Abstract
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.