VIGILANCE: THE IMPORTANCE OF THE ELICITED OBSERVING RATE.

Observing may be elicited by regularly repeated events that occasionally become signals. Such events were presented at rates of either 5 per minute or 30 per minute, and signals averaged 15 per hour during an 80-minute vigil. Observers missed about 10 percent of the signals with the low event rate and about 70 percent of the signals with the high event rate. The experiment supports a decisiontheory approach to observing behavior.