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Neuropsychology 1993, Vol. 7, No. 1, 5-13

Status of Recognition Memory in Amnesia

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Mieke Verfaellie and Jonathan R. Treadwell The contribution of fluency and recollection to amnesics' recognition memory was examined by comparing performance in a condition in which patients were asked to include items presented in the first phase of the experiment with performance in a condition in which they were asked to exclude those same items. The performance of amnesics, unlike that of controls, did not significantly differ as a function of task instruction. Use of Jacoby's (1991) subtraction procedure indicated that amnesics were much less likely to use conscious recollection as a basis for recognition judgments. However, amnesics were as likely as controls to base their recognition judgment on the fluency with which an item came to mind. Discrepancies in previously reported recognition results with amnesics may reflect the variable contribution of fluency and recollection to recognition memory.

During the past decade, the study of amnesics' implicit memory performance has been extremely extensive and productive (for a review, see RichardsonKlavehn & Bjork, 1988). In contrast, during this same period relatively little effort has been directed toward elucidating the nature of amnesics' impaired performance on explicit memory tasks. This has undoubtedly been influenced by the widely held view that explicit memory is mediated by a separate memory system, which is thought to be uniformly disrupted in amnesia (Shimamura & Squire, 1988). Recently, however, a growing emphasis has been placed on delineating distinct cognitive processes that may operate within a unitary system (Jacoby, 1983; Roediger, Weldon, & Challis, 1989). In the present study, we

Mieke Verfaellie and Jonathan R. Treadwell, Memory Disorders Research Center, Boston University School of Medicine and Psychology Service, Boston Department of Veterans Affairs Medical Center. This research was supported by Grant NS26985 from the National Institute of Neurological and Communicative Disorders and Stroke to Boston University School of Medicine and by the Medical Research Service of the Department of Veterans Affairs. We thank Larry Jacoby and Maggie Keane for helpful discussions and suggestions. John T. Rosen provided statistical advice. Correspondence concerning this article should be addressed to Mieke Verfaellie, Memory Disorders Research Center (116B), Department of Veterans Affairs Medical Center, 150 South Huntington Avenue, Boston, Massachusetts 02130.

applied this processing approach to the study of recognition memory in amnesia on the assumption that an analysis of amnesics' recognition memory in terms of underlying cognitive processes could advance understanding of amnesics' recognition impairments and might help resolve some of the current controversies regarding the status of recognition memory in amnesia. On the basis of occasional reports indicating that amnesics' recognition memory can be quite good (Huppert & Piercy, 1976; Jacoby & Witherspoon, 1982; Johnson & Kim, 1985) and sometimes even comparable to that of control subjects (Bowers, Verfaellie, Valenstein, & Heilman, 1988; Hirst & Volpe, 1982), Hirst and his colleagues (Hirst et al., 1986; Hirst, Johnson, Phelps, & Volpe, 1988) suggested that amnesia may disrupt recall disproportionately compared with recognition. To examine this claim directly, they equated the recognition performance of amnesic patients and controls by extending the study time for amnesics (Hirst et al., 1986) or by testing control subjects after a longer delay (Hirst et al., 1988). They found that amnesics' free recall was still significantly below that of the control subjects, even though their recognition memory was equivalent. In direct contrast to these findings, Shimamura and Squire (1988) found that, when recognition memory for the last words of sentences was equated by testing control subjects after a delay, the performance of their amnesic subjects on a test of cued recall did not differ from that of control subjects. Likewise, in a study examining the relationship between free recall and recognition, equating performance on a recognition


