Associative retrieval processes in free recall

Transcription

1 Memry & Cgnitin 1996,24 (1), Assciative retrieval prcesses in free recall MICHAEL J. KAHANA Brandeis University, Waltham, Massachusetts I present a new methd fr analyzing assciative prcesses in free recall. Whileprevius research has emphasized the prminence f semantic rganizatin, the present methd illustrates the imprtance f assciatin by cntiguity. This is dne by examining cnditinal respnse prbabilities in the utput sequence. Fr a given item recalled, I examine the prbability and latency that it fllws an item frm a nearby r distant input psitin. These cnditinal prbabilities and latencies, pltted as a functin f the lag between studied items, reveal several regularities abut utput rder in free recall. First, subjects tend t recall items mre ften and mre rapidly frm adjacent input psitins than frm remte input psitins. Secnd, subjects are abut twice as likely t recall adjacent pairs in the frward than in the backward directin and are significantly faster in ding s. These effects are bserved at all psitins in the utput sequence. The asymmetry effect is theretically significant because, in cued recall, nearly symmetric retrieval is fund at all serial psitins (Kahana, 1995; Murdck, 1962). An attempt is made t fit the search f assciative memry mdel (Raaijmakers & Shiffrin, 1980, 1981) with and withut symmetric interitem assciatins t these data. Other mdels f free recall are als discussed. The finding that subjects, when tld t recall a list f items "in any rder," recall categrically r assciatively related items in neighbring utput psitins has prvided a fundatin fr much f the rganizatinal therizing n human memry. One might even argue that it was these findings which caused a shift frm the study f paired assciate learning and serial recall in the 1950s and early 1960s t the study f free recall in the mid t late 1960s. Research n serial recall was lng cncerned with distinguishing theries f psitinal assciatins frm chained assciatins (Harcum, 1975), whereas research n free recall fcused n interitem similarity and cntext-t-item assciatins as the bases fr retrieval (Shuell, 1969; Tulving, 1968). What happened t the idea that items studied fr free recall are related by virtue ftheir cntiguity? Asch and Ebenhlz (1962) fund that during free recall nly 18% f the ttal number f sequential respnses matched adjacent sequences flist items in the frward rder. They als fund n significant difference in the verall number ffrward and backward transitins (nt necessarily adjacent).' On the basis fthese findings, they cncluded that "the rder in which items were prduced in free recall (which registered the curse f acquisitin) did nt crrespnd ntably t the rder f earlier experience" (Asch & Ebenhlz, 1962, p. 19). This research was supprted in part by an NIH Individual NRSA (I F32 NS ) t the authr and the W. M. Keck Fundatin. I am thankful t Ben Murdck fr prviding me with the raw data frm his experiments and fr helpful discussins f many fthe ideas presented in this article. Crrespndence cncerning this article shuld be addressed t M. 1. Kahana, Center fr Cmplex Systems, Brandeis University, Waltham, MA ( kahana@fechner.ccs. brandeis.edu). It is unlikely that this ne paper extinguished the beliefin chained assciatins in free recall. Rather, it seems that the success f the rganizatinal therists in deriving imprtant principles fmemry frm the free-recall task led t a ttal disregard fr the rle f chained assciatins in free recall. As Tulving (1968) ntes, "It lks as ifthe cnceptual analyses ffree recall have been develped nt just in islatin, but almst in defiance fthe traditinal S-R mdels fbehavir." Anther factr cntributing t the shift f interest away frm an assciatinist apprach t free recall was the theretical entanglement f the free-recall methd with mdels based n the tempral partitining fmemry int separate shrt- and lng-term stres. With these mdels, the emphasis became ne fstructure ver prcess, and the challenge t researchers was t explain the numerus dissciatins between prerecency and recency prtins f the serial psitin curve (e.g., Atkinsn & Shiffrin, 1968; Glanzer & Cunitz, 1966). In this paper, I present a new methd fr examining the rle f pairwise assciatins in free recall. Befre turning t the prpsed methd, I discuss the majr methds fr analyzing "primary rganizatin" in single-trial free recall. Serial Psitin Curves and Mean Output Psitin Curves In free recall, the serial psitin curve is characterized by a small primacy effect, a large recency effect, and a generally flat middle regin (usually called asymptte). Figure I shws the classic serial psitin data frm ne f the cnditins reprted in Murdck (1962). Output rder effects have been summarized by pltting mean utput psitin as a functin f serial (input) psitin. 103 Cpyright 1996 Psychnmic Sciety, Inc.

2 104 KAHANA SERIAL POSITION Figure 1. Serial psitin curve and mean utput psitin curve in single-trial free recall. Data are frm Murdck (1962). In this cnditin, 15 subjects studied 80 lists f30 cmmn wrds presented auditrily at a t-sec rate. Errr bars reflect 95% cnfidence intervals arund each mean. TheLftus and Massn (1994, Appendix B) prcedure fr cmputing cnfidence intervals in within-subject desigus was used. sumed that retrieval fasympttic items reflects a semantically and/r cntextually guided search thrugh lngterm memry. One way f interpreting the dynamics f retrieval in the asympttic prtin f the serial psitin curve is t examine cnditinal respnse prbabilities. What is the likelihd f recalling item x immediately fllwed by item y, cnditinal n recall fy? An even higher rder statistic might measure the likelihd frecalling item x fllwed by item y fllwed by item z cnditinal n recall fz. As a means fcharacterizing these sequential cntingencies in recall rder, the prbability frecalling itemy after item x, cnditinalized n recall fitem y, is pltted as a functin f the lag (x-y) fr all items recalled afterthe third utputpsitin (see Figure 2). A lag f+ I implies that item y = x + 1. Similarly, a lag f -1 8 The basic pattern is that items frm the recency prtin fthe serial psitin curve are recalled first, while items frm asymptte are recalled last. Furthermre, the items frm the asympttic prtin fthe serial psitin curve are at asymptte in the utput psitin curve. The high crrelatin between the serial psitin curve and mean utput psitin curve was nted by Deese and Kaufman (1957). One interesting difference between mean utput psitin curves and serial psitin curves is the "hk" at the end f the recency prtin f the mean utput psitin curve. Fr auditrily presented lists fwrds, recall begins abut three items back, prceedsin frward rdert the end fthe list, and then mves t items in earlier list psitins (Nilssn, Wright, & Murdck, 1975). This pattern f recall prduces the hk in the mean utput psitin curve. The item that is recalled first (n average) is abut tw r three items frm the end f the list. In cntrast, with visually presented wrd lists, recall tends t begin with the last item and g backwards in a generally mntnic fashin. Cnditinal Respnse Prbability and Latency Curves One fthe central theretical questins that cmes up in the study ffree recall is the nature fsubject-generated retrieval cues. Neither serial psitin curves nr mean utput psitin curves prvide us with useful infrmatin abut the specific item-by-item cntingencies in utput rder. The equivalence f recall prbability and utput psitin fr asympttic items (ften assumed t be retrieved frm lng-term memry) has suggested that there are n cnsistent relatins between input rder and utput rder fr these items. Rather, it is generally as DISTANCE FROM LASTITEMRECALLED Figure 2. Cnditinal respnse prbability curves fr six studies f single-trial free recall. Panels A-D are based n data frm Murdck (1962). Panel E is based n data frm Murdck and Okada (1970). Panel F is basedn data frm Murdckand Metcalfe (1978). (A) List length = 20,auditry,2 sec/item. (B) Listlength = 20, auditry, 1 sec! item. (C) List length = 30, auditry, 1 sec/item. (0) List length = 40, auditry, 1 sec/item. (E) List length = 20, visual, 1 sec/item and 0.5 sec/item cmbined. (F) List length = 20, visual, 5 sec/item. Errr bars reflect 95% cnfidence intervals arund each mean. The Lftus and Massn (1994, Appendix B) prcedure fr cmputing cnfidence intervalsin within-subjectdesigns was used. See text fr details n cmputing cnditinal respnse prbability curves. F

