Contextual conditional discriminations

Three experiments used a discriminated operant procedure to study conditional discrimination learning in rats. The first experiment showed that rats were capable of learning a biconditional discrimination in which two contexts served as conditional cues signalling the reinforcement contingencies associated with two discriminative stimuli. The discrimination was learned equally well when one discriminative stimulus signalled food, the other its absence, and when one stimulus signalled food, the other extinction plus mild footshock.

In Experiment 2 it was shown that prior training on such a conditional discrimination enhanced the subsequent context specificity of simple conditioning relative to control groups of animals for whom the prior training had not been conditional. Experiment 3 showed that a reversal of the significance of one pair of discriminative stimuli produced no spontaneous reversal in performance to a second, target, pair.

The pattern of results is best accounted for by an analysis of contextual conditional discrimination learning in terms of stimulus configurations and offers no support for the notion that rats may learn a general conditional rule or set.     

Stress, reactivity, and immune function in healthy men.

We examined the effects of acute psychological stress on lymphocyte proliferation and circulating levels of interleukin-1 and -2. Healthy men were exposed to two viewings of a gruesome surgery film and were asked to recall details of the film twice during a 30-min period. These subjects were compared to a nonstress control group. Lymphocyte proliferation to the mitogen concanavalin A (Con A; 5 micrograms/ml) was decreased during and after exposure to the stressor when compared to the control group. This decrease was more pronounced in subjects exhibiting greater blood pressure reactivity while viewing the film than in subjects showing smaller blood pressure responses. None of the other immunological measures was significantly affected by the stressor. Cortisol was not correlated with lymphocyte responsiveness. Possible explanations for these results and implications for further research are discussed.     

Cardiovascular reactivity to psychological stress in aerobically trained versus untrained mild hypertensives and normotensives

Cardiovascular reactivity to video game and mental arithmetic stressors was compared among three groups of men: aerobically trained mild hypertensives, untrained mild hypertensives, and a comparison group of untrained normotensives. Relative to the untrained hypertensives, the trained hypertensives reacted to the video game with marginally smaller systolic blood pressure and diastolic blood pressure, but there were no significant differences between these groups in reactivity during the mental arithmetic task. Comparisons between each hypertensive group and the normotensive group showed that blood pressure (BP) reactivity of normotensives during the video game was generally similar to that of trained hypertensives but smaller than that of untrained hypertensives. These results indicate that aerobic training, which has been found to reduce resting BP in mild hypertensives, may also exert a favorable impact in reducing cardiovascular reactivity of hypertensives during some stressful situations.     

PREDICTING ORGANIZATIONAL EFFECTIVENESS FROM COMMUNICATION ