The operant conditioning of response variability: Free-operant versus discrete-response procedures

The operant conditioning of response variability under free-operant and discrete-response procedures was investigated. Two pigeons received food only if their pattern of four pecks on two response keys differed from the patterns emitted on the two immediately preceding trials. Under the free-operant procedure, the keys remained illuminated and operative throughout each trial. There was little variability in the response patterns that resulted, and the pigeons received fewer than one third of the available reinforcers. Under the discrete-response procedure, a brief timeout period followed each response. Variability increased under this procedure, and the pigeons obtained three fourths of the available reinforcers. Previous successes and failures to produce response variability may have been due to the use or failure to use, respectively, a discrete-response procedure. Respondent effects inherent in the free-operant procedure may encourage the development of response stereotypy and, in turn, prevent the development of response variability.     

Type A behavior,anger expression,and reactions to anger imagery

The experiment investigated the effects of Type A behavior, anger expression, and gender on perceptions of control and heart rate. Jenkins Activity Survey defined Type A and B subjects, categorized as either high or low in anger expression, were asked to recall, image, and generate self-referent statements about angry situations. State anger and heart rate were measured during all of the anger induction conditions, and ratings of imagery vividness and perceptions of control for self and others were taken following the recalled and imaged anger conditions. The results, with both the heart rate and self-report measures, indicated that the effects of the independent variables were interactive and situationally dependent. Type A behavior was associated with increased heart rate in two experimental conditions (mood anger and recalled anger), and, in one instance, this effect was amplified in male subjects (recalled anger). The self-report results yielded interactional effects that most commonly took the form of high anger expression, with male Type A's providing higher ratings of state anger, more vivid anger imagery, and lower perceived self-control ratings than did other categories of subjects. Taken together, these results suggest that anger expressiveness, particularly among males, amplifies the usual reactions attributed to Type A's, and that such effects are mediated by the threat of loss of control. Further, the observed interactive relationships limit the generalizability of A/B differences and raise definitional questions about Type A behavior.     

Theologies from Africa,Asia and Latin America,including Black Theology: a Bibliography

During the last few years the library of the Ecumenical Centre, in line with its worldwide acquisition policy, has added to its collection many works by theologians from Africa, Asia and Latin America. A consultation of several such theologians took place recently in Geneva. Prominent at the Vancouver Assembly were theologians speaking out of their own context. This is therefore an appropriate moment for rendering a service to theological professors and students in the realm of contextual theology. All the titles indicated in the bibliography are available in the library and can be borrowed.     

Variations in explicitly unpaired training are differentially effective in producing conditioned inhibition

To evaluate a contingency interpretation of conditioned inhibition (CI), rats were given “explicity unpaired” training in which the locus and duration of a CS within the inter-US (shock) interval were systematically manipulated for different groups. Summation and retardation tests in Experiment 1 indicated that stronger CI resulted from both a backward and a trace CS than from a midlocus CS of equal or greater duration. Complementing these findings, the same tests in Experiment 2 showed that, by comparison with novel-stimulus controls, CI developed to a trace CS but not to a mid-locus CS, nor to a trace CS that was accompanied by an immediate signal for the US. These findings argue against a contingency interpretation of CI and favor a contiguity interpretation stressing the short-term rehearsal of stimulus events. Such rehearsal of the US allows a backward CS, but not a mid-locus CS with an extended US-CS interval, to be discriminated as a signal for nonreinforcement, and thus to develop as a conditioned inhibitor. Similarly, excitatory conditioning to the memory trace of a CS allows the nominal trace CS to develop as a signal for nonreinforcement, and thus as a conditioned inhibitor, but not when its memory trace is overshadowed by another CS that immediately precedes the US. In short, the development of CI is facilitated when excitation is mediated by the memorial processing of either the US or a discrete CS for the US rather than by contextual cues.