Dissociations in infant memory: Rethinking the development of implicit and explicit memory.

Extending the Jacksonian principle of the hierarchical development and dissolution of function to the development and dissolution of memory, researchers have concluded that implicit (procedural) memory is a primitive system, functional shortly after birth, that processes information automatically, whereas explicit (declarative) memory matures late in the 1st year and mediates the conscious recollection of a prior event. Support for a developmental hierarchy has only been inferred from the memory performance of adults with amnesia on priming and recognition-recall tests in response to manipulations of different independent variables. This article reviews evidence that very young infants exhibit memory dissociations like those exhibited by adults with normal memory on analogous memory tests in response to manipulations of the same independent variables. These data demonstrate that implicit and explicit memory follow the same developmental timetable and challenge the utility of conscious recollection as the defining characteristic of explicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depression and implicit memory: A commentary.

Reviews 4 studies in which the issue of whether depression affects priming on implicit memory tests was examined. The authors conclude that a depressive mood does not affect the amount of priming on several implicit memory tests under conditions in which marked effects are shown on conscious recollection (explicit memory). The mood congruity effect (depressives remember depression-related words better than controls; controls remember other types of material better than depressives) also largely disappears on perceptual implicit memory tests. The authors speculate about reasons for discrepancies in the literature, relate the findings to some current theories of individual differences in memory, and suggest some directions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manipulation of attention at study affects an explicit but not an implicit test of memory

We investigated the impact of attention during encoding on later retrieval. During study, participants read some words aloud (ignoring the print color) and named the print color of other words aloud (ignoring the word). Then one of two memory tests was administered. The explicit test--recognition--required conscious recollection of whether a word was studied. Previously read words were recognized more accurately than were previously color named words. This contrasted sharply with performance on the implicit test--repetition priming in lexical decision. Here, words that were color named during study showed priming equivalent to words that were read during study; both were responded to faster than unstudied words. Thus, an attentional manipulation during study had a strong effect on an explicit test of memory, but almost no effect on an implicit test. Focal attention during study is crucial for remembering consciously but not necessarily for remembering without awareness.     

Implicit memory: History and current status.

Memory for a recent event can be expressed explicitly, as conscious recollection, or implicitly, as a facilitation of test performance without conscious recollection. A growing number of recent studies have been concerned with implicit memory and its relation to explicit memory. This article presents an historical survey of observations concerning implicit memory, reviews the findings of contemporary experimental research, and delineates the strengths and weaknesses of alternative theoretical accounts of implicit memory. It is argued that dissociations between implicit and explicit memory have been documented across numerous tasks and subject populations, represent an important challenge for research and theory, and should be viewed in the context of other dissociations between implicit and explicit expressions of knowledge that have been documented in recent cognitive and neuropsychological research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociative effect of massed repetition on implicit and explicit measures of memory.

Ss saw or heard words presented once, or repeated 4 or 16 times in massed fashion, and then received an implicit or explicit memory test. Massed repetition did not increase priming on word fragment completion beyond that obtained from a single presentation but did enhance performance on various explicit tests (free recall, recognition, question cued recall, and word fragment cued recall) and an implicit general knowledge test. Modality of presentation affected implicit and explicit word fragment cued tests but did not affect performance on any of the other tests. Levels of processing affected performance on implicit and explicit question cued tests. These results are consistent with a transfer appropriate processing account of dissociations among memory measures and imply that massed repetition promotes conceptual processing but does not entail a repetition of perceptual-based processes responsible for priming on word fragment completion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct comparison of two implicit memory tests: Word fragment and word stem completion.

In 3 experiments, the implicit memory tests of word fragment and word stem completion showed comparable effects over several variables: Study of words produced more priming than did study of pictures; no levels-of-processing effect occurred for words; more priming was obtained from pictures when Ss imaged the pictures' names than when they rated them for pleasantness; and forgetting rates were generally similar for the tests. A different pattern of results for the first 3 variables occurred under explicit test conditions with the same word fragments or word stems as cues. It is concluded that the 2 implicit tests are measuring a similar form of perceptual memory. Furthermore, it is argued that both tests are truly implicit because they meet the D. L. Schacter et al (1989) retrieval intentionality criterion: Levels of processing of words have a powerful effect on explicit versions of the tests but no effect on implicit versions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociable effects of conscious emotion regulation strategies on explicit and implicit memory.

