Implicit and explicit memory in young and older adults.

In three experiments, young and older adults were compared on both implicit and explicit memory tasks. The size of repetition priming effects in word completion and in perceptual identification tasks did not differ reliably across ages. However, age-related decrements in performance were obtained in free recall, cued recall, and recognition. These results, similar to those observed in amnesics, suggest that older adults are impaired on tasks which require conscious recollection but that memory which depends on automatic activation processes is relatively unaffected by age. (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)     

Serial position effects in implicit and explicit tests of memory.

The effects of serial position at study on implicit and explicit tests of memory were investigated. Both primacy and recency effects were observed in implicit tests of word-stem completion. These effects, however, were transient. No serial position effects were found in the 2nd half of testing (Exps 1 and 3) or when testing followed a 1-min, filled delay (Exp 2). Serial position effects were also examined on explicit tests of cued recall. When performance on explicit cued recall was below ceiling levels, a primacy effect persisted throughout testing (Exp 3). Similarly, in explicit tests of free recall, primacy effects were consistently observed, both with immediate testing (Exps 1 and 3) and when testing followed a filled delay (Exp 2). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recall and stem-completion priming have different electrophysiological correlates and are modified differentially by directed forgetting.

The notion that different aspects of memory are assessed by explicit and implicit memory tests was supported by behavioral and electrophysiological results. In a study–test procedure, 24 Ss were instructed to remember some words and to forget other words. Free recall and cued recall were better for words associated with the remember instruction, whereas directed forgetting did not influence stem completion (an implicit memory test). Event-related brain potentials elicited during study differed as a function of subsequent memory performance for free recall and cued recall, but not for stem completion. These results implicate encoding differences in the distinction between the 2 types of memory test. Factors governing whether explicit retrieval affects performance on an implicit memory test, mechanisms that may underlie directed-forgetting effects, and the importance of electrophysiological correlates of memory are also discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Differential effects of aging and Alzheimer's disease on conceptual implicit and explicit memory.

The effects of aging and Alzheimer's disease (AD) on conceptual explicit and implicit memory were examined. Three groups of participants patients with AD; age-matched, older control participants; and younger control participants made deep (semantic) or shallow (nonsemantic) judgments about low-dominant category exemplars. Explicit memory was measured by category cued recall and implicit memory was measured by priming on a category-exemplar generation task. Younger participants had enhanced cued recall and priming following deep, relative to shallow, encoding; this indicated that both memory measures were conceptually driven. Aging reduced explicit, but not implicit, test performance, and it did not reduce conceptually driven processes for either test. In contrast, AD reduced explicit and implicit test performance, and it impaired conceptually driven memory processes for both tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparing word fragment completion and cued recall with letter cues.

Cued recall with word stems as cues and fragment completion rely on different types of letter cues and also differ in the explicit–implicit nature of the retrieval orientation. Despite these differences, variables effective in one task may be effective in the other because both rely on letter cues. Two variables known to affect cued recall were manipulated: Lexical set size (number of words that fit the letter cue) and meaning set size (number of associates generated to the studied words). Across four experiments, subjects in each task were less likely to recover targets from larger lexical sets. However, meaning set size affected cued recall but not fragment completion. These results indicate that fragment completion and letter-cued recall are based on lexical search but that cued recall also involves a semantic search component. Furthermore, type of retrieval cue had a greater effect than type of retrieval orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of age on state of awareness following implicit and explicit word-association tasks.

Younger and older participants did word-association tasks after implicit and explicit instructions and a read-generate study manipulation. No age differences were shown in the implicit version of the test. A generation effect for both age groups suggested that word-association priming can be classified as a conceptually driven task and a new task at which older adults show a relatively preserved memory function. However, the younger group did better on the explicit test in the generate condition. Participants were asked to examine their implicitly produced responses to make them accessible to conscious retrieval. Remember (R) and Know (K) measures of conscious awareness were applied to both postimplicit and postexplicit word-association responses. Age and awareness showed opposite effects in postimplicit retrieval. Younger participants tended to make more R responses than did the older adults, and K responses did not vary with age, but the older group was unaware of more primed items as study list members. Age differences were also shown in R but not in K responses after word-association cued recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of reducing attentional resources on implicit and explicit memory after severe traumatic brain injury.

