Role of visual familiarity in the word-superiority effects obtained with the simultaneous-matching task

Three experiments assessed the effect of visual familiarity of words on same-different reaction times (RTs) in a simultaneous-matching task. Visual familiarity was disrupted by using upper- and lowercase letters within sequences. The results for same judgments in Experiments 1 and 2 indicated that visual familiarity was responsible for most of the large word-superiority effect obtained. The third experiment investigated the extent to which the effects obtained with word-frequency and orthographic-regularity manipulations were due to visual familiarity. For same RTs the results indicated both types of familiarity effects were dependent on visual familiarity. With pure-case stimuli, high-frequency words were processed faster than low-frequency words. Low-frequency words and orthographically regular nonwords produced similar reaction times, and both were processed faster than unpronounceable nonwords. These effects were not evident with mixed-case stimuli. All three studies showed visual familiarity to be responsible for differences in slope over sequence length between words and nonwords. Results with different judgments were dissimilar enough from the pattern of results for same judgments to present problems of interpretation, and it was suggested that additional or alternative processes were involved. The implications of these data for models of word processing were discussed.