3 ASSOCIATIVE RETRIEVAL PROCESSES IN FREE RECALL 105 means that item y = x-i. As such, the abslute value f the lag is a measure f the degree f remteness (at input) f successively recalled items. The sign fthe lag indicates whether recall is in the frward (psitive) r backward (negative) directin. Figure 2 shws cnditinal respnse prbability curves based n free-recall data frm six large free-recall experiments reprted in three papers (Murdck, 1962; Murdck & Metcalfe, 1978; Murdck & Okada, 1970).2 Cnditinal respnse prbability curves frm all f these experiments shw essentially identical patterns. When a given item is recalled, it tends t fllw an item frm a nearby input psitin and is twice as likely t fllw the preceding adjacent item as it is the fllwing adjacent item. In summary, items at cntiguus input psitins tend t be recalled tgether and in the frward rder. This asymmetry is theretically significant because cued recall yields equivalent frward and backward respnse prbabilities acrss serial psitins (Kahana, 1995; Murdck, 1962). S far, these analyses have been based n data averaged acrss utput psitins (excluding the first three items recalled). A mre detailed picture f recall rder can be seen by lking at the cnditinal respnse prbabilities at each psitin in the utput sequence. Instead f examining transitins at each lag individually, I cnsider the average number f adjacent and remte, frward and backward transitins at each psitin in the utput sequence. This analysis, applied t data frm Murdck (1962; list length = 30), is shwn in Figure 3. It can be seen frm these data that the advantage f frward-adjacent recalls is present at all utput psitins. 1.0, , , Data frm Murdck (1962) LL=30, 1 wrd I sec. :J iii jj'j 0.8 It: ll z ll.. II) 0.4..I < Z i= 0.2 s z Frward Adjacent Backward Adjacent -- Frward Remte Backward Remte 0.0 "'-l...l.j...l..l-l.j-..l..j...±..-..l-l...l...l-l...l..l-l...l...l-l...j PAIR OUTPUT POSITION Figure 3. This figure shws adjacent(lag = 1) and remte (sum f all lags> 3) frward and backward cnditinal respnse prbabilities at each pair utput psitin (data frm Murdck, 1962; list length = 30). Pair utput psitin x refers t actual utput psitins x and x + 1. Cnsider an item frm serial psitin y recalled in utput psitinx. A frward-adjacent recall refers t recalling itemy + 1 in utput psitin x + 1; a frward remte recall refers t the summed cnditinal prbabilities f recalling itemsy + 4,y + 5,..., y + (list length -1) in utput psitin x + 1. Errr bars reflect 95% cnfidence intervals arund each mean. The Lftus and Massn (1994, Appendix B) prcedure fr cmputing cnfidence intervals in within-subject designs was used. 2.0 w :E 1.8 i= wu) z A- U) W a::: en Data frm Murdck & Okada (1970) 0.8 L...!_...L._L--L_..L--..l._...L._L--L.J DISTANCE FROM LAST RECALLED ITEM Figure 4. Cnditinal respnse-latency curve fr data cllapsed acrss bth 1- and 2-sec presentatin rates in Murdck and Okada (1970). Lg interrespnse times is cmputed as In(l + IRT). Errr bars reflect 95% cnfidence intervals arund each mean. The Lftus andmassn (1994, AppendixB) prcedurefr cmputingcnfidence intervals in within-subject designs was used. In early stages frecall, mst transitins are frward adjacent. Later, frward and backward remte transitins are apprximately fequal prbability. It is unlikely that these late transitins are randm; rather, they prbably reflect semantic assciatins between list items. Differences in strength are ften assciated with differences in respnse latency. Analyzing data n interrespnse times cllectedby Murdckand Okada (1970)3 allws us t ascertain whether asymmetry and adjacency effects bserved in recall rder are als bserved in recall latency. Figure 4 shws the cnditinal respnse and latency curves fr data cllected by Murdck and Okada. The cnditinal respnse latency curve fllws the same cnventins as the cnditinal respnse prbability curves described abve. Lg latencies were cmputed t reduce the effects f variability caused by lng interrespnse