The effect of set on encoding and rehearsal processes in memory.

An experiment was conducted to determine the effect of manipulating S's preparation for what he will see on a given trial on his ability to mentally keep track of the number of occurrences of each of several different stimuli in a sequence. It was found that, when the same stimuli were used from trial to trial, performance was significantly better than when different stimuli were used. Foreknowledge of the specific stimuli to be used on a given trial did little to improve performance per se, but it did reduce labeling errors. The results were discussed in terms of the "spatial window" model of keeping-track performance.