REINFORCEMENT AS INPUT: CYCLIC VARIABLE-INTERVAL SCHEDULE.

Daily exposure of pigeons to four cycles of a reinforcement schedule in which the density of reinforcements varied cyclically as a function of time induced a periodicity in their responding matching that of the schedule, but out of phase with it. The technique used of presenting the same sequence of interreinforcement intervals in every session may have useful application in determining animals' adjustment to more complex temporal patterns of reinforcement. Investigation of animals' response to cyclic schedules of different frequencies suggests links with engineering methods of frequency analysis.