PROBABILISTICALLY REINFORCED CHOICE BEHAVIOR IN PIGEONS†
This paper is based on a thesis submitted to the Department of Psychology, Brown University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The research was partially supported by USPHS Grant MH-02456 (D.S. Blough, principal investigator) and by the author's NSF Graduate and Postdoctoral Fellowships. The author wishes to acknowledge his deep indebtedness to his adviser, Donald S. Blough.
Abstract
A single principle, “momentary maximizing”, may account for much of a pigeon's steady-state behavior in both probability learning and concurrent variable interval experiments. The principle states that a pigeon tends to choose the alternative that momentarily has the higher probability of reinforcement. A successive discrimination procedure, which produced matching in an earlier experiment, produced here a tendency to maximize if training were adequately extended. Maximizing was produced also by other procedures, in which no reinforcing event was presented on some trials: one procedure did and two did not provide a bird with information about the availability of reinforcement on a key after an unreinforced response on the other key. The latter two procedures were analogous to concurrent variable interval schedules in two respects: the reinforcement probability on one key increased while a bird responded on the other key; and they produced matching. But sequential statistics suggested that matching resulted from momentary maximizing. Depending on the procedure, the tendency to maximize produced different relative frequencies of pecking a key for a fixed relative frequency of reinforcement. Computer simulation of maximizing behavior in several concurrent variable interval schedules produced matching and sequential statistics similar to those produced by a real bird.
