The relationship between Fisher's exact test and Pearson's chi-square test: A bayesian perspective

It is demonstrated in this paper that two major tests for 2 × 2 talbes are highly related from a Bayesian perspective. Although it is well-known that Fisher's exact and Pearson's chi-square tests are asymptotically equivalent, the present analysis shows that a formal similarity also exists in small samples. The key assumption that leads to the resemblance is the presence of a continuous parameter measuring association. In particular, it is shown that Pearson's probability can be obtained by integrating a two-moment approximation to the posterior distribution of the log-odds ratio. Furthermore, Pearson's chi-square test gave an excellent approximation to the actual Bayes probability in all 2×2 tables examined, except for those with extremely disproportionate marginal frequencies.     

Positive behavioral contrast when pigeons press treadles during multiple schedules

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.     

Stimulus-specific contrast effects during operant discrimination learning

In two experiments, pigeons' responding was equally reinforced in the presence of four line-orientation stimuli. Responding was then reinforced when only two of the four orientation stimuli were present; the remaining two orientations appeared during extinction. Response rates were often highest in the stimulus adjacent to the orientations presented during extinction and often lowest in that orientation adjacent to the orientations presented with reinforcement. These effects were stronger and more persistent when the stimuli were separated by a smaller angle, rendering the discrimination more difficult. These and other data suggest that discrimination training may not be accurately explained in terms of the simple effects of reinforcement and nonreinforcement associated with isolated stimuli, nor by accounts that depend upon stimulus generalization. Recent accounts of contrast that depend upon “emotionality” produced by nonreinforced responding or upon reinforcement-elicited responses are also difficult to apply to these data.     

Elicited responding to signals for reinforcement: the effects of overall versus local changes in reinforcement probability

Pigeons were studied on a three-component multiple schedule where all reinforcement was independent of responding. Two components were cued by different keylights and were associated with different rates of reinforcement. The third was always a no-key period associated with extinction. After a few sessions, pecking was elicited by the keylights signalling the reinforcement and continued to be maintained indefinitely. The duration and sequence of the three components were varied to determine if the primary controlling variable was differences in the overall probability of reinforcement, or if it was the immediate change in reinforcement signalled by the onset and/or offset of the stimulus. Both variables were found to control behavior. When 30-sec components were used, the primary controlling variable was the overall probability of reinforcement, but when 3-min components were used, overall probability had little effect. Control by local changes in reinforcement also occurred, although the type of local control varied both across subjects and experimental conditions. Some behaviors were controlled more by the change in reinforcement signalled by the onset of the stimulus, while others were controlled more by the change signalled by the offset of the stimulus.     

Behavioral contrast of time allocation

Pigeons' standing on a platform produced food reinforcement according to two-component multiple schedules in which either both components consisted of the same variable-interval schedule or one of these was replaced with a component without reinforcement (extinction). The components of the multiple schedule alternated every 30 sec, and were signalled by changes in the color of diffuse overhead illumination. Changing the schedule of one of the components to extinction increased the percentage of time spent on the platform during the unchanged component (behavioral contrast). This result casts doubt on accounts that attribute behavioral contrast to variations in the rate of noninstrumental elicited responses.     

Absolute and relative measures of dimensional contrast.

Two sets of experiments examined the discriminative performance of pigeons on a visual flicker-rate continuum using a maintained generalization procedure. In the first experiment, responses during the intermediate stimulus value were not reinforced, whereas responses during all other stimuli were reinforced periodically. In the second experiment, training was similar to the first, with the exception of one condition in which stimuli adjacent to the negative stimulus border were eliminated from the discrimination set. Results from both experiments show that positive dimensional contrast seems to represent a relative enhancement of discrimination gradient form, rather than an absolute increase in responding with respect to prior baseline. Further, the form and magnitude of positive dimensional contrast are not predictable from the form and magnitude of baseline response rates. Results from the second experiment indicate that eliminating border stimuli increased response-rate differences between positive and negative stimuli, but did not necessarily diminish the magnitude of positive dimensional contrast.     

TEACHER POPULARITY AND CONTRAST EFFECTS IN A CLASSROOM TOKEN ECONOMY

There is a common fear that the use of a token economy in one classroom might harm pupil performance in situations where the contingencies are not in effect. This study investigated potential contrast effects on measures of children's productivity and attitudes toward teachers. Six children with reading deficits participated. A multiple baseline design was used to assess the effects of a token economy which was systematically introduced across three teachers. Dependent measures included two rating forms of teacher popularity and work rate on a programmed reading series. The results indicated that the token system was effective in increasing the children's productivity and that no consistent behavioral contrast effects occurred. Furthermore, children's attitudes toward teachers did not appear to be influenced by the token economy until only one teacher was not delivering tokens. At this point, her popularity declined until she also delivered tokens. The token economy manipulation appeared to have a specific, desirable effect on the targeted behavior (i.e., work rate) and had minimal negative or positive “side effects” on teacher popularity.     

Some parameters of behavioral contrast and allocation of interim behavior in rats

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.     

态度及其与行为模式述评

态度一直是社会心理学的核心问题,态度对于预测行为具有重要作用。本文阐述了态度的界定、态度的结构模型及态度预测行为模型的各种理论,在这些理论的基础上,提出了态度预测行为的另一模型。     

De-polarizing verbal irony

In three studies participants were asked to rate the degree of irony perceived in comments relating to five variations of a scenario, ranging from one pole to the opposite pole and passing through three in-between states. In study 1, the comments pertained to the polar extremes of a dimension, e.g. “It’s uphill!” stated with reference to varying degrees of steepness both uphill and downhill (i.e. steep, slightly steep, flat, slightly sloping downhill and steeply sloping downhill). In study 2, the comments were of an “intermediate” nature (e.g. “This hill is neither uphill nor downhill!”) and, as in Study 1, they were used to refer to the same five varying degrees of the same dimension. Study 3 involved the stimuli from both of the first two experiments in a between-participants design.

The results consistently demonstrated that verbal irony does not only apply to (weakly or strongly) polarised statements and situations, but it can also apply to intermediate comments and experiences. The perceptual structure of the dimensions involved modulates the effect.