Comparing Common Procedures Used to Manipulate Reinforcer Magnitude

Reinforcer magnitude is one of several parameters of reinforcement. In the present study, it referred to the quantitative value of the reinforcer in terms of duration of access to a finite supply of grain pellets. Pigeons responded on concurrent-chain schedules earning one of several reinforcer durations depending on response allocation and experimental conditions. Experiment 1 consisted of relatively long reinforcer durations available for completing one chain compared to relatively short durations available on the other. Response allocation in the initial link determined the reinforcer duration, but responses in the terminal link produced no change in the upcoming reinforcer. This arrangement allowed for the comparison of response-correlated and experimenter-controlled changes in reinforcer magnitude in terms of the control by reinforcer magnitude they produced. Additional changes in reinforcer durations were programmed between experimental conditions to allow for comparisons of within-sessions and between-conditions changes in magnitude as well. Experiment 2 was procedurally similar to the first, but the total reinforcer duration was identical for each chan. Instead, reinforcer durations were segmented into bins on one chain and kept continuous on the other (e.g., two 4-s reinforcers separated by a brief blackout period compared to one, continuous 8-s reinforcer). Control by reinforcer magnitude was most apparent when changes were response correlated and within-sessions, but behavior change was also observed on the between-conditions scale. No magnitude effects were observed in changes in magnitude were experimenter controlled (i.e., not correlated to behavior). Further, the observed effects seemed to be mediated by eating efficiency. It is recommended that future research on reinforcer magnitude include thorough measurement of the consummatory chain to fully describe the role of eating efficiency in control by reinforcer magnitude

Mirror, Mirror in the Chamber: Effects of Social Stimuli on Operant Behavior

The variables affecting social behavior are myriad, making the prediction and control of behavior occurring in social contexts relatively difficult. One can attempt to create a controlled social context in the laboratory by introducing a second organism into an operant chamber. To investigate effects of social stimuli on operant responding, key pecking responses of three pigeons were maintained on a variable-interval (VI) schedule of reinforcement in Experiment 1, and the key pecking responses of three additional pigeons were maintained on a three-component multiple schedule in Experiment 2. The components included a variable-ratio (VR) schedule, a fixed-interval (FI) schedule, and a differential reinforcement of low rate behavior (DRL) schedule. No social stimuli were present in the operant chamber during the baseline conditions of either experiment. During experimental conditions a mirror was introduced into the operant chamber to simulate the presence of another organism. The mirror covered one side wall of the chamber adjacent to the work panel containing the response key. Relative decreases in rates of responding were observed during each experiment when the pigeons had access to their reflections compared to when no mirror was present. Response rates returned to baseline levels when the mirror was removed in the subsequent conditions, suggesting that access to visual-social stimuli disrupted pigeon behavior controlled by different schedules of reinforcement