Abstract
Vigilance performances consisting of auditory threshold, latency of response, and false-positive response measures were obtained from 24 Navy and civilian Os during the course of six daily 48-min. monitoring sessions in which O pressed a microswitch to report single tones in signal trains of increasing intensity. Six signal rates from 2.5 to 120 signals per hour and six intersignal intervals ranging up to 108 sec. around a signal rate of 1 per minute were found to have some differential effect on auditory threshold. An improvement of 3.25 db in signal/noise detection occurred when signal rate was increased from 2.5 to 15 per hour. Higher rates were not additionally effective. Below the rate of 15/hr., response latency increased regularly with the slower rates, although there was no further improvement with higher signal rates. Thus a rate of about 1 signal every 4 min. was the most efficient. Time-on-watch analysis revealed large individual differences. An analysis of false-positive responding indicated that false alarms were unrelated to signal rate, intersignal variability, or listening session.
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