Aaron J. Brownstein

Schedule control of eating by fixed-time schedules of water presentation

Eating was measured in water-deprived rats when water was presented at regular intervals ranging from 30 to 240 sec. The temporal patterning of eating resembled that of schedule-induced behavior in that the probability of eating was high early in the interval and declined in the end of the interval. Additionally, (a) the number of pellets consumed was controlled by relative time in the interwater interval, (b) the pellets consumed per water presentation was inversely related to water rate, and (c) food-ingestion rate was directly related to water rate. These relationships parallel those found with behavior regarded as schedule induced.

The role of response suppression in behavioral contrast: Signaled reinforcement

After responding was maintained on multiple variable-interval schedules of reinforcement, a signaling procedure was added to one component. The signaling procedure consisted of illuminating the key, the only source of illumination in the chamber, only when responding would be reinforced. Rate of responding in the unaltered component increased. When the signaling procedure was removed, rate of responding decreased in the component in which reinforcement had never been signaled. Obtained rates of reinforcement in both components were equal throughout the experiment.

Behavioral contrast in multiple schedules with equal reinforcement rates

After responding was maintained on multiple fixed-interval schedules of reinforcement, a cuing procedure was added to one component. Cuing was accomplished by illuminating a lamp just prior to reinforcement availability. This procedure produced positive behavioral contrast. The rate of responding in the cued component decreased, and the rate of responding in the uncued component increased. When the cue was removed, negative behavioral contrast occurred. Rate of responding in the component from which the cue had been removed increased, and rate of responding in the other component decreased. Throughout the experiment, rates of reinforcement in both components were held constant.

Schedule-Induced Running and Chamber Size

Running-wheel behavior was examined as a function of the floor area of the experimental chamber in three food-deprived rats when a food pellet was delivered each minute and when it was omitted. Running-wheel behavior when food was omitted was unsystematically related to the floor area. When food was scheduled, three measures of running-wheel behavior were found to be decreasing functions of floor area: percentage of the session time spent in the wheel, percentage of the interfood intervals with a wheel entry, and the mean stay time per interfood interval with a wheel entry. Wheel revolutions per session varied unsystematically, and the local rate of running was an increasing function of floor area when food was scheduled. These results explicate some inconsistent findings in the literature, and provide support for the notion that wheel-running is not a schedule-induced behavior.

A search for conditioned reinforcement effects in negative automaintenance of keypecking

The relationship between pecking and keylight termination was systematically varied to assess possible conditioned reinforcement effects of keylight termination in negative automaintained pecking. Pecking was observed under conditions where pecking produced sustained keylight termination, brief keylight termination, or had no effect on key illumination. The proportion of trials with a peck was unrelated to the peck-termination contingency. The latency on trials with a peck was shortest in the sustained termination condition. The rate of pecking on trials with a peck was highest in the condition where termination was independent of pecking. Overall, the results provide little support for the notion that keylight termination functions as a conditioned reinforcer in the negative automaintenance paradigm.

Immediacy Of Reinforcement In Autoshaping With Pigeons

Acquisition and maintenance of autoshaped keypecking with pigeons were studied as a function of immediacy of reinforcement. The basic design manipulated the immediacy of reinforcement following the trial onset while keeping the rate of reinforcement within the trial constant and manipulated the rate of reinforcement within the trial while keeping the immediacy of reinforcement constant. Seven groups of birds were studied at trial durations of either 24 or 60 seconds and immediacy intervals of either 3, 12, 24, or 60 seconds. All groups were exposed to a 180-s inter-food cycle. Acquisition rates varied as a function of the ratio of cycle to trial duration. Higher ratio groups (24 s) resulted in faster acquisition than did lower ratio (60 s). Immediacy of reinforcement exerted a less powerful effect upon acquisition than did the ratio of cycle to trial duration. During maintenance training, probability and rate of responding were positively related to immediacy of reinforcement and unaffected by trial duration. A modification of a scalar expectancy model was shown to account for these results.

Effects of changeover delay in concurrent schedules of reinforcement of key pecking by pigeons

Examination of pigeons’ key-pecking performance, reinforced on concurrent variable-interval 1-min variable-interval 3-min schedules, as a function of the changeover delay revealed the following relationships. As the changeover delay was increased from 0 through 20 sec (1) relative response frequency on the key color associated with the 1-min schedule increased, (2) relative time spent in the 1-min schedule increased, (3) obtained relative frequency of reinforcement in the 1-min schedule increased, and (4) changeover rate decreased.