Effects of amount and kind of prior target-uncertainty reduction in the repeated presentations paradigm

Single letters were presented for varying numbers of repeated brief exposures. The S reported on the target after each presentation, identifying only those symbols perceived with certainty. A d’ analysis of the results revealed that target-uncertainty reduction produced significant facilitation in the average level of perceptual sensitivity only in a condition in which the target symbol was exposed prior to each trial. Prior knowledge of the target symbol without prior exposure produced a measurable, but nonsignificant, facilitation in sensitivity. The data suggested that the growth curve normally associated with the repeated-presentations paradigm may be the result of a progressive liberalization of the S’s criterion for reporting in some studies. The data further showed that prior exposure and perhaps prior knowledge can significantly alter the shape of the repetition curve when the target is a single letter. These findings were interpreted as an indication that both amount and kind of target-uncertainty reduction can produce significant changes in the repetition effect for single letters.