The use of correlated stimulus information in card sorting

Subjects were required to sort three packs of cards into six piles. On the cards of one pack were a number (one to six) of xs. In the second pack the cards had a single digit (1 to 6). On the third pack the two kinds of information were perfectly correlated, i.e., there were three 3s, four 4s, etc. This pack was sorted more quickly than either of the other two. It is provisionally concluded that the Ss were processing information in parallel rather than serially, and that evidence from two sensory analyzers was being combined rather than the outcome from two decision mechanisms. This conclusion is tempered by the observation that only a detailed study of the reaction times to individual stimuli can provide us with an unqualifled verdict.