Drug effects on responding maintained by stimulus-reinforcer and response-reinforcer contingencies.

The effects of pentobarbital and d-amphetamine were assessed on key pecking by pigeons under conventional single-key multiple schedules and under two-key multiple schedules in which discriminative stimuli appeared on one key (stimulus key) while pecks on a second key (constant key) produced food. Pecks on the stimulus key had no scheduled consequences. A 60-second variable-interval schedule operated in one component of each multiple schedule: either extinction or a 60-second variable-time schedule operated in the alternate component. When the alternate-component schedule was extinction, a high rate of responding was maintained in the variable-interval component of the single-key schedule; responding on both keys was maintained in the variable-interval component of the two-key schedule. Pentobarbital increased responding in the variable-interval component of the single-key schedule and increased stimulus-key, but not constant-key responding in that component of the two-key schedule. When the alternate-component schedule was changed to variable time, responding declined in the variable-interval component of the single-key schedule; stimulus-key responding was no longer maintained under the two-key schedule. Pentobarbital decreased responding in the variable-interval component of both schedules. With an exception, d-amphetamine only decreased responding in the variable-interval component of the single- and two-key schedules both when the alternate-component schedule was extinction and when it was variable time. The results suggest that the effects of pentobarbital, but not d-amphetamine, depend on the nature of the contingency (stimulus-reinforcer, response-reinforcer) that maintains responding.     

Behavioral contrast as differential time allocation

In Experiment I, hooded rats were exposed to multiple variable-interval schedules of reinforcement in which manipulanda and reinforcement magazines at opposite ends of the experimental chamber were associated with the different components. Time allocated to each component was measured by recording the time spent by the subject in the appropriate half of the chamber. Positive behavioral contrast was observed for the comparison between multiple variable-interval 30-second variable-interval 30-second and multiple variable-interval 30-second variable-interval 90-second conditions for both response frequency and time allocation measures, but not for mean local response rate (response frequency per time allocated to a component). In Experiment II, rats were exposed to multiple variable-time schedules in which reinforcement was response independent. Time allocated to each component was measured for two conditions, multiple variable-time 30-second variable-time 30-second and multiple variable-time 30-second variable-time 90-second. Positive behavioral contrast of time allocation was exhibited. The results indicated that time allocation was differentially sensitive to changes in reinforcement probability, and that behavioral contrast may result from the differential allocation of time to the different components of the multiple schedule.     

The effects of different component response requirements in multiple and concurrent schedules

Six pigeons were trained on multiple and concurrent schedules. The reinforcement rates were varied systematically (a) when lever pressing was required in one component and key pecking in the successive component; (b) when lever pressing was required in both multiple components; (c) when key pecking was required in both multiple components; and (d) when key pecking was required on one schedule and lever pressing was required on the concurrently-available schedule. Only the absolute level of responding was changed by different response requirements. Analyzed by the generalized matching law, performance under different response requirements resulted in a bias toward key pecking, and the measured response bias was the same in multiple and concurrent schedule arrangements. The bias in time measures obtained from concurrent schedule performance was reliably smaller than the obtained response biases. The sensitivity to reinforcement-rate changes was ordered: concurrent key-lever; multiple key-key; multiple lever-key; and, the least sensitive, multiple lever-lever. The results confirm that requirements of different topographical responses can be handled by the generalized matching law mainly in the bias parameter, but problems for this type of analysis may be caused by the changing sensitivity to reinforcement in multiple schedule performance as response requirements are changed.     

A note on analyzing ordered alternatives

A general method of devising stepwise multiple testing procedures with fixed experimentwise error is applied to the problem of non-parametric randomized block design with ordered alternatives. In addition, the method is applied to other models with ordered alternatives.The author wishes to thank the referees for helpful suggestions.     

THE EFFECTIVENESS OF INTERPERSONAL SKILLS TRAINING ON THE SOCIAL SKILL ACQUISITION OF MODERATELY AND MILDLY RETARDED ADULTS

Sixteen moderately and mildly retarded adults were selected from a group residential facility and randomly assigned to experimental and control groups. The experimental group received a 12-session interpersonal skills training program consisting of instruction in the following areas: (1) Introductions and Small Talk, (2) Asking for Help, (3) Differing with Others, and (4) Handling Criticism. The social skills instructional package included verbal instruction, modeling, role playing, feedback, contingent incentives, and homework. As a result of this training program, moderately and mildly retarded adults acquired new social skills as evidenced by performance on a situation role play assessment. These gains generalized to untrained role play situations but did not result in significant group differences when assessed in a more natural setting (i.e., local grocery store).     

Magnitude and duration of the effects of cocaine on conditioned and adjunctive behaviors in the chimpanzee.

