Vigilance performance and physiological responses under fixed and variable signal schedules. Techn Rep: NAVTRADEVCEN IH-71.

Abstract : The investigation was designed to: (1) determine the effects of signal patterning upon physiological responses and RT to the signals; and (2) provide some information with respect to the roles of expectancy and arousal in monitoring performance. Monitoring performance and physiological responses with variable interval (VI) and fixed interval (FI) signal patterns were studied in four Ss over an average of 10 days each. The Ss were required to expend some effort in order to obtain the critical signals. Reaction time (RT) was used as the performance measure while heart rate (HR), palmar skin conductance (PSC) and galvanic skin responses (GSRs) were the physiological measures. The RTs were significantly faster under the FI schedule than with VI. The PSC and GSR measures were significantly higher under FI than with VI, while HR was significantly greater with VI as compared to FI. Cumulative records showed typical response patterning to FI and VI schedules for three or four Ss. On the basis of these results it was suggested that: (1) faster RTs under the FI schedule reflect greater learning of the signal pattern under the FI schedule and perhaps the existence of an internal timing mechanism; (2) signal patterning does have an effect on physiological response and RT; (3) the difference between conductance phenomena and heart responses to the two signal patterns may be due to differential responsivity of the autonomic nervous system; (4) monitoring performance contains elements of both expectancy and arousal. (Author)