times. As shwn in Figure 4, latencies were shrtest when items frm successive input psitins were recalled in frward rder. Latencies were smewhat lnger fr backward recalls. Bth frward and backward recalls exhibit gradients as a functin f lag. Summary fthe Data Three basic findings emerge frm these analyses. First, the prbability f successive recall frm adjacent input psitins is abut three times higher than the prbability f successive recall frm remte input psitins. Secnd, the prbability f adjacent frward recalls is abut twice that f adjacent backward recalls. This frwardrecall advantage is present at all utput psitins. Third,

4 106 KAHANA adjacency and asymmetry effects are bserved fr latency as well as accuracy measures. Theretical Analysis At a very general level, perhaps ne can say that the cnditinal respnse prbability and cnditinal respnse latency curves prvide evidence fr the rle f cntiguitybased assciatins in free recall. Mre specifically, hwever, it is useful t examine these curves in terms fthe predictins ffrmal mdels fthe free-recall task. Of all the mdels prpsed t accunt fr free recall, the search fr assciative memry (SAM) mdel (Gillund & Shiffrin, 1984; Raaijmakers & Shiffrin, 1980, 1981) presents the mst cmprehensive accunt f data frm this task. What fllws is a very brief summary fthe SAM mdel. Fr a cmplete presentatin, see Raaijmakers and Shiffrin (1980). The SAM Mdel ffree Recall The SAM mdel f free recall is an utgrwth f the Atkinsn and Shiffrin (1968) buffer mdel. It cnsists f tw strage systems: A limited-capacity shrt-term stre (STS) and a lng-term strage (LTS) assciative netwrk. Each new studied item enters STS. Once all fthe registers in STS are full, a newly studied item replaces a randmly chsen item already in STS. Accrding t SAM, items in STS are always available fr immediate recall. A fur-item rehearsal buffer will typically yield a gd fit t the recency prtin f the serial psitin curve. LTS in SAM is mdeled as an assciative netwrk. Items can be assciated with each ther, themselves, r cntext. Fr each unit ftime that an item spends in STS, the strength f its assciatin t cntext is incremented by parameter a and its self-strength is incremented by parameter c. Fr each unit f time that tw items spend tgether in STS, the strength ftheir assciatin in LTS is incremented by parameter b. Items that are never tgether in STS have a residual interitem assciatin given by parameter d. InGillund and Shiffrin (1984), variability was intrduced int the basic SAM mdel. T prduce variability in the assciative netwrk, each assciative strength is multiplied by a randm variable drawn frm a three-pint distributin (1, 1 - v, r 1 + v, where v is the variability parameter f the mdel). Retrieval in SAM invlves sampling memry with multiple cues. Initially, cntext is used as a cue t "sample" items in memry. If an item is "recvered," it is used, tgether with cntext, t sample anther item frm memry. An item cannt be recvered if the same retrieval cues failed t recver the item previusly r ifthe item has already been recalled. Once there have been L max cnsecutive failures at "recvery," retrieval is attempted with cntext alne. The verall prcess repeats itself until there are K max "recvery" failures t any cues. Whenever an item is recvered, its self-strength is incremented by parameter g, its assciatin t cntext is incremented by parameter e, and ifanther item was ne fthe retrieval cues, the interitem assciative strength is incremented by parameterf The equatins fr sampling and recvery prbabilities are given in Raaijmakers and Shiffrin (1980). SAM differs frm ther cntemprary memry mdels in that it des nt make explicit assumptins abut the representatin fitems in memry r the assciative mechanism. Rather, SAM maintains an abstract