Recognition and recall in amnesics

Although there is considerable agreement that performance in direct memory tasks (e.g., recall, recognition) is more disrupted by amnesia than performance in indirect memory tasks (e.g., mirror reading, word completion), one may be able to further circumscribe the deficit within the domain of direct memory tasks. The present article explores whether recall is disproportionately disrupted by amnesia compared to recognition. If amnesia affects memory uniformly across different direct memory measures, recall of normal controls should not differ from the recall of amnesics when recognition scores of these two groups are equated. On the other hand, if recall is disproportionately disrupted, normal recall should be superior to amnesic recall even when recognition is equated. The present study equated amnesic recognition with that of controls by providing amnesics with 8 s of study time and normal subjects with 0.5 s. Amnesics with Korsakoff's syndrome, amnesics with other etiologies, and appropriate controls were examined. Normal recall was superior to amnesic recall even when no differences were found in recognition. The results further specify the selective nature of amnesia.     

Rate of forgetting in amnesia: I. Recall and recognition of prose.

Three experiments explored the rate at which amnesic participants' free recall, cued recall, and recognition of prose declined over short filled delays. In Experiment 1, after performance had been matched to that of controls at 15s, amnesics showed accelerated forgetting over delays of up to 10 min in a free-recall condition, whereas recognition performance declined normally over delays of up to 1 hr. This pattern of results was replicated in Experiment 2, which showed that amnesic rate of forgetting on a test of cued recall was influenced by level of cuing. Experiment 3 showed that excessive sensitivity to interference was unlikely to be the cause of the amnesic patients' accelerated forgetting rate, which is instead explained in terms of storage deficit accounts of amnesia.     

Amnesics Have a Disproportionately Severe Memopry Deficit for Interactive Context

Two experiments were used to compare the recognition memory of amnesic and normal subjects for intentionally encoded words (targets) and for incidentally encoded words that were meaningfully related to the targets and presented at the same time (interactive context). In both experiments the target recognition of the two groups was matched at a high level by presenting the amnesics with much shorter lists of words to remember. Experiment 1 compared 20 amnesics and their matched controls and showed that whereas the amnesics' recognition of the target words did not benefit significantly when they were presented together with their interactive context words (relative to their recognition when the target words were presented alone), that of the controls did. Experiment 2 compared 14 amnesics and their matched controls and showed that when patients and their controls were matched on their target word recognition in isolation, then the patients still showed worse recognition for the interactive context words. These effects were not found only in Korsakoff patients, and their size did not correlate with behavioural measures of frontal-lobe damage. It is concluded that amnesics may be more impaired at recognizing incidentally encoded interactive context than they are at recognizing target material, and this deficit may be an essential feature of the syndrome.     

Disproportionate deficit in associative recognition relative to item recognition in global amnesia

In two experiments, we tested the hypothesis that medial temporal lobe (MTL) amnesic patients and, likewise, diencephalic (DNC) amnesic patients evidence a disproportionate deficit in memory for associations in comparison with memory for single items. In Experiment 1, we equated item recognition in amnesic and control participants and found that, under these conditions, associative recognition remained impaired both for MTL patients and for DNC patients. To rule out an alternative interpretation of the results of Experiment 1, in Experiment 2 we compared the performance of amnesic and control participants on a one-item recognition task and a two-item recognition task that required no memory for the association between members of word pairs. In the MTL group, when single-item recognition was equated to that of the controls, two-item nonassociative pair memory was equivalent as well. In the DNC group, nonassociative pair memory was impaired, but this impairment did not fully account for the impairment in associative memory. These findings indicate that memory for novel associations between items is disproportionately impaired in comparison with memory for single items in amnesia.     

Rate of forgetting in amnesia: II. Recall and recognition of word lists at different levels of organization.

Amnesic rate of decline of free recall, cued recall, and recognition of word lists with different levels of organization was investigated in 2 experiments. In Experiment 1, it was found that amnesic free recall of semantically related word lists declined at an accelerated rate, whereas free recall of lists of unrelated words declined at a normal rate. Cued recall and recognition performance of both kinds of word lists appeared to decline at a normal rate. In Experiment 2, the results of the free-recall and recognition conditions were replicated using an improved experimental design. The observed amnesic forgetting pattern is interpreted as arising from an impairment in consolidation of long-term memory for complex associations between 2 or more items and their study context that is caused by extended hippocampal system lesions.     

