<p>Anticipating the occurrence of a future event is an ability that helps people prepare for various daily activities. This preparation is regarded as a non-specific process because it is initiated by a warning signal that does not contain specific information about the critical event. Previous research reported that the intertrial repetition of a stimulus-response event in a choice-reaction task shortened the reaction time more at the short foreperiod (interval between the end of the warning signal and onset of the target stimulus). I conducted four experiments to investigate whether the interaction was due to the event sequence effect being overridden by preparation processes (“overriding” hypothesis) or the quick-decaying characteristic of the event sequence effect itself (“quick-decay” hypothesis). Experiments 1 and 2 manipulated the relative magnitudes of the preparation effect by changing how foreperiods were distributed within a trial block. The results showed similar asymmetric event sequence effects, which indicated that whether preparation was better at the short or long foreperiod did not affect the event-based modulation. Experiment 3 manipulated the temporal distance between two consecutive stimulus-response events across trial blocks and found that the asymmetric event-based modulation on preparation was diminished by a long enough inter-trial interval. The final experiment compared alerting trials with no-alerting trials and found an asymmetric event-based modulation caused by the absence of repetition benefit in a certain context (an alerting trial preceded by a no-alerting trial). Therefore, the event sequence effect is not directly related to “nonspecific preparation”, but this event-specific component could be embedded in the measurement of preparation in some scenarios, which could lead to misinterpretation of the preparation effect itself. This finding clarifies the mechanism underlying the interaction between preparation and event sequence. The conclusion also questions the validity of the current measures of nonspecific preparation, including temporal preparation and phasic alertness.</p>