The authors manipulated emotion regulation strategies at encoding and administered explicit and implicit memory tests. In Experiment 1, participants used reappraisal to enhance and decrease the personal relevance of unpleasant and neutral pictures. In Experiment 2, decrease cues were replaced with suppress cues that directed participants to inhibit emotion-expressive behavior. Across experiments, using reappraisal to enhance the personal relevance of pictures improved free recall. By contrast, attempting to suppress emotional displays tended to impair recall, especially compared to the enhance condition. Using reappraisal to decrease the personal relevance of pictures had different effects depending on picture type. Paired with unpleasant pictures, the decrease cue tended to improve recall. Paired with neutral stimuli, the decrease cue tended to impair recall. Emotion regulation did not affect perceptual priming. Results highlight dissociable effects of emotion regulation on explicit and implicit memory, as well as dissociations between regulation strategies with respect to explicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistent repetition priming in picture naming and its dissociation from recognition memory.

The current experiments investigated the longevity of repetition priming and dissociations between different memory measures. Picture-naming latencies revealed robust repetition priming in four separate studies: Previously named pictures were named faster than new pictures. The magnitude of this naming facilitation was stable across 1 to 6 weeks. The apparent temporal invulnerability of repetition priming was in marked contrast to the decline in episodic recognition memory across 6 weeks, suggesting a dissociation between implicit and explicit memory. Additional evidence of this dissociation was observed within each session: Naming facilitation for repeated pictures occurred regardless of whether those particular pictures were consciously recognized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of attention during encoding in implicit and explicit memory.

In 5 experiments, participants read study words under conditions of divided or full attention. Dividing attention reduced performance on the general knowledge test, a conceptual implicit test of memory. Likewise, dividing attention reduced conceptual priming on the word association task, as well as on a matched explicit test, associate-cued recall. In contrast, even very strong division of attention did not reduce perceptual priming on word-fragment completion, although it did reduce recall on the matched explicit test of word-fragment-cued recall. Finally, dividing attention reduced recall on the perceptual explicit tests of graphemic-cued recall and graphemic recognition. The results indicate that perceptual implicit tests rely minimally on attention-demanding encoding processes relative to other types of memory tests. The obtained pattern of dissociations is not readily accommodated by the transfer-appropriate-processing (TAP) account of implicit and explicit memory. Potential extensions of the TAP view are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Affective valence of words, explicit and implicit memory in clinical depression

Explicit and implicit memory for affectively valenced words (positive, negative or neutral) were investigated in 30 patients suffering from a major depressive episode (DSM-III-R criteria) and 30 normal control subjects. Explicit memory was assessed with a free-recall and a recognition task and implicit memory with a word-stem completion task. Depressed and control subjects recalled more emotional, i.e., positive and negative, words than neutral ones. They recognized less negative than neutral words. In contrast, to recall and recognition performance, word-completion performance was not sensitive to the affective valence of words: depressed and control subjects exhibited equivalent priming of positive, negative and neutral words. These results indicate that, in depressed and normal subjects, the affective valence of words influences memory when conscious, intentional recollection is required but is devoid of effect when such a recollection is not required.     

On the relationship between recognition familiarity and perceptual fluency: evidence for distinct mnemonic processes

Fluent reprocessing of perceptual aspects of recently experienced stimuli is thought to support repetition priming effects on implicit perceptual memory tests. Although behavioral and neuropsychological dissociations demonstrate that separable mnemonic processes and neural substrates mediate implicit and explicit test performance, dual-process theories of memory posit that explicit recognition memory judgments may be based on familiarity derived from the same perceptual fluency that yields perceptual priming. Here we consider the relationship between familiarity-based recognition memory and implicit perceptual memory. A select review of the literature demonstrates that the fluency supporting implicit perceptual memory is functionally and anatomically distinct from that supporting recognition memory. In contrast to perceptual fluency, recognition familiarity is more sensitive to conceptual than to perceptual processing, and does not depend on modality-specific sensory cortices. Alternative possible relationships between familiarity in explicit memory and fluency in implicit memory are discussed.     

Preserved priming across study-test picture transformations in patients with Alzheimer's disease

Picture-naming priming was examined across different study-test transformations to explore the nature of memory representations of objects supporting implicit memory processes in patients with Alzheimer's disease (AD). Although severely impaired in explicit memory for pictures and words, AD patients demonstrated normal priming across perceptual transformations in picture orientation (Experiment 1) and picture size (Experiment 2) and across symbolic transformations from words to pictures (Experiment 3). In addition, the priming across alterations in picture size was invariant. This demonstrates that AD patients have preserved implicit memory for high-level, abstract representations of objects.     

