CHOICE BEHAVIOR OF PIGEONS ON PROGRESSIVE AND MULTIPLE SCHEDULES - A TEST OF OPTIMAL FORAGING THEORY

Pigeons were first trained on a depleting progressive schedule and on a multiple schedule that produced food at one of four constant rates. The birds were then allowed to choose between the schedules presented concurrently to see if, as predicted by optimal foraging theory, they switched from the progressive schedule to an alternate fixed component of the multiple schedule in a manner that maximized the benefit/cost ratio: time (T) of access to the food hopper/number (N) of pecks required to earn food. The T/N ratio was varied in two mathematically equivalent but procedurally different ways: The ratio group was trained on schedules in which N was manipulated (T was a constant 2.50-s access to the food hopper), and the time group was trained on schedules in which T was manipulated (N was a constant 50-response requirement). The results revealed that the ratio group was more sensitive to the different T/N values than was the time group, both in terms of separate schedule and choice behaviors. Yet for both groups the number of reinforcers earned on the progressive schedule during choice tests was a decreasing function of the T/N value of the alternative fixed schedule. Although choice performance was thus in qualitative accord with optimality, it did not quantitatively match the predictions of optimal foraging theory, in that subjects generally exhibited premature switching from the progressive schedule to the fixed alternative. Nevertheless, predictions based on optimal foraging theory better approximated actual choice behavior than did those based on performance under the individual schedules.