A brief delay decreases perceived similarity and improves discrimination

A same-different discrimination between the colors of 2 halves of a circle was poorer when the halves were viewed simultaneously than when the delay between viewing them was 33 ms. The simultaneous discrimination also produced a poor performance on different stimuli relative to same stimuli in comparison to the successive discrimination. Poor-on-different performance should indicate high perceived similarity. The simultaneous colors were also judged as more similar. The delay did not alter the physical similarity of the colors. Thus, the delay may have decreased assimilation (perceived similarity) and thereby improved discrimination, in support of the hypothesis that perceived similarity frequently affects discrimination.