Academic journal article Memory & Cognition

Performance Benefits and Costs in Forced Choice Perceptual Identification in Amnesia: Effects of Prior Exposure and Word Frequency

Academic journal article Memory & Cognition

Performance Benefits and Costs in Forced Choice Perceptual Identification in Amnesia: Effects of Prior Exposure and Word Frequency

Article excerpt

Accuracy in identifying a perceptually degraded word (e.g., stake) can be either enhanced by recent exposure to the same stimulus or reduced by recent exposure to a similar stimulus (e.g., stare). In the present study, we explored the mechanisms underlying these benefits and costs by examining the performance of amnesic and control groups in a forced choice perceptual identification (FCPI) task in which briefly flashed words (that were identical to studied words, similar to studied words, or new) had to be identified, and two response choices were provided that differed from each other by one letter. Control participants showed a performance benefit and cost in FCPI with both high- and low-frequency words. Amnesic participants showed a benefit (but no cost) with high-frequency words and a benefit and a cost with low-frequency words. The benefit/cost pattern with low-frequency words in amnesia was obtained even when the to-be-identified stimulus in the FCPI task was eliminated (Experiment 2), suggesting that this effect was driven by processes operating at the level of the response choices. Our findings suggest that implicit memory effects in FCPI reflect the operation of multiple mechanisms, the relative contributions of which may vary with the frequency of the test stimuli. The results also highlight the need for caution in interpreting results from normal participants in the FCPI task, since those findings may reflect a contribution of explicit memory processes.

Accuracy in identifying words and pictures can be affected by recent exposure to the same words or pictures. Importantly, this priming effect can occur even in the absence of explicit memory for the prior encounter with the stimuli: Priming effects are preserved in amnesic participants who have impaired explicit memory for recently encountered stimuli (for a review, see Verfaellie & Keane, 2001), and priming is often unaffected by experimental manipulations that reduce the availability of explicit memory in control participants (Roediger & McDermott, 1993). One of the major theoretical goals of memory research over the past several decades has been to understand the nature of the implicit memory processes that support priming effects. Although priming effects may reflect perceptual or conceptual processes (Blaxton, 1989; Roediger & Blaxton, 1987), much of the theoretical work in the field has been concerned with perceptual-priming effects (Graf & Ryan, 1990; Moscovitch, Goshen-Gottstein, & Vriezen, 1994; Schacter, 1990, 1992), and those effects form the basis of the present discussion.

For many years, theoretical and functional accounts of priming focused on the essentially beneficial nature of the phenomenon. Priming was thought to reflect the experience-dependent enhancement or tuning of processes that support accurate identification of words and objects (e.g., Tulving & Schacter, 1990). Thus, it has been said that "priming in the perception of particular objects or words exists to improve the identification process after an initial occasion" (Roediger, 2003, p. 14). On this view, priming reflects enhanced perceptual discriminability of (or enhanced sensitivity to) recently encountered stimuli. Indeed, the literature is replete with demonstrations of priming-induced enhancements in stimulus identification accuracy.

A growing body of evidence, however, demonstrates that priming may be associated with performance costs as well as benefits. One of the paradigms used most frequently to demonstrate these costs and benefits is the forced choice perceptual identification (FCPI) task introduced by Ratcliff, McKoon, and Verwoerd (1989). The stimuli in this paradigm are word pairs that differ from each other by one letter (e.g., case-care). For each pair, either one member or neither member is presented to participants in a study phase. In a subsequent FCPI task, words are flashed very briefly on a computer screen and are followed by two response choices, including the flashed word and its orthographic mate. …

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