Absence tasks of the set-size effect in memory-search in the absence of a preprobe delay

In the traditional Sternberg (1966) paradigm, response latency increases linearly with increases in the size of the positive set (the set-size effect). The results of four experiments converge on the conclusion that this set-size effect depends on a delay before the presentation of the memory probe. In Experiment 1, subjects were required to respond as soon as a repetition occurred in a series of digits. Despite the similarity of this task to memory-search tasks that invariably show set-size effects, there was no increase in response latency with increasing series length. Neither the inclusion of negative trials (Experiment 2) nor the explicit designation of the test digit (Experiment 3) resulted in the typical set-size effect. However, the introduction of a 1-sec preprobe delay (Experiment 4) resulted in a set-size effect of 31 msec/item.