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Journal of Experimental Psycho! logy: Learning, Memory, and Cognition el Copyright 1995 by ths American Psychological Association, Inc. Add 0278-7393/93/43.00 Creating False Memories: Remembering Words Not Presented in Lists Henry L. Roediger TI and Kathleen B. McDermott Rice University "Two experiments (modeled after J. Deese's 1959 study) revealed remarkable levels of false recall and false recognition in a list learning paradigm. In Experiment 1, subjects studied lists of 12 words (2. bed, rest, awake); each list was composed of associates of 1 nonpresented word (e-g., sleep). On immediate free recali tests, the nonpresented associates were recalled 40% of the time and were later recognized with high confidence. In Experiment 2, a false recall rate of 55% was obtained with an expanded set of lists, and on a later recognition test, subjects produced false alarms to these items at a rate comparable to the hit rate. The act of recall enhanced later remembering of both studied and nonstudied material, The results reveal a powerful illusion of memory: People remember events that never happened. False memories—cither remembering events that never happened, or remembering them quite differently from the way they happened—have recently captured the attention of both psychologists and the public at large. The primary impetus for this recent surge of interest is the increase in the number of cases in which memories of previously unrecognized abuse are reported during the course of therapy. Some researchers have argued that certain therapeutic practices can cause the creation of false memories, and therefore, the apparent “recovery” of memories during the course of therapy may actually represent the creation of memories (Lindsay $ Read, 1994; Loftus, 1993). Although the concept of false memories is currently enjoying an increase in publicity, it is not new; psychologists have been studying false memories in several laboratory paradigms for years, Schacter (in press) provides an historical overview of the study of memory distortions. Bartlett (1932) is usually credited with conducting the first experimental investigation of false memories; he had subjects read an Indian folktale, “The War of the Ghosts,” and recall it repeatedly. Although he reported no aggregate data, but only sample protocols, his results seemed to show distortions in subjects” memories over repeated attempts to recall the story. Interestingiy, Bartlet's repeated reproduction results never have been successfully replicated by later researchers (see Gauld £ Stephenson, 1967; Roediger, Wheeler, $ Rajaram, 1993), indeed, Wheeler and Roediger (1992) showed that recall of prose passages (including ““The War of the Ghosts”) This research was supported by Grant F49620-92-J-0437 from the Air Force Office of Scientific Research. We thank Ron Haas and Lubna Manal for aíd in conducting this research. Also, we thank Endel Tulving for bringing the Deese (1959) report to our attention. The manuscript benefited from comments by Doug Hintzman, Steve Lindsay, Suparna Rajaram, and Endel Tulving. Correspondence concerning this article should be addressed to Henry L. Roediger III or Kathleen B. MeDermott, Department of Psychology, MS 25, Rice University, 6100 S, Main Street, Houston, Texas 77005-1892. Electronic mail may be sent via Internet to roddyOrice.edu or medermoOricevmn.rice.edu. 803 actually improved over repeated tests (with very few errors) if short delays occurred between study and test. Nonetheless, Bartlett's (1932) contribution was an enduring one because he distinguished between reproductive and recon- structive memory. Reproductive memory refers to accurate, rote production of material from memory, whereas reconstruc- tive memory emphasizes the active process of filling in missing elements while remembering, with errors frequently occurring. It generally has been assumed that the act of remembering materials rich in meaning (e.g., stories and real-life events) gives rise to reconstructive processes (and therefore errors), whereas the act of remembering more simplified materials (e.g., nonsense syllables, word lists) gives rise to reproductive (and thus accurate) memory. Bartlett (1932) wrote that “I discarded nonsense materials because, among other difficul- ties, its use almost always weights the evidence in favour of mere rote recapitulation” (p. 204). The investigators of false memories have generally followed Bartlett's (1932) lead. Most evidence has been collected in paradigms that use sentences (Bransford $ Franks, 1971; Brewer, 1977), prose passages (Sulin é: Dooling, 1974), slide sequences (Loftus, Milter, £ Burns, 1978), or videotapes (Loftus £ Palmer, 1974). In all these paradigms, evidence of false memories has been obtained, although the magnitude of the effect depends on the method of testing (McCloskey de Zaragoza, 1985; Payne, Toglia, de Anastasi, 1994). The predomi- nance of materials that tell a story (or can be represented by a script or schema) can probably be attributed to the belief that only such materials will cause false memories to occur. There is one well-known case of false memories being produced in a list learning paradigm: Underwood (1965) introduced a technique to study false recognition of words in Y Bartlett (1932) results from the serial reproduction paradigm—in which one subject recalls an event, the next subject reads and then recalls the first subject's report, and so on-—replicates quite well (e.g., 1. H. Paul, 1959). However, the repeated reproduction research, in which a subject is tested repeatedly on the same material, is more germane to the study of false memories in an individual over time, To our knowledge, no one has successfuly replicated Bartlett's observa- tions in this paradigm with instructions that emphasize remembering (see Gauld 8: Stevenson, 1967). 