Active selection of items to be remembered: The role of timing

A series of experiments was carried out in which Ss were required to extract critical stimuli from a stream of nine spoken inputs, presented at various rates, and report on these after the presentation of each list. The critical items were normally digits at positions 2, 4, 6, and 8 in the input sequence. Subjects were required to employ either an “active” extraction strategy, aimed at achieving temporary storage only of items to be remembered, or a “passive” strategy, involving storage of all inputs with subsequent extraction of critical items. The initial experiment showed that the active strategy markedly improved performance efficiency as the presentation rate decreased; passive performance remained relatively stable. Experiments 2 and 3 indicated that the level of active performance was higher when critical items were categorically different from unwanted items. There were indications that this effect was independent of the effect of changes in the presentation rate.The final experiments in the series showed that when Ss were denied the opportunity of predicting the time of arrival of critical items active performance hardly benefitted from a reduction in rate.A “controlled activation” process is proposed as a basis for S's ability to modulate his state of alertness, so as to maximize receptivity for critical stimuli arriving at well-defined points in time.