Human schedule-induced cardiovascular response

Sixty-six students were randomly assigned to a vigilance task during which observing responses produced targets according to either a fixed-interval or random-interval 90-sec schedule. During the task, interbeat interval, masseter (EMG) activity, blood pressure and digital blood volume pulse were monitored. Vasoconstriction was initiated within a 4 to 6-sec period following target detection for the majority of subjects assigned to each schedule. Vasomotor tone returned to prechange levels approximately 16 sec after target detection. Transient heart rate increases also occurred during the post-event period, but were more prevalent with subjects in the fixed than in the random-interval group. Post-event masseter activity was exhibited infrequently and only by subjects assigned to the fixed-interval group. The involvement of cardiovascular responsiveness with human schedule-induced behavior and the implications of this involvement for arousal theories of schedule-induced behavior are discussed.