The Effects of Signal and Response Complexity on Eighteen Hours of Visual Monitoring

Subjects monitored a complex display composed of three rows of four digital display boxes each containing a constant reference number. A change in the number lasting six seconds, was the signal to be detected. Signals occurred for different groups of subjects at rates of either 16 or 64 per hour. Response complexity was varied by having some subjects merely report the change while others evaluated the size of the change. Four groups of 15 subjects received a different combination of rate and complexity. Neither rate nor complexity influenced performance. All groups showed significant vigilance decrement during the session. The magnitude of the decrement was relatively trivial, however, and in substantial agreement with other studies. In complex tasks man seems to be an adequate monitor over rather extended time periods.