Timing of expectancy peak in simple reaction time situation

The present study attempted to determine the moment of the peak expectancy of the imperative stimulus in a simple reaction-time situation with constant foreperiods of 0.25, 0.5, 1, 2 and 4 sec. Four Ss were instructed to indicate the expected moment of the presentation of the imperative stimulus by a key press, i.e., to try to synchronize the key press with the onset of the imperative stimulus. Also a parallel simple reaction-time task was given using these foreperiods. It was found that when the foreperiod was prolonged from 0.5 sec on, the accuracy of prediction of the moment of the imperative stimulus as well as the reaction speed were continuously decreased.