Measurements of the post-reinforcement pause and response rate were obtained from four birds on a range of fixed ratio schedules from 25 to 150. The results indicated a consistent increase in the length of the pause as the ratio was increased. Response rate tended to decrease, but these data were less consistent and some reversals were apparent.

No abstract

Two pigeons were trained on a multiple VI-1; VI-4 min schedule for food reinforcement until a stable differential rate of response was established. Each component of the multiple schedule was in effect for 10 min and was separated from the other by 1 min time out. An Estes-Skinner conditioned suppression procedure was superimposed on each component of the schedule. The relative magnitude of the suppression behavior was measured during its acquisition and extinction, and at CS durations of 100, 200, and 300 sec. The initial magnitude of the suppression behavior was less severe on the VI-1 baseline than on the VI-4, and it extinguished more rapidly on the VI-1. As the relative duration of the CS was increased, the suppression behavior became less severe on both baselines, but the initial differential magnitude in the suppression remained intact.Recent studies of the Estes-Skinner conditioned suppression procedure indicate that the procedure used to maintain the baseline performance is an important variable in determining the degree of suppression that will be achieved. In particular, studies by Stein, Sidman, and Brady (1958) and by Carlton and Didamo (1960) point to the frequency with which the reinforcement is provided as a significant feature of the situation. In the present study, this variable is examined directly, through the use of a multiple schedule baseline. Thus, the degree of suppression obtained with two different reinforcement schedules can be compared within the same organism. The effects of these schedules are also compared as the relative duration of the conditioned stimulus is increased, to determine the interaction between these two factors.METHOD

Two pigeons were trained on an FR 150 schedule of reinforcement. An Estes-Skinner conditioned suppression procedure was then superimposed on this performance at varied intervals. If the CS occurred during the early stages of the ratio run, complete suppression resulted. If the CS occurred during the later stages of the run, the birds continued to respond until the reinforcement was obtained, which was then followed by complete suppression.

Two auditory stimuli, separated by a fixed intertrial interval, were alternately presented to two rats in a closed environment. The positive conditioned stimulus (CS+) terminated with the offset of a 2-mA, 0.75-sec shock. The negative conditioned stimulus (CS-) terminated without shock. The incidence of the "stereotyped fighting posture" was recorded during the CS+, the CS-, the intertrial interval, and shock. The results showed an increase in the percentage of conditioned responses during the CS+, and a decrease during both the CS- and the intertrial interval, when the duration of the conditioned stimuli and the intertrial interval was 16 sec. Appropriate changes in the incidence of aggression during the two stimuli were obtained following the reversal of the stimulus functions. During the acquisition and reversal phases there was a between-session decrement and a within-session improvement in the incidence of aggression during the CS+, defined as warm-up. The presentation of free shocks before the conditioning sessions was effective in reducing the warm-up only when the interval between shocks was 64 sec. These data were interpreted as demonstrating classical conditioning of shock-elicited aggression, with little chance of non-associative factors contributing to the measurement of the conditioned response.