Preference for a Stimulus that Follows a Relatively Aversive Event: Contrast or Delay Reduction? (original) (raw)
Related papers
Journal of the Experimental Analysis of Behavior, 2007
When behavior suggests that the value of a reinforcer depends inversely on the value of the events that precede or follow it, the behavior has been described as a contrast effect. Three major forms of contrast have been studied: incentive contrast, in which a downward (or upward) shift in the magnitude of reinforcement produces a relatively stronger downward (or upward) shift in the vigor of a response; anticipatory contrast, in which a forthcoming improvement in reinforcement results in a relative reduction in consummatory response; and behavioral contrast, in which a decrease in the probability of reinforcement in one component of a multiple schedule results in an increase in responding in an unchanged component of the schedule. Here we discuss a possible fourth kind of contrast that we call within-trial contrast because within a discrete trial, the relative value of an event has an inverse effect on the relative value of the reinforcer that follows. We show that greater effort, longer delay to reinforcement, or the absence of food all result in an increase in the preference for positive discriminative stimuli that follow (relative to less effort, shorter delay, or the presence of food). We further distinguish this within-trial contrast effect from the effects of delay reduction. A general model of this form of contrast is proposed in which the value of a primary or conditioned reinforcer depends on the change in value from the value of the event that precedes it.
Preference for the outcome that follows a relatively aversive event: Contrast or delay reduction?
Learning and Motivation, 2011
Pigeons prefer a positive discriminative (S+) stimulus that follows a less preferred event (a large number of required responses, a longer delay, or the absence of food) over a different S+ with a similar history of reinforcement that follows a more preferred event (a single required response, no delay, or food). We proposed that this phenomenon results from contrast (referred to as withintrial contrast) between the less preferred initial event and the signal for reinforcement. Delay reduction theory can account for these results by proposing that the less preferred initial event lengthens the duration of the trial, thereby allowing the S+ stimulus to occur later in the trial and thus become a better predictor of reinforcement. In the present experiments, we further explored this effect. In Experiment 1, we controlled for trial duration by using a fixed ratio response (30 pecks) as one initial event and the absence of pecking for the same duration as the other initial event (0 pecks). The pigeons showed a reliable preference for the positive stimulus that followed the least preferred initial event. In Experiment 2, we controlled for trial duration by using 30 pecks as one initial event and 1 peck followed by a delay that matched the duration of the preceding 30-peck trial. (Group Time Same). For Group Time Different, there was no delay following the 1-peck initial event. For Group Time Same, preference for the initial event negatively predicted the pigeons' preference for the S+ stimulus that followed, supporting the contrast account. A somewhat greater preference for the discriminative stimulus that followed the least preferred initial event was found for Group Time Different suggesting that in addition to contrast, delay reduction also may play a small role. However, the greater initial-event preference found for Group Time Different suggests that contrast can account for the group difference as well.
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 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.
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.
Suppression by reinforcement, a model for multiple-schedule behavioral contrast
Behavioural Processes, 1987
MC Sweeney, F.K., 1987. Suppresion by reinforcement, a model for multiple-schedule behaviroral contrast. Behav. Process., The present paper argues that multiple-schedule behavioral contrast occurs because delayed reinforcers suppress behavior. According to this idea, some reinforcers delivered in the second component of a multiple schedule suppress responding during the first component because they follow that responding after a delay.
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.
Within-trial contrast: The effect of probability of reinforcement in training
Behavioural Processes, 2009
There is evidence that pigeons prefer conditioned reinforcers that are preceded by greater effort over those that are preceded by less effort (an effect that has been attributed to within-trial contrast). In past research the probability of reinforcement for correct choice of the conditioned reinforcer has been 100%, however, the high level of reinforcement for both alternatives in training may result in a performance ceiling when choice between those alternatives is provided on test trials. In the present study we tested this hypothesis by including a group for which the probability of reinforcement in training was only 50%. Pigeons were trained on two simultaneous discriminations, one that was preceded by a 30-peck requirement the other by a single-peck requirement. On test trials, we found a significant preference for the S+ that required the greater effort in training for pigeons trained with 100% and a small but nonsignificant effect for pigeons trained with 50% reinforcement. Although the hypothesis that the within-trial contrast effect was constrained by a performance ceiling was not confirmed, we did find a reliable within-trial contrast effect with 100% reinforcement.
Primary and secondary negative incentive contrast in differential conditioning
Journal of experimental psychology, 1973
The present study investigated the mechanism of incentive contrast and the role of cue similarity in differential conditioning. A negative contrast effect in running speeds was found for both a constant-delay-differential-rewardmagnitude (AW g) condition and a constant-reward-magnitude-differentialdelay (AT B) condition. There was no evidence for a corresponding positive contrast effect; rather, during intermediate training, performance on S + trials was suppressed relative to the S+ control. For both conditions of contrasted reward, cue similarity affected the rate at which the discrimination was formed, but not the magnitude of contrast or suppression effects. Importantly, the present study found a primary negative contrast effect relating to reduced consummatory vigor in the AW g condition. There was no evidence for a corresponding primary positive contrast effect. A modified frustration interpretation was offered to explain the primary contrast effect for consummatory behavior, as well as the secondary contrast effect for running speeds.