The Claparède phenomenon: A further example in amnesics,a demonstration of a similar effect in normal people with attenuated memory,and a reinterpretation

Three amnesics and four controls were asked to find hidden objects in cartoon drawings, and their success rate and search speed were noted over five learning trials. When latency on the first trial was equated in the two groups, amnesics were shown to learn the location of the test objects less rapidly than controls. Savings scores at seven weeks were similar in the two groups when amount of exposure during learning was equivalent. At seven weeks amnesics failed to recognize items that they were able to show savings on in terms of speed of search (the Claparede phenomenon), but a similar effect was demonstrated in the control group when tested some 17 months later. The implications of the results for various retrieval-deficit views of the amnesic syndrome were discussed.     

Do alcoholic amnesic patients passively rehearse verbal information?

Recently it has been claimed that alcoholic amnesic patients mainly engage in passive repetitive rehearsal during spontaneous learning and that this contributes to their memory problem. To test this hypothesis further, two experiments were conducted which compared list learning in amnesic patients and normal controls. In Experiment I both groups of subjects were required either to learn a list which was presented five times consecutively with free recall following each presentation, or they were asked to repeat each word out loud as they saw it and carry on doing so until the next word was shown. Five presentation trials were given and free recall was again tested after each presentation. It was predicted that if the amnesics' spontaneous form of learning involved only passive repetition there should be no difference between learning and repetition for this group while the controls should show an impairment in repeating compared to learning. The results showed that both groups of subjects were impaired to the same extent with repeating compared to learning and it was concluded that spontaneous learning was similar in both groups and that neither group merely passively rehearsed during spontaneous learning. A second experiment examined recognition performance of the two groups of subjects after learning or repeating lists of 20 words. Recognition was tested with distractors which were irrelevant, acoustically similar, graphemically similar, or semantically similar to the target word. It was found there were no differences between either of the groups in the pattern of errors made over the different distractor types. It was thus concluded that there was no encoding or rehearsal abnormality in the amnesic group. The possibility of differences between groups of alcoholic amnesics was discussed as well as the putative role of slow cognitive processing in their memory problems.     

Intention to learn influences the word frequency effect in recall but not in recognition memory

Watkins, LeCompte, and Kim (2000) suggested that the recall advantage for rare words in mixed lists is due to a compensatory study strategy that favors the rare words. They found the advantage was reversed when rare and common words were studied under incidental learning conditions. The present study investigated the possibility that the rare-word advantage in recognition memory is also the result of a compensatory study strategy. Experiment 1 replicated the findings of Watkins et al. that the rare-word advantage in recall is eliminated under incidental learning conditions. In contrast, Experiment 2 showed that the rare-word advantage in recognition memory is maintained under both intentional and incidental learning conditions. Experiment 3 replicated the results of Experiments 1 and 2 using different stimuli and a different orienting task. Finally, Experiment 4 showed that the rare-word advantage in recognition is maintained with pure lists. These findings show that the rare-word advantage in recognition memory is not the result of a compensatory study strategy. Instead, rare words are encoded more distinctively than common words, irrespective of participants' intention to remember them.     

Contextual cuing and memory performance in brain-damaged amnesics and old people

In Experiment 1, groups of Korsakoff amnesics and alcoholic controls learned a list of paired-associate words in a standard testing room or in a room with distinctive contextual features. Recall was tested 48 hr later in the same or other context. This procedure was repeated in Experiment 2 with old people living in institutions or in the community, but matched for age, health, education, and socioeconomic background. The amnesic patients and institutionalized old people, relative to their comparison groups, were more impaired in recalling the lists under standard conditions and were more responsive to contextual cuing, especially when the distinctive cues were provided during original learning. The results highlight the susceptibility to interference of Korsakoff amnesics and institutionalized old people and offer further evidence that both groups are more responsive to salient contextual cues than either young people or old people living in the community.     

