HABITUATION OF THE ORIENTING RESPONSE IN ALERT AND DROWSY SUBJECTS.

Abstract : Alert and drowsy subjects were compared in two experiments for psychophysiological habituation of the orienting response. Subjects in Experiment I (N = 30) received 10 presentations of a doorbell-type buzzer, and in Experiment II (N = 69) they received 10 presentations of a 500 cps tone. Comparisons were made of: (1) galvanic skin response (GSR); (2) spontaneous GSR's between trials; (3) heart rate (HR) responses; (4) finger vasoconstriction responses; (5) finger temperature responses; and (6) respiration. Results showed that there were no differences between groups in GSR; however, the drowsy group showed consistently fewer spontaneous GSR;s. Cardiovascular response measures of the drowsy groups showed consistently and significantly greater responses on the later trials and, therefore, no habituation of these responses. This finding was more consistent for HR than vasomotor response. In the discussion of these results, the authors were able to rule out several possible explanations, but the reasons for this differential autonomic response are as yet unknown. (Author)