804 HENRY L. ROEDIGER !IIl AND KATHLEEN B. MCDERMOTT lists. He gave subjects a continuous recognition task in which they decided if each presented word had been given previously in the list, Later words bore various relations to previously studied words. Underwood showed that words associatively related to previously presented words were falsely recognized. Anisfeld and Knapp (1968), among others, replicated the phenomenon. Although there have been a few reports of robust false recognition effects (Hintzman, 1988), in many experiments the false recognition effect was either rather small or did not occur at all. For example, in a study by L. M. Paul (1979), in which synonyms were presented at various lags along with other, unrelated Jures, the false recognition effect was only 3% (a 20% false-alarm rate for synonyms and a 17% rate Tor unrelated lures). Gillund and Shiffrin (1984) failed to find any false recognition effect for semantically related fures in a similar paradigm. In general, most research on the false recognition effect in list learning docs little to discourage the belief that more natural, coherent materials are needed to demonstrate powerful false memory effects. Interestingly, most research revealing false memory effects has used recogni- tion measures; this is true both of the prose memory literature (e.g., Bransford £ Franks, 1971; Sulin £ Dooling, 1974) and the eyewitness memory paradigm (Loftus et al., 1978; McClos- key 8: Zaragoza, 1985). Reports of robust levels of false recall are rarer, We have discovered a potentially important exception to these claims, one that reveals false recall in a standard list learning paradigm. lt ís represented in an experimental report published by Deese in 1959 that has been largely overlooked for the intervening 36 years, despite the fact that his observa- tions would seem to bear importantly on the study of false memories. Deese's procedure was remarkably straightforward; he tested memory for word lists in a single-trial, free-recall paradigm. Because this paradigm was just gaining favor among experimental psychologists at that time and was the focus of much attention during the 1960s, the neglect of Deese's report is even more surprising. However, since the Social Science Citation Index began publication in 1969, the article has been cited only 14 times, and only once since 1983. Most authors mentioned it only in passing, several authors apparently cited it by mistake, and no one has followed up Deese”s interesting observations until now, although Cramer (1965) reported similar observations and did appropriately cite Deese's (1959) article. (While working on this article, we learned that Don Read was conducting similar research, which is described briefiy in Lindsay 8 Read, 1994, p. 291.) Deese (1959) was interested in predicting the occurrence of extralist intrusions in single-trial free recall. To this end, he developed 36 lists, with 12 words per list. Each list was composed of the 12 primary assocíates af a critical (nonpre- sented) word. For example, for the critical word needle, the list words were thread, pin, eye, sewing, sharp, point, pricked, thimble, haystack, paín, hurt, and injection, He found that some of the lists reliably induced subjects to produce the critical nonpresented word as an intrusion on the immediate free recall test. Deese's interest was in determining why some lists gave rise to this effect, whereas others did not. His general conclusion was that the lists for which the associations went in a backoward (as well as forward) direction tended to elicit false recall. That is, he measured the average probability with which people produced the critical word from which the list was generated when they were asked to associate to the individual words in the list. For example, subjects were given sewing, point, thimble, and so on, and the average probability of producing needle as an associate was measured. Deese ob- tained a correlation of .87 between the probability of an intrusión in recall (from one group of subjects) and the probability of occurrence of the word as an associate to members of the list (from a different group). Our interest in Deese's materials was in using his best lists and developing his paradigm as a way to examine false memory phenomena. Our first goal was to try to replicate Deese's (1959) finding of reliable, predictable extralist intrusions in a single-trial, free- recall paradigm. We found his result to be surprising in light of the literature showing that subjects are often extremely accu- rate in recalling lists after a single trial, making few intrusions unless instructed to guess (sec Cofer, 1967; Roediger d: Payne, 1985). As previously noted, most prior research on false memory phenomena has employed measures of recognition memory or cued recall. Deese's paradigm potentially offers a method to study false recollections in free recall. However, we also extended Deese's paradigm to recognition tests. In Experi- ment 1, we examined false recali and false recognition of the critical nonpresented words and the confidence with which subjects accepted or rejected the critical nonpresented words as having been in the study lists. In Experiment 2, we tested other lists constructed to produce extralist intrusions in single- trial free recall, to generalize the finding across a wider set of materials. In addition, we examined the extent to which the initial false recall of items led to later false recognition of those same items. Finally, we employed the remember-know proce- dure developed by Tulving (1985) to examine subjects' phenom- enological experience during false recognition of the critical nonpresented items. We describe this procedure more fully below. Experiment 1 The purpose of Experiment 1 was to replicate Deese's (1959) observations of false recall by using six lists that produced among the highest levels of erroneous recall in his experiments. Students heard and recalled the lists and then received a recognition test over both studied and nonstudied items, including the critical nonpresented words. Method Subjects. Subjects were 36 Rice University undergraduates who participated as part of a course project during a regular meeting of the class, Psychology 308, Human Memory. Materials. We developed six lists from the materials listed in Deese's (1959) article. With one exception, we chose the six targets that produced the highest intrusion rates in Deese's experiment: chair, mountain, needle, rough, sleep, and sweet. As in Deese's experiment, for each critical word, we constructed the corresponding list by obtaining 2 Some people know of Deese's (1959) paper indirectly because Appleby (1986) used itas the basisof a suggested classroom demonstra- tion of déja va. 806 HENRY L. ROEDIGER III AND KATHLEEN B, MCDERMOTT Other intrusions also occurred in recall, albeit at a rather low rate. Subjects intruded the critical lure on 40% of the lists, but any other word in the English language was intruded on only 14% of the lists. Therefore, subjects were not guessing wildly in the experíment; as usual in single-trial free recall, the general intrusion rate was quite low. Nonetheless, subjects falsely recalled the critical items at a high rate. Recognition. The recognition test was given following study and recall of ali six lists, and thus the results were likety affected by prior recall. (We consider this issue in Experiment 2.) The proportion of responses for each of the four confidence ratings are presented in Table 1 for studied (old) items and for the three different types of lures: unrelated words, weakly related words, and the critical words from which the lists were derived, Consider first the proportion of items subjects called old by assigning a rating of 3 (probably old) or 4 (sure old). The hit rate was 86% and the false-alarm rate for the standard type of unrelated lures was only 2%, so by usual criteria subjects showed high accuracy. The rate of false alarms was higher for the weakly related lures (.21) than for the unrelated lures, (35) = 7.40, SEM = .026, p < .001. This outcome replicates the standard false-recognition effect first reported by Under- wood (1965). The false-recognition rate for weakly related lures was greater than obtained in many prior studies (e.g., L. M. Paul, 1979), and the rate for the critical nonpresented words was dramatically larger than the rate for the weakly related words. As shown in Table 1, the false-alarm rate for the critical nonstudied hures (84) approached the hit rate (.86), +(35) < 1, SEM = .036,ns. Consider next the results based on subjects high-confidence responses (i.e., when they were sure the item had appeared in the study list and rated it a “4”), The proportion of unrelated and weakly related lures falling into this category approached zero. However, subjects were still sure that the critical nonstud- ied items had been studied over half the time (.58). The hit rate for the studied items remained quite high (.75) and was reliably greater than the false-alarm rate for the critical lures, 1(35) = 3.85, SEM = .044, p < .001. Itis also interesting to look at the rates at which subjects classified items as sure new. Unrelated lures were correctly rejected with high confidence 80% of the time. Related lures received this classification only 44% of the time, and critical lures were confidently rejected at an even lower rate, 8%, which is similar to the rate for studied words (5%). Table 1 Recognition Results for Experiment 1: The Proportion of liems Classified As Sure Old (a Rating of 4), Probably Old (3), Probably New (2), or Sure New (1) and the Mean Ratings of Htems As a Function of Study Status Old New —— —— Mean Study status 4 3 2 1 rating Studied ys 41 09 Os 36 Nonstudied Unrelated lure 110] 02 18 80 1.2 Weakly related lure q 17 35 44 18 Critical lure 58 26 08 08 33 Table 1 also presents the mean ratings for the four types of items on the 4-point scale. This measure seems to tell the same story as the other two: The mean rating of the critical lures (3.3) approached that of studied items (3.6); the difference did reach significance, £(35) = 2.52, SEM = .09, p < .05. In general, the judgments subjects provided for the critical lures appeared much