Characteristic patterns of conditioned key-pressing were maintained in the chimpanzee under a multiple 30-response fixed-ratio, 10-minute fixed-interval schedule of food presentation. Adjunctive drinking occurred with regularity during the fixed-interval schedule and, with less frequency, during 1-minute timeout periods that followed each food presentation; drinking seldom occurred during the fixed-ratio schedule. Cocaine increased key pressing under the fixed-interval schedule at doses between .1 and 3.0 mg/kg, but adjunctive drinking and key pressing under the fixed-ratio schedule did not increase at any dose. Conditioned and adjunctive behaviors were disrupted and suppressed for different durations at 10,0 mg/kg, a dose which induced convulsive seizures within 10 minutes after intramuscular injection. A time-course analysis showed the magnitude and duration of the effects of cocaine on key pressing under the fixed-interval schedule and on adjunctive drinking to be dose-related. Moreover, a given dose of cocaine had diverse effects, depending on the behavior and the time since drug administration.     

Response strength in multiple periodic and aperiodic schedules

Responding in multiple periodic and aperiodic schedules of equal mean reinforcement rate was examined during extinction, satiation, and in the presence of various free-food schedules. In Experiments I and II, pigeons were trained on multiple variable-interval–fixed-interval schedules. Decreases in the rate of responding due to extinction, satiation, or food schedules were approximately equal regardless of the temporal pattern of reinforcer presentation. In Experiment III, pigeons responded on a two-component multiple schedule in which each component was a two-member homogeneous response chain terminating in a fixed-interval schedule during one component and in a variable-interval schedule during the other. The length of both terminal links was varied over a series of conditions. Initial-link responding in the fixed-interval component was reduced more by increasing terminal-link length than was initial-link responding in the variable-interval component. However, no differences in resistance to satiation and extinction were obtained across the fixed and variable components. If the relative decrease in responding produced by satiation and extinction is used as an index of the “value” of the conditions maintaining responding, then these data suggest that fixed and variable schedules of equal mean length are equally valued. This conclusion, however, is not consistent with findings of preference for variable over fixed schedules obtained in studies using concurrent-chain procedures.     

Positive conditioned suppression: Transfer of performance between contingent and noncontingent reinforcement situations

Five homing pigeons were trained on concurrent variable-interval schedules. A fixed-duration stimulus was occasionally presented on one key; and, in various conditions, this stimulus terminated (a) without reinforcement, (b) in noncontingent reinforcement, (c) with reinforcement contingent on a response on the key on which the stimulus was presented, and (d) with reinforcement contingent on a response on the key on which the stimulus was not presented. Initially, a stimulus terminating in noncontingent reinforcement generally produced decreased response rates on both keys during the stimulus. Contingencies, however, reliably produced increased rates during the stimulus on the key on which the contingency was arranged, relative to the rate on the concurrently available key. Contingency conditions were followed by noncontingency conditions in which the separation of rates caused by contingencies was maintained. When rates during the stimulus were compared with response rates on the same keys in the absence of the stimulus, contingency-caused rate increases and decreases were again found, but only the rate decreases were maintained in subsequent noncontingency conditions. Further data suggested that the contingency-caused rate changes were not maintained when the stimulus terminated without reinforcement, and that they were unaffected by a threefold decrease in the reinforcement rate provided by the baseline schedules. The results support the suggestion that performance in the positive conditioned suppression procedure results from concurrent and multiple schedule interactions. They further suggest that the production of either acceleration or suppression is dependent on adventitious and historical contingencies.     

Contrast and undermatching as a function of reinforcer duration and quality during multiple schedules

Eight pigeons pecked keys under multiple variable-interval two-minute variable-interval two-minute schedules. In Experiment 1, the reinforcers were 2, 4, or 8 seconds access to a food magazine. In Experiments 2 and 3, the reinforcers were grains that had been determined to be most-, moderately-, or non-preferred. Both positive and negative behavioral contrast occurred when the reinforcers in one component were held constant and the duration or type of reinforcer obtained in the other component varied. Undermatching occurred when the relative rate of responding during a component was plotted as a function of the relative duration of the reinforcers in that component.     

The following schedule of reinforcement as a fundamental determinant of steady state contrast in multiple schedules

Two experiments investigated whether steady-state interactions in multiple schedules depend exclusively on the following schedule of reinforcement. Experiment 1 used a four-component multiple schedule in which two components were associated with the same constant schedule of reinforcement, and where rate of reinforcement was varied in the component that followed one of these. Contrast effects were reliable only in the component that preceded the point of reinforcement variation, although some contrast did occur otherwise. In those instances where contrast other than the following-schedule effect did occur, it was accounted for by the effect of the preceding schedule, an effect for which there were consistent individual differences among subjects, and which varied with component duration. Experiment 2 used a three-component schedule, in which reinforcement rate was varied in the middle component. The results were consistent with Experiment 1, as the following-schedule effect was the only consistent effect that occurred, although an effect of the preceding schedule did occur for some subjects under some conditions, and was especially evident early in training. The conclusion from both experiments is that there is no general effect of relative rate of reinforcement apart from the sum of the effects of the preceding and following schedules, and that the following-schedule effect is the fundamental cause of steady-state interactions.