a repetitin f the last item shuld eliminate the preterminal suffix effect fr bth fast and slw rates f presentatin. EXPERIMENT 2 Methd Subjects. Thirty-fur students f elementary psychlgy vlunteered t be tested fr curse credit. They were tested individually in a small sund-shielded rm. Prcedure. Eighty lists f nine digits each were randmly generated by a prgram, with the cnstraint that n digit be repeated in a list. The lists were divided int fur blcks f 20 lists each, with each blck t be presented in ne f the fur cnditins. Presentatin rate was I digit/sec fr half f the subjects and 4 digits/sec fr the ther half f the subjects. The fur cnditins, three f which were identical t the first experiments, were: (1) the nnsuffix cntrl cnditin (NS), (2) the standard suffix cnditin (S), in which the suffix "G" was appended at the end f the list in synchrny with the list items, (3) a suffix cnditin in which the "G" was fllwed by visual presentatin f the last digit (S VLD), and (4) a suffix cnditin in which the last digit was always repeated as the suffix (S-LDR). Cnditins was a within-subjects variable, and the rder f cnditins was randmized fr each subject. The instructins were identical t thse used in Experiment I with the necessary additins fr the S-LDR cnditin, emphasizing that the last digit had t be recalled nly nce and that the repetitin culd be ignred r used as a recall cue, whichever 1/sec. was desired. Recall was written n answer sheets with nine bxes drawn n them fr each list. Results The all Of nne scring prcedure was used fr this experiment, and the results are shwn in Figure 2, with the I-digit/sec grup n the left and the 4igit/sec grup n the right. Obviusly, the preterminal suffix effect remains regardless f whether the last item is made available by visual presentatin, S-VLD, r by the last item's being repeated as the suffix, S-LDR. This was supprted by the cnditins main effect [F(3,96) = 22.4, P<.01, MSe =.03] and the Cnditin by Serial Psitin interactin [F(24,768) =22.6, P <.01, MSe =.01]. Pst hc analyses revealed significant preterminal suffix effects fr all three suffix cnditins fr Psitin 8 fr the I-digit/sec rate and fr Psitins 7 and 8 fr the 4-digit/sec rate. The S-VLD cnditin replicated the fmdings f the first experiment in rmding the preterminal suffix effect. The S-LDR cnditin, likewise, shwed the preterminal suffix effects even when the last digit was made available withut shifting mdalities. These findings appear t belie the validity f the lst retrieval cue hypthesis, and, cnsequently, they supprt the hypthesis that the preterminal suffix effects are a result f interference r masking f echic infrmatin fr these psitins in much the fashin, if t less a degree, as ccurs fr the last item in the list. Since Crwder and Mrtn's (1969) thery seems t make specific predictins abut the effect f presentatin rate, the tw typical cnditins, NS and S, were 4/sec. j - C c t NS "--S 0--0 S-LDR 0--0 S-VLD !!---!--!--...L-.L.._ Figure 2. Prprtin crrect recall as a functin f input psitin and rate f presentatin fr the nnsuffix cnditin (NS), suffix cnditin (S), and suffix cnditins with visual last digit (S-VLD) and with last digit repeated (S-LDR). 9

4 250 ENGLE subjected t a separate analysis f variance fr the effects f rate, cnditins, and serial psitin. These data are redrawn in Figure 3 s that an easier cmparisn can be made. Recall perfrmance was abut the same fr the tw rates, as evidenced by the absence f a rate main effect (F < 1.0). Als f interest was the fact that the magnitude f the sufftx effect was slightly, but nnsignif icantly, different fr the tw rates. The suffix caused a decrement f 13% at the l digit/sec rate and 22% at the 4 digit/sec rate, but the Rate by Cnditin interactin nly apprached significance [F(1,32) = 2.84, P <.10]. If nly the last three psitins are cnsidered, hwever, the magnitude f the decrement caused by the suffix varied cnsiderably with rate, with a 28% decrement ccurring in the l digit/sec rate and a 51 % decrement ccurring in the 4-digit/sec rate. Inspectin f Figure 3 shws that, while the magnitude f the sufftx effect ver all psitins was marginally larger fr the faster rate, the effect appears t have been much mre cncentrated ver the fmal three psitins, whereas fr the slwer rate, the decrement that did ccur was spread ver mre psitins. This is indicated by the significant Cnditins by Rate by Serial Psitin interactin [F(8,256) = 3.1, P <.01, MSe =.01]. An interesting nte is that