Effects of CS Duration and Instructional Set on Cardiac Anticipatory Responses to Stress in Field Dependent and Independent Subjects

The study showed that within a modified delayed conditioning paradigm the shape of the anticipatory cardiac response to shock can be modified by changing the CS duration. When the tone (CS) duration was only 4 sec, there was a significant HR acceleration. With the CS duration increasing stepwise, from 4 to 12 sec, the anticipatory cardiac response to the UCS became biphasic. The acceleratory component of this response was bound to the CS and time locked, and, on the average, reached its peak within 5 sec after the onset of the CS. The deceleratory component was directly related to the length of the time interval between the onset of the CS and the UCS: there was no anticipatory deceleration when the tone duration was 4, 5, or 6 sec; the most pronounced deceleration was observed during the 10 sec interval. Instructional sets did not significantly affect cardiac activity by themselves, but did influence responses in interaction with the individual difference variable of field dependence; this was found to be the case only on the first trial. Field dependence was also a meaningful variable, and accounted for some of the differences in the patterns of HR responding in anticipation of shock.