more similar to those of studied items than to the other types of lures. Discussion The results of Experiment 1 confirmed Deese's (1959) observation of high levels of false recall in a single-trial, free-recall task, albeit with six lists that were among his best. We found that the critical nonpresented items were recalled at about the same level as items actually presented in the middle of the lists, This high rate of false recall was not due to subjects guessing wildly. Other intrusions occurred at a very low rate. In addition, we extended Deese's results to a recognition test and showed that the critical nonpresented items were called old at almost the same level as studied items (i.e., the false-alarm rate for the critical nonpresented items approximated the hit rate for the studied items). The false-alarm rate for the critical nonpresented items was much higher than for other related words that had not been presented. Finally, more than half the time subjects reported that they were sure that the critical nonstudied item had appeared on the list. Given these results, this paradigm seems a promising method to study false memories. Experiment 2 was designed to further explore these false memories. Experiment 2 We had four aims in designing Experiment 2. First, we wanted to replicate and extend the recall and recognition results of Experiment 1 to a wider set of materials. Therefore, we developed twenty-four 15-item lists similar to those used in Experiment 1 and in Deese's (1959) experiment. (We included expanded versions of the six lists used in Experiment 1.) Second, we wanted to examine the effect of recall on the subsequent recognition test. In Experiment 1 we obtained a high level of false recognition for the critical nonpresented words, but the lists had been recalled prior to the recognition test, and in 40% of the cases the critical item had been falsely recalled, too. In Experiment 2, we examined false recognition both for lists that had been previously recalled and for those that had not been recalled. Third, we wanted to determine the false-alarm rates for the critical nonpresented items when the relevant list had not been presented previously (e.g., to determine the false-alarm rate for chair when related words had not been presented in the list). Although we considered it remote, the possibility existed that the critical nonpresented items simply elicit a high number of false alarms whether or not the related words had been previously presented. The fourth reason—and actually the most important one— Tor conducting the second experiment was to obtain subjects” judgments about their phenomenological experience while recognizing nonpresented items, We applied the procedure developed by Tulving (1985) in which subjects are asked to CREATING FALSE MEMORIES 807 distinguish between two states of awareness about the past: remembering and knowing. When this procedure is applied in conjunction with a recognition test, subjects are told (a) to judge each item to be old (studied) or new (nonstudied) and (b) to make an additional judgment for each item judged to be old: whether they remember or know that the item occurred in the study list. A remember experience is defined as one in which the subject can mentally relive the experience (perhaps by recalling its neighbors, what it made them think of, what they were doing when they heard the word, or physical characteris- tics associated with its presentation). A know judgment is made when subjects are confident that the item occurred on the list but are unable to reexperience (i.e., remember) its occurrence. In short, remember judgments reflect a mental reliving of the experience, whereas know judgments do not. There is now a sizable literature on remember and know judgments (see Gardiner 4 Java, 1993; Rajaram de Roediger, in press), but we will not review it here except to say that evidence exists that remember-know judgments do not simply reflect two states of confidence (high and low) because variables can affect remember-know and confidence (sure— unsure) judgments differently (e.g., Rajaram, 1993). Our purpose in using remember—know judgments in Experi- ment 2 was to see if subjects who falsely recognized the critical nonpresented words would report accompanying remember experiences, showing that they were mentally reexperiencing events that never occurred. In virtually all prior work on false memories, it has been assumed that subjects” incorrect re- sponses indicated false remembering. However, if Tulving's (1985) distinction is accepted, then responding on a memory test should not be equated with remembering. Further metame- morial judgments such as those obtained with the remember- know procedure are required to determine if subjects are remembering the events. In fact, in most experiments using the remember-know procedure, false alarms predominantly have been judged as know responses (e.g., Gardiner, 1988; Jones de Roediger, 1995). This outoome would be predicted in our experiment, too, if one attributes false recognition to a high sense of familiarity that arises (perhaps) through spreading activation in an associative network, Therefore, in Experiment 2 we examined subjects' metamemorial judgments with respect to their false memories to see whether they would classify these memories as being remembered or known to have occurred. In Experiment 