Perceptual fluency as a cue for recognition judgments in amnesia

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Copyright 1999 by the American Psychological Association, Inc. 0894-4105/99/$3.00

Neuropsychology 1999, Vol. 13, No. 2,198-205

Perceptual Fluency as a Cue for Recognition Judgments in Amnesia Laird S. Cermak

Mieke Verfaellie

Boston University School of Medicine and Veterans Affairs Medical Center, Boston

This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

Boston University School of Medicine

This study investigated the extent to which amnesic patients use fluency of perceptual identification as a cue for recognition. Perceptual fluency was measured by having participants gradually unmask words before making recognition judgments. In Experiment 1, familiarity was the only possible basis for recognition because no words had been presented in the study phase. In Experiment 2, recollection provided an alternative basis for recognition because words had appeared in the study phase. Amnesic patients were as likely as normal controls to use perceptual fluency as a cue for recognition in Experiment 1 but were more likely than controls to do so in Experiment 2. For both groups, perceptual fluency affected judgments for studied and unstudied items to the same extent in Experiment 2. These findings suggest that amnesic patients do use perceptual fluency cues, but reliance on perceptual fluency does not necessarily elevate recognition accuracy. of recognition memory. This raises the possibility that amnesic patients' recognition ability is in some way related to their perceived sense of familiarity for recently experienced stimuli. This possibility emanates logically from models of recognition memory that posit two bases for recognition performance, one shared with other explicit memory tasks (recollection) and one not shared (familiarity) (Gardiner, 1988; Jacoby, 1991; Mandler, 1980). In light of these models, it can be proposed that amnesic patients' poor performance across a variety of explicit memory tasks reflect the extent to which these tasks depend on recollection, the intentional search process that leads to recovery of item-specific or contextual information associated with an episode. On the other hand, amnesic patients' relatively preserved performance on recognition tasks may reflect the fact that performance on these tasks can be supported in part by familiarity, an automatic process that is based on the fluency of stimulus processing. There are several reasons why the proposal of familiaritybased recognition in amnesia remains controversial. First, isolation of the contribution of familiarity to recognition has been difficult (see, for example, Verfaellie & Treadwell, 1993; Yonelinas, Kroll, Dobbins, Lazzara, & Knight, 1998). Second, familiarity itself is likely to be multidetermined. Early work by Jacoby and his colleagues (Jacoby, 1983; Jacoby & Dallas, 1981; Jacoby & Whitehouse, 1989) suggested that feelings of familiarity are caused by the perceptual overlap between stimuli at study and test and may be based on the same mechanisms that support perceptual priming. However, subsequent studies demonstrated that feelings of familiarity can also be produced by conceptually driven processing (Jacoby, 1991; Wagner, Gabrieli, & Verfaellie, 1997; Whittlesea, 1993) and can be dissociated from the perceptual processing that supports priming (Wagner et al., 1997). Thus, the effectiveness of familiarity-based recognition for amnesic patients may depend on the nature of the processes that support familiarity in any particular task.

Damage to bilateral medial temporal and diencephalic structures leads to an amnesic disorder characterized by a dense impairment in recall and recognition. Despite this general impairment in explicit memory, clinicians report that patients with amnesia often experience a sense of familiarity for recently encountered people or events. This feeling of familiarity is striking because patients remain at a loss to describe where or when they encountered these people or experienced these events. Yet, the nature of this familiarity and its precise impact on patients' behavior have received only limited attention from research investigators to date. What has been demonstrated is that amnesic patients can sometimes perform quite well on standard recognition tests (Bowers, Verfaellie, Valenstein, & Heilman, 1988; Huppert & Piercy, 1976; Johnson & Kim, 1985), exceeding the level expected from their recall performance (Hirst et al., 1986; Hirst, Johnson, Phelps, & Volpe, 1988). These findings remain controversial (Haist, Shimamura, & Squire, 1992; Shimamura & Squire, 1988) and may depend on the precise demands of the recognition test used as well as on the nature of the patients tested (for discussion, see Verfaellie & Treadwell, 1993); yet, a recent meta-analysis of a large number of recognition memory studies (Aggleton & Shaw, 1996) reached the conclusion that amnesic patients with focal lesions in the limbic system do show a relative sparing Mieke Verfaellie, Memory Disorders Research Center, Boston University School of Medicine; Laird S. Cermak, Memory Disorders Research Center, Boston University School of Medicine, and Veterans Affairs Medical Center, Boston. This research was supported by Program Project Grant NS 26985 from the National Institute of Neurological Disease and Stroke and Grant MH 57681 from the National Institute of Mental Health. We thank Ken Chase for research assistance and Margaret Keane for helpful discussions and suggestions. Correspondence concerning this article should be addressed to Mieke Verfaellie, Memory Disorders Research Center (151 A), Department of Veterans Affairs Medical Center, 150 South Huntington Avenue, Boston, Massachusetts 02130.

