The original version ofthe counter modeljorperceptual identification assumed that word frequency and prior study act solely to bias the identification process (i.e., subjects have a tendency to prefer high-frequency and studied low-frequency words, irrespective of the presented word). In a recent study, using a two-alternative forced-choice paradigm, we showed an enhanced discriminability effect for high-frequency and studied low-frequency words When subjects identify briefly flashed words, their performance is affected if they have studied the flashed word previously, even though they have no explicit recollection of the study episode. This effect of long-term priming in implicit memory has attracted attention from several theorists (Bowers, 1999;Masson & Bodner, 2000;Masson & MacLeod, 1996;Schacter, 1994). proposed an original and quantitative account of such implicit memory phenomena. Using a two-alternative forced-choice paradigm (e.g., LIED is briefly flashed and masked, followed by preRene Zeelenberg was supported by a grant from the Foundation for Behavioral and Social Sciences of the Netherlands Organization for Scientific Research. We thank Rich Shiffrin for helpful discussions and comments on an earlier draft of this paper. Correspondence concerning this article can be addressed to E.-J. M. Wagenmakers or R. Zeelenberg, Department of Psychonomics, Roetersstraat 15, 1018 WB Amsterdam, The Netherlands (e-mail: pn_wagenmakers@macmail.psy.uva.nl or pn_zeelenberg@macmail.psy.uva.nl).sentation of the response alternatives LIED and DIED), Ratcliff and McKoon claimed that subjects tended to prefer the studied alternative, regardless of whether that alternative had been flashed or not. Such a tendency would lead to benefits when the target (e.g., LIED) had been studied, but to costs when the foil (e.g., DIED) had been studied. Further, they found that the size ofthe benefits about equaled the size of the costs (e.g., Ratcliff, Allbritton, & McKoon, 1997;Rouder, Ratcliff, & McKoon, 2000). Hence, the effect of prior study was supposed to reflect a bias rather than some kind of enhancedperceptualprocessing of the flashed word.I Additional evidence for this idea came from the observation that even if performance was at chance when neither alternative was studied, effects of prior study were still present and thus appeared to be independent of information extracted from the flashed stimulus. Similarly, subjects had a preference to choose a high-frequency (HF) alternative such as MILE over a low-frequency (LF) alternative such as TILE. Therefore, effects of word frequency were likewise attributed solely to bias. Importantly, the biases for prior study and word frequency are supposedly mediated by different mechanisms, an issue debated by Wagenmakers, Zeelenberg, and Raaijmakers (2000). Wewill return to this later. For ease of reference, we will term the original version of the counter model the counter model I.The counter model I is one of the few models to provide a quantitative account of repetition priming effe...