MIEKE VERFAELLIE AND JONATHAN R. TREADWELL

test resulted in equivalent performance on a free recall test (Haist, Shimamura, & Squire, 1992). We suggest that the variable relationship between recognition and recall may reflect the fact that there are multiple bases for responding on recognition tasks. Several investigators have shown that recognition memory can be mediated by two qualitatively different processes (Jacoby, 1983; Mandler, 1980, 1991). Jacoby proposed that memory can reflect the automatic effect of the fluency of processing, or the intentional effect of reconstructing the context in which information was presented, or some combination. Because recognition memory tasks vary in their encoding and retrieval demands, it is likely that they also differ in their reliance on automatic versus controlled processes. On the basis of the hypothesis that amnesics may be impaired in their use of controlled processes as a basis for memory judgments (Cermak & Verfaellie, 1992), we predicted that amnesics' recognition memory would be relatively preserved in a task that promoted the use of fluency (an automatic process) but would be impaired, possibly to the same degree as their performance on recall tasks, in a recognition task that required the use of conscious recollection (a controlled process). One problem with this analysis is that it is difficult, if not impossible, to design recognition tasks that, a priori, can be said to rely only on automatic fluency or conscious recollection. Most recognition tasks probably require a combination of fluency and recollection, with the precise contribution of these two factors depending on specific subject and task parameters. Consequently, even if the overall performance of amnesic and control subjects could be matched, there would be no guarantee that the underlying bases for recognition memory would be matched. What is needed is a means for separately estimating the contribution of fluency and conscious recollection to recognition performance. A procedure that provides a way to do so has recently been developed by Jacoby and his colleagues (Jacoby, 1991; Jacoby & Kelley, 1992). They have shown that the effects of fluency and conscious recollection can be separated by comparing performance on a traditional memory task (in which fluency and recollection affect performance in the same direction) with performance on a task in which the effects of conscious recollection are placed in opposition to the effects of fluency. Both conditions are designed so that fluency remains constant but conscious recollection has the opposite effect. Because of this property, the difference between the two conditions can be used

as an estimate of conscious recollection. This estimate, in turn, can then be used to estimate the contribution of fluency to task performance. In the present study, this approach was implemented in a recognition memory task similar to that used by Jacoby (1991). In the first phase of the experiment, patients were asked to read words or solve anagrams presented on a computer screen. In the second phase, they were asked to remember a list of words presented auditorily. This was followed by a recognition test that included items from Phase 1 (solved or read) and Phase 2 (heard), as well as new words. In an inclusion condition, patients were told to respond with the word old to all stimuli that were previously presented, including items from Phase 1 as well as from Phase 2. In the exclusion condition, they were told to respond with the word old only to the words that they had just heard and had been told to remember. Stimuli that had been presented during Phase 1, either as words read or as solutions to anagrams, were to be considered new. Given these instructions, the probability of calling an item presented in Phase 1 old in the inclusion task (O]) reflected the combined effects of fluency (F) and conscious recollection (R). That is, an item could be endorsed either because it was recollected as having been presented earlier (R) or because, if recollection failed, its fluency was sufficient for endorsement on a recognition test [F(l - R)]. Stated formally, O, = R + F(l - R).

(1)

In contrast, in the exclusion condition, an item presented in Phase 1 would be called old (OE) only if it was fluent but not recollected. Thus,

-R).

(2)

The probability of calling an item old on the basis of recollection can be estimated by subtracting Equation 2 from Equation 1: R = O, - OE.

(3)

Given an estimate of R, F can then be solved in Equation 2 by dividing OE by the estimated probability of a failure in recollection (1 - R). Using this subtraction procedure, we estimated the contribution of fluency and recollection to the recognition performance of amnesics and controls. This was done separately for anagrams and for words read during Phase 1. The advantage of memory for words solved compared with words read during the study phase, commonly referred to as the generation effect (Slamecka & Graf, 1978), is well documented in the literature. It has generally been ascribed to subjects'


