Concurrent schedule control of human observing during auditory vigilance.

Six adult humans experienced a vigilance task which required them to detect auditory signals and report their occurrence by pressing a button. A subject sat on a chair with his or her head between two small panels. When the subjects pressed his or her head against one of the panels, white noise was presented from a speaker set behind the panel. Signals for the left speaker were presented according to a variable-interval schedule and those for the right speaker were presented according to another variable-interval schedule (concurrent variable-interval variable-interval schedule). All subjects showed systematic variations of time allocation, although slopes of choice proportions showed severe undermatching according to the generalized matching law. The remaining three subjects, who were first exposed to some concurrent schedules, also showed such a tendency. Then, they experienced a training in which they were exposed to each variable-interval schedule successively before being exposed to them concurrently. This procedure reduced the amount of undermatching. These findings were in good agreement with previous studies reporting conformity of human observing responses to the generalized matching law.