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.

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.

1484The Stroop color-naming task (Stroop, 1935) is well suited for evaluating flexibility in the control of cognitive processes and behavior. In the congruent condition of the task, stimulus word matches stimulus color (e.g., BLUE in blue ink) and participants may rely on well-learned reading processes to produce fast and accurate responding. In the incongruent condition, in contrast, accurate responding requires participants to use cognitive control mechanisms to dampen word reading and activate color-naming processes. The additional time that is taken to name the ink color in the incongruent relative to the congruent condition is referred to as Stroop interference. Although the task might seem relatively simple, the literature is replete with reports of robust Stroop interference effects (for a review, see MacLeod, 1991). Close to 1,000 articles have been published on the topic, yet the control mechanism(s) used to dampen word reading and activate color-naming processes remain to be fully explicated.A complicating (or revealing, as we will argue) factor is the different instantiations (e.g., blocked conditions vs. intermixed trials) of the Stroop color-naming task appearing in the literature. Different task contexts appear to elicit different forms of cognitive control, precluding a unitary account of control mechanisms. Proportion congruence is one prominent factor that influences the control mechanisms that are adopted within a given task. Traditionally, proportion congruence is manipulated at a list-wide level by disproportionately presenting congruent and incongruent trials within a list. Participants can use frequencies to predict what type of trial is most likely to occur next, and control processes can be biased toward (as in a mostly congruent list) or away from (as in a mostly incongruent list) word reading prior to stimulus onset on the basis of these expectancies. Such contexts seem to induce a preparatory, goal-driven control mechanism that is implemented in a sustained fashion across trials (i.e., the bias toward or away from word reading remains constant throughout a list), analogous to the proactive control mechanism recently posited in the dual-mechanisms-of-control account (Braver, Gray, & Burgess, 2007). In contrast, in other task contexts, congruent and incongruent trials occur equally often within a list, and one is unable to anticipate the upcoming trial type and prepare control processes accordingly. These contexts demand a more flexible control mechanism that is capable of modulating word-reading and color-naming processes in a transient fashion on a trial-by-trial basis. Because such modulation occurs after stimulus onset, such a control mechanism must operate rapidly.By this analysis, different cognitive control mechanisms underlie Stroop performance. One control mechanism appears to operate slowly and strategically at a list level, acting prior to stimulus onset. A second appears to operate rapidly at a trial or item-specific level, and acts after the stimulus has been presented. This...

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 Merikle's 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.

(1995) claim to have shown that the independence assumption underlying the process-dissociation procedure (L. L. Jacoby, 1991) is not justified. They argued that correlations between processes at the level of items can result in an underestimation of automatic processes large enough to produce artifactual dissociations between process estimates. In contrast, the authors show that the effects of extremely high correlations at the level of items are likely to be trivial, and not differential across conditions. Curran and Hintzman's dissociations probably reflect violations of boundary conditions for use of the process-dissociation procedure, rather than violations of independence. It is important to distinguish between automatic and consciously controlled memory processes. For example, although amnesic patients are often unable to consciously remember previously presented words on direct memory tests, such as recall or recognition tests, they use the words on indirect memory tests, such as stem-or fragmentcompletion tests, more often than would be expected by chance (Moscovitch, Vriezen, & Gottstein, 1993). Similar dissociations are found in people with normally functioning memory (Roediger & McDermott, 1993). Comparing direct and indirect memory tests has significantly advanced our understanding of automatic and controlled processes. However, performance rarely reflects only one process acting in isolation; that is, controlled processes often influence performance on indirect memory tests (Holender, 1986; Toth, Reingold, & Jacoby, 1994), and automatic processes affect performance on direct memory tests (Jacoby, Toth, & Yonelinas, 1993). The process-dissociation procedure (Jacoby, 1991) was designed to separate automatic and controlled memory processes when both are affecting performance. As a brief introduction to the process-dissociation procedure, consider Experiment IB reported by Jacoby et al. (1993). Subjects studied words under full or divided attention and then were tested with word stems (e.g., mot for