Behavioral contrast in pigeons and rats: A comparative analysis (original) (raw)
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Behavioral contrast as a function of component duration and baseline rate of reinforcement
Learning & Behavior, 1986
Three experiments examined changes in size of multiple-schedule behavioral contrast with changes in an independent variable. Experiment 1 found that positive contrast generally increased with increases in component duration when pigeons pressed treadles. Experiments 2 and 3 found that positive and negative contrast generally increased with increases in the baseline rates of reinforcement when pigeons pecked keys. The experiments show
A re-examination of local contrast in multiple schedules1
Journal of the Experimental Analysis of Behavior, 1975
Pigeons were presented with multiple schedules of alternating 90-sec components. When components in which grain was never presented alternated with components in which grain was presented on a variable-interval schedule, the average rate of responding in the variable-interval components increased, showing overall positive behavioral contrast. Unlike previous reports, this study found that the response rates for all birds increased toward the end of the variable-interval components as training proceeded. This increase in local response rate disappeared when the multiple schedule was composed solely of variable-interval components and reappeared when the variable-interval components were again alternated with extinction. This finding cannot be predicted or explained by recent theories of behavioral contrast based on autoshaping, and thus questions their sufficiency. We suggest that this local response-rate increase results from the predictable change from high to low density of reinforcement at the end of the fixed-duration component. Thus, the present effect apparently illustrates a different type of interaction between components of a multiple schedule than that described by previous theories of contrast. In a given procedure, either or both types of interaction may occur; neither provides a complete account of behavioral contrast.
Some parameters of behavioral contrast and allocation of interim behavior in rats
Journal of the Experimental Analysis of Behavior, 1985
Two experiments examined the effects of baseline reinforcement rate and component duration on behavioral contrast and on re-allocation of interim behavior in rats. Positive behavioral contrast occurred during multiple variable-interval 10-second extinction (VI 10 EXT) after a multiple VI 10 VI 10 baseline condition, but not during multiple VI 60 EXT following multiple VI 60 VI 60 baseline. Component duration had no significant effect on contrast. These results differed from those found in studies of pigeons' key pecking. Contrast was accompanied by an increased rate of drinking in the changed component, but drinking in the constant component did not decrease. These results are not consistent with the competition theory of contrast, but are consistent with the predictions based on the matching law. However, no current theory seems to account for all instances of behavioral contrast.
Analysis of incentive and behavioral contrast in the rat
Journal of Comparative and Physiological Psychology, 1971
Rats were trained to shuttle freely in two parallel runways. The subjects were reinforced in both runways on one of two variable-interval (VI) schedules of reinforcement (VI 1.5 min. or VI 3.75 min.) and with one of two reward magnitudes (two or five pellets). After performance had stabilized, the VI schedule in one of the runways was shifted to the other schedule. The contrasted condition continued for 8 sessions, after which the baseline schedule was reinstated for another 12 sessions. The magnitude of reinforcement was then contrasted. Response rate and one measure of latency following each of the shift phases showed contrast effects. A perceptual-motivational interpretation was offered to explain the findings.
Behavioral contrast using different reinforcers: effect of baseline rate of reinforcement
Behavioural Processes, 1998
The present study determined whether behavioral contrast would occur when different reinforcers were delivered in the different components and whether its size would vary at different baseline rates of reinforcement. Pigeons pecked keys on a multiple variable-interval schedule. Mixed grain was the reinforcer in one component and wheat was the reinforcer in the other component. In contrast conditions, the rate of wheat reinforcement was increased or decreased, from the baseline delivery rate, by a factor of four. Contrast was studied at four different baseline rates of reinforcement. Contrast was usually observed and its size almost always varied directly with the programmed baseline rate of reinforcement. The present results indicate that changes in the condition of reinforcement of a different reinforcer can produce contrast. They also broaden the potential implications of behavioral contrast.
Learning & Behavior, 2004
Pigeons’ keypecking was reinforced by food on baseline schedules of multiple variable interval (VI)x VIx and on contrast schedules of multiple VIx VIy. Deprivation of food was varied by maintaining subjects at 75%, 85%, and 95% (±2%) of their free-feeding weights. Positive and negative behavioral contrast were observed. The size of the contrast was not systematically altered by changes in deprivation. Positive and negative contrast were both larger later in the session than they were earlier. Withinsession decreases in responding were steeper for the baseline than for the contrast schedules for positive contrast. Within-session decreases were steeper for the contrast than for the baseline schedules for negative contrast. These results were predicted by the idea that different amounts of habituation to the reinforcer during the baseline and contrast schedules contribute to behavioral contrast. The results show that contrast occurs under conditions that reduce the effect of the following component. The results support the assumption that positive and negative contrast are produced by symmetrical theoretical variables.
Behavioral contrast in rats when qualitatively different reinforcers are used
Behavioural Processes, 1987
Higa, J. J. and McSweeney, F. K. (1987). Behavioral contrast in rats when qualitatively different reinforcers are used. Behav. Process.,15:131-142. 1961). Only a few have examined whether contrast occurs when the type Of reinforcer is varied. For instance, Ettinger, McSweeney, 0376-6357/87/$03.50 0 1987 Elsevier Science Publishers B.V. (Biomedical Division)
Positive behavioral contrast when pigeons press treadles during multiple schedules
Journal of the Experimental Analysis of Behavior, 1983
Pigeons were placed on multiple variable-interval 15-second variable-interval 15-second and on multiple variable-interval 15-second extinction schedules in which treadle presses produced food reinforcers. Positive behavioral contrast occurred. That is, rates of responding were higher during the variable-interval 15-second component when the other component was extinction than when it was another variable-interval 15-second schedule. These results contradict the findings of other studies, which failed to find positive contrast when pigeons pressed treadles for food reinforcers. They may also question the additive theories of behavioral contrast that predict that contrast should not occur in this situation.
A Theory of Behavioral Contrast
Journal of the Experimental Analysis of Behavior
The reinforcers that maintain target instrumental responses also reinforce other responses that compete with target responses for expression. This competition and its imbalance at points of transition between different schedules of reinforcement causes behavioral contrast. A model for this theory is constructed by expanding the coupling coefficient of MPR (Killeen, 1994). The coupling coefficient gives the degree of association of a reinforcer with the target response (as opposed to other competing responses). Competing responses, often identified as interim or adjunctive or superstitious behavior, are intrinsic to reinforcement schedules, especially interval schedules. In addition to that base-rate of competition, additional competing responses may spill over from the prior component, causing initial contrast; and they may be modulated by conditioned reinforcement or punishment from stimuli associated with subsequent component change, causing terminal contrast. A formalization of these hypotheses employed (a) a hysteresis model of off-target responses giving rise to initial contrast, and (b) a competing traces model of the suppression or enhancement of ongoing competitive responses by signals of following-schedule transition. The theory was applied to transient contrast, the following schedule effect, and the component duration effect.
Journal of the …, 1981
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.