Implicit and explicit memory were examined in individuals with severe traumatic brain injury (TBI) under conditions of full and divided attention. Participants included 12 individuals with severe TBI and 12 matched controls. In Experiment 1, participants carried out an implicit test of word-stem completion and an explicit test of cued recall. Results demonstrated that TBI participants exhibited impaired explicit memory but preserved implicit memory. In Experiment 2, a significant reduction in the explicit memory performance of both TBI and control participants, as well as a significant decrease in the implicit memory performance of TBI participants, was achieved by reducing attentional resources at encoding. These results indicated that performance on an implicit task of word-stem completion may require the availability of additional attentional resources that are not preserved after severe TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form-specific explicit and implicit memory in the right cerebral hemisphere.

Results from 2 divided visual field (DVF) experiments indicate that in some conditions both explicit and implicit memory are greater when same-letter-case stimuli are presented directly to the right cerebral hemisphere (in the left visual field) than when they are presented directly to the left (in the right visual field). Explicit memory was measured with word-stem cued recall, and implicit memory was measured with word-stem completion priming. Words were presented centrally during encoding, and word stems were presented directly to the right hemisphere or to the left hemisphere during testing. Results for explicit memory contrast with findings from a previous DVF study that used a different procedure, those for implicit memory replicate previous DVF findings, and both results corroborate positron emission tomography findings. It is suggested that a form-specific system in the right hemisphere may contribute to both explicit and implicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of surface and conceptual information to performance on implicit and explicit memory tasks.

Four experiments examined the effects of perceptual and conceptual processing operations on 2 implicit and 2 explicit memory tasks. Results show an advantage of visual over auditory presentation for word-fragment completion, word-stem completion, and word-stem cued recall; there was no such advantage in recognition memory. Conceptual processing had no effect on the implicit tasks, a small effect on word-stem cued recall, and a large effect on recognition. It is concluded that there is no necessary trade-off between the 2 types of information. Speculatively, the use of perceptual information may be all or none and relatively automatic, whereas the use of conceptual information appears to be graded and more under conscious control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of forgetting in an implicit and explicit memory task.

Among possible criteria for distinguishing separate memory systems for implicit and explicit memory is that of substantial differences in either the form or rate of forgetting. Prior literature has claimed both differential forgetting and equivalent forgetting for implicit and explicit tasks. Existing experimental data for word-stem completion and explicit control tasks were reviewed and shown to be inconclusive. Our experiments measure forgetting in comparable implicit and explicit memory tasks of stem completion and stem cued recall. The form and the rate of forgetting are essentially the same for these implicit and explicit tasks. Levels of processing and task conditions differ only in the level of initial learning or availability. Thus, either the implicit and explicit task reflect traces in the same memory system or they reflect traces in different systems that have identical forgetting dynamics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

One-trial associative priming of nonwords in young and older adults.

In this article, three experiments in which single-trial associative priming for nonwords was investigated in young and older adults in a pronunciation task are reported. During an encoding task, associative priming was observed for young and older adults, although cued recall was near zero for both groups. Associative priming for young and older adults was found under full attention conditions, but when attention was divided at study, associative priming was observed in Experiment 3, but not in Experiment 2. Divided attention also disrupted recognition memory for new associations in young and older adults. The results limit the generality of findings of age-related decrements in associative priming by showing an absence of such decrements in tasks that do not require elaborative processing during encoding. They also argue against G. Musen and L. Squire's (see record 1993-34212-001) suggestion that formation of new connections in implicit memory requires multiple study opportunities, whereas declarative memory is specialized for rapid acquisition of new associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in explicit and implicit memory for pictures.

In the present study, the authors examined age effects in memory for nonverbal material. A picture fragment completion task was used to test explicit and implicit memory in a younger and an older group. Explicit memory was indexed by free recall of pictures, whereas implicit memory was indexed by perceptual learning (priming). Both free recall and perceptual learning performance were found to be impaired in the older group. A measure of executive functioning was found to be predictive of both explicit and implicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A further examination of the time-dependent effects of oxazepam and lorazepam on implicit and explicit memory

Until recently, research indicated that all benzodiazepines impair explicit memory, while only lorazepam impairs priming. Stewart and associates provided preliminary data which indicated that both oxazepam and lorazepam may impair implicit memory, but in a time-dependent fashion. The present study was designed to replicate Stewart et al.'s findings after overcoming several limitations of the original study. Thirty subjects were administered an acute dose of lorazepam (2 mg), oxazepam (30 mg) or a placebo and were tested with an implicit (word-stem completion) test and an explicit (cued recall) test. However, subjects were only tested at 170 min post-drug (close to oxazepam's theoretical peak concentration) to rule out the possible "explicit memory contamination" explanation of the Stewart et al. implicit memory findings. Consistent with previous research, both drugs impaired explicit memory relative to placebo. Also, both lorazepam and oxazepam impaired priming performance, supporting the "time-dependence" interpretation of the Stewart et al. findings. The results also indicate that episodic memory is impaired by both benzodiazepines in a time-dependent fashion even when the research methodology used involves everyday memory demands.     