Learning About Categories in the Absence of Training: Profound Amnesia and the Relationship Between PerceptualCategorization and Recognition Memory

Previous evidence suggests that amnesics can categorize stimuli as well as normal individuals but are significantly worse at recognizing those stimuli. In an extreme case, a profoundly amnesic individual, E.P., was found to have near-normal categorization, yet, unlike most amnesics, was unable to recognize better than chance. This evidence has been used to argue against the possibility that a common memory system underlies these cognitive processes. However, we provide evidence that the experimental procedures typically used to test amnesic individuals may be flawed in that initial exposure to category members may be unnecessary to observe accurate categorization of test stimuli. We experimentally "induced" profound amnesia in normal individuals by telling them they had viewed subliminally presented stimuli, which were never actually presented. Using the same experimental paradigm used to test amnesics, we observed that participants' recognition performance was completely at chance, as should be expected, yet categorization performance was quite good.     

Paired-associate learning and priming effects in amnesia: a neuropsychological study

Despite severe deficits of recall and recognition, amnesic patients can exhibit normal priming effects. Amnesic patients have also been reported to perform well on tests of paired-associate learning that involve related word pairs (e.g., table-chair). The present study investigated the role of priming effects in paired-associate learning. Experiment 1 illustrated the distinction between the memory impairment of amnesic patients and their intact priming ability. Amnesic patients were markedly deficient in learning unrelated word pairs, despite exhibiting normal priming as measured by a word-completion test involving the same words. In Experiment 2A, amnesic patients showed good paired-associate learning for related word pairs, though control subjects still performed significantly better. In addition, the good performance by amnesic patients was short-lived, and performance fell to baseline after a 2-hr delay. Control subjects performed well above baseline at all delay conditions. Experiment 2B showed that the forgetting of related word pairs by amnesic patients followed the same time course as the decay of word priming. Experiment 3 showed that amnesic patients were as good as control subjects at learning related word pairs when incidental learning and test procedures were used (a word-association test). The advantage of control subjects over amnesic patients in Experiments 2A and 2B could therefore be attributed to the explicit learning instructions that are standard in paired-associate tests. Finally, Experiment 4 showed that amnesic patients exhibited normal priming when they were asked to "free associate" to words (e.g., child) that were semantically related to previously presented words (e.g., baby). The results indicate that both priming effects and paired-associate learning of related word pairs depend on activation, a process that is preserved in amnesia. Activation can account for the findings of good performance by amnesic patients on tests of word priming (Experiments 1 and 2B), related paired associates (Experiments 2A and 2B), and word association (Experiments 3 and 4). Activation is a transient phenomenon presumed to operate on and facilitate access to preexisting representations. Control subjects can establish new associations and can strengthen preexisting associations by engaging processes that are impaired in amnesia. As a result, when explicit learning instructions are used to test paired-associate learning of related word pairs, control subjects can learn better and can remember longer than can amnesic patients (Experiments 2A and 2B).(ABSTRACT TRUNCATED AT 400 WORDS)     

Teaching an amnesic a complex cognitive skill

G.P., a Korsakoff's amnesic, was able to learn an algorithm for squaring two-digit numbers mentally over a 7-day period at a rate comparable to that of age-matched controls. He failed to show normal positive transfer to specific problems or to specific numbers used in components of the task. He also exhibited slight improvement in simple naming speed, forward digit span, simple multiplication speed, but no apparent improvement for the recall of repeated supraspan digit strings. He was unable to state the algorithm he had learned to square two-digit numbers, though he could implement it successfully. The results suggest that the compilation of a skill may involve two dissociable components: composition and proceduralization, with the former, but not the latter, occurring at normal rates for Korsakoff's amnesics.     

Relaxing decision criteria does not improve recognition memory in amnesic patients

An important question about the organization of memory is whether information available in non-declarative memory can contribute to performance on tasks of declarative memory. Dorfman, Kihlstrom, Cork, and Misiaszek (1995) described a circumstance in which the phenomenon of priming might benefit recognition memory performance. They reported that patients receiving electroconvulsive therapy improved their recognition performance when they were encouraged to relax their criteria for endorsing test items as familiar. It was suggested that priming improved recognition by making information available about the familiarity of test items. In three experiments, we sought unsuccessfully to reproduce this phenomenon in amnesic patients. In Experiment 3, we reproduced the methods and procedure used by Dorfman et al. but still found no evidence for improved recognition memory following the manipulation of decision criteria. Although negative findings have their own limitations, our findings suggest that the phenomenon reported by Dorfman et al. does not generalize well. Our results agree with several recent findings that suggest that priming is independent of recognition memory and does not contribute to recognition memory scores.     

