Discriminability and bias in the word-superiority effect

Abstract

Functions relating four-alternative, forced-choice recognition of target letters to exposure duration were obtained in word (W), pronounceable-nonword (PN), and unpronounceable-nonword (UN) contexts. Advantages were found for letters in W over letters in PN contexts and for letters in both W and PN over letters in UN contexts, with uniformly large effects when displays were terminated by pattern masks but small or absent effects when there was no postmask. Analyses in terms of models that allow separate estimates of discriminability and bias effects showed that both contributed strongly to the advantage of W and PN over UN contexts with generally close parallelism of discriminability and bias measures over types of context, mask condition, and display duration. The findings are interpreted in terms of a two-stage conception of letter processing, with the effects of context localized in the competition among character representations for transition from the early parallel stage (visual buffer) to the later serial stage (working memory). The better recognition of letters in words and pronounceable nonwords is attributed to their advantage in competition for access to working memory, which is conferred by the encoding of familiar letter groups as units. © 1987 Psychonomic Society, Inc.