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FLUENCY AS A CUE FOR RECOGNITION IN AMNESIA

The purpose of the present study was to examine the extent to which amnesic patients use the feeling of familiarity created by perceptual fluency as a basis for recognition. Studies in normal individuals have addressed the role of perceptually based familiarity by directly manipulating the fluency with which words are perceived in a recognition test. This has been accomplished by varying the level of noise in which these words are presented (Whittlesea, 1993; Whittlesea, Jacoby, & Girard, 1990), by immediately preceding words by their own masked presentations (Bernstein & Welch, 1991; Jacoby & Whitehouse, 1989; Rajaram, 1993) or by having participants perform a separate task on the test words immediately prior to the recognition judgment (Johnston, Hawley, & Elliot, 1991; Johnston, Dark, & Jacoby, 1985; Luo, 1993). These studies have demonstrated that manipulations that increase perceptual fluency can enhance a participant's willingness to endorse items on a recognition test, regardless of whether or not these items have actually been studied. It appears, therefore, that normal individuals do use perceptual fluency as an attributional source for recognition judgments. To examine whether amnesic patients' recognition judgments are similarly influenced by the perceptual fluency of items on a recognition test, we performed two experiments that examined the effects of natural variations in perceptual fluency on recognition. These experiments differed in the likelihood that normal individuals would use familiarity as a basis for recognition. In Experiment 1, familiarity was the only basis for recognition, whereas in Experiment 2, recollection provided an alternative basis for recognition. We hypothesized that amnesic patients would attribute the perceptual fluency of items in a recognition test to their prior occurrence to the same extent as normal individuals in Experiment 1, but would rely more heavily on familiarity than normal individuals in Experiment 2. This hypothesis was based on the notion that recollection is almost totally unavailable to amnesic patients, leaving familiarity as their only basis for recognition judgments.

Experiment 1 In several experiments, Johnston et al. (1991) asked normal participants to identify words as they gradually came into view and then had the participants judge whether these words had previously been studied. Regardless of whether words had actually been studied, Johnston et al. found that words identified more quickly were more likely to be judged old, indicating that natural fluency of perception served as a basis for recognition. Moreover, they found that fluency of perception was more likely to be used as a cue for recognition as explicit memory decreased. Indeed, the effects of fluency were most prominent when explicit memory (and recollection) was totally absent. The present experiment examined whether amnesic patients would also use natural fluency of perception as a cue for making recognition judgments. Potential effects of explicit memory were eliminated by using a mock subliminal procedure in the study phase. Participants were told that words were being presented very briefly, but in reality, no

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words were presented. Eliminating explicit memory in this manner not only served to maximize the effects of fluency on recognition, but it also allowed us to examine the effects of fluency under conditions that were strictly equivalent for the amnesic patients and nonamnesic individuals. Method Participants. Fourteen amnesic patients (3 women, 11 men) and 14 control participants (2 women, 12 men) took part in the experiment. Seven amnesic patients had a diagnosis of Korsakoff syndrome and were residing in various chronic care facilities in the Boston metropolitan area. They all had histories of chronic alcoholism, were unable to recall day-to-day events, and had extensive retrograde amnesia. Of the other 7 amnesic patients, 3 suffered from encephalitis, 2 suffered from anoxia secondary to cardiac arrest, 1 underwent removal of a left hematoma following head injury and subsequently became amnesic following an episode of status epilepticus, and 1 became amnesic after a bilateral medial thalamic infarction. These patients all lived at home and, like the Korsakoff patients, displayed a severe memory disorder. The two groups of patients performed very similarly on the experimental tasks described below, and therefore, they are treated as a single amnesic group in the analyses that follow. The combined group had a mean age of 53.4 years and a mean of 13 years of education. The control group consisted of 7 individuals with a history of chronic alcohol abuse who had been abstinent for at least one month and 7 individuals with no history of alcohol abuse. They were matched to the amnesic group on the basis of age (M = 50.1 years) and education (M =13.9 years). On the Wechsler Adult Intelligence Scale—Revised (WAIS-R; Wechsler, 1981), the amnesic patients obtained a mean verbal IQ of 99.1, a score which did not differ from that obtained by the control participants (M = 107.1), ?(26) = 1.55. On the Wechsler Memory Scale—Revised (WMS-R; Wechsler, 1987) the amnesic group obtained a general memory index of 74 and a delayed recall index of 57. Their attentional abilities were within normal limits, as evidenced by an attention-concentration index of 101. Materials and design. Ninety words with a frequency range of 8-21 per million (Francis & Kucera, 1982) were used as stimuli. Eighty words were randomly selected to serve as critical items during the recognition test. The remaining 10 words served as practice items at the beginning of the recognition test. During the study phase, an eight-character mask was presented for each of 40 trials. No stimuli were actually presented behind the mask. During the test phase, 90 words appeared one at a time in a 3.0 X 0.8-cm rectangular frame in the center of the screen. When a word was first presented, it was masked by 323 black blobs (1 blob = 2 X 2 pixels) that covered 70% of the rectangle. These blobs were gradually and randomly removed at a rate of 3 blobs (0.6%) per 100 ms, until the word could be identified. The first 10 words served as practice trials. Procedure. During the study phase, participants viewed a mask on each of 40 trials. The mask was exposed for 83 ms, with a 1-s intertrial interval. Participants were told that single words were being presented at a speed too quick to allow perception but that, nonetheless, might allow them to pick up some information so that they could later judge these words as having been presented. During the test phase, participants were presented with words that were unmasked gradually and continuously. They were asked to press a response key as soon as they could identify each word. As soon as they responded, the unmasking was stopped, and if the word had been identified correctly, the remainder of the blobs were

