Age differences in implicit memory: conceptual, perceptual, or methodological?

The authors examined age differences in conceptual and perceptual implicit memory via word-fragment completion, word-stem completion, category exemplar generation, picture-fragment identification, and picture naming. Young, middle-aged, and older participants (N = 60) named pictures and words at study. Limited test exposure minimized explicit memory contamination, yielding no reliable age differences and equivalent cross-format effects. In contrast, explicit memory and neuropsychological measures produced significant age differences. In a follow-up experiment, 24 young adults were informed a priori about implicit testing. Their priming was equivalent to the main experiment, showing that test trial time restrictions limit explicit memory strategies. The authors concluded that most implicit memory processes remain stable across adulthood and suggest that explicit contamination be rigorously monitored in aging studies.     

Effects of attentional load and ageing on word-stem and word-fragment implicit memory tasks

The joint effects of reduced attention and age on repetition priming in implicit memory tests of word-fragment completion (WFC) and word-stem completion (WSC) were investigated. An attention load during the study phase reduced the extent of repetition priming in the WSC condition but not in WFC. This finding provides support for the view that WSC and WFC involve different processes. However, there was no evidence of an age effect on either of these two types of implicit tasks. The data also revealed an overall significant effect of age and reduced attention on explicit cued recall tasks.     

Correlational analyses of explicit and implicit memory performance

Sixty-four subjects were administered two tests of explicit memory (selective recall and recognition) and four tests of implicit memory (identification in a perceptual clarification procedure, word-fragment completion, tachistoscopic identification, and anagram solution). Each test drew on a different subset of a long list of previously displayed words. Although the four implicit memory tests showed sizable priming effects, correlational and factor analyses showed striking dissociations. On the one hand, performance on the perceptual clarification procedure and word-completion tests were related to one another, as well as to recall and recognition. On the other hand, performance on tachistoscopic identification and anagram solution were related to one another, but not to the measures for the other tasks. A framework is proposed to reconcile these new results with current knowledge on the explicit/implicit memory distinction, based in particular on studies of amnesic subjects. It is argued that a small number of tasks, especially tachistoscopic identification, may serve as relatively uncontaminated and ubiquitous indicators of implicit memory. However, explicit remembering could affect performance in so-called implicit memory tasks that allow for a strategy of controlled selection of candidate responses from accumulating cues, in experimental conditions that make the explicit remembering of relevant events possible.     

Transfer across modality in perceptual implicit memory

We examined whether words studied in one modality (visual or auditory) would prime performance in the opposite modality in five different perceptual implicit memory tests: auditory perceptual identification, auditory stem completion, visual perceptual identification, visual stem completion, and visual fragment completion. Significant transfer across modality was observed in all five tasks. However, a large proportion of the subjects reported using explicit retrieval strategies during the implicit tests. Those subjects who claimed not to have used explicit retrieval processes during the test phase demonstrated transfer across modalities in the stem completion tests and the perceptual identification tests, but not in the fragment completion test. The results indicate that implicit visual word-fragment completion is unique, in the sense that it relies exclusively on perceptual memory processes, whereas the other tasks rely, in part, on nonperceptual memory processes.     

The properties of retrieval cues constrain the picture superiority effect

In three experiments, we examined why pictures are remembered better than words on explicit memory tests like recall and recognition, whereas words produce more priming than pictures on some implicit tests, such as word-fragment and word-stem completion (e.g., completing -l-ph-nt or ele----- as elephant). One possibility is that pictures are always more accessible than words if subjects are given explicit retrieval instructions. An alternative possibility is that the properties of the retrieval cues themselves constrain the retrieval processes engaged; word fragments might induce data-driven (perceptually based) retrieval, which favors words regardless of the retrieval instructions. Experiment 1 demonstrated that words were remembered better than pictures on both the word-fragment and word-stem completion tasks under both implicit and explicit retrieval conditions. In Experiment 2, pictures were recalled better than words with semantically related extralist cues. In Experiment 3, when semantic cues were combined with word fragments, pictures and words were recalled equally well under explicit retrieval conditions, but words were superior to pictures under implicit instructions. Thus, the inherently data-limited properties of fragmented words limit their use in accessing conceptual codes. Overall, the results indicate that retrieval operations are largely determined by properties of the retrieval cues under both implicit and explicit retrieval conditions.     

