Jeffrey P. Toth

Separating conscious and unconscious influences of memory: Measuring recollection

How can conscious and unconscious influences of memory be measured? In this article, a processdissociation procedure (L. L. Jacoby, 1991) was used to separate automatic (unconscious) and consciously controlled influences within a task. For recall cued with word stems, automatic influences of memory (a) remained invariant across manipulations of attention that substantially reduced conscious recollection and (b) were highly dependent on perceptual similarity from study to test. Comparisons with results obtained through an indirect test show the advantages of the process-dissociation procedure as a means of measuring unconscious influences. The measure of recollection derived from this procedure is superior to measures gained from classic test theory and signal-detection theory. The process-dissociation procedure combines assumptions from these 2 traditional approaches to measuring memory. Dissociations between performance on direct and indirect tests of memory supply examples of effects of the past in the absence of remembering (for reviews, see Hintzman, 1990; Richardson-Klavehn & Bjork, 1988). In an indirect test, subjects are not asked to report on memory for an event as they would be in a direct test, such as in a test of recognition or recall; rather, they engage in some task that can indirectly reflect memory for the occurrence of that event. Word stemand fragment-completion tasks are among the most popular indirect tests of memory (e.g., Graf & Mandler, 1984; Tulving, Schacter & Stark, 1982; Warrington & Weiskrantz, 1974). For a stem-completion task, subjects might read the word scalp and then be presented with the stem sea— with instructions to complete that stem with the first word that comes to mind. Evidence of automatic influences of memory that are dissociated from performance on a direct test is provided by the finding that prior presentation of a word increases the likelihood of that word being used to complete a stem, even though a direct test reveals no memory for the prior presentation of the word. Some of the most striking examples of dissociations come from the performance of patients suffering a neurological deficit. Korsakoff amnesics, for example, show near-normal effects of memory in their performance of a stem-completion task, even though

Unconscious influences revealed: Attention, awareness, and control.

Recent findings of dissociations between direct and indirect tests of memory and perception have renewed enthusiasm for the study of unconscious processing. The authors argue that such findings are heir to the same problems of interpretation as are earlier evidence of unconscious influences--namely, one cannot eliminate the possibility that conscious processes contaminated the measure of unconscious processes. To solve this problem, the authors define unconscious influences in terms of lack of conscious control and then describe a process dissociation procedure that yields separate quantitative estimates of the concurrent contributions of unconscious and consciously controlled processing to task performance. This technique allows one to go beyond demonstrating the existence of unconscious processes to examine factors that determine their magnitude.

Toward a Redefinition of Implicit Memory: Process Dissociations Following Elaborative Processing and Self-Generation

Does conceptual processing affect unconscious uses of memory? We used a process-dissociation procedure to separate automatic (unconscious) and consciously controlled uses of memory in a stem-completion task. Contrary to results from indirect test conditions, estimates derived from our procedure showed no effect of self-generation and no differential effect of semantic and nonsemantic study conditions on automatic uses of memory. These results provide evidence that (a) indirect tests are often contaminated by conscious uses of memory and (b) stem completion is highly dependent on prior perceptual (and perhaps lexical) processing. The experiments demonstrate the advantages of using process-dissociation procedures over comparisons between direct and indirect tests.

Aging, subjective experience, and cognitive control: Dramatic false remembering by older adults

Recent research suggests that older adults are more susceptible to interference effects than are young adults; however, that research has failed to equate differences in original learning. In 4 experiments, the authors show that older adults are more susceptible to interference effects produced by a misleading prime. Even when original learning was equated, older adults were 10 times as likely to falsely remember misleading information and were much less likely to increase their accuracy by opting not to answer under conditions of free responding. The results are well described by a multinomial model that postulates multiple modes of cognitive control. According to that model, older adults are likely to be captured by misleading information, a form of goal neglect or deficit in inhibitory functions.

Effects of Aging on Efficiency of Task Switching in a Variant of the Trail Making Test

The Trail Making Test (TMT; R. M. Reitan, 1958, 1992) is extensively used in research in neuropsychology and in aging, in part because it has been postulated to reflect executive processes, such as planning and switching. However, neurocognitive and individual-difference-based analyses of this test are complicated because of different spatial arrangements of targets, the use of letters only in Version B, and potential order effects when Version A is administered prior to Version B. The present article examines a variant of a TMT (called the Connections Test) that attempts to remedy these deficiencies. A structural equation model suggested that there were no direct effects of age on either the nonalternating or alternating versions of the Connections Test (analogous to TMT Versions A and B, respectively); rather, all age-related effects were mediated through effects on perceptual speed. Moreover, although the nonalternating and alternating versions were strongly related to one another, only the latter had significant independent relations with measures of higher order cognition.