characterizatin fthe prbability fsuccessful retrieval given a set fretrieval cues. Because items in nearby input psitins spend mre time tgether in the rehearsal buffer, cnditinal respnse prbabilities shuld be greater fr adjacent items than fr remte items. Hwever, because interitem assciatins in SAM are bidirectinal, the bserved asymmetry in frward and backward recall may nt be predicted. Simulatins T fully examine the SAM mdel's ability t accunt fr the free-recall data, the mdel was simultaneusly fit t the serial psitin curve, mean utput psitin curve, and cnditinal respnse prbability data frm the 30 item/l-sec cnditin in Murdck (1962). In fitting SAM t these data, three parameters were fixed: The size f the rehearsal buffer, r, was set at 4 and the K max and L max parameters were set at 30 and 3, respectively. Simplex (NeIder & Mead, 1965) was used t estimate the remaining 8 parameters that minimized the chi-square statistic. Fr each simplex iteratin, results were averaged ver 10,000 replicatins fthe SAM mdel. The best-fitting parameters were: a = , b = , c = , d = , e = 0.546,/= , g = , and v = The fit fthe mdel t the data is depicted in Figure 5. The fits fthe serial psitin [X 2(22) = 168.7] and utput psitin [X 2(22) = 122.2] curves were reasnable. In cntrast, the mdel was largely unsuccessful in fitting the cnditinal respnse prbabilities [X 2(32) = 1,169]. T see if these results were stable, I repeated the simulatin fr different values fthe fixed parameters. Setting the size fthe rehearsal buffer t 3 instead f 4 increased the chi-square values cnsiderably, and trying several different values fk max and L max als did nt imprve the fit. As can be seen in Figure 5, the SAM mdel fails t accunt fr the difference between frward- and backwardadjacent recalls at any f the utput psitins. At early utput psitins, SAM far verpredicts the prbability f frward remte recalls. Finally, SAM predicts an abrupt transitin in remte recalls after the furth utput psitin, whereas the data shw a gradual transitin. Why des SAM make these predictins, and hw culd it be fixed t handle the data? First, SAM assumes symmetric assciatins between items in memry. This may accunt fr SAM's inability t prduce the asymmetry in frward and backward recall. Secnd, because retrieval in SAM reflects utput frm the shrt-term stre fllwed by search f assciative memry, there is a sudden shift

5 ASSOCIATIVE RETRIEVAL PROCESSES IN FREE RECALL 107 buffer, the mre likely it will be displaced. This scheme results in mre rehearsals fr recently studied items than fr remte items. Taken alne, this change in SAM greatly imprved the fit t the cnditinal respnse prbability data, but als wiped ut the primacy effect. T recver the primacy effect, an attentinal weighting factr was added t the rehearsal buffer. This factr was used in Gillund and Shiffrin (1984), but nt in Raaijmakers and Shiffrin (1981). Finally, with the primacy effect back, the fit fthe revised mdel is as shwn in Figure 6. The best-fitting parameters were: a = 0.082, b I = (frward), b2 = (backward), c = 0.777, d = 0.075, e = 0.401,II = (frward), 12 = (backward),g = 0.619, v = 0.197, 0= A majr imprvement can be seen in the mdel's fit t the cnditinal respnse prbability data. Althugh the fit is nt numerically spectacular, the revised mdel actually prvides a reasnable accunt fthe retrieval prcess [X 2(29) = ]. The revised mdel's fit t the Figure 5. This figure shws the best fit fthe SAM mdel ffree recall (Raaijmakers & ShitTrin, 1980) t the serial psitindata and mean utput psitin data (tp panel) and the cnditinal respnse prbability data (bttm panel) frm the 30-1 cnditin in Murdck (1962). Errr bars reflect 95% cnfidence intervals arund each mean. The Lftus and Massn (1994, Appendix B) prcedure fr cmputing cnfidence intervals in