RECOGNITION IN AMNESIA use of more distinctive encoding operations, which enhance the number of potential cues for retrieval. This, in turn, is thought to benefit conscious recollection (Gardiner, 1988; Graf, 1980; Jacoby, 1983). Consequently, the recollection scores of control subjects were expected to be higher for anagrams than for words that were read. With respect to the performance of amnesics, we hypothesized that amnesics would be impaired in their use of controlled processes as a basis for recognition. This hypothesis was based on the results of recent implicit memory studies in which an oppositional approach was used. In these studies, we found that amnesics, like controls, showed consistent automatic effects of memory; however, unlike controls, they had very little control over their performance (Cermak, Verfaellie, Butler, & Jacoby, 1992; Cermak, Verfaellie, Sweeney, & Jacoby, in press). Consequently, we predicted that in recognition memory as well, amnesics' estimates of fluency would be equivalent to those obtained for the control subjects, whereas their estimates of recollection would be significantly below normal. In addition, the difference in recollection between solving anagrams and reading words was predicted to be smaller for amnesics than for control subjects. Method Subjects Two groups of adult subjects participated in this experiment. The first group consisted of 12 amnesic patients, 11 men and 1 woman. Seven of these patients had a diagnosis of Korsakoff s syndrome and were residing in various chronic care facilities in the Boston metropolitan area. All had histories of chronic alcoholism, were unable to recall day-to-day events, and had extensive retrograde amnesia. Of the other amnesics, 2 patients suffered from anoxia secondary to cardiac arrest. In one patient, neuroimaging studies revealed no observable structural changes, whereas in the other, enlarged ventricles and diffuse cortical atrophy were prominent. Another patient underwent removal of a left hematoma following a head injury and subsequently became amnesic after an episode of status epilepticus. MRI scans were interpreted as consistent with extensive loss of tissue in the left temporal lobe, including all of the anterior hippocampus, amygdala, and anterior efferent pathways. Another patient, who has been the subject of several single case studies (Cermak, 1976; Cermak & O'Connor, 1983), suffered from encephalitis in 1971 and has extensive bilateral damage to the medial and anterolateral temporal lobes. Finally, one patient became amnesic after a bilateral medial thalamic infarction that was confirmed by computed tomography imaging. These patients all lived at home and, like the

Korsakoff's patients, displayed a severe memory disorder. The mean age of the entire amnesic group was 57 years (SD = 15.3), with an average of 14 years of education (SD = 3.2). On the Wechsler Adult Intelligence Scale—Revised (WAIS-R; Wechsler, 1981) the average Verbal IQ score for this group was 101 (SD = 14.0), and on the Wechsler Memory Scale—Revised (WMS-R; Wechsler, 1987), the mean Attention/Concentration index was 105 (SD = 14.2), the General Memory index was 72 (SD = 12.4), and the Delayed Memory index was 57 (SD = 8). The control group consisted of 12 male chronic alcoholics living in private homes or local public halfway houses. None of these men evidenced any signs of neurological or psychiatric illness. All had abstained from alcohol for at least one month prior to participation in this experiment. Their average age was 58 years (SD = 5.5), with an average of 13 years of education (SD = 2.0). This group's mean WAIS-R Verbal IQ score was 108 (SD = 13.5), and the mean WMS-R Attention/Concentration index was 105 (SD = 12.6), the General Memory index was 110 (SD = 15.3), and the Delayed Memory index was 108 (SD = 12.8).

Materials and Design Stimuli for this experiment consisted of 140 five-letter nouns with frequencies ranging from 40 to 470 per million (Francis & Kucera, 1982). Half of these nouns were used to create the study and test lists for the inclusion condition, whereas the other half were used to create the study and test lists for the exclusion condition. The assignment of lists to conditions was counterbalanced across subjects. For each condition, 25 words were selected as stimuli for Phase 1. Thirteen of these were designated to be read aloud by the subject, and the remaining 12 were presented in anagram format. Anagrams were created by underlining the second and fourth letter of a word and maintaining them in their correct positions. Two of the remaining three letters were randomly reversed (e.g., c/ssa = class). With these criteria, the target word became the only possible solution for each anagram. Next, 30 stimuli were selected to be presented auditorily during Phase 2. Finally, the remaining 15 stimuli served as foils for the recognition test. All assignments of words to conditions were random. In addition to the 15 foils, the recognition test contained 15 stimuli from Phase 1 (8 words that were read and 7 anagrams) as well as the 30 stimuli from Phase 2. Thus, the total number of anagrams, read words, and new words equaled the number of words that were heard.

Procedure Using five practice anagrams, patients were first familiarized with the task of solving anagrams. They were told that the second and fourth letter of each anagram, which were underlined, were in their correct positions. It was emphasized that only the remaining letters should be trans-


