Priming is not all bias: Commentary on Ratcliff and McKoon (1997)

R. Ratcliff and G. McKoon (1997) reported a set of findings they claim is inconsistent with all prior accounts of long-term priming, including (a) a pattern of benefits and costs in an identification task suggestive of a bias interpretation of priming and (b) a restriction on priming such that benefits and costs are obtained only when the alternatives in the forced-choice task are similar. On the basis of these and related findings, Ratcliff and McKoon developed a bias theory of visual word priming that is implemented in a mathematical model. However, the present article shows that their empirical findings are ambiguous and can be explained more parsimoniously within more traditional frameworks. Furthermore, 8 studies are reported that directly contradict their model. On the basis of these and related findings, it is argued that priming is best understood as a by-product of learning within perceptual systems whose main function is to categorize inputs.