within-subject designs was used. in strategy at the furth utput psitin. This prblem might be slved if the size f the rehearsal buffer were varied acrss simulated trials. In an effrt t bring SAM's predictins clser t the data, fur mdificatins were intrduced. First, separate parameters fr frward and backward interitem assciatins were added (bth during study and test). Secnd, the rehearsal buffer size, r, was randmly set t 2, 3, 4, 5, r 6 n each trial (with prbabilities f 0.1,.22,.36,.22, and.10, respectively). Third, the rehearsal rule emplyed by Phillips, Shiffrin, and Atkinsn (1967) was adpted. Accrding t that rule, the prbability fthe ith buffer item being displaced was calculated as: d(i) = 0(1 - Of-, I - (I - 8) where 8 is a new free parameter f the mdel. Using this rehearsal scheme, the lder the item in the rehearsal 0.9 ff1! fft f!lllft!t!fffl m ::J iii 6 z 4( III c: j!ll c: "II 11. c: -l..j 0.4..J 4 "II 4( 0 (J 0.3 w 3 :::! c: z ::J iii 4( III SERIAL POSITION r ' _ Frward Adjacent - Frward Remte Backward Adjacent 0 Backward Remte Z J 0.2 is z (J 0.0 e...t..:.i:...l-l-'-j.-l-'-.l..i-'-.l..l-'-.l..l-'-.l..l-l-':-j PAIR OUTPUT POSITION Figure 6. This figure shws the best fit fa mdified versin fthe SAM free-recall mdel t the serial psitin data and mean utput psitin data (tp panel) and the cnditinal respnse prbability data (bttm panel) frm the 30-1 cnditin in Murdck (1962). Errr bars reflect 95% cnfidence intervals arund each mean. The Lftus and Massn (1994, Appendix B) prcedure fr cmputing cnfidence intervals in within-subject designs was used. ;', 30 8

6 108 KAHANA serial psitin curve [X 2(19) = 85.0] and utput psitin curve [X 2(19) = 199.8] did nt change substantially (with the exceptin fthe exaggerated hk nw present in the utput psitin curve). Cnclusins This paper presents a quantitative methd fr examining the rle finteritem assciatins in free recall. Pltting the prbability f recalling an item frm serial psitin x fllwed by an item frm serial psitin y fr different lags reveals strng adjacency effects, a frward-recall advantage, and shallw gradients beynd lag 2. The tendency t recall adjacent pairs in the frward rder is highly prnunced fr the first few utput psitins and then settles t a level fabut twice the backward-recall prbability fr the rest fthe recall prcess. The SAM mdel prvides a reasnable fit t bth serial psitin and mean utput psitin curves. Hwever, in its riginal versin, the mdel des nt adequately accunt fr the cnditinal respnse prbability data. The riginal mdel assumes symmetric increments ffrward and backward interitem assciatins. T bring the mdel within striking distance fthe data, three basic mdificatins were needed: (1) separate parameters fr frward and backward interitem assciatins, (2) a variable buffer size, and (3) a rehearsal rule that prefers nearby items (Phillips et ai., 1967). Anther successful mdel fsingle-trial free recall is Metcalfe and Murdck's (1981) chaining mdel. The chaining mdel belngs t a class fdistributed memry mdels that use cnvlutin and crrelatin as the assciative strage and retrieval mechanisms. Becausecnvlutin is cmmutative, frward and backward assciatins are f equal strength. Metcalfe and Murdck suggestthat recall begins by cuing memrywith the lastrehearsed item. Chaining thrugh memry cntinues until a specified number fsuccessive retrieval failures. Subsequently, retrieval is reinitiated with a beginningf-list cue (assciated with the first studied item). Frward chaining cntinues until anther series fretrieval failures. Because fthis tw-stage retrieval prcess, cnditinal respnse prbabilities shuld exhibit a backwardrecall advantage fr early utputpsitins, and a frwardrecall advantage fr late utput psitins. It is clear frm Figure 3 that this is nt the case. Adjacent frward recalls