JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR PREFERENCE FOR LOCUS OF PUNISHMENT IN A RESPONSE SEQUENCE'

Food-deprived pigeons pecked a key under a schedule in which grain was made available after the seventieth peck. In each sequence of 70 responses, either the first, middle, or final response was followed by electric shock. Before the first response of each sequence, each response on a second key changed the color of the food key and the schedule of shock that was correlated with the food key color. Each pigeon preferred a schedule of shock, in that each of the three shock schedules did not occur equally often. The pre-ferred shock schedule and the strength of the preference varied among the pigeons. The overall rate of responding by a pigeon under a given shock schedule was directly related to the pigeon's relative preference for that schedule, except when shock after the first response in the sequence was the most preferred schedule. The delivery of a noxious stimulus in a re-sponse sequence can influence both the tem-poral pattern of responding and rate of re-sponding within the sequence. Investigations have shown that punishing either the initial, middle, or final response of sequences main-tained under fixed-ratio (FR) reinforcement schedules differentially modifies the typical bi-valued performance (Dardano, 1970; Dar-dano and Sauerbrunn, 1964; Holz, 1967). In general, these studies have shown that the punishing stimulus exerts a strong effect on pre-punishment responses, less on the pun-ished responses, and little effect on the post-punishment responses of the sequence. Church (1969) reported a greater suppression of mean response rate when punishment was scheduled on the first response than when scheduled on a later response in the sequence. The greater suppression of performance when punishment occurs early in the sequence implies that the degree of aversiveness of a given punishing stimulus depends partly on when it is delivered. The present study at-tempted to specify any differences in the aver-siveness of response-dependent shock when scheduled on the first, middle, or final response 'Research supported by Grants NsG 189-61 and NGR 21-001-069 from the National Aeronautics and Space Administration. Appreciation is expressed to E. Taylo