there is a general shift in the curves as we vary presentatin rate. This is mst clearly reflected by the nnsuffix curves, with the 4-digit/sec grup shwing better perfrmance ver the early psitins and the I-digit/sec grup shwing better perfrmance ver the middle and end psitins. These cnclusins are based n the significant Rate by Serial Psitin interactin [F(8,256) =4.7, p<.oi, MSe =.02], in cmbinatin with the absence f an ver all main effect f rate, with mean prprtin f.57 fr the I-digit/sec grup and.55 fr the 4-digit/sec grup. A rather bvius defect in the first tw experiments is that the different suffix cnditins were blcked s that the subject knew when a list was being presented what the sufftx wuld be like. It is pssible that this led t the subject's attending r rehearsing the lists differently in the varius cnditins. The third experiment was designed t remedy this defect. Anther ptential prblem with the first tw experiments was that the suffix in the straight suffix cnditin ("G") was always the same item, whereas the suffix in the last digit repeated cnditin and the visual lastdigit cnditin varied frm list t list. The next experi ment cntrlled fr this by using, as ne type fsuffix, a letter selected randmly frm a pl the same size as that frm which the last digit was chsen. In additin, the third experiment was designed t lk at the interactin f type f recall instructins with suffix cnditins. It might have been nted that the sufftx effect extended ver mre psitins in Experi ment 1 than in Experiment 2. The tw experiments differed in many ways, but the nature f the recall instructins seemed t be a variable that might affect the results in the manner just described. It is typical in ur labratry t instruct subjects in suffix effect studies t recall in a serial manner, but subjects are typically nt clsely mnitred t insure that recall is perfrmed as requested. In reviewing the prcedures fr the first tw experiments, we nticed that it appeared that, as a cnsequence f having tw different experimenters, there was mre emphasis given t the left t right nature f recall in Experiment 2 than in Experiment 1. T determine whether this wuld influence the extent f the sufftx effect, nature frecall instructins was manipulated in the third experiment EXPERIMENT 3 i.9... N51 C i C N54 0--<>54 :e I 0 I Q. I.. Q. I.3 b-.., I '0..-<1 I 0 A -.. P Figure 3. Prprtin crrect recall as a functin f input psitin fr the suffix and nnsufflx cnditins fr the I-digit/ sec and 4-digit/sec rates f presentatin. Methd Subjects. Frtyight students frm the same ppulatin used in the first tw studies were tested in small grups. Prcedure. Seventy-tw digit lists f nine items each were generated by a prgram, with the cnstraints that n digit be repeated in a list and, ver lists, each digit ccur in each serial psitin an equal number f times. The lists were cmpsed f the digits l{i and The lists were recrded at a 2-digit/sec rate and were presented ver stere speakers in a small sundshielded rm t small grups fsubjects. The nly betweenbjects variable was the nature f recall instructins. Twenty-seven f the subjects received strict serial recall instructins. They were tld t recall the lists in exactly the same manner in which they were presented, writing a digit in the leftmst bx n the recall sheet befre ging t the next ne. It was further emphasized that this mde f recall was prbably unlike what they wuld want t d, but that it was imperative that they recall in exactly the manner described. If they were unsure abut the crrect digit t be written in a particular bx, they were t guess. The recall behavir f these subjects was clsely mnitred, and the data f three subjects were eliminated due t failure t fllw instructins. The ther 21 subjects, in the free cnditin, were instructed

5 SUFFIX EFFECT 251 t recall the digits in any sequence they wished as lng as the crrect digit was in the bx representing the crrect input psitin. They were als instructed t guess if unsure abut which digits shuld g in which bxes. The ther variables, all within subjects, were suffix cnditin and serial psitin. There were fur different suffixes, ne f which fllwed each list. The rder f suffix cnditin was randm acrss the 72 lists, s that the subject culd nt anticipate which suffix wuld ccur. The fur suffixes were: (l) a tne (T), (2) the last digit repeated (LDR), (3) a letter (L) chsen frm a pl f nine letters in a manner analgus t the way the last digit was chsen, and (4) the wrd "G." Results Scring was perfrmed using bth the all-r-nne prcedure and the partial prcedure described fr Experiment 1. The tw prcedures again yielded identical cnclusins, and, again, nly the results f the all-r-nne prcedure will be presented. It is clear frm the results, shwn in Figure 4, that u! U c 'fc -Q. c:: III G) 1.00r , FREE Serial Psitin DR !...