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removed to display the word clearly. If the word was not correctly identified, gradual unmasking resumed until the word was identified. At that point, participants were asked to indicate verbally whether or not they felt the word had been presented briefly during the study phase. The experimenter recorded the participant's response and initiated the next trial. Participants were told that half of the words had been displayed briefly during the study phase and that half were new words. Guessing was encouraged.

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Results The percentage of words judged as old averaged 18% for the amnesic group and 40% for the control group. This difference was significant, f(26) = 2.05, p = .05, and was largely due to the extremely conservative response bias exhibited by some amnesic participants. Some control participants also showed a conservative response bias, but this was offset by a single participant with an extremely liberal response bias (all old responses). To allow an evaluation of perceptual fluency associated with old and new responses, we eliminated participants who provided fewer than 5% responses in either category from subsequent analyses. This restricted group of participants consisted of 8 amnesic patients and 10 control participants. The control participants were still more likely to judge words as old (M = 46%) than were amnesic patients (M = 31%), but this difference was no longer significant, f(16) = 1.33. Table 1 presents the mean density of the mask (i.e., the percentage of remaining blobs) at which amnesic and control participants could identify critical words. Both groups identified words judged to be old at a higher density of masking than words judged to be new. This effect was numerically more pronounced for the amnesic patients than it was for the control participants, but results of the analysis of variance (ANOVA) indicated that only the effect of judged status was significant, F(\, 16) = 5.3, MSB = 12.1, p < .05. Neither the effect of group nor Group X Judged Status were significant. Thus, items judged to be old were associated with greater fluency than items judged to be new for both groups. To further test the hypothesis that participants used variations in fluency as a cue for recognition judgments, we divided the test words into quartiles based on the density of masking at which each individual participant could identify the words. Thus, for each participant, all 80 words were ranked according to density of masking. The first quartile consisted of the 20 words identified with the lowest density of masking (i.e., least fluent), and the fourth quartile consisted of the 20 words identified with the highest density of masking (i.e., most fluent). Following Johnston et al. (1991), we refer to these quartiles as fluency quartiles because they reflect the natural fluency with which each participant could identify words.1 Table 2 summarizes the percentage of old judgments as a function of fluency quartile for each group. An ANOVA revealed that only the effect of quartile was significant, F(3, 48) = 3.7, MSB = 1.8, p < .05, indicating that for both groups, the percentage of old responses increased from the least fluent to the most fluent quartile.

Table 1 Mean Mask Density (Percentage of Remaining Black Blobs) and Standard Deviation for Words Judged to Be Old or New in Experiment 1 Judged new

Judged old Group

M

SD

M

SD

Amnesic Control

25 24

9 1

21 23

9 5

Discussion Both amnesic and control participants identified test words judged to be old at a higher masking level than test words judged to be new. Furthermore, the difference in perceptual fluency associated with items judged as old versus items judged as new was of approximately the same magnitude in the two groups. Thus, it can be concluded that amnesic patients were as sensitive as control participants to variations in the ease of perceptual identification. Does the relationship between perceptual fluency and recognition judgments necessarily indicate that perceptual fluency was used as a basis for recognition? On the basis of their studies in normal individuals, Watkins and Gibson (1988) argued that the observed relationship was due to item-selection effects—items that are perceived more fluently also happen to be more likely to be endorsed on a recognition test. However, item-selection effects have been ruled out as a basis of the observed relationship in subsequent normative studies (Johnston et al., 1991). They also seem an unlikely explanation for the present findings because there are large variations between participants in which items were perceived more fluently. It was for this reason that fluency quartiles were defined on an individual basis, so that they could directly mirror the fluency with which each participant identified specific items. Nevertheless, the proportion of old judgments systematically increased across quartiles. Thus, as items were perceived more fluently, they were more likely to be judged as old. Because no items were presented during the study phase of this experiment, the observed effects were obviously independent of actual memory for the test items. Therefore, we agree with the notion that the feeling of familiarity created by perceptual fluency can best be thought of as an illusion of memory (Luo, 1993; Whittlesea, 1993). Fluently perceived items are felt to be familiar because their fluency is attributed to the past. This familiarity, in turn, serves as a basis for recognition. Studies in normal individuals have demonstrated that depending on the task demands, fluency of processing can give rise to a variety of feelings about the past, including the familiarity, duration, and recency of past 1

Johnston et al. (1991) created fluency quartiles based on the average performance of a group of participants. We did not follow this approach, however, because pilot studies indicated considerable variability in the relative ease with which certain words could be identified, both between subjects and across different observations within subjects. Instead, fluency quartiles were defined on an individual basis within the context of the experiment.