Aging affects word-stem completion and recognition but not category generation

In this study, we investigated the effect of aging on two implicit memory tasks, word-stem completion and category generation, and on explicit recognition. We compared the performance of young and older adults on these implicit memory tasks with those of explicit recognition. We expected better performance of young than older adults in the explicit memory task and similar priming in both implicit memory tasks. The results showed that young adults performed better than older adults in the recognition task. Moreover, both age groups showed priming in the implicit memory tasks, although priming was greater in young adults compared to older adults in the word-stem completion memory task, whereas both age groups showed similar levels of priming in the category generation task. The present results showed dissociations as a function of age not only between the explicit and the implicit tasks but also between the implicit tasks.     

Effects of depth-of-processing and ageing on word-stem and word-fragment implicit memory tasks: Test of the lexical-processing hypothesis

The joint effects of depth-of-processing and age on repetition priming in implicit memory tests of word-fragment completion (WFC) and word-stem completion (WSC) were investigated. The experiment consisted of three study tasks (perceptual, lexical, and semantic) and four memory conditions: implicit (WSC and WFC) and explicit (WS cued recall and WF cued recall). In the WSC condition, semantic and lexical study processing produced equal priming, both superior to the perceptual study processing, whereas the WFC test showed equal priming for these three study conditions. This finding provides clear evidence, consistent with the lexical-processing hypothesis, that depth-of-processing in WSC priming reflects a lexical rather than a semantic process. It also provides support for the view that WSC and WFC involve different processes. However, there was no evidence of an age effect on either of these two implicit tasks. The data also revealed an overall significant effect of age and depth-of-processing, and an interaction between these variables on explicit cued recall tasks, indicating that older adults benefited less than younger ones from a deep encoding condition.     

Effects of exact repetition and conceptual repetition on free recall and primed word-fragment completion.

Experiments are reported in which effects of repeating words exactly (e.g., elephant, elephant) or repeating some meaningful aspect--a synonym (pachyderm), an associate (tusk), or a category coordinate (hippopotamus)--were examined on free recall and word-fragment completion. In free recall, large effects of both exact repetition and conceptual repetition were found; the magnitude of the latter was about half that of the former. In contrast, in primed word-fragment completion, repetition effects were rather small and there was no evidence of indirect (or conceptual) priming. Also, presentation of synonyms, associates, and coordinates in isolation failed to prime word-fragment completion. The results provide further evidence that the basis of primed word-fragment completion is different from that of free recall; the former seems to have a perceptual (or perhaps lexical) basis, whereas the latter relies more on meaningful processing.     

The Directed Forgetting Effect in Word-fragment Completion: An Application of the Process Dissociation Procedure

In three experiments, subjects were asked to remember and forget study words. In line with previous studies, a directed forgetting effect was observed in a word-fragment completion task: Instructions to remember increased the completion of target fragments compared with instructions to forget (Experiment 1). Using the process dissociation procedure (Jacoby, 1991), it appeared that instructions to remember increased the estimates of intentional influences of memory but did not affect the estimates of automatic uses of memory (Experiments 1, 2 and 3). This suggests that directed forgetting effects in word-fragment completion reflect the surreptitious influence of explicit memory in a nominally implicit memory task. However, a meta-analysis indicated that directed forgetting instructions affected automatic and intentional influences of memory in opposite directions. This finding casts doubt on the assumption of independence between automatic and intentional uses of memory. The implications for use of the process dissociation procedure are discussed.     