2, subjects were presented with 16 lists; after half they received an immediate free recall test, and after the other half they did math problems. After all lists had been presented, subjects received a recognition test containing items from the 16 studied lists and 8 comparable lists that had not been studied. During the recognition test, subjects made old-new judgments, followed by remember-know judgments for items judged to be old. Method Subjects. Thirty Rice University undergraduates participated in a one hour session as part of a course requirement. Maseríals.. We developed 24 lists from Russell and Jenkins's (1954) norms in a manner similar to that used for Experiment 1. For each of 24 target words, 15 associates were selected for the list. These were usually the 15 words appearing first in the norms, but occasionally we substituted other related words when these seemed more appropriate (.e., more likely to elicit the nonpresented target as an associate), The ordering of words within lists was held constant; the strongest associates generally occurred first. An example of a list for the target word sleep is: bed, rest, awake, tired, dream, wake, night, blanket, doze, slumber, snore, pillow, peace, yawn, drowsy. All the lists, corrected for a problem noted in the next paragraph, appear in the Appendix. The 24 lists were arbitrarily divided into three sets for counterbalanc- ing purposes. Each set served equally often in the three experimental conditions, as described below. The reported results are based on only 7 of the 3 lists in each set because the critical items in 2 of the lists inadvertently appeared as studied items in other lists; dropping 1 list in each of two sets eliminated this problem and another randomty picked list from the third set was also dropped, so that each scored set was based on 7 lists. Witb these exceptions, none of the critical items occurred in any of the lists. Design. The three conditions were tested in a within-subjects design. Subjects studied 16 lists; 8 lists were foilowed by an immediate free recall test, and $ others were not followed by an initial test. The remaining 8 lists were not studied. Htems from all 24 lists appeared on the later recognition test. On the recognition test, subjects judged items as old (studied) or new (nonstudied) and, when old, they also judged if they remembered the itern from the list or rather knew that it had occurred. Procedure. Subjects were told that they would be participating in a memory experiment in which they would hear lists of words presented by means of a tape player. They were told that after each list they would hear a sound (either a tone or a knock, with examples given) that would indicate whether they should recall items from the tist or do math problems. For half of the subjects, the tone indicated that they should recall the list, and the knock meant they should perform math problems; for the other half of the subjects, the signals were reversed. They were told to listen carefully to each list and that the signal would occur after the list had been presented; therefore, subjects never knew during list presentation whether the list would be recalled. Words were recorded in a male voice and presented approximately at a 1.5-s rate. Subjects were given 2 min after cach list to recall the words or to perform multiplication and division problems. Recall occurred on 4 inch by 11 inch sheets of paper, and subjects turned over each sheet after the recall period, so the recalled items were no longer in view. The first part of the experiment took about 45 min. The recognition test occurred about 5 min after the test or math period for the 16th list. During this time, subjects were given instructions about making old-new and remember-know judgments. They were told that they would see a long list of words, some of which they had heard during the earlier phase of the experiment. They were to circle either the word old or new next io each test item to indicate Whether the item had been presented by means of the tape player. Ifan item was judged old, subjects were instructed that they should further distinguish between remembering and knowing by writing an R or Kin the space beside the item. Detailed instructions on the remember Know distinction were given, modeled after those of Rajaram (1993). Essentially, subjects were told that a remember judgment should be made for items for which they had a vivid memory of the actual presentation; know judgments were reserved for items that they were sure had been presented but for which they lacked the feeling of remembering the actual occurrence of the words. They were told that a remember judgment woutd be made in cases in which they remem- bered something distinctive in the speaker's voice when he said the word, or perhaps they remembered the item presented before or after it, or what they were thinking when they heard the word. They were always told to make the remember-know judgment about a word with respect to its presentation on the tape recorder, not whether they CREATING FALSE MEMORIES 809 rate of remember judgments dropped to 53%, although this figure is still quite high. Intercstingly, the corresponding percentages for items actually studied were about the same: 72% for remember judgments for lists that were recalled and 63% for lists that were not recalled. One point that vitiates the