MIEKE VERFAELLIE AND JONATHAN R. TREADWELL posed to form a word. Once patients had solved the practice items and fully understood this task, the experiment was initiated. In the first phase of the experiment, patients were asked to read words and solve anagrams presented on a computer monitor interfaced with a Macintosh Ilex computer. They were told that a series of stimuli would be presented, some of which would be anagrams that they should try and solve, and some of which would be words in normal form, which they should simply read aloud. Whenever a patient read a word or gave a correct solution to an anagram, the experimenter depressed a computer key to end the trial. Approximately 2 s later, the next trial was initiated. This procedure was repeated for a total of 25 trials. If a patient incorrectly solved an anagram, he or she was encouraged to continue trying to solve the anagram until a maximum of 1 min had elapsed. At this point, the experimenter provided the solution and allowed the patient to compare the solution with the anagram to ensure that the solution was correct. Also, throughout the study phase, amnesic patients were occasionally reminded that the second and fourth letters of each anagram need not be changed. Upon completion of Phase 1, the second phase of the experiment was immediately initiated. Words were auditorily presented at a rate of one every 3 s by means of a tape recorder. Patients were told that they should repeat each word and try and remember it for a future memory test. Finally, during the recognition test phase of the experiment, a series of words was presented on the monitor. Patients were asked to decide, for each word that appeared, whether it was old or new. In the inclusion condition, the patients were instructed to call an item old if it had been presented earlier as an anagram, if it had been read earlier, or if it had been heard earlier. In the exclusion condition, patients were instructed to call an item old only if it had just been heard through the tape recorder. They were warned that the test list would also include words that they had previously read or given as solutions to anagrams but that these words should be called new. The inclusion and exclusion conditions of the experiment were administered to each patient on the same day, with at least a 5-min break between conditions. Care was taken to emphasize that the instructions for the recognition test were different in the two conditions. During each condition, subjects were frequently reminded about the appropriate instructions.

For each patient, the probability of calling an item old in the recognition phase was computed as a function of the different experimental conditions. Anagrams presented in the recognition phase that were not solved during the allotted time in the study phase were excluded from the analysis. This resulted in exclusion of 7% of the anagram recognition trials. Because a preliminary analysis comparing the performance of the Korsakoff's patients and other amnesics revealed no significant group differences, data from these two groups were combined in subsequent analyses. Data for the amnesics and control subjects are summarized in Table 1. In the inclusion condition, the probability of calling an item old reflects hit rates for anagrams, read words, and heard words and false alarm rates for new words. In the exclusion condition, it reflects hit rates for heard words and false alarm rates for anagrams, read words, and new words. An analysis of variance (ANOVA) with group (amnesics, controls) as the between-subjects variable and test condition (inclusion, exclusion) and presentation (anagram, read, heard, new) as within-subjects variables revealed a significant effect of presentation, F(3, 63) = 25.9, p < .01, as well as significant interactions between group and presentation, F(3, 63) = 8.30, p < .01, and between group, test condition, and presentation, F(3, 63) = 4.28, p < .01. To examine these results in further detail, we analyzed the probabilities for read words and anagrams by means of a 2 (group) X 2 (test condition) X 2 (presentation: anagram vs. read) ANOVA. This analysis revealed a Group X Test Condition X Presentation interaction, F(l, 21) - 5.87, p < .05, indicating that the likelihood of calling anagrams and read words old as a function of test condition differed for the amnesics and alcoholic controls. To follow up on this result, we first analyzed the data of the amnesics and controls separately. In the analysis of the amnesic

Table 1 Proportion of Old Responses in the Inclusion and Exclusion Conditions Group and type of word

Results Data from one patient with KorsakofF s syndrome were eliminated because he correctly solved only 33% of the anagrams. The remaining amnesic patients solved an average of 90% (SD = 10.9%) of the anagrams, and the control subjects solved an average of 94% (SD = 7.6 %) of the anagrams, t(2l) = 1.08, ns.

