Mental Set and Mental Shift Revisited

In 1927, Jersild found that alternately subtracting 3 from a two-digit number and giving the common opposite to a word in a mixed list of numbers and words was faster than the average speed of subtracting 3s from a pure list of numbers and giving the opposites to a pure list of words. Experiment I replicated those findings: mixed lists were slightly, albeit nonsignificantly, faster than pure lists. Experiments II, III, and IV were designed to determine why changes of set did not slow performance on mixed lists: the results suggest that a shift of operations will take little or no time if the stimulus can serve as a retrieval cue for the operation to be performed on it. But changes of set will have a large effect when the selection of the appropriate operation requires that one keep track of previously performed operations.