Biomedical subjects

C P Shimp

Publications and source records attributed to C P Shimp.

39 records · Page 3Linked to original sources

PubMed1967

The reinforcement of short interresponse times.

Five contingencies were superimposed successively on a variable-interval schedule of reinforcement. In each of the resulting conditions, a different short, interresponse time was reinforced and an interresponse-time distribution was obtained from each of three pigeons. The lower bound of the reinforced interresponse times ranged from 0.3 to 2.4 sec. The resulting distributions were combined, according to a rationale based upon concurrent operants, induction, and a property of variable-interval schedules, to describe the interresponse-time distributions from a variable-interval schedule.

Animals↗

PubMed1967

Reinforcement of least-frequent sequences of choices.

When a pigeon's choices between two keys are probabilistically reinforced, as in discrete trial probability learning procedures and in concurrent variable-interval schedules, the bird tends to maximize, or to choose the alternative with the higher probability of reinforcement. In concurrent variable-interval schedules, steady-state matching, which is an approximate equality between the relative frequency of a response and the relative frequency of reinforcement of that response, has previously been obtained only as a consequence of maximizing. In the present experiment, maximizing was impossible. A choice of one of two keys was reinforced only if it formed, together with the three preceding choices, the sequence of four successive choices that had occurred least often. This sequence was determined by a Bernoulli-trials process with parameter p. Each of three pigeons matched when p was (1/2) or (1/4). Therefore, steady-state matching by individual birds is not always a consequence of maximizing. Choice probability varied between successive reinforcements, and sequential statistics revealed dependencies which were adequately described by a Bernoulli-trials process with p depending on the time since the preceding reinforcement.

Journal Article↗

PubMed1966

Probabilistically reinforced choice behavior in pigeons.

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.

Animals↗