FLUENCY AS A CUE FOR RECOGNITION IN AMNESIA

Table 2 Mean Percentage and Standard Deviation of Old Responses to Critical Test Words in Experiment 1 as a Function of Fluency Quartile

Q2

Ql

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Method

Q3

Q4

Group

M

SD

M

SD

M

SD

M

SD

Amnesic Control

21 40

22 23

33 44

20 28

32 48

25 29

40 50

25 28

Note.

201

Q = fluency quartile.

events (Whittlesea, 1993). Likewise, fluency resulting from prior experience can be attributed to causes in the present and can affect judgments of pleasantness (Zajonc, 1980), duration (Witherspoon & Allen, 1985), or clarity (Jacoby, Allen, Collins, & Larwill, 1988) of currently experienced events. It has already been demonstrated that amnesic patients can make normal attributions of fluency to present characteristics of stimuli, including pleasantness (Johnson, Kim, & Risse, 1985), duration (Paller, Mayes, McDermott, Pickering, & Meudell, 1991), and fame (Cermak, Verfaellie, Butler, & Jacoby, 1993). The present findings suggest that amnesic patients are also able to make normal attributions of fluency to the past. Experiment 2 Because Experiment 1 established that amnesic patients use natural variations in perceptual fluency as a cue for recognition judgments when no other information is available, Experiment 2 assessed whether fluency is also used as a cue for recognition when other (veridical) information is potentially available to support recognition. To accomplish this, we introduced a study phase with clearly visible items. We felt that under these conditions, nonamnesic individuals might rely less on fluency because they could use actual recollection of studied items as a basis for recognition. Because amnesic individuals are impaired in recollection, we reasoned that they would continue to rely on perceptual fluency and would do so to a greater extent than normal individuals. With the introduction of study items, perceptual fluency could potentially arise from two different sources. Studied and unstudied items both vary in their natural ease of identification, but, in addition, previously studied items are easier to identify than new items—the well-known effect of perceptual implicit memory (e.g., Jacoby & Dallas, 1981). Thus, both natural variations in fluency and study-induced fluency could potentially affect performance. If natural variations in fluency and study-induced fluency have additive effects on recognition, the effects of natural variations in fluency should be parallel for studied and unstudied items. Alternatively, if perceptual fluency that arises from previous study interacts with the natural ease of identification, then the effect of natural variations in fluency should be different for studied and for unstudied items.

Participants. Twelve amnesic patients (2 women, 10 men) participated in this experiment. These patients were the same as those who participated in Experiment 1, with the exception that 1 Korsakoff patient and 1 encephalitic patient were no longer available for testing. The mean age of this patient group was 55 years, and they had a mean of 13.5 years of education. The control group consisted of 6 individuals with a history of chronic alcohol abuse and 6 individuals with no history of alcohol abuse. Two of the alcoholic controls had participated in Experiment 1; the others were newly recruited. As a group, the controls were matched with the amnesic patients in terms of age (M = 50.8 years) and education (M = 1 2 years). On the WAIS-R, the amnesic group obtained a mean verbal IQ of 101.2, a score that did not differ from that of the controls (M = 110.8), t(22) = 1.72. On the WMS-R, the amnesic group obtained a general memory index of 76 and a delayed recall index of 58, both indicative of their severe memory problems. Their attentional capabilities were in the average range, as indicated by a mean attention-concentration index of 102. Materials, design, and procedure. One hundred eighty words with a frequency range of 8-21 per million (Francis & Kucera, 1982) and four or five letters in length served as stimuli. These words were subdivided into two lists of 90. For each set of 90 stimuli, 10 served as practice trials at the beginning of the recognition test. The remaining 80 words were critical items, and half of these were also presented during the study phase. The assignment of items as targets or distractors was counterbalanced across participants. The procedure was identical to that in Experiment 1, except for the fact that actual items were shown in the study phase and no masking procedure was used. Participants were asked to read each word aloud. Forty words were presented for 2 s each, with an interstimulus interval of 500 ms. During the test phase, participants again identified masked words and judged whether these words had been previously presented. We administered two sessions, each using a different set of 90 words, at least 1 week apart.

