Effects of Performance Context on Processing Speed and Performance Ratings

The present study demonstrated that the presence of evaluatively polarized context performances not only produces contrast and halo effects on judgments of a target performance, but also causes judgments to be made much faster. Processing speed and positive halo were highly correlated, supporting the notion that halo in performance ratings results from raters' recall and use of a single, general impression. Furthermore, regression analyses demonstrated that processing speed mediates the relationship between context and halo. The relationship between these findings, halo, processing speed, and general impressions, as well as implications for performance appraisals, are discussed.     

Social Identity versus Reference Frame Comparisons: The Moderating Role of Stereotype Endorsement

Two studies tested the prediction that belief in a negative stereotype about an in-group will cause members to shift from viewing their in-group as a social identity to viewing it as a frame of reference. The stereotype that was the focus of inquiry was the belief that women have less aptitude at math and spatial tasks than do men. In both studies, female participants took a test of math and spatial ability and then received social comparison information about their abilities relative to a male and a female confederate. In Study 1, participants felt enhanced when the two women outperformed the male confederate, even when this meant that the participants themselves performed worse than the other woman. If participants were first reminded of the negative stereotype, however, they felt best when they outperformed the other woman, even if this meant that the two women performed worse than the man. Study 2 showed that the effects of stereotype activation were especially pronounced among female participants who showed moderate to high levels of stereotype endorsement. These findings suggest that belief in stereotypes about the in-group can lead to in-group comparison and contrast, even in contexts in which a group member's ability level challenges the validity of the stereotype.     

Varieties of contrast: a review of incentive relativity by charles f. Flaherty

The phenomenon of contrast has been studied from two quite separate perspectives, one derived from the classic studies of incentive contrast such as Crespi (1942) and the other from the study of behavioral contrast within behavior analysis. This book reviews both of these types of contrast effects and finds both differences and similarities between them. Still at issue is the validity of the interpretation of contrast that assumes that the value of some target level of reward is modified in inverse relation to the level of reward from other sources in the same context. This concept works well for the classic studies of incentive contrast, but is challenged by the emerging importance of anticipatory contrast and the finding in both of the separate research traditions that anticipatory contrast is inversely related to other measures of reinforcement value.     

Contrast and reallocation of extraneous reinforcers between multiple-schedule components

Four pigeons responded in components of multiple schedules in which two responses were available and reinforced with food. Pecks on the left key (“main” key) were reinforced at a constant rate in one component and at a rate that varied over conditions in the other component. When reinforcer rate was varied, behavioral contrast occurred in the constant component. On the right key (“extra” key), five variable-interval schedules and one variable-ratio schedule, presented conjointly, arranged reinforcers for responses in all conditions. These conjoint schedules were common to both multiple-schedule components—rather than unique to particular components—and reinforcers from these schedules could therefore be arranged in one component and obtained during the other component. In this way, the additional reinforcers were analogous to the “extraneous” reinforcers thought to maintain behavior other than pecking in conventional multiple schedules. Response rate on the extra key did not change systematically over conditions in the constant component, and in the varied component extra responding was inversely related to main-key reinforcement. All subjects obtained more extra-key reinforcers in whichever component arranged fewer main-key reinforcers. Consistent with the theory that reallocation of extraneous reinforcers may cause behavioral contrast, absolute reinforcer rate for the extra key in the constant component was low in conditions that produced positive contrast on the main key and high in those that produced negative contrast. Also consistent with this theory, behavioral contrast was reduced in two conditions that canceled extra-key reinforcers that had been arranged but not obtained at the end of components. Thus, a constraint on reallocation markedly reduced the extent of contrast.     

Competition between stimulus-reinforcer contingencies and anticipatory contrast.