are higher than adjacent backward recalls at all utput psitins, but especially at early utput psitins. Subjects' tendency t mve backward at early stages f utput and frward at later stages futput is seen nly in remte recalls. In additin t the SAM buffer mdel (Raaijmakers & Shiffrin, 1981) and the assciative chaining mdel (Metcalfe & Murdck, 1981), tw ther appraches t studying free recall deserve attentin. In an effrt t accunt fr the ubiquity fexpnential interrespnse time functins in free recall, Rhrer and Wixted (1994) reintrduced the traditinal ntin f randm search withut replacement. The analyses presented in this paper demnstrate that free recall f items frm asympttic serial psitins simultaneusly exhibit expnential grwth in interrespnse times and cnditinal respnse latency effects (see Figure 4 and Murdck & Okada, 1970). A randm-search mdel cannt accunt fr cnditinal respnse latency effects (r the effects f semantic clustering reprted elsewhere in the literature). Despite these limitatins, Rhrer and Wixted's apprach may still be useful. The fundamental questin they raise, which is nt addressed by the present data, is whether the increase in respnse latency with utput psitin is a cnsequence fthe resampling fitems already recalled r sme ther prcess. Glenberg and Swansn's (1986) tempral distinctiveness thery (TOT) has been develped t accunt fr free recall in the cntinuus distractr paradigm. In this paradigm, direct interitem assciatins are either weakened r eliminated by the distractr task and the fcus is n tempral retrieval strategies. Accrding t TOT, items are sampled frm temprally defined search sets in memry. These search sets are assumed t be narrw fr recent items but brad fr prir list items. In the absence fstrng interitem assciatins, this type fmdel predicts symmetric gradients in the cnditinal respnse prbability curves. The gradients shuld be narrw early in recall and braden with utput psitin. Althugh TOT makes testable predictins abut cnditinal respnse prbability functins in free recall, these predictins cannt be tested using data frm the standard versin fthe task. Summary Previus research n free recall has fcused n semantic relatins between list items (e.g., Brwn, Cnver, Flres, & Gdman, 1991; Cke, Durs, & Schvaneveldt, 1986; Rmney, Brewer, & Batchelder, 1993; see Shuell, 1969, fr a review fthe earlier literature) t the exclusin f assciatin by cntiguity. Sme ptential reasns fr this were discussed in the intrductin. Cnditinal respnse prbability and latency analyses f a number f large free-recall studies suggest that the neglect fcntiguity-based assciative prcesses in free recall is unwarranted. In rder t predict free-recall perfrmance, bth cntiguity-based assciative prcesses and semantic relatins amng list items need t be cnsidered. REFERENCES ASCH, S. E., & EBENHOLTZ, S. M. (1962). The prcess f free recall: Evidence fr nn-assciative factrs in acquisitin and retentin. Jurnal fexperimental Psychlgy, 54, ATKINSON, R. C., & SHiFFRIN, R. M. (1968). Human memry: A prpsed system and its cntrl prcesses. In K. W. Spence & 1. T. Spence (Eds.), The psychlgy f learning and mtivatin: Advances in research and thery (Vl. 2, pp ). New Yrk: Academic Press. BROWN, S. c, CONOVER, J. N., FLORES, L. M., & GOODMAN, K. M. (1991). Clustering and recall: D high clusterers recall mre than

