Monitoring of Complex Visual Displays— II. Effects of Visual Load and Response Complexity on Human Vigilance

Abstract

A vigilance experiment was performed on the characteristics of visual monitoring behavior in complex tasks like those found in modern semi-automatic systems. The activationist hypothesis, which contends that human alertness is a function of stimulation level, served as framework for the experiment. Under investigation were sources of environmental and response-produced stimulation that might he related to hitman alertness. A. simulated semi-automatic air defense surveillance task was used. Environmental stimulation was manipulated by requiring six or thirty-six visual stimulus sources to be monitored for a 3-hr observation period. Response-produced stimulation was a function of response complexity. No vigilance decrement was found for per cent of signals correctly detected. Response latency declined significantly, but slightly, for groups that had simple response conditions but not for groups with complex response requirements. Results were discussed in terms of issues in operationally defining sources of stimulation for the activationist hypothesis, and the cautions that must be observed in generalising from the simple tasks of most vigilance experiments to the complex tasks of semi-automatic systems.