Selective preparation and time uncertainty.

Discrete two-choice reaction time experiments were performed under two time-uncertainty conditions provided by constant foreperiods of either 5.0 or 0.5 sec. The problem was how to know whether selective preparation may be maintained over time or whether it is a short-term process. Selective preparation of one of the two stimuli was induced through monetary incentive in Experiment 1 and through frequency unbalance in Experiment 4, it was assessed through prediction in Experiments 3 and 4. With all three manipulations the effects of selective preparation and of time uncertainty were found to combine additively. Those results support the idea that selective preparation can be maintained over time. On the other hand, the improvement in reaction time due to a reduction of time uncertainty is achieved by a short-term preparatory adjustment which is not stimulus-specific.