correspondence between the results for studied and nonstudied items in Table 2 is that the false-alarm rates for the types of items differed when the relevant lists had not been studied. The rate for the regular list words was .11, whereas the rate for the critical lures (when the relevant prior list had not been studied) was ,16, t(29) = 2.27, SEM = .022, p = .03, two-tailed. However, the difference was not great, and in both cases falsc alarms gave rise to more know responses than remember responses. One further analysis is of interest. In the study + recall condition, we can consider recognition results for items that were produced in the recall phase (whether representing correct responding or false recal!) relative to those that were not produced, Although correlational, such results provide an interesting pattern in comparing the effects of prior correct recall to prior false recal! on later recognition. Table 3 shows the results of this analysis, including the means for studied items and for the critical items. For the studied items, recognition of items that had been correctly recalled was essentialy perfect, and most old responses were judged to be remembered. ltems not produced on the recall test were recognized half the time, and responses were evenly divided between remember and know judgments. These effects could have been due to the act of recall, to ¡tera selection effects, or to some combination. Nonetheless, they provide a useful point of comparison for the more interesting results about the fate of falsely recalled items, as shown in Table 3. The recognition results for the falsely recalled critical items closely resemble those for correctly recalled studied items. The probability of recognizing falsely recalled items was quite high (93), and most of these items were judged to be remembered (-73) rather than known (20). More remarkably, the critical items that were not produced were later (falsely) recognized at a higher rate (.65) than were ¡items actually studied but not produced (.50); this difference was marginally significant, t(29) = 1.81, SEM = .083, p = .08, two-tailed. In addition, these falsely recognized items were judged to be remembered in 58% of the cases (i.c., .38 + .65 x 100), or at about the same Table 3 Proportion of Items Judged to be Old on the Recognition Test in the Study + Recall Condition of Experiment 2 As a Function of Whether the Items Were Produced on the immediate Free Recall Test Production Recognition rate of free —.—— Condition recall Overall R K Studied Produced 62 98 2 19 Not produced 38 50 26 2 Critical lure Produced 55 sa m2 Not produced 45 65 38 27 Note. R = remember judgment; K = know judgment. rate as for words that were studied but not produced (52%). These analyses reveal again the powerful false memory effects atwork ín this paradigm, with people falsely remembering the critical nonstudied words at about the same levels (or even greater levels) as presented words. General Discussion The primary results from our experiments can be summa- rized as follows: First, the paradigm we developed from Deese's (1959) work produced high levels of false recall in single-trial free recall. In Experiment 1, with 12-word lists, subjects recalled the critical nonstudied word after 40% of the lists, In Experiment 2, with 15-word lists, false recall increased, occurring on 55% of the occasions, Second, this paradigm also produced remarkably high levels of false recognition for the critical items; the rate of false recognition actually approached the hit yate. Third, the false recognition responses were frequently made with high confidence (Experiment 1) or were frequently accompanied by remember judgments (Experiment 2). Fourth, the act of recall increased both accurate recogni- tion of studied items and the false recognition of the critical nonstudied items. The highest rates of false recognition and the highest proportion of remember responses to the critical nonstudied items occurred for those items that had been falsely recalled. We discuss our results (a) in relation to prior work and (b) in terms of theories that might explain the basic effects. We then discuss (c) how the phenomenological experience of remember- ing events that never happened might occur, and (d) what implications our findings might have for the wider debates on false memories. Relation to Prior Work. Prior work by Underwood (1965) has shown false recogni- tion for Jures semantically related to studied words, but as we noted in the introduction, these effects were often rather small in magnitude. In our experiments, we found very high levels of Talse recall and false recognition. Our recognition results are similar to those obtained by investigators in the 1960s and 1970s who used prose materials and found erroneous recogni- tion of related material, For example, Bransford and Franks (1971) presented subjects with sentences that were related and created a coherent scene (e.g., The rock rolled down the mountain and crushed the hut. The hut was tiny). Later, they confidently recognized sentences that were congruent with the meaning of the complex idea, although the sentences had not actually been presented (e.g., The rock rolled down the mountain and crushed the tiny hut). Similarly, Posner and Kcele (1970) showed subjects dot patterns that were distor- tions from a prototypic pattern. Later, they