Spatial Location Memory in Amnesia: Binding Item and Location Information Under Incidental and Intentional Encoding Conditions

Items located within an array were presented to alcoholic Korsakoff and nonalcoholic mixed-etiology amnesics and to alcoholic and normal controls. Recognition memory for the locations of items was tested after incidental and intentional encoding. When equated on item recognition, neither Korsakoff amnesics nor alcoholic controls benefited from intentional, relative to incidental, encoding instructions. Furthermore, Korsakoff amnesics showed neither disproportionately impaired incidental nor intentional location recognition memory relative to alcoholic controls. In contrast, mixed-etiology amnesics profited significantly from intentional location acquisition relative to incidental instructions, and were impaired somewhat in incidental, but not intentional, location memory relative to normal controls. We discuss these data in relation to Mayes' (1992) contextual memory deficit hypothesis and Hirst's (1982) automatic encoding deficit account, and propose an alternative framework in which the location memory deficit observed in mixed-etiology amnesics is interpreted as a disruption to the ability to bind item and location information.     

Part-list cuing in amnesic patients: evidence for a retrieval deficit

Part-list cuing--the detrimental effect of the presentation of a subset of learned items on recall of the remaining items--was examined in amnesic patients and healthy control subjects. Subjects studied two types of categorized item lists: lists in which each category consisted of strong and moderate items and lists in which each category consisted of weak and moderate items. The subjects recalled a category's strong and weak items in either the presence of or absence of the moderate items serving as retrieval cues. In healthy subjects, part-list cuing impaired recall of the strong items but not of the weak items; in amnesics, part-list cuing impaired recall of both types of items. Part-list cuing is often attributed to a change in the retrieval process from a more effective one when cues are absent to a less effective one when they are present. On the basis of this view, our results indicate that part-list cuing causes a stronger retrieval inefficiency in amnesic patients than in healthy people.     

A single-system interpretation of dissociations between recognition and categorization in a task involving object-like stimuli

In previous research (Reed, Squire, Patalano, Smith, & Jonides, 1999), amnesic patients performed at near normal levels in a categorization task involving stimuli with discrete features, but showed impaired recall of the features. These results were taken as evidence of the existence of separate memory systems for categorization and recall/recognition. The present research addresses a single-system account of this dissociation. In Experiment 1, results closely matching the dissociation pattern were obtained when normal participants' classification and recognition performance was tested either immediately or after a week delay. In addition, formal modeling of the data suggested that participants use only a few of the dimensions in the categorization task, whereas they must use many dimensions in the cued-recall task. In Experiment 2, we found that many participants could perform the categorization task without any exposure to the training sequence. These results suggest that different memory demands across the two tasks may be responsible for the observed dissociation—separate memory systems are not necessarily involved.     

The information that amnesic patients do not forget

The performance of three kinds of amnesic patients and control subjects was assessed using four methods for testing memory: free recall, recognition, cued recall, and word completion. Whereas amnesic patients were impaired on free recall, recognition, and cued recall, they were normal on word completion. Moreover, performance on the word-completion test declined at a normal rate reaching chance after about 120 min. The word-completion test resembled the cued-recall test in that the initial letters of previously presented words were given as cues. It differed from cued recall only in the instructions, which directed subjects away from the memory aspects of the test and asked them to complete each three-letter cue with the first word that came to mind. The present results offer an explanation of conflicting findings that have been obtained with amnesic patients on tests of the cued-recall type. The results are considered in terms of a process (activation or procedural learning), which is spared in amnesia and not dependent on the integrity of the damaged brain regions.     

On the relationship between recall and recognition memory.

The relationship between recall and recognition has been a central topic for the study of memory. A test of alternative views about recall and recognition was arranged by studying amnesic patients. In amnesia, damage has occurred to a brain system important for declarative (conscious) memory, but skill learning, priming, and other forms of nonconscious memory are intact. Recall and recognition were found to be proportionately impaired in amnesic patients, and confidence ratings for the recognition judgments were commensurate with the level of impaired performance. The results are contrary to views that either recognition memory or associated confidence judgments are ordinarily supported significantly by nonconscious memory. The results favor the view that recall and recognition are related functions of declarative memory and equivalently dependent on the brain system damaged in amnesia.