Results Averaged across the two sessions, the amnesic patients judged 36% of studied words and 24% of unstudied words to be old. The corresponding percentages were 70% and 13%, respectively, for the controls. An ANOVA performed on these data revealed a significant Group X Actual Status interaction, F(\, 22) = 83.3, MSE = 12.0, p < .001. Follow-up analyses revealed that amnesic patients endorsed significantly fewer studied items, r(22) = 4.1, p < .001, and marginally more unstudied items, f(22) = 2.05, p < .06, than did controls. Because 2 amnesic patients responded old to fewer than 5% of all items, their data were eliminated from subsequent analyses. To examine the relationship between perceptual fluency and recognition performance, we computed the weighted mean mask density across sessions as a function of an item's actual status as well as its judged status for each participant (see Table 3). For both groups, the mean mask density was higher for studied items (amnesic group = 22%, control group = 27%) than for unstudied items (amnesic group = 21%, control group = 24%). However, this effect was more pronounced for the control participants, primarily

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Table 4 Mean Percentage and Standard Deviation of Old Responses to Unstudied and Studied Items in Experiment 2

Table 3 Mean Mask Density (Percentage of Remaining Black Blobs) and Standard Deviation as a Function of Actual Status and Judged Status in Experiment 2

Item and group

Actual status

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Group and judged status Amnesic Old New Control Old New

M

SD

M

SD

22 21

10 8

21 20

9 8

29 26

5 6

24 25

4 4

because of the fact that this pattern was accentuated for items judged as old. Both groups also identified words judged to be old at a higher density of masking (amnesic group = 22%, control group = 26%) than words judged to be new (amnesic group = 20%, control group = 25%). However, whereas judged status affected the masking density of both studied and unstudied items in the amnesic patients, it affected the masking density of studied items only in the control participants. These observations were confirmed in an ANOVA, which revealed an effect of actual status, F(l, 20) = 18.2, MSB = 4.38, p < .001, judged status, F(l, 20) = 12.53, MSE = 2.22, p < .01, and an interaction between group, actual status, and judged status, F(l, 20) = 29.4, MSE = 2.88, p < .01. Follow-up analyses for the amnesic patients indicated that there was a significant effect of judged status, F(l, 9) = 10.9, MSE = 2.24, p < .01, and a trend toward an effect of actual status, F(l, 9) = 3.17, MSE = 3.38, p = .10. The interaction between actual and judged status was nonsignificant. For controls, the effect of actual status was significant, F(l, 9) = 17.7, MSE = 5.21, p < .01, as was the Actual Status X Judged Status interaction, F(l, 11) = 66.2, MSE = 2.6, p < .001. Simple effects revealed that items judged as old were identified faster than items judged as new only when they were actually studied, F(l, 11) = 21.4, MSE = 2.6, p < .001. Consistent with these different patterns of performance across the two groups, Table 3 shows that amnesic patients identified unstudied words judged as old more easily than studied words judged as new, whereas the opposite was true for control participants. We again divided words into fluency quartiles to examine whether the likelihood of judging an item to be old was affected by variations in perceptual fluency. Fluency quartiles were defined separately for studied and unstudied items in each session, and a weighted mean percentage of old responses across the two sessions was then computed. The mean percentage of old responses to items that were not previously studied (see Table 4) was first analyzed to allow a direct comparison with the results of Experiment 1. As in that experiment, old judgments for these items could not reflect actual memory, and differences in the percentage of old judgments as a function of fluency quartile therefore reflected sensitivity to natural fluency variations. For amnesic patients, the percentage of old responses increased from

Q4

Q3

Q2

Ql M

SD

M

SD

M

SD

M

SD

22 15

15 8

28 12

17 6

32 11

16 10

33 12

20 12

37 63

19 17

41 67

23 19

42 73

22 17

50 79

27 16

Unstudied Amnesic Control Studied Amnesic Control

Note.

Overall false alarm rate = 29% for the amnesic group and

13% for the control group. Q = fluency quartile.

the least to the most fluent quartile, but this did not occur for the control participants. An ANOVA on this data revealed a significant effect of group, F(l, 20) = 10.91, MSE = 50.7, p < .01, as well as a significant Group X Quartile interaction, F(l, 20) = 3.96, MSE = 6.3, p < .01. Thus, amnesic patients, but not control participants, used variations in perceptual fluency as a cue for their recognition judgments. Table 4 also presents the mean percentage of old responses to previously studied items. Here, old responses for both groups were affected by the fluency with which items could be identified. Results of the ANOVA revealed a significant effect of group, F(l, 20) = 12.7, MSE = 132.8, p < .01, as well as quartile, F(l, 20) = 9.17, MSE = 8.9, p < .001. The Group X Quartile interaction was not significant. Finally, a combined analysis of the percentage of old responses to studied and unstudied items was performed. A significant Group X Status X Quartile interaction was obtained, F(3,60) = 2.97, MSE = 7.18, p < .05, confirming that fluency quartile affected the performance of old and new items differently for the two groups. Follow-up analyses were then performed for each group separately to examine whether the effects of perceptual fluency were similar for studied and unstudied items. The ANOVA of the amnesic patients' data revealed significant effects of actual status, F(l, 9) = 29.3, MSE = 13.2, p < .001, and quartile, F(3, 27) = 5.37, MSE = 10.1, p < .01, but the Status X Quartile interaction was nonsignificant (F < 1). Thus, amnesic patients used fluency similarly in making recognition judgments for studied and unstudied words. The ANOVA of the control group's performance revealed main effects of status, F(l, 11) = 177.1, MSE = 44.9, p < .001, and quartile, F(3, 33) = 3.4, MSE = 6.3, p < .05, as well as a significant interaction, F(3,33) = 6.22, MSE = 6.3,p < .01, indicating that old responses to studied items but not unstudied items varied as a function of perceptual fluency.