recognized the prototype (that had never been presented) at a high rate, and forgetting of the prototype showed less decline over a week than did dot patterns actually presented. Jenkins, Wald, and Pittenger (1986) reported similar observations with pictorial stimuli. In cach of the experiments just described, and in other related experiments (see Alba 4: Hasher, 1983, for a review), 810 HENRY L. ROEDIGER NI AND KATHLEEN B. MCDERMOTT subjects recognized events that never happened if the events fit some general schema derived from the study experiences. A similar interpretation is possible for our results, too, although most researchers have assumed that schema-driven processes occur only in prose materials. Yet the lists for our experiments were generated as associates to a single word and therefore had a coherent form (e.g., words related to sleep or to other simitar concepts). The word sleep, for example, may never have been presented in the list, but was the “prototype” from which the list was generated, and therefore our lists arguably encour- aged schematic processing. Although our results are similar to those of other research revealing errors in memory, several features distinguish our findings. First, we showed powerful false memory effects in both recall and recognition within the same paradigm. The findings just cited, and others described below, all used recognition paradigms. Although some prior studies have reported false recall (c.g., Brewer, 1977; Hasher de: Griffin, 1979; Spiro, 1980), these researchers used prose materials. Second, we showed that subjects actually claimed to remember most of the falsely recognized events as having occurred on the list. The items did not just evoke a feeling of familiarity but were consciousiy recollected as having occurred. Third, we showed that the effect of prior recall increased both accurate and false memories and that this effect of recall was reflected in remember responses. Explanations of False Recall and False Recognition How might false recall and false recognition arise in our paradigm? Actually, the earliest idea about false recognition— the implicit associative response—still seems workable in helping to understand these phenomena, although today we can elaborate on the idea with new models now available. Underwood (1965) proposed that false recognition responses originated during encoding when subjects, secing a word such as hot, might think of an associate (cold). Later, if cold were presented as a Jure, they might claim to recognize its occur- rence in the list because of the earlier implicit associative response. Some writers at the time assumed that the associative response had to occur consciously to the subject during study, so it was implicit only in the sense that it was not overtly produced. Another possible interpretation is that the subject never even becomes aware of the associative response during study of the lists, so that its activation may be implicit in this additional sense, too. Activation may spread through an associative network (e.g., Anderson £ Bower, 1973; Collins £e Loftus, 1975), with false-recognition errors arising through residual activation. That is, it may not be necessary for subjects to consciously think of the associate while studying the list for false recall and false recognition to occur. On the other hand, the predominance of remember responses for the critical lures on the later recognition test may indicate that the critical nonpresented words do occur to subjects during study of the list. That may be why subjects claim to remember them, through a failure of reality monitoring (Johnson $: Raye, 1981). In 2. support of the idea that associative processes are critically important in producing false recall, Deese (1959) showed that the likelihood of false recail in this paradigm was predicted well by the probability that items presented in the list elicited the critical nonpresented word in free association tests, In other words, the greater the likelihood that ist members produced the critical nonpresented target word as an associate, the greater the level of false recall (see also Nelson, Bajo, McEvoy, dí Schreiber, 1989). It is worth noting that some of Deese's lists that contained strong forward associations— including the famous “butterfly” list used in later research— did not lead to false recall. The particular characteristics of the lists that lead to false memories await systernatic experimental study, but in general Deese reported that the lists that did not lead to false recall contained words that did not produce the critical targets as associates. The butterfly list did not elicit even one false recall in Deese's experiment, Tf false recall and false recognition are produced by means of activation of implicit associative responses, then the reason our false-recognition results were more robust than those usually reported may be that we used lists of related words rather than single related words. Underwood (1965) and others had subjects study single words related to later lures on some dimension, and they showed only modest levels of false recognition, or in some cases none at all (Gillund d Shiffrin, 1984). In the present experiments, subjects studied lists of 12-15 items and the false-recognition effect was quite large. Hall and Kozloff (1973), Hintzman (1988), and Shiftrin, Huber, and