Ellen R. Stoltzfus’s research while affiliated with University of South Carolina and other places

Three experiments examined whether negative priming is a dually determined effect produced by inhibitory mechanisms and by a memorial process. Younger adults (Experiment 1) and older adults (Experiments 1-3) were tested in procedures that varied the likelihood of inducing retrieval of the prior trial. This was done by making test-trial target decoding difficult (Experiments 1 & 2) or by making prior information useful on some nonnegative priming trials (Experiment 3). Younger adults demonstrated negative priming under retrieval and nonretrieval conditions, with patterns of performance indicating different sources of negative priming effects. Older adults showed negative priming only under retrieval-inducing conditions, consistent with the view of deficient inhibitory mechanisms for older adults. The data suggest that contextual variables critically determine whether negative priming is largely due to inhibition or to episodic retrieval.

This chapter discusses the status of the inhibitory view of working memory and its relation to aging. It considers evidence for the conceptualizations of working memory that stress its purported limited capacity and presents an alternative view which focuses on the inhibitory control of the contents of working memory. The chapter also discusses current research evidence concerning adult age differences in attention, memory, and language.

The purpose of this book is to compare and contrast different conceptions of working memory. This is one of the most important notions to have informed cognitive psychology over the last twenty years, and it has been used in a wide variety of ways. This, in part, is because contemporary usage of the phrase "working memory" encapsulates various themes that have appeared at different points in the history of research into human memory and cognition. The book presents three dominant views of working memory.

In two experiments, the pattern of persistence of negative priming effects across delay intervals of 500 and 2,500 msec was assessed using a within-subjects, random sequencing of delays. Neill and Valdes (1992; Neill, Valdes, Terry, & Gorfein, 1992) have argued that a within-subject experimental design is required for decay of negative priming to be seen, in contrast to results reported elsewhere (e.g., Tipper, Weaver, Cameron, Brehaut, & Bastedo, 1991) showing stable negative priming effects across delays. In neither experiment was substantial evidence of decay detected, raising questions for the notion that suppression necessarily declines across brief temporal intervals and for the assertion that episodic retrieval is the sole source of negative priming.

Two experiments sought to elicit distractor suppression in older adults (aged 62–78 yrs). Exp 1 used a procedure that increased suppression in younger adults (aged 17–25 yrs), thus creating a more sensitive measure of suppression in older adults. To compensate for older adults' slowed processing, Exp 2 used a longer stimulus exposure duration. Neither experiment produced suppression in older adults; both experiments, however, included trial types that elicited parallel facilitatory effects for both age groups. Older adults thus seemed to process distractors but failed to engage inhibitory mechanisms in their rejection of distracting stimuli. Finally, both experiments tested the relationships among suppression, interference, and everyday cognitive failure. Neither experiment suggested relationships between reaction time (RT) effects and self-reported cognitive lapses. Results are discussed within L. Hasher and R. T. Zacks's (1988) attentional framework. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Across two studies comparing younger and older adults, age differences in optimal performance periods were identified (Study 1), and then shown to be an important determinant of memory differences (Study 2). A norming study showed that while most younger adults were Evening or Neutral types, as determined by a standard questionnaire, the vast majority of older adults were Morning types. A second study compared the recognition performance of younger and older adults tested in the morning or in the late afternoon. Substantial age differences were found in the late afternoon, when younger but not older adults were at their optimal times. However, no age differences in memory performance were found in the morning, when older but not younger adults were at their peak period. Thus, synchrony between optimal performance periods and the time at which testing is conducted may well be a critical variable in determining group differences in intellectual performance, particularly between older and younger adults.

Previous work (Hasher, Stoltzfus, Zacks, & Rypma, 1991) suggested the existence of adult age-related differences in the ability to suppress or inhibit irrelevant information. This investigation explored age differences in the time course of suppression. Experiments 1 and 2 showed that younger adults demonstrate the same level of suppression at 300 as they do at 1,700 ms after a selection response. Older adults consistently show no suppression. Experiments 2 and 3 also examined the relationship between suppression and the degree to which distractors interfere with concurrent selection. The absence of a reliable relationship--both within and across age groups--together with other findings in the literature, raise questions about the function of suppression as a mechanism of concurrent selection. Another function, one that aids in the establishment of a coherent thought stream, is proposed.