Discussion The present experiment yielded three main findings. First, consistent with our hypothesis, amnesic patients' recognition judgments were more affected by fluency of perception than were those of nonamnesic controls. For the amnesic

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FLUENCY AS A CUE FOR RECOGNITION IN AMNESIA

patients, masking density depended more on the judged status of a test word than on its actual status, and regardless of actual status, words judged as old were identified more fluently than words judged as new. In the nonamnesic group, masking density depended more on the actual status of a test word than on its judged status, and only studied words judged as old were identified more fluently than studied words judged as new. Moreover, when we examined the proportion of old responses across fluency quartiles, a different pattern was obtained for the amnesic and nonamnesic participants. Amnesic patients became increasingly more likely to endorse unstudied items as old as the fluency of these items increased. We take this pattern, which also occurred in Experiment 1, as a signature of fluency effects on recognition because no veridical information could have contributed to judging these items to be old. For normal controls, in contrast, the likelihood of judging unstudied items as old did not change across fluency quartiles, suggesting that nonamnesic individuals did not rely on fluency as a cue for recognition. These findings are consistent with the results of Johnston et al. (1991), who found across several studies in normal individuals that the contribution of perceptual fluency to recognition judgments decreased as recognition performance increased. A second major finding of this experiment is that amnesic patients' fluency of identification was less affected by an item's actual status than was the case for nonamnesic controls. This impairment in perceptual implicit memory was unexpected because several laboratories (Haist, Musen, & Squire, 1991; Hamann, Squire, & Schacter, 1995; Hamann & Squire, 1997), including our own (Cermak, Talbot, Chandler, & Wolbarst, 1985; Keane, Gabrieli, Noland, & Ingemanson McNealy, 1995), have demonstrated intact perceptual priming in amnesic patients using both words and nonwords as stimuli. The failure of amnesic patients to show normal priming in the present task, therefore, is more likely due to the control participants' ability to use explicit memory strategies than to amnesic patients' impaired implicit memory. Our use of a gradual identification procedure may have elicited the use of explicit retrieval strategies (see Haist et al., 1991), such that nonamnesic individuals could use their memory for the words in the study phase to test hypotheses about the nature of the fragmented cues presented during the test phase. The use of explicit memory as an aid to identification of test items also explains the relationship that existed between perceptual fluency and recognition judgments for old words for the normal participants. Old words that were recognized were perceived more fluently than old words that were not recognized, and the percentage of old responses increased across fluency quartiles. These findings are unlikely to reflect the use of fluency as a basis for recognition in nonamnesic controls, as the same pattern was not obtained in their judgments of new words; instead, they are consistent with the notion that explicit memory for studied items served as a cue for their identification, artificially inflating their perceptual fluency. A third result of this study is that natural variations in fluency affected amnesic patients' recognition judgments in

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a similar way for studied and unstudied items. This finding suggests that fluency attributions occur in the same manner, regardless of whether fluent perceptions arise from natural ease of identification or from previous exposure. Johnston et al. (1991) also reported that whenever variations in fluency affected performance, these effects were parallel for studied and unstudied words. Taken together then, these findings suggest that ease of perceptual fluency, regardless of its source, gives rise to an undifferentiated sense of familiarity and an increased likelihood of making old judgments. The implications of this finding for the functional utility of perceptual fluency as a basis for recognition are discussed in the General Discussion.

General Discussion This investigation found that both amnesic patients and nonamnesic individuals can use variations in perceptual fluency as a cue for recognition. However, differences between the two groups were also evident. Amnesic patients used natural variations in fluency as a basis for recognition, regardless of whether or not items had been presented during the study phase, but nonamnesic individuals did so only when no study items had been presented. This finding extends the observation of Johnston et al. (1991) that recognition judgments are more likely to be supported by perceptual fluency when explicit memory is low. For normal individuals, recollection typically provides a reliable basis for recognition and perceptual fluency is only used in the absence of recollection. For amnesic patients, in contrast, the use of perceptual fluency becomes the default strategy because of their severe impairments in recollection. The notion that normal individuals but not amnesic patients used a different basis for recognition depending on the availability of information that can support recollection receives further support from a direct comparison between the two experiments. In Experiment 1, the only basis for recognition judgments was item fluency, whereas in Experiment 2, both recollection and perceptual fluency could potentially be used as bases for recognition. Normal participants endorsed a much greater percentage of unstudied words in Experiment 1 (M = 40%) than in Experiment 2 (M= 13%), t(24) = 2.8, p < .01. The availability of veridical information that can support recollection (i.e., the presentation of actually studied items) led normal individuals to rely less on fluency: Even if unstudied items were fluent, these items were less likely to be endorsed because they could not be recollected. Amnesic patients, in contrast, did not show a similar change in the basis of their recognition judgments. They endorsed slightly, but nonsignificantly, more unstudied items in Experiment 2 (M = 24%) than in Experiment 1 (M = 18%), t(26) < 1, suggesting that fluency remained the principal mechanism underlying their recognition. In light of amnesic patients' reliance on attributions of fluency, it is important to consider the functional utility of perceptual fluency for their recognition memory. As discussed earlier, attributions of fluency are not a direct product