Divided attention and indirect memory tests

Attentional state during acquisition is an important determinant of performance on direct memory tests. In two experiments we investigated the effects of dividing attention during acquisition on conceptually driven and data-driven indirect memory tests. Subjects read a list of words with or without distraction. Memory for the words was later tested with an indirect memory test or a direct memory test that differed only in task instructions. In Experiment 1, the indirect test was categoryexemplar production (a conceptually driven task) and the direct test was category-cued recall. In Experiment 2, the indirect test was word-fragment completion (a data-driven task) and the direct test was word-fragment cued recall. Dividing attention at encoding decreased performance on both direct memory tests. Of the indirect tests, category-exemplar production but not word-fragment completion was affected. The results indicate that conceptually driven indirect memory tests, like direct memory tests, are affected by divided attention, whereas data-driven indirect tests are not. These results are interpreted within the transfer-appropriate processing framework.     

增龄性记忆改变规律及影响因素的研究

本研究用多维记忆量表对280名50～91岁的老年人做了测查,同时收集了一般资料,以探讨增龄性记忆改变的规律和年龄、教育和职业等因素对增龄性记忆改变的影响。结果表明：随年龄增长,各记忆组合分和分测验成绩均呈下降趋势,外显记忆成绩在70岁后呈快速下降,内隐记忆和日常生活记忆在75岁后才有明显下降;记忆总分、外显记忆和日常生活记忆均受年龄和教育的影响,内隐记忆不受教育的影响。结果提示老年人记忆随年龄增长呈渐渐下降,不同记忆功能开始下降的年龄和下降速率不同,教育对增龄性记忆改变有保护作用。     

Perceptual and Conceptual Priming of Individual Words in Coherent Texts

This study explores implicit memory within the domain of text processing. Three experiments were designed to study priming in word-fragment completion, wordstem completion, and free association tests following presentation of target words in the context of a coherent text. In order to examine the time course of perceptual and conceptual processes we investigated the priming effects by manipulating the perceptual context in which the target words had been read and the time given to the subjects for each test-cue. Three main results emerged. First, we found a significant priming effect in the three implicit tests for words previously studied in a text. Second, the magnitude of the priming effect only varied when the task demands required perceptual and conceptual processing, as was the case with the completion tests. Third, priming effects did not depend on subjects' comprehension of the text read. These results are discussed in the framework of the transfer appropriate processing view proposed by Roediger, Weldon, and Challis (1989).     

The effects of divided attention on auditory priming

Traditional theorizing stresses the importance of attentional state during encoding for later memory, based primarily on research with explicit memory. Recent research has begun to investigate the role of attention in implicit memory but has focused almost exclusively on priming in the visual modality. The present experiments examined the effect of divided attention on auditory implicit memory, using auditory perceptual identification, word-stem completion and word-fragment completion. Participants heard study words under full attention conditions or while simultaneously carrying out a distractor task (the divided attention condition). In Experiment 1, a distractor task with low response frequency failed to disrupt later auditory priming (but diminished explicit memory as assessed with auditory recognition). In Experiment 2, a distractor task with greater response frequency disrupted priming on all three of the auditory priming tasks as well as the explicit test. These results imply that although auditory priming is less reliant on attention than explicit memory, it is still greatly affected by at least some divided-attention manipulations. These results are consistent with research using visual priming tasks and have relevance for hypotheses regarding attention and auditory priming.     

The generation effect in primed word-fragment completion reexamined

Summary Two experiments were designed to test a claim made by Gardiner (1988) that there are generation effects in implicit memory as measured by word-fragment completion. Subjects either read words at study or generated the words from fragments. As in previous research, fragments were completed to a greater extent if they were identical at study and test than if they differed. In Experiment 1 it was found that subjects could recognize explicitly the exact form of fragments that had been used for self-generation and distinguish these from other forms of fragments. An analysis of the contingency relations between recognition of fragments and fragment completion showed a high degree of dependence between the two tests. In Experiment 2 it was found that the match of surface features between study and test was a necessary, but not sufficient, condition to produce enhancement of priming. The results are interpreted as supporting the claim that generation does involve a data-driven component in addition to semantic elaboration.This research was supported by a grant from the Swedish Council for Research in the Humanities and Social Sciences to Lars-Göran Nilsson.     