Procedures used to study anticipatory contrast are conceptually similar to those used to study autoshaping, in that two target stimuli signal either higher or lower rates of reinforcement in the following components of the schedule. Despite this signal contingency, anticipatory contrast entails response rates that are higher to the target stimulus followed by the lower rate of reinforcement. To determine the relation between such effects and autoshaping, different variations of the procedure were used in which the signal contingency was presented in the absence of reinforcement in the target components themselves and in which the reinforcement schedules in the different following components were signaled by the same stimulus. Autoshaping effects of this signal contingency were demonstrated when no reinforcement was available during the target-component signals themselves. Intermediate patterns of behavior occurred when reinforcement was available during the target-component signals and when their different following schedules were correlated with the same stimulus. Attempts to isolate these signal and contrast effects functionally by using the signal-key procedure were unsuccessful. The results demonstrate that Pavlovian stimulus contingencies are in competition with the dynamics of anticipatory contrast, thus reducing its occurrence under some circumstances.     

Independence of response force and reinforcement rate on concurrent variable-interval schedule performance

Five pigeons were trained over 43 experimental conditions on a variety of concurrent variable-interval schedules on which the forces required on the response keys were varied. The results were well described by the generalized matching law with log reinforcement ratios and log force ratios exerting independent (noninteractive) effects on preference. A further analysis using the Akaike criterion, an information-theoretic measure of the efficiency of a model, showed that overall reinforcement rate and overall force requirement did not affect preference. Unlike reinforcement rate changes, force requirement increases did not change the response rate on the alternate key, and an extension of Herrnstein's absolute response rate function for force variation on a single variable-interval schedule is suggested.     

Undermatching and contrast within components of multiple schedules

Six multiple variable-interval schedules each comprised one variable-interval sixty second component and an alternated component which was varied. Four pigeons' responses were recorded in five successive subintervals of each component. Response rate changes across subintervals revealed instances of local contrast and small local induction effects in the changed component. In the constant component, smaller local contrast and larger local induction effects obtained. Accordingly, the magnitude of behavioral contrast, defined as an inverse relation between response rate in the constant component and reinforcement rate in the changed component, did not change reliably across subintervals of the constant component. Ratios of response rates in initial subintervals were highly sensitive to reinforcement ratios. Sensitivity decreased sharply over the first two-fifths of the components and remained constant for the remainder. The results demonstrated that changes in multiple schedule sensitivity are a function of time since the alternation of successive components.     

Multiple determinants of the effects of reinforcement magnitude on free-operant response rates

Four experiments examined the effects of increasing the number of food pellets given to hungry rats for a lever-press response. On a simple variable-interval 60-s schedule, increased number of pellets depressed response rates (Experiment 1). In Experiment 2, the decrease in response rate as a function of increased reinforcement magnitude was demonstrated on a variable-interval 30-s schedule, but enhanced rates of response were obtained with the same increase in reinforcement magnitude on a variable-ratio 30 schedule. In Experiment 3, higher rates of responding were maintained by the component of a concurrent variable-interval 60-s variable-interval 60-s schedule associated with a higher reinforcement magnitude. In Experiment 4, higher rates of response were produced in the component of a multiple variable-interval 60-s variable-interval 60-s schedule associated with the higher reinforcement magnitude. It is suggested that on simple schedules greater reinforcer magnitudes shape the reinforced pattern of responding more effectively than do smaller reinforcement magnitudes. This effect is, however, overridden by another process, such a contrast, when two magnitudes are presented within a single session on two-component schedules.     

Local contrast in behavior allocation during multiple-schedule components

Allocation of responses between two keys was studied during two alternating multiple-schedule components. Responses were recorded in successive quarters of each component. Variable-interval reinforcer schedules on the two keys were constant throughout the experiment for one (constant) component and were varied over conditions on one key for the other, producing changes in reinforcer ratios for the varied component. Behavior allocation for the first quarter of the constant component was inversely related to varied-component reinforcer ratios, a form of local contrast, but this relationship was not observed later in the component. During the first quarter of the varied component, slopes of matching lines were high and decreased later in the component. It is argued that this form of local contrast cannot be explained in terms of reallocation of extraneous reinforcers between components, and that the matching law for concurrent operants does not capture some sources of control over behavior allocation. A simple extension of the matching law is offered that adequately describes behavior changes during both components. A version of this formulation can predict contrast effects in absolute response rates.     

A re-examination of local contrast in multiple schedules

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.