-!2!--3-!'4--!56!--+7-!8-9!-'" Figure 4. Prprtin crrect recall as a functin f input psitin, suffix cnditin, and nature f recall instructins. the preterminal suffix effect is still bserved even if the subject cannt predict which sufftx will ccur, but it is als clear that the extent f the sufftx effect depends n recall instructins. While the sufftx caused a decrement fr Psitins 4-9 in the free recall cnditin, the decrement ccurred nly fr Psitins 8 and 9 in the strict recall cnditin. This was supprted by the significant Recall Instructins by Suffix Cnditin by Serial Psitin interactin [F(24,1l04) =1.7, p <.05, MSe =.009]. The main effect f recall instructins [F(1,46) = 5.5, P <.025, MSe =.56] and the Instructins by Serial Psitin interactin [F(8,368) =7.8, p <.001, MSe =.04] reflected the fact that subjects in the free cnditin perfrmed abut 17% better than thse in the strict cnditin, and nearly all f this difference was ver the final five serial psitins. The facts that these were the same psitins shwing significant preterminal suffix effects fr the free grup and that the curve fr the prest suffix cnditin in the free recall grup (L) was nearly identical t the nnsuffix cnditin (T) in the strict recall grup may be cincidental. On the ther hand, it may suggest that the free recall grup had available t them at the initiatin f recall a surce f infrmatin abut the terminal items that was highly transient and was lst bth in the prcess f a strict left-t-right recall and as a cnsequence f a speech suffix. This additinal surce f infrmatin culd be sensry in nature, such as the echic trace r smething mre refined. Which explanatin is crrect remains t be determined. GENERAL DISCUSSION These three experiments were directed t the hypthesis that the decrement in recall in the sufftx cnditin fr psitins prir t the last ne ccurs because the last item is n lnger available t serve as a retrieval cue t the items presented just prir t it. All three experiments shwed marked decrements in recall fr preterminal psitins, even when the last item was made available either by visual presentatin f the last digit fllwing the suffix r by repetitin f the last digit as the suffix. Further, it makes n difference whether the subject can r cannt predict the particular suffix. This appears t discnfirm the lst retrieval cue hypthesis. One alternative hypthesis fr the preterminal sufftx effect is that the echic trace persists much lnger than has previusly been believed and that mre list items than just the last ne benefit frm auditry presentatin by being stred in the echic memry in additin t being stred in the mdality independent f shrt-term memry. This hypthesis is less bjectinable in light f recent arguments by Watkins and Watkins (1979) that the echic trace persists fr cnsiderably lnger than the 1-2 sec estimated by Crwder (1978), perhaps 15 sec r lnger. Anther pssible explanatin is that the sufftx

6 252 ENGLE causes the decrement in perfrmance n the preterminal psitins and n the last psitin thrugh different mechanisms. Mrtn (1976) has suggested that, in additin t the passive verwriting f echic infrmatin, the suffix intrudes upn the attentin f the subject, wh cannt distinguish the suffix frm list items. This autmatic gruping ntin, first prpsed by Kahneman (1973) t explain the entire suffix effect, might be used t explain the preterminal suffix effect. It is pssible that the suffix effect fr the fmal psitin is a result f the masking f echic infrmatin by the suffix and that the decrement fr preterminal psitins is caused by attentinal factrs nt related t the strage fprimitive auditry infrmatin. Hwever, this thery wuld predict that any cnditin increasing the distinctiveness f the suffix and list items wuld lessen the decrement caused fr preterminal psitins but nt fr the final psitin. In fact, Mrtn (1976) shwed that three identical suffixes in sequence, a cnditin that suppsedly caused the list items and suffixes t be rganized int separate grups r chunks, reduced the suffix effect fr the final psitin but, if anything, increased it fr the preterminal psitins. This suggests that the autmatic gruping explanatin is nt