Abstract
Ss judged whether the second of two visually presented letters was the same as the first. In previous experiments of this type the occurrence of the first letter effectively partitioned the letters that could occur second into two sets of unequal size: the single letter to which the correct response would be “same” and several letters to which the correct response would be “different.” In the present experiment, the stimulus set contained only two letters; thus given the occurrence of the first stimulus, one (second) letter would require the response “same” and one would require the response “different.” As in the earlier studies, RTs associated with the decision “same” tended to be shorter than those associated with the decision “different.”