Amnesics Anagram Read Heard

New Controls Anagram Read Heard

New

Inclusion

Exclusion

.45 .49

.44 .38

.40 .32

.41 .27

.67 .45

.34 .33

.64 .17

.56 .19


RECOGNITION IN AMNESIA

data, none of the effects were significant, suggesting that amnesics were equally likely to call anagrams and read words old and that these probabilities were no different in the exclusion and inclusion conditions. In contrast, for the alcoholic controls, a main effect of presentation revealed that they were more likely to call anagrams old than they were to call read words old, F(l, 11) = 7.24, p < .05. Also, a main effect of condition indicated that both types of words were more likely to be called old in the inclusion condition than in the exclusion condition, F(l, 11) = 14.2, p < .01. Most important, the Test Condition X Presentation interaction was marginally significant, F(l, 11) = 3.77, p < .08, indicating that, for the control subjects, differences in test condition had a larger effect on anagrams than on read words. Evaluation of underlying simple effects indicated that, in the inclusion condition, anagrams were more likely to be called old than were read words, F(l, 11) = 13.4, p < .01, but this was not the case in the exclusion condition, F(l, 11) = 0.01, ns. Second, we also analyzed the results from the inclusion and exclusion conditions separately. Analysis of the inclusion data revealed a significant Group X Presentation interaction, F(l, 21) = 6.14, p < .05. Evaluation of underlying simple effects indicated that amnesic patients recognized anagrams less well than did the controls, F(l, 33) = 4.13, p < .05, although this difference was not significant for read words, F(l, 33) = 0.14, ns. No effects were significant in the analysis of the exclusion data, indicating that amnesics' performance did not differ from that of controls. To evaluate patients' ability to discriminate between heard and new words as a function of test condition, we performed a 2 (group) X 2 (test condition) X 2 (presentation: heard vs. new) ANOVA. This analysis revealed a significant Group X Presentation interaction, F(l, 21) = 25.7, p < .01. Testing of simple effects indicated that the amnesic patients called heard words old less frequently than did the alcoholic controls, F(l, 32) = 9.52, p < .01, whereas they tended to call new words old more frequently than did the controls, F(l, 32) = 3.0, p < .10. The ability to discriminate between heard and new words did not differ as a function of test condition. Given the finding that the amnesics' performance overall was far inferior to that of the controls, we next examined whether the amnesics' performance did in fact exceed chance. For each patient, chance performance was defined separately for each condition as the likelihood of identifying a word as old, irrespective of its actual presentation status on the recognition

test. The likelihood of an amnesic's correctly calling an anagram, read, or heard word old in the inclusion condition was significantly higher than chance, r(10) = 2.56, p < .05. Likewise, the likelihood of an amnesic's correctly calling a heard word old in the exclusion condition was significantly above chance, f(10) = 1.94, p < .05. Also, in both the inclusion and exclusion conditions, the likelihood of an amnesic's incorrectly calling a new word old was significantly lower than chance: inclusion, f(10) = -2.53, p < .05; exclusion, f(10) = -4.83, p < .01. Finally, the subtraction method described in the introduction was used to estimate for each patient the probability that anagrams and read words were recognized on the basis of recollection or fluency. These values are reported in Table 2. An ANOVA performed on the recollection scores revealed a significant Group X Presentation interaction, F(l, 21) = 5.88, p < .05. Testing of simple effects indicated that, for anagrams, the amnesics' mean recollection score was significantly smaller than that of the alcoholic controls, F(l, 34) = 6.21, p < .05, whereas for read words, amnesics' mean recollection score did not differ from that of the controls. Also, the alcoholic controls were more likely to recollect anagrams than read words, F(l, 21) = 5.25, p < .05, but this was not the case for the amnesic patients. An ANOVA performed on the fluency scores revealed a marginally significant effect of presentation, F(l, 21) = 3.14, p < .10, indicating that anagrams tended to be recognized on the basis of their fluency more frequently than did read words. The effect of group was not significant and did not interact with presentation, indicating that amnesics and controls relied equally on fluency in making their recognition judgments.

Discussion In the present experiment, we examined the contribution of fluency and recollection to recognition Table 2 Recollection and Fluency Scores for Amnesics and Control Subjects Group and type of word Amnesics Anagram Read Controls Anagram Read