Implicit memory and depression: An analysis of perceptual and conceptual processes

A small number of studies have reported impaired explicit memory and intact implicit memory performance in participants classified as depressed. In the present study we examined this finding taking account of the distinction between datadriven and conceptually driven processing. The performance of participants diagnosed with depression was examined on implicit and explicit memory tasks which were designed to tap either predominantly perceptual or conceptual processes. Depressed participants demonstrated performance deficits on both the implicit and explicit conceptual tasks (category association and free recall, respectively) but showed intact performance in the implicit perceptual task (word-fragment completion). These results suggest that people with severe depression show deficits in conceptual processing and that this deficit occurs under both explicit and implicit task instructions.     

Production and identification repetition priming in amnestic mild cognitive impairment

The experiment reported here examined implicit memory function, as measured through repetition priming, in amnestic mild cognitive impairment (MCI) to examine whether impairments exist in this aspect of memory function. Young adults, healthy older controls, Alzheimer's disease patients, and MCI participants were asked to perform two types of implicit memory tests (word stem completion and threshold identification repetition priming tasks), as well as a recognition test for studied items. As expected, young adults performed better than the other participants on the recognition test and the word stem completion task; there was equivalent priming across groups on the word identification task. While both the older control and MCI participants showed lower levels of priming on the word stem completion task relative to the young adults, the magnitude of priming was equivalent for these two groups, and reliably greater than that of the dementia participants. These results suggest that not all aspects of memory function are impaired in MCI relative to healthy aging.     

Production and Identification Repetition Priming in AmnesticMild Cognitive Impairment

ABSTRACT

The experiment reported here examined implicit memory function, as measured through repetition priming, in amnestic mild cognitive impairment (MCI) to examine whether impairments exist in this aspect of memory function. Young adults, healthy older controls, Alzheimer's disease patients, and MCI participants were asked to perform two types of implicit memory tests (word stem completion and threshold identification repetition priming tasks), as well as a recognition test for studied items. As expected, young adults performed better than the other participants on the recognition test and the word stem completion task; there was equivalent priming across groups on the word identification task. While both the older control and MCI participants showed lower levels of priming on the word stem completion task relative to the young adults, the magnitude of priming was equivalent for these two groups, and reliably greater than that of the dementia participants. These results suggest that not all aspects of memory function are impaired in MCI relative to healthy aging.     

Perceptual and conceptual priming of individual words in coherent texts.

This study explores implicit memory within the domain of text processing. Three experiments were designed to study priming in word-fragment completion, word-stem completion, and free association tests following presentation of target words in the context of a coherent text. In order to examine the time course of perceptual and conceptual processes we investigated the priming effects by manipulating the perceptual context in which the target words had been read and the time given to the subjects for each test-cue. Three main results emerged. First, we found a significant priming effect in the three implicit tests for words previously studied in a text. Second, the magnitude of the priming effect only varied when the task demands required perceptual and conceptual processing, as was the case with the completion tests. Third, priming effects did not depend on subjects' comprehension of the text read. These results are discussed in the framework of the transfer-appropriate processing view proposed by Roediger, Weldon, and Challis (1989).     

On the differential nature of implicit and explicit memory

In this article, we report two experiments that provide further evidence concerning the differential nature of implicit and explicit memory. In Experiment 1, subjects first undertook a sentenceverification task. While carrying out this task, half of the subjects were also required to carry out a secondary processing task involving tone monitoring. Twenty-four hours later, the subjects’ memory for target items in the sentence-verification task was tested explicitly by means of a recognition task and implicitly by examining the extent to which the items primed fragment completion. Recognition performance was significantly impaired by the imposition of secondary processing demands during the original learning phase. In contrast, fragment completion was completely unaffected by this additional processing, even though substantial priming was observed. In Experiment 2, we examined whether priming in fragment completion is influenced by the nature of repetition during initial learning. Subjects studied a list of target items that were each repeated twice. Halfthe items were repeatedimmediately (lag 0) and halfwere repeated after six intervening items (lag 6). Memory for the itemswas assessed by recognition and by priming in fragment completion. Recognition was affected by lag, with lag 6 items being recognized better than lag 0 items. However, although significant priming was obtained, the extent of this priming was uninfluenced by lag. These data indicate two additional dimensions along which implicit and explicit memory differ and, furthermore, they support recent conceptualizations of processing differences underlying these two forms of memory.