7 ASSOCIATIVE RETRIEVAL PROCESSES IN FREE RECALL 109 lw clusterers because f clustering? Jurnal fexperimental Psychlgy: Learning, Memry, & Cgnitin, 17, COOKE, N. M., DURSO, F. T, & SCHVANEVELDT, R. W. (1986). Recall and measures f memry rganizatin. Jurnal f Experimental Psychlgy: Learning, Memry, & Cgnitin, 12, DEESE, J., & KAUFMAN, R. A. (1957). Serial effects in recall f unrganized and sequentially rganized verbal material. Jurnal fexperimental Psychlgy, 54, GILLUND, G., & SHIFFRIN, R. M. (1984). A retrieval mdel fr bth recgnitin and recall. Psychlgical Review, 91, GLANZER, M., & CUNITZ, A. R. (1966). Tw strage mechanisms in free recall. Jurnal f Verbal Learning & Verbal Behavir, 5, GLENBERG, A. M., & SWANSON, N. G. (1986). A tempral distinctiveness thery f recency and mdality effects. Jurnal fexperimental Psychlgy: Learning, Memry. & Cgnitin, 12,3-15. HARCUM, E. R. (1975). Serial learning and paralearning. New Yrk: Wiley. KAHANA, M. J. (1995). Assciative symmetry and memry thery. Manuscript submitted fr publicatin. LOFTUS, G. R., & MASSON, M. E. J. (1994). Using cnfidence intervals in within-subject designs. Psychnmic Bulletin & Review, 1, METCALFE, J. A., & MURDOCK, B. B. (1981). An encding and retrieval mdel fsingle-trial free recall. Jurnal fverbal Learning & Verbal Behavir, 20, MURDOCK, B. B. (1962). The serial psitin effect ffree recall. Jurnal fexperimental Psychlgy, 64, MURDOCK, B. B., & METCALFE, J. A. (1978). Cntrlled rehearsal in single-trial free recall. Jurnal fverballearning & VerbalBehavir, 17, MURDOCK, B. B., & OKADA, R. (1970). Interrespnse times in singletrial free recall. Jurnal f VerbalLearning & Verbal Behavir, 86, NAIRNE, J. S., RIEGLER, G. L., & SERRA. M. (1991). Dissciative effects fgeneratin n item and rder retentin. Jurnal fexperimental Psychlgy: Learning, Memry, & Cgnitin, 17, NELDER, J. A., & MEAD, R. (1965). A simplex methd fr functin minimizatin. Cmputer Jurnal, 7, NILSSON, L.-G., WRIGHT, E., & MURDOCK, B. B. (1975). The effects f visual presentatin methd n single-trial free recall. Memry & Cgnitin, 3, PHILLIPS, J. L., SHIFFRIN, R. J., & ATKINSON, R. C. (1967). The effects f list length n shrt-term memry. Jurnal f VerbalLearning & VerbalBehavir, 6, RAAIJMAKERS, J. G. w., & SHIFFRIN, R. M. (1980). SAM: A thery f prbabilistic search f assciative memry. In G. H. Bwer (Ed.), The psychlgy flearning and mtivatin: Advances in research and thery (Vl. 14, pp ). New Yrk: Academic Press. RAAIJMAKERS, J. G. W., & SHIFFRIN, R. M. (1981). Search fassciative memry. Psychlgical Review, 88, ROHRER, D., & WIXTED, 1. T (1994). An analysis f latency and interrespnse time in free recall. Memry & Cgnitin, 22, ROMNEY, A. K., BREWER, D, D., & BATCHELDER, W. H. (1993). Predicting clustering frm semantic structure. Psychlgical Science, 4, SHUELL, T J. (1969). Clustering and rganizatin in free recall. Psychlgical Bulletin, 72, TuLVING,E. (1968). Theretical issues in free recall. In T R. Dixn & D. L. Hrtn (Eds.), Verbal behavir and general behavir thery (pp. 2-36). Englewd Cliffs, NJ: Prentice-Hall. NOTES I. In a mre recent study, Nairne, Riegler, and Serra (1991) fund sme evidence fr frward seriatin in the free-recall f eight-item lists. The percentage fadjacent recalls in the frward directin was 0.68, reliably abve the chance level fo T get reliable data n cnditinal respnse prbabilities, ne needs fairly large data sets. Murdck (1962) is prbably the largest freerecall study ever cnducted with practiced subjects. Datafr each cnditin are averaged frm ver 1,200 free-recall trials. In Murdck and Okada (1970), there are 720 trials fr each fthe presentatin-rate cnditins (slw = I item/sec, fast = 2 items/sec). Because fthe lw recall levels in this study, data frm the tw presentatin-rate cnditins were cmbined fr the cnditinal analyses. In Murdck and Metcalfe (1978), there are 512 lists in the vert rehearsal cnditin. 3. T determine interrespnse times, Murdck and Okada (1970) tested subjects individually in sundprf rms where the entire test sessin was tape-recrded. The recrded prtcls were analyzed using a sund meter and a pltter t measure the nset-nset interrespnse times fr all fthe recalled wrds. (Manuscript received December 21, 1993; revisin accepted fr publicatin March 13, 1995.)