Monitoring of Complex Visual Display: V. Effects of Repeated Sessions and Heavy Visual Load on Human Vigilance

An earlier experiment on repeated monitoring sessions used a complex visual display with a moderate load of six stimulus sources. Nine consecutive daily sessions, a seven-day rest, and a tenth session were administered. Each daily session was 3 hr. The present study used the same experimental design as the earlier study but extended it by using a heavy visual load of thirty-six stimulus sources that required extensive visual scanning. A single group of twelve subjects was used. Reliable vigilance decrement was found within sessions, but the overall trend with sessions was one of increasing performance level, suggesting learning. The small amount of decrement commonly found for complex monitoring tasks is discussed, and an optimistic note is sounded for man's tolerance of boredom.