crrect either, but it des suggest that the preterminal and terminal suffix effects are mediated by different mechanisms. Baddeley and Hull (1979) have recently argued that the suffix effect fr preterminal psitins is mediated by a prcess different frm the ne that mediates the decrement fr the last psitin. They base their argument n a set f studies that shwed that, as the number f syllables in the suffix increased, the preterminal suffix effect als increased. It is difficult t tell frm their results sectin what effect this manipulatin had n the last item, because the effect n the last item was figured with respect t the perfrmance n the previus item in the same cnditin and nt with respect t the last psitin in the cntrl cnditin. It appears that if the last psitin in the cntrl cnditin is taken as the reference, then the increase in syllables in the suffix has n effect n the size f suffix effect n the last psitin. In this case, their studies shw that increasing the number f syllables in the suffix increases the preterminal suffix effect beynd what it wuld nrmally be but has n nticeable effect n the terminal sufflx effect. This des nt necessarily mean that the suffix is nt at least cntributing t the preterminal suffix effect by interfering with echic infrmatin fr thse items, but it is rather suggestive f a tw-factr thery f the tw suffix effects. Baddeley and Hull (1979) argue that the preterminal suffix effect and the respnse prefix effect are caused by a cmmn mechanism. They assume the cmmn mechanism is a delay in rehearsal caused by the time it takes t say the prefix r prcess the suffix. It is nt clear, hwever, why the subject wuld prcess the redundant suffix r even hw the subject culd prcess a nnsensical speech sund (e.g., a wrd played in reverse thrugh the tape player) in a manner that wuld interfere With the rehearsal buffer. While the precise nature f a separate mechanism fr the preterminal suffix effect is unclear, there appears t be sme supprt fr its existence. One further line f supprt cmes frm ur labratry: Balta and Engle (Nte 1) have fund that extensive practice with suffix lists reduces the magnitude f the preterminal suffix effect but nt the effect n the last psitin. Even if the tw-factr thery is nt crrect and the preterminal suffix effect is a result f masking f lingering primitive auditry infrmatin, it is nt entirely clear what this means t the thery f echic memry. It undubtedly means that echic memry persists lnger than has previusly been assumed, but whether any thery explaining the suffix effect fr the single final psitin can, unaltered, als explain suffix effects fr preterminal psitins as well remains t be seen. Fr example, Crwder (1978) explains the diminutin f the suffix effect with multiple suffixes by arguing that the additinal suffixes partly mask the effect f the riginal suffix thrugh a frm f lateral inhibitin. This wuld seem t suggest, hwever, that the effect f a single suffix wuld be t inhibit the masking effect f the last digit n the echic trace fr the penultimate digit, thus increasing its prbability f recall cmpared with the cntrl cnditin. This bviusly is nt the case and pints ut the necessity fr cnsideratin f the preterminal suffix effect in any thery fechic memry. REFERENCE NOTE I. Balta, D. A., & Engle, R. W. Structural and cntrl elements in the stimulus suffix effect. Paper presented at the meeting f the Midwestern Psychlgical Assciatin, St. Luis, Missuri, REFERENCES BADDELEY, A., & HULL, A. Prefix and suffix effects: D they have a cmmn basis? Jurnal f Verbal Learning and Verbal Behavir, 1979, 18, CROWDER, R. G. Visual and auditry memry. In J. F. Kavanaugh & L G. Mattingly (Eds.), Language by eye and by ear: The relatin between speech and learning t read. Cambridge, Mass: M.LT. Press, CROWDER, R. G. Inferential prblems in echic memry. In P. M. A. Rabbit & S. Drnic (Eds.), Attentin and perfrmance V. New Yrk: Academic Press, CROWDER, R. G. Mechanisms fauditry backward masking in the stimulus suffix effect. Psychlgical Review, 1978,85, CROWDER, R. G., & MORTON, J. Precategrical acustic strage (PAS). Perceptin & Psychphysics, 1%9,5, KAHNEMAN, D. Attentin and effrt. Englewd Cliffs, N.J: Prentice-Hall,1973. MORTON, J. Tw mechanisms in the stimulus suffix effect. Memry & Cgnitin, 1976,4, WATKINS, O. C., & WATKINS, M. J. The mdality effect and echic persistence. Jurnal f Experimental Psychlgy: General, in press. (Received fr publicatin June 5,1979; revisin accepted January 7, 1980.)