The Relationship Between Stimulus Oriented Changes In Heart Rate And Detection Efficiency In A Vigilance Task

The study was designed to assess the relationship between detection efficiency and beat-to-beat changes in heart rate around task stimuli in a vigilance task. Thirty-six subjects, instrumented for continuous recording of EKG and respiration, individually stood a 96 minute vigil. They monitored a light which flashed on (stimulus event) for 500ms. once every 6.0 seconds and were to report the occasional brighter flashes (signals). Half of the subjects (high signal density group) received 240 signals; the remaining 18 subjects (low signal density group) received but 16 signals. By urging the subjects to do their best, a motivational condition was induced in a six minute post-test. As expected, detection efficiency was higher and better sustained by the high signal density group. Detection efficiency of the low signal density group decayed appreciably over time. In the motivational post-test condition the performance of both groups improved significantly. Measures of changes in heart rate, analyzed both in terms of overall shifts in heart rate over the vigil and beat-to-beat changes in heart rate around each stimulus event, revealed: (1) The median heart rate in succeeding quarters of the vigil, did not differ significantly between the two groups. (2) Heart rate preceding a stimulus event decelerated. (3) In the post-test the significant recovery in detection efficiency was accompanied by an increase in the magnitude of stimulus-oriented cardiac deceleration and by a decrease in overall heart rate. (Author).

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This volume contains the proceedings of a symposium held in St. Vincent, Italy, on August 3-6,1976, entitled "Vigilance II: Relationships Among Theory, Physiological Correlates, and Opera tional Performance." The symposium was sponsored jointly by the Human Factors Panel of the Scientific Affairs Division of NATO and by the Physiology Programs Office of the U.S. Office of Naval Research (Contract N00014-76-C-0722). These sponsorships, and the helpful assistance of Dr. Donald P. Woodward and Dr. John A. Nagay, are gratefully acknowledged. Following the editor's introduction, the papers appear in the order they were given at St. Vincent. In general they are grouped according to the main topical themes of the symposium: keynote ad dress, vehicle operation, monitoring and inspection, physiological correlates, stress effects, individual differences, and theoretical considerations. I must point out, however, that individual papers often overlapped several of these topical areas and thus no defini tive partitioning of the proceedings has been attempted. I wish to acknowledge the many contributions of my colleague, Dr. James O'Hanlon, to both the planning of the symposium and the preparation of the manuscript, and the invaluable role of my wife, Shirley Jean, in making the symposium such a pleasant one for all. In addition, I wish to recognize the countless contributions of Lynda Lee Chilton and Katherine Peimann whose performance in compos ing, typing, and proofing the manuscript is certainly a tribute to human vigilance, and endurance as well.

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