Marinelli (1995) have shown that false recognition is directly related to the number of related words in a list. For example, Hintzman (1988, Experiment 1) presented from 0 to 5 items from a category in a list and showed that both accurate recognition of studied category members, as well as false recognition of lures from that category, increased as a function of category size. False recognition increased from about 8% when no category members were included in the list to around 35% when five category members occurred in the list. (These percentages were estimated from Hintzman's Figure 11.) Our lists were not categorized, strictly speaking, but the words were generally related. For our 15-item lists in Experiment 2 that did not receive recall tests, false recognition was 72%, the corresponding figure for recalled lists was 81%. It will be interesting to see if longer versions of standard categorized lists will produce false recognition at the same levels as the lists we have used and whether the average probability that items in the líst evoke the lure as an associate will predict the level of false recognition. We are now conducting experiments to evaluate these hypotheses. If the errors in memory occurring on both recall and recognition tests arise from associative processes, then formal models of associative processing might be expected to predict them. At least at a general level, they would seem to do so, For example, the search of associative memo1y (SAM) model, first proposed by Raaijmakers and Shiffrin (1980) and later ex- tended to recognition by Gillund and Shiffrin (1984), provides for the opportunity of false recognition (and presumably recall) by means of associative processes. Although it was not the main thrust of their paper, Shiffrin et al. (1995) demon- strated that the SAM model did fit their observation of an increased tendency to produce false alarms to category mem- 812 HENRY L. ROEDIGER III AND KATHLEEN B. MCDERMOTT a memory (Johnson de Raye, 1981). Thus, in our paradigm, if subjects fuently generate (in recall) or process (in recognition) the word sleep (on the basis of recent activation of the concept) and if this ftuency allows them to construct a clear mental image of how the word would have sounded if presented in the speaker's voice, then they would likely claim to remember the word's presentation. The act of recall increases the ease of producing an event and may thereby increase the experience of remembering. Jacoby et al.'s (1989) analysis offers promising leads for further research. Implications The results reported in this article identify a striking memory illusion. Just as perceptual illusions can be compelling even when people are aware of the factors giving rise to the illusion, we suspect that the same is true in our case of remembering events that never happened. Indeed, informal demonstration experiments with groups of sophisticated sub- jects, such as wily graduate students who knew we were trying to induce false memories, also showed the effect quite strongly. Bartlett (1932) proposed a distinction between reproductive and reconstructive memory processes. Since then, the common assumption has been that list learning paradigms encourage rote reproduction of material with relatively few errors, whereas paradigms using more coherent (schematic) material (e.g., sentences, paragraphs, stories, or scenes) are necessary to observe constructive processes in memory retrieval, Yet we obtained robust false memory effects with word lists, albeit with ones that contain related words. We conclude that any contrast between reproductive and reconstructive memory is ili-founded; all remembering is constructive in nature, Materi- als may difíer in how readily they lead to error and false memories, but these are differences of a quantitative, not qualitative, nature. Do our results have any bearing on the current controversies raging over the issue of allegedly false memories induced in therapy? Not directly, of course. However, we do show that the illusion of remembering events that never happened can occur quite readily. Therefore, as others have also pointed out, the fact that people may say they vividiy remember details surround- ing an event cannot, by itself, be taken as convincing evidence that the event actually occurred (Johnson d Suengas, 1989; Schooler, Gerhard, £ Loftus, 1986; Zaragoza € Lane, 1994). Our subjects confidently recalled and recognized words that were not presented and also reported that they remembered the occurrence of these events. A critic might contend that because these experiments occurred in a laboratory setting, using word lists, with college student subjects, they hold questionable relevance to issues surrounding more spectacular occurrences of false memories outside the lab. However, we believe that these are all reasons to be more impressed with the relevance of our results to these issues. After all, we tested people under conditions of intentional learning, with very short retention intervals, in a standard laboratory procedure that usually produces few errors, and we used college students— professional memorizers—as subjects. In short, despite condi- tions much more conducive to veridical remembering than those that typically exist outside the lab, we found dramatic evidence of false memories. 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