Uncertainty, timekeeping, and simple reaction time

Implications of the hypothesis that effects on simple RT of event and time uncertainty are due to S's unwillingness to prepare for an unlikely event were tested. In 2 experiments, RT was compared for the foreperiod method and the new transit-signal method. Alternative hypotheses based on faulty reinstatement of foreperiods were invalidated. The inverse relation of RT to event uncertainty persisted for the transit-signal method which is free of memory effects. With time uncertainty the initial gradient of RT was steeper with the transit-signal method. There S had before him exact time information for estimating momentary probability of a signal. The uncertainty effect occurred even though it was evident that S could overcome it, so the term unwillingness is appropriate. Consequences of inaccurate timekeeping were examined; the contention that it simply and invariably increases RT was not supported. Unwillingness was examined in terms of the utility associated with preparation.