Associative Processes in False Recall and False Recognition

Studying a list of words associated to a critical nonpresented word results in high rates of false recall and false recognition for that nonpresented item (Roediger & McDermott, 1995). Two experiments examined the effect of manipulating the number of associates presented on false recall and later false recognition of a nonpresented item: In Experiment 1, associate lists of varying lengths were studied; in Experiment 2, list length was held constant and the number of associates within the list was manipulated. In both experiments, the rate of critical intrusions in recall increased steadily with increasing number of associates studied. Most notably, the filler words used in Experiment 2 to equate the list lengths did not affect the rate of critical intrusions, although they did depress recall of studied words. False recall and false recognition appear to be tied to the total, not the mean, associative strength of items in the list. False memory for an event may be induced by the study of associated events. Deese (1959) demonstrated this phenomenon by having subjects study and recall lists of the 12 most common associates to a nonpresented item and then examining the probability with which the nonpresented item intruded during recall. For example, subjects studied the words bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, and nap, all of which are strongly related to the nonstudied item sleep. Deese noted that for some of the lists, the probability of false recall of the nonpresented item {sleep) was very high, with intrusions occurring on 30% to 40% of subjects' recall protocols. Roediger and McDermott (1995) revived the paradigm, first using six of Deese's (1959) 12-item study lists, and then expanding the materials to consist of twenty-four 15-item lists. For the 12word lists, Roediger and McDermott reported a mean false recall probability of .40 (Experiment 1); use of the 15-word lists produced a mean false recall probability of .55 (Experiment 2). Rates of false recognition for the nonpresented items in some cases equaled the rates of correct recognition for studied words. Other researchers have reported similar findings (McDermott, 1996; Payne, Elie, Blackwell, & Neuschatz, 1996; Read, 1996; Schacter, Verfaellie, & Pradere, 1996). Of note, several researchers have used Tulving's (1985) remember/know procedure, in which subjects are asked to indicate whether they actually remember the presentation of a nonpresented item in a study list or simply know that it occurred; these researchers have consistently found that subjects are highly likely to report remembering the occurrence of the critical items that were never presented (Roediger & McDermott, 1995; Payne et al., 1996; Read, 1996). Additionally, Payne et al. (1996, Experiment 3) demonstrated that subjects in this paradigm would willingly report whether a particular item had been presented in a male or a female voice when in fact that word had not been presented. The mechanisms underlying the powerful false recollection observed in this paradigm remain the subject of debate. Underwood (1965) proposed that the study of a list item may produce an implicit associative response (IAR), or the unintentional conscious activation of a word that is strongly related to that studied item. As a consequence, nonpresented items that are strongly associated to study items may be encoded during study along with the actual list words. This account suggests that, during recall, the nonpresented associate items should behave similarly to the studied items. Roediger and McDermott (1995) reported that it is indeed the case that the nonpresented items are recalled with approximately the same probability as the studied items in the middle serial positions of a study list. In addition, they showed that in a recognition test, subjects judge critical nonstudied words to be old at rates comparable to the hit rates for studied items. Finally, they found that subjects readily report remembering (as opposed to knowing) that the nonstudied items were presented, lending support to the hypothesis that the nonstudied items were encoded during study along with the list words. In his original discussion of this paradigm, Deese (1959) proposed a slightly different account. He suggested that "the probability of a particular word occurring as an intrusion in immediate free recall of a list of words may be predicted from the tendency for the intruding word to occur as a response in free association to the items on the list" (p. 21). Note that the associative strengths referred to by Deese represent the probabilities with which the critical item will be elicited by the various list items, or backward association strengths. These values are the reverse of the associative strengths used in constructing the study lists, which refer to the probabilities of the individual list words being elicited by the critical item {forward association strengths). Deese (1959) concluded that "the probability of intrusion is very well predicted by the simple mean ... of the associative tendencies for the intrusion to be elicited by the test words" (p. 21). According to Deese, this account "implies that in the process of recollection, words and concepts associated with remembered items will be added" (p. 21). In other words, Deese suggested that during recall, a nonstudied item will intrude to the extent that the average associative strength of the studied words to that specific intrusion is high. Indeed, he reported that the correlation between the average associative strength of the list items to the critical nonpresented word (or mean backward association strength of the list) and probability of intrusion of that word was +.87 across his lists. Address correspondence to Kerry J. Robinson or Henry L. Roediger, III, Department of Psychology, Box 1125, Washington University in St. Louis, One Brookings Dr., St. Louis, MO 63130-4899; e-mail: kjrobins @artsci.wustl.edu or roediger@artsci.wustl.edu. VOL. 8, NO. 3, MAY 1997 231 This content downloaded from 128.252.57.215 on Mon, 22 Jun 2015 21:27:51 UTC All use subject to JSTOR Terms and Conditions PSYCHOLOGICAL SCIENCE Associative Processes in False Memory In evaluating this hypothesis, Deese (1959) used lists that consisted of exactly 12 study items. In two experiments reported here, we examined the pattern of false recall and false recognition that occurs when study lists of varying lengths are used. We tested recall and recognition of 3-, 6-, 9-, 12-, and 15-item lists of related words taken from the Roediger and McDermott (1995) materials. As already mentioned, the study lists were constructed specifically of items that are strongly associated to a critical nonpresented item. Because of the limited number of potential study items that are strongly related to a critical item, longer study lists will necessarily include some items that are less strongly associated to that item. Thus, a short list consisting of, say, the six strongest associates of a critical item will have a higher mean associative strength than a long list. If forward and backward association strengths are related, then the same pattern should be expected for the lists' mean backward association strengths, or the mean association strengths of the list words back to the critical item. Indeed, when the lists were compared, the mean backward association strength of the lists to the critical items was reliably greater for shorter than for longer lists, as discussed in the next section. Consequently, if Deese's hypothesis were to be extended to study lists of varying lengths, it would predict that shorter lists would produce higher levels of false recall of a critical item than longer lists because of the greater average backward association strength for the shorter lists. It should be noted, however, that this strong form of the hypothesis was never explicitly stated by Deese (1959). An analogous pattern would be expected if the mechanism were similar to Underwood's (1965) IAR proposal. According to this perspective, the strongly associated critical item should behave as an additional study list word. It has been well established that as length of a study list increases, the probability of correct recall of any specific studied item decreases systematically (Murdock, 1961). The total number of correct items recalled increases with list length, of course, but the probability of any single item being recalled drops as additional items are added to the study list. If highly associated nonstudied items behave as if they had appeared on the study list, then one would again expect the probability of false recall of a critical item to decrease with increasing list length. Thus, according to predictions drawn from both Deese's (1959) and Underwood's (1965) hypotheses, the rate of false recall of a critical nonpresented item should correlate negatively with the number of associates in a study list. Other considerations suggest the opposite pattern: that a greater number of studied associates should lead to higher levels of false recall for the critical item. For example, false recall of a highly associated nonpresented item may be predicted not by the mean association strength of the list words, but by the total associative strength of these words. That is, the greater the total associative strength of the list the more the words are associated to the critical nonpresented item the greater the probability that the item will be falsely recalled and recognized. Thus, a longer list of associates should produce higher levels of false recall and false recognition of the critical item than should a shorter list, because a long list of associates will have a higher total association strength for that item. Not only does this prediction seem intuitive, but if list length is held constant, it is very similar to Deese's (1959) hypothesis implicating the average associative strength of the list.