Exact and conceptual repetition dissociate conceptual memory tests: Problems for transfer appropriate processing theory.

Tested whether a conceptual implicit memory test exhibited repetition effects similar to those found in free recall. 555 Ss participated in 3 experiments. In Exp 1, Ss rated a series of target words and their associates according to their degree of pleasantness in the implicit word-fragment completion and cued recall, and category cued and free recall tests. In Exp 2, Air Force recruits were tested on the category instance generation (CIG) and 4 additional tests in Exp 1. Exp 3 tested the Ss for CIG or category cued recall using instructions for relational process. Both CIG and category cued recall exhibited conceptual repetition effects. Category cued recall showed important differences between CIG and free recall. Theoretical implications are discussed. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The attentional demands of encoding and retrieval in younger and older adults: I. Evidence from divided attention costs.

Four studies examined the effects of divided attention in younger and older adults. Attention was divided at encoding or retrieval in free recall (Experiment 1), cued recall (Experiments 2 and 3), and recognition (Experiment 4). Dividing attention at encoding disrupted memory performance equally for the two age groups; by contrast, for both age groups, dividing attention at retrieval had little or no effect on memory performance. Secondary task reaction times (RTs) were slowed to a greater extent for the older adults than for the younger adults, especially at retrieval. Age-related differences in RTs costs at retrieval were largest in free recall, smaller in cued recall, and smallest in recognition. These results provide evidence for an age-related increase in the attentional demands of encoding and retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of automatic associative activation on explicit and implicit memory tests.

Ss made either a graphemic or a semantic decision concerning word pairs during a study phase. Pair relatedness effects were observed in behavioral measures for the semantic task only, but a physiological measure (event-related potential) showed relatedness effects for both study tasks. Relatedness at study helped subsequent memory for tests involving word generation (fragment completion and cued recall). These effects were independent of those of the level of processing on memory. The results support P. Graf and G. Mandler's (1984) 2-process model of implicit and explicit remembering and demonstrate that automatically activated associations can have significant effects on both types of remembering. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A test of the frontal lobe functioning hypothesis of age deficits in production priming.

Older adults have been hypothesized to show reduced priming relative to younger adults on implicit memory tests that require production of a response because these tasks place high demands on attentional processes associated with frontal lobe function, which are often reduced with age (see D. A. Fleischman & J. D. E. Gabrieli, 1998). The current study directly tested this frontal lobe hypothesis of age effects in production priming. Younger adults and older adults who differed in their attentional abilities as measured by a battery of neuropsychological tests were given two production priming tasks, word stem completion and category production, followed by explicit free recall tests. Results showed that explicit memory performance was reduced by age and older adults' frontal functioning. Age and frontal functioning influenced category production priming but not word stem completion priming. Results failed to support the frontal account of age reductions in production priming. Instead, results implicate the influence of other processes often involved in production priming tasks, such as explicit memory strategies and response competition, as critical for understanding age effects in implicit memory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Skill learning in the elderly: Diminished implicit and explicit memory for a motor sequence.

Studied explicit and implicit memory for a cognitive-motor sequence in elderly and young adults. Implicit memory was examined in a serial reaction time (RT) paradigm in which sequences of hand postures repeated cyclically, then shifted to random sequences. Two control groups received random sequences throughout. Movement times (MTs) across the 1st 4 blocks did not improve more in the elderly-repeated than in the elderly-random group. In contrast, the young-repeated group showed greater improvement in MT across these blocks than the young-random group. MT was less affected in the elderly than in the young by shifts between repeated and random sequences, indicating impaired implicit memory. Explicit memory, which was assessed by free recall and cued recall, also was impaired in the elderly. Diminished implicit memory in the elderly could not be explained solely by the possible intrusion of conscious recollection strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)