Recollection

Fluency

.00 .11

.46 .41

.33 .11

.50 .36


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memory by comparing performance in an inclusion condition (in which subjects were asked to select for items presented in Phase 1) with performance in an exclusion condition (in which subjects were asked to select against those same items). As expected, control subjects endorsed many more items in the inclusion condition than in the exclusion condition. In contrast, the performance of the amnesic patients did not significantly differ in the two conditions, suggesting that they were unable to reliably use conscious recollection as a basis for their recognition judgments. Estimates of fluency, in contrast, did not differ between the two groups, suggesting that amnesics were as likely as controls to base their recognition judgments on the ease with which items were processed. Although these findings demonstrate that different processes may underlie recognition memory in amnesic patients and controls, it is equally important to point out that this need not be so in all circumstances. As hypothesized, control subjects were most likely to use recollection when stimuli were previously presented as anagrams during the study phase. These elaborate encoding conditions facilitated the use of conscious retrieval processes for the control subjects but had no such effect on the amnesics, hence creating a qualitatively different pattern of performance. In contrast, when stimuli were previously read during the study phase, both amnesic patients and controls relied largely, if not exclusively, on fluency to make their recognition judgments, and no difference in the contribution of recollection was obtained between the groups. These findings are important because they suggest that the presence of qualitative differences in the processes underlying recognition judgments in amnesics and controls may critically depend on the nature of the task and stimulus parameters. Another way to conceptualize the present findings might be with reference to amnesics' deficits in processing contextual information (Hirst & Volpe, 1982; Mayes, Meudell, & Pickering, 1985). In the exclusion condition, subjects had to distinguish between items presented in the first and second phase of the experiment, a demand not imposed in the inclusion test. Therefore, one might argue that amnesics' deficits in the present task simply reflect their impaired source monitoring. In line with Johnson and her colleagues (Johnson, Hashtroudi, & Lindsay, in press), however, we argue that source monitoring and recognition may draw in part on the same processes. Specifically, those processes involved in the recollection of the context of a prior event that are mandatory for source moni-

toring may also be used as an analytic basis for recognition judgments. From this perspective, it is noteworthy that source monitoring deficits have been related specifically to Korsakoff's syndrome and have been attributed to frontal lobe dysfunction (Shimamura, Janowski, & Squire, 1990; Squire, 1982). In the present study, Korsakoff's patients and amnesics with other etiologies, some of whom did not have frontal dysfunction, were equally impaired in recollection. A possible explanation for this discrepancy lies in the varying demands imposed by different contextual memory tasks. In the studies in which contextual memory deficits were correlated with frontal function, stimuli had to be assigned to one of two different contexts. This may entail a decision process not involved in the current task, in which subjects decided whether or not stimuli belonged to a single specified context. Interestingly, one other study that did not find a correlation between contextual memory deficits and frontal lobe function involved task demands more akin to the ones imposed in the present task (Parkin, Leng, & Hunkin, 1990). The finding that recognition memory can variably depend on fluency and recollection has important implications for the relationship between recall and recognition memory in amnesia. If a recall and a recognition task are both mediated by conscious recollection, proportionate impairments may be found on both tasks. However, if performance on a recall task is mediated predominantly by recollection, but recognition judgments are largely fluency based, then amnesic patients may demonstrate disproportionate sparing of recognition memory. Finally, task conditions can even be created in which recognition is more severely impaired than recall, if both targets and distractors on a recognition test are equally fluent and attribution of this fluency to the correct source is impeded (see, e.g., Brown & Brown, 1990; Brown, Lewis, Brown, Horn, & Bowes, 1982). These outcomes might explain the discrepancies in previously reported recognition memory tasks with amnesics. Although recall and recognition tasks are rarely process-pure, several factors can be identified that influence the contribution of fluency and conscious recollection to task performance. Shimamura and Squire (1988) pointed out the significance of the type of recall task used. Free recall tasks may require more extensive use of conscious retrieval strategies than do cued recall tasks because in the latter, the presence of a perceptual cue may facilitate responding. Consequently, the processes underlying cued recall and recognition tasks may be more similar than those under-


RECOGNITION IN AMNESIA

lying free recall and recognition tasks. Consistent with this analysis, Shimamura and Squire found proportionate impairments in amnesics' cued recall and recognition, whereas Hirst and his colleagues (Hirst et al., 1986, 1988) obtained disproportionate impairments in free recall when recognition was matched (but see Haist et al., 1992, for contradictory results). Another critical variable affecting the relationship between recall and recognition may relate to the method by which recognition memory is matched in amnesics and control subjects. The present findings suggest that amnesics' recognition judgments are largely fluency based, even in conditions which favor the use of conscious recollection in control subjects. Consequently, when recognition memory is matched by increasing the study time for amnesics, it is unlikely that the underlying processes contributing to their performance are also matched. Control subjects may use conscious recollection, but the performance of amnesic patients is still likely to be mediated predominantly by fluency. In fact, when manipulating study time directly in the context of a stem-completion task, we found that even when a list of words was presented five times to amnesic patients, they were still unable to use conscious recollection to reject studied items (Cermak, Verfaellie, Sweeney, & Jacoby, in press). It is of note that in the only study in which recognition was matched by manipulating the amnesics' study time (Hirst et al., 1986), disproportionate impairment in the amnesics' recall performance was found. In contrast, a very different situation may arise when recognition memory is matched by testing control subjects after a longer delay than amnesics. Gardiner and his colleagues (Gardiner, 1988; Gardiner & Java, 1991) demonstrated that recollective judgments decline sharply with increasing delay, whereas judgments based on fluency remain relatively unchanged. Likewise, Johnston and his colleagues (Johnston, Hawley, & Elliot, 1991) suggested that the contribution of perceptual fluency to recognition increases as recollective ability decreases. Therefore, it is likely that when control subjects are tested after a longer delay, their performance may be more closely matched to that of amnesics in terms of underlying processes, in that both groups will rely heavily on fluency as a basis of their recognition judgments. Consistent with this interpretation, all but one (Hirst et al., 1988) of the studies in which recognition memory has been equated by varying the study-test delay found that recognition and recall were proportionately impaired in amnesia. Interestingly, similar data led