Effects of elaborative processing on implicit and explicit memory for new associations.

Explored the relation between elaborative processing and implicit memory for new associations (i.e., the phenomenon that priming effects on word-completion tests are influenced by newly acquired associations between normatively unrelated words) in 4 experiments, using a total of 240 undergraduates. Results indicate that implicit memory for new associations, like explicit memory, depended on encoding of meaningful relations between paired words in the study list. However, variations in degree and type of associative elaboration had a large effect on explicit memory, as revealed by performance on letter-cued recall and paired-associate tests, but had little effect on implicit memory, as revealed by performance on a word-completion test. Discussion focuses on the theoretical implications of the observed similarities and differences between implicit and explicit memory for new associations. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Explicit memory and repetition priming in dementia: evidence for a common basic mechanism underlying conscious and unconscious retrieval deficits

The present study was designed to assess performance of Alzheimer's (AD) and Multi-infarct (MID) demented patients on the explicit and implicit versions of two memory tasks, namely Word-Stem Completion and Word-Pair Learning. Consistently with previous studies, the AD patients were deficient on the explicit and implicit versions of both tasks. In MID patients, a dissociation emerged between normal implicit and deficient explicit Word-Stem Completion. Two multiple regression analyses were performed to evaluate patients' ability on measures of lexical-semantic competence, explicit memory, and global intellective efficiency in predicting level of repetition priming. The results demonstrate a close association between explicit and implicit memory performance in AD patients but no relation between repetition priming level and measures of lexical-semantic competence or general intelligence. Overall, the results of the present study do not support previous conceptualizations suggesting that a breakdown in the structure of semantic memory is at the root of deficient priming in demented patients. Alternative interpretations of the deficient repetition priming effect in dementia, based on a common mechanism underlying conscious and unconscious retrieval deficits, are discussed.     

Selective effects of interference on implicit and explicit memory for new associations.

Examined the effects of interference manipulation on explicit and implicit memory for pairs of normatively unrelated words in 2 experiments, involving 128 undergraduates. Findings show that interference affected explicit memory, as indexed by performance on cued recall, pair matching, and modified free-recall tests, but it did not affect implicit memory, as indexed by performance on a word-completion test. This pattern of results complements several previous findings, including those of the present authors (see PA, Vol 73:12203 and 29150), on performance dissociations between explicit and implicit memory for new associations. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition Priming and Recognition Memory in Younger and Older Persons: Temporal Stability and Performance.

The dissociation between intact priming and reduced explicit memory in aging has been called into question on the basis of limited information that suggests that priming measures are less reliable than explicit memory measures. No aging study to date, however, has offered a comprehensive examination of the reliability of these measures. Age-related performance and test-retest stability coefficients for multiple priming and explicit memory tasks were compared. Age effects were found on some tasks but not others, and stability was not related to task performance. Stability was similar for implicit versus explicit task instructions, younger versus older persons, and studied versus unstudied items. Results indicate that dissociations between priming and explicit memory performances cannot be accounted for by differential reliability of the measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit false memory in the DRM paradigm: Effects of amnesia, encoding instructions, and encoding duration.

Recent studies with the Deese/Roediger–McDermott (Deese 1959; Roediger & McDermott, 1995) paradigm have revealed that amnesic patients do not only show impaired veridical memory, but also diminished false memory for semantically related lure words. Due to the typically used explicit retrieval instructions, however, this finding may reflect problems at encoding, at recollection, or both. Therefore, the present experiments examined implicit as well as explicit false memory in patients suffering from Korsakoff’s syndrome and controls. In Experiment 1, encoding instructions either focused on remembering individual list words, or on discovering semantic relationships among the words. In Experiment 2, different presentation durations were used. Results emphasize the distinction between automatic and intentional retrieval: Korsakoff patients’ veridical and false memory scores were diminished when explicit recollection was required, but not when memory was tested implicitly. Encoding manipulations only significantly affected veridical memory: Priming was reduced with thematic encoding, and explicit retrieval was facilitated when given more study time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct comparison of four implicit memory tests.

Four verbal implicit memory tests, word identification, word stem completion, word fragment completion, and anagram solution, were directly compared in 1 experiment and were contrasted with free recall. On all implicit tests, priming was greatest from prior visual presentation of words, less (but significant) from auditory presentation, and least from pictorial presentations. Typefont did not affect priming. In free recall, pictures were recalled better than words. The 4 implicit tests all largely index perceptual (lexical) operations in recognizing words, or visual word form representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)