Effects of background symmetry on same-different pattern matching: a compromise-criteria account.

Two experiments are reported, which were designed to test predictions of an account of same-different matching that assumes that bilaterally symmetric backgrounds provide extraneous evidence toward same, whereas asymmetric backgrounds provide evidence toward different. When all backgrounds within a block of trials are of the same type, appropriate adjustments of response criteria can be made to accommodate the irrelevant evidence and thus maintain acceptable levels of accuracy. However, when backgrounds of different types are mixed randomly, compromise criteria are adopted. This compromise-criteria account predicts distinctive interaction patterns for reaction times when blocked versus mixed presentations of various background types are compared. The predicted interactions were obtained for asymmetric- and no-noise backgrounds in Experiment 1 and for symmetric-, asymmetric-, and no-noise backgrounds in Experiment 2. The findings support the general view that extraneous display attributes are weighted into the evidence for same and different, with criteria settings used that minimize errors under the noisiest conditions.