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Haist et al. (1992) to conclude that perceptual fluency does not contribute to amnesics' recognition memory. They reasoned that, if recognition was no better than would have been predicted from the level of recall, there was no need to invoke a process other than the one underlying recall to explain recognition performance. In contrast to Haist et al.'s view, the present findings suggest that recognition judgments in amnesics, as well as controls, are very likely mediated by a combination of fluency and recollection. Most important, findings of equivalent performance across groups need not imply mediation by the same underlying processes. The present view is similar to that forwarded by Hirst (1989; Hirst et al., 1988) in that it stresses that different processes may underlie performance on recall and recognition tasks. It differs from Hirst's view, however, in the way we view the relationship between recognition and implicit memory tasks. Whereas Hirst (1989) suggested that amnesics' recognition performance is independent of their performance on implicit memory tasks, we propose that both reflect, at least in part, common automatic influences of memory (Cermak & Verfaellie, 1992). With respect to the nature of these influences, it is commonly assumed that the match between the perceptual characteristics of an item at study and at test is solely responsible for the fluency with which it is processed (Jacoby & Dallas, 1981; Mandler, 1980). However, the finding in the present experiment that anagrams were more likely to be called old on the basis of their fluency than were read words, along with similar findings by Jacoby (1991), argues that fluency is not solely perceptually based. Instead, fluency may reflect the global knowledge one has about an item, including not only its perceptual characteristics but also what one did earlier with the item. The present findings suggest that amnesic patients are as likely as controls to use this global knowledge as a nonanalytic basis for recognition judgments (Jacoby, 1988). In conclusion, the present findings suggest that whereas amnesics are severely impaired in their use of conscious recollection as a basis for recognition memory, they use fluency as much as do control subjects. Although the processing demands of recognition tasks may vary considerably from task to task, the oppositional approach used here illustrates a means by which recognition performance can be analyzed in terms of its underlying processes. Such analysis not only leads to a better understanding of the status of recognition memory in amnesia but also provides a useful means

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of examining the relationship between recognition memory and other explicit, as well as implicit, memory tasks.


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RECOGNITION IN AMNESIA Roediger, H. L., Weldon, M. S., & Challis, B. H. (1989). Explaining dissociations between implicit and explicit measures of retention: A processing account. In H. L. Roediger & F. I. M. Craik (Eds.), Varieties of memory and consciousness (pp. 3^tl). Hillsdale, NJ: Erlbaum. Shimamura, A. P., Janowski, J. S., & Squire, L. R. (1990). Memory for the temporal order of events in patients with frontal lobe lesions and amnesic patients. Neuropsychologia, 28, 803-813. 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. Slamecka, N. J., & Graf, P. (1978). The generation effect:

Delineation of a phenomenon. Journal of Experimental Psychology: Human Learning and Memory, 4, 592-604. Squire, L. R. (1982). Comparisons between forms of amnesia: Some deficits are unique to Korsakoff's syndrome. Journal of Experimental Psychology: Learning, Memory and Cognition, 8, 560-571. Wechsler, D. (1981). Wechsler Adult Intelligence ScaleRevised [manual]. New York: Psychological Corp. Wechsler, D. (1987). Wechsler Memory Scale—Revised [manual]. New York: Psychological Corp.

Received April 27, 1992 Revision received July 8, 1992 Accepted July 8, 1992

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