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of memory. Therefore, the question remains as to whether these attributions can provide amnesic patients with a valid basis for making recognition judgments. In Experiment 2, natural variations in fluency had a similar effect on amnesic patients' recognition of studied and unstudied items. This suggests that natural variations in fluency and study-induced fluency are functionally equivalent. If this is the case, then the discriminatory power of perceptual fluency depends directly on the magnitude of study-induced fluency relative to natural variations in fluency. In Experiment 2, studyinduced changes in fluency were quite small: Differences in mask density averaged 1% for amnesic patients and 3% for nonamnesic individuals. Natural variations in fluency, on the other hand, were much larger, with differences in masking level between items in the first and fourth fluency quartile on the order of 20%. Therefore, the influence of natural variations in fluency far overpowered the effects of studyinduced fluency, resulting in very low discriminatory power (see Johnston et al., 1991, for similar findings). Under such conditions, perceptual fluency does not provide a valid basis for recognition. Whether laboratory situations can be created in which the magnitude of study-induced perceptual fluency exceeds natural variations in fluency remains to be determined. It is possible that the poor discrimination afforded by perceptual cues in the present study is due to the fact that the gradual clarification procedure makes natural differences in fluency very salient. In standard recognition tasks, items are presented in clear view. Under these conditions, natural differences in perceptual fluency may be less obvious and may not overshadow study-induced changes in perceptual processing. Furthermore, in traditional recognition tasks, conceptual fluency—the ease with which the meaning of an item is processed (Blaxton, 1989)—may also serve as a salient cue for recognition (Whittlesea, 1993). It remains to be determined whether conceptual fluency alone or conceptual and perceptual fluency in combination provide a more valid cue for amnesic patients' recognition. The potential use of a fluency heuristic outside the laboratory also remains unknown. Johnston et al. (1991) suggested that perceptual fluency may provide a mechanism for novelty detection in more naturalistic environments. Because the perceptual environment is usually processed quite fluently, the presence of an object associated with low fluency might signal the occurrence of a novel or unfamiliar item. However, uncovering the role of fluency in everyday situations will require a better understanding of the range of fluency cues that can be used in recognition (Poldrack & Logan, 1997). In conclusion, our findings suggest that at least one fluency cue, ease of identification of degraded stimuli, can be used successfully by amnesic patients. However, reliance on this cue does not in itself elevate recognition accuracy. Perceptual fluency becomes a valid basis for recognition only to the extent that fluent perceptions are study-induced and reflect perceptual memory rather than inherent stimulus properties.

References Aggleton, J. P., & Shaw, C. (1996). Amnesia and recognition memory: A re-analysis of psychometric data. Neuropsychologia, 34, 51-62. Bernstein, I. H., & Welch, K. R. (1991). Awareness, false recognition, and the Jacoby-Whitehouse effect. Journal of Experimental Psychology: General, 120, 324-328. Blaxton, T. A. (1989). Investigating dissociations among memory measures: Support for a transfer-appropriate processing framework. Journal of Experimental Psychology: Learning, Memory, and Cognition, 15, 657-668. Bowers, D., Verfaellie, M., Valenstein, E., & Heilman, K. M. (1988). Impaired acquisition of temporal information in retrosplenial amnesia. Brain and Cognition, 8, 47-66. Cermak, L., Verfaellie, M., Butler, T., & Jacoby, L. L. (1993). Attributions of familiarity in amnesia: Evidence from a fame judgment task. Neuropsychology, 7, 510-518. Cermak, L. S., Talbot, N., Chandler, K., & Wolbarst, L. R. (1985). The perceptual priming phenomenon in amnesia. Neuropsychologia, 23, 615-622. Francis, W. N., & Kucera, H. (1982). Frequency analysis of English usage: Lexicon and grammar. Boston: Houghton Mifflin. Gardiner, J. M. (1988). Functional aspects of recollective experience. Memory and Cognition, 16, 309-313. Haist, F., Musen, G., & Squire, L. (1991). Intact priming of words and nonwords in amnesia. Psychobiology, 19, 273-285. Haist, P., Shimamura, A. P., & Squire, L. R. (1992). On the relationship between recall and recognition memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 18, 691-702. Hamann, S., Squire, L., & Schacter, D. (1995). Perceptual thresholds and priming in amnesia. Neuropsychology, 9, 3-15. Hamann, S. B., & Squire, L. R. (1997). Intact priming for novel perceptual representations in amnesia. Cognitive Neuropsychology, 9, 699-713. Hirst, W., Johnson, M. K., Kim, J. K., Phelps, E. A., Risse, G., & Volpe, B. T. (1986). Recognition and recall in amnesics. Journal of Experimental Psychology: Learning, Memory, and Cognition, 72,445^51. Hirst, W., Johnson, M. K., Phelps, E. A., & Volpe, B. T. (1988). More on recognition and recall in amnesics. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 758-762. Huppert, R, & Piercy, M. (1976). Recognition memory in amnesic patients: Effect of temporal context and familiarity of material. Cortex, 12, 3-20. Jacoby, L. L. (1983). Perceptual enhancement: Persistent effects of an experience. Journal of Experimental Psychology: Learning, Memory, and Cognition, 9, 21-38. Jacoby, L. L. (1991). A process dissociation framework: Separating automatic from intentional uses of memory. Journal of Memory and Language, 30, 513-541. Jacoby, L. L., Allen, L. G., Collins, J. C., & Larwill, L. K. (1988). Memory influences subjective experience: Noise judgments. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 240-247. Jacoby, L. L., & Dallas, M. (1981). On the relationship between autobiographical memory and perceptual learning. Journal of Experimental Psychology: General, 110, 306-340. Jacoby, L. L., & Whitehouse, K. (1989). An illusion of memory: False recognition influenced by unconscious perception. Journal of Experimental Psychology: General, 118, 126-135.