Multiple levels of control in the Stroop task

Multiple levels of control may be used in service of reducing Stroop interference. One is list-wide, whereby interference is reduced strategically in lists that include disproportionately more incongruent trials. A second, item-specific control is observed when proportion congruence is manipulated at the level of items. Item-specific control reduces interference for mostly incongruent relative to mostly congruent items. First, we show that item-specific control may drive both list-wide and item-specific proportion congruence effects (Experiment 1). We then show that item-specific control affects Stroop interference similarly when a single feature (a word) as opposed to a feature combination (a word 1 font type) signals proportion congruence (Experiment 2). Although this suggests that font type offers little advantage for controlling Stroop interference beyond the word, a novel, font-specific proportion congruence effect is observed in Experiment 3, indicating that font type can be used to control interference. These findings support the idea that multiple levels of control are used in reducing Stroop interference.

Perceptual identification, fragment completion, and free recall: concepts and data.

The effects of orthographically distinctive and orthographically common words were compared on tests of free recall, fragment completion, perceptual identification, and lexical decision. Orthographic distinctiveness is argued to effect data-driven processing and, in light of recent theory, should have little effect upon free recall but substantial effects upon fragment completion and perceptual identification. The results showed superior recall and fragment completion of orthographically distinctive words but more accurate perceptual identification of orthographically common words. Latency of lexical decision was longer for orthographically distinctive than for orthographically common words. The visual complexity of orthographically distinctive words may require more extensive sensory processing than is possible within the temporal constraints of perceptual identification tests. The effect of orthographic distinctiveness upon free recall reveals a certain inadequacy in the notion of transfer-appropriate processing.

The Relationship Between Conscious and Unconscious Influences: Independence or Redundancy?

Determining the relationship between conscious and unconscious influences is essential for obtaining valid estimates of the 2 types of influence. S. Joordens and P. M. Merikle (1993) recently argued that a redundancy relationship provides a plausible alternative to the independence model proposed by L. L. Jacoby, J. P. Toth, and A. P. Yonelinas (1993). In this article, the authors address Joordens and Merikles concerns and still find the independence model preferable: First, the redundancy model requires the questionable assumption that a direct test (inclusion) is process pure. Second, results obtained with the independence model, but not with the redundancy model, converge with results from indirect tests. Finally, conclusions drawn from the independence model are in accordance with the theorizing that surrounds the concept of automaticity.

Fluency, familiarity, aging, and the illusion of truth.

ABSTRACT Research has shown that repeated statements are rated as more credible than new statements. However, little research has examined whether such “illusions of truth” can be produced by contextual (nonmnemonic) influences, or compared to the magnitude of these illusions in younger and older adults. In two experiments, we examined how manipulations of perceptual and conceptual fluency influenced truth and familiarity ratings made by young and older adults. Stimuli were claims about companies or products varying in normative familiarity. Results showed only small effects of perceptual fluency on rated truth or familiarity. In contrast, manipulating conceptual fluency via semantic/textual context had much larger effects on rated truth and familiarity, with the effects modulated by normative company familiarity such that fluency biases were larger for lesser-known companies. In both experiments, young and older adults were equally susceptible to fluency-based biases.

A response to graf and komatsu's critique of the process dissociation procedure: When is caution necessary?

Abstract In a recent paper, Graf and Komatsu (1994) argued that the process dissociation procedure (Jacoby, 1991) is limited in its ability to separate and measure conscious and unconscious forms of memory and so should be “handled with caution”. Given that the study of unconscious influences has always posed a difficult problem for memory researchers, we agree with the general emphasis on caution. In this paper, we too advocate caution, especially as it applies to the use of indirect tests, assessing Graf and Komatsus critique, and using the process dissociation procedure. We address the substantive issues raised by Graf and Komatsu and also point out the errors, both factual and logical, in their paper. Any method proposing to provide separate measures of conscious and unconscious influences requires judicious use and a careful examination of its underlying assumptions. The assumptions underlying the process dissociation framework are supported by a large number of experiments spanning a diverse range ...