CONTEXTUAL CONTROL OF ACCRUAL THRESHOLDS
Current theories of decision processing in a wide variety of binary choice tasks posit some form of evidence accumulation over time until a threshold or criterion is reached. In the context of discrimination of visual extent, we show that evidence accrual criteria for any particular stimulus pair are dependent upon the overall, global, difficulty context. In particular, response times (RTs) on a target set of stimulus pairs of moderate difficulty were increased when embedded in a difficult context. Moreover, when easy to discriminate pairs were included along with difficult pairs, RTs were the same as when in a difficult context alone, consistent with the additional finding that target pair RTs were uninfluenced by the inclusion of easy pairs. Thus, the most difficult stimulus pair encountered over the course of the experiment controls evidence accrual criteria. The absence of contextual effects on either discriminative accuracy or confidence ratings is also entirely consistent with the Slow and Fast Guessing theory (Petrusic, 1992) based views of contextual difficulty effects.