This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

FLUENCY AS A CUE FOR RECOGNITION IN AMNESIA Johnson, M. K., & Kim, J. K. (1985). Recognition of pictures by alcoholic Korsakoff patients. Bulletin of the Psychonomic Society, 23, 456-458. Johnson, M. K., Kim, J. K., & Risse, G. (1985). Do alcoholic Korsakoffs syndrome patients acquire affective reactions? Journal of Experimental Psychology: Learning, Memory, and Cognition, 11, 22-36. Johnston, W. A., Hawley, K. J., & Elliot, J. M. (1991). Contribution of perceptual fluency to recognition judgments. Journal of Experimental Psychology: Learning, Memory, and Cognition, 17, 210-223. Johnston, W. A., Dark, V. J., & Jacoby, L. L. (1985). Perceptual fluency and recognition judgments. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11, 3-11. Keane, M. M., Gabrieli, J. D. E., Noland, J. S., & Ingemanson McNealy, S. (1995). Normal perceptual priming of orthographically illegal nonwords in amnesia. Journal of the International Neuropsychological Society, 1, 424-433. Luo, C. R. (1993). Enhanced feeling of recognition: Effects of identifying and manipulating test items on recognition memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 19, 405^13. Mandler, G. (1980). Recognizing: The judgment of previous occurrence. Psychological Review, 87, 252-271. Paller, K. A., Mayes, A. R., McDermott, M., Pickering, A., & Meudell, P. R. (1991). Indirect measures of memory in a duration-judgement task are normal in amnesic patients. Neuropsychologia, 29, 1007-1018. Poldrack, R. A., & Logan, G. D. (1997). Fluency and response speed in recognition judgments. Memory and Cognition, 25, 1-10. Rajaram, S. (1993). Remembering and knowing: Two means of access to the personal past. Memory and Cognition, 31, 89-102. Shimamura, A. P., & Squire, L. R. (1988). Long-term memory in amnesia: Cued recall, recognition memory, and confidence ratings. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 763-770.

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Verfaellie, M., & Treadwell, J. (1993). Status of recognition memory in amnesia. Neuropsychology, 7, 5-13. Wagner, A. D., Gabrieli, J. D. E., & Verfaellie, M. (1997). Dissociations between familiarity processes in explicit recognition and implicit perceptual memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 23, 305-323. Watkins, M. J., & Gibson, J. M. (1988). On the relation between perceptual priming and recognition memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 477-483. Wechsler, D. (1981). Wechsler Adult Intelligence Scale—Revised (Manual). San Antonio, TX: Psychological Corporation. Wechsler, D. (1987). Wechsler Memory Scale—Revised (Manual). San Antonio, TX: Psychological Corporation. Whittlesea, B. W. A. (1993). Illusions of familiarity. Journal of Experimental Psychology: Learning, Memory, and Cognition, 19, 1235-1253. Whittlesea, B. W. A., Jacoby, L. L., & Girard, K. (1990). Illusions of immediate memory: Evidence of an attributional basis for feelings of familiarity and perceptual quality. Journal of Memory and Language, 29, 716-732. Witherspoon, D., & Allen, L. G. (1985). The effects of prior presentation on temporal judgments in a perceptual identification task. Memory and Cognition, 13, 101-111. Yonelinas, A. P., Kroll, N. E. A., Dobbins, L, Lazzara, M., & Knight, R. T. (1998). Recollection and familiarity deficits in amnesia: Convergence of remember-know, process dissociation, and receiver operating characteristic data. Neuropsychology, 12, 323-339. Zajonc, R. B. (1980). Feeling and thinking: Preferences need no inferences. American Psychologist, 35, 151-175.

Received May 1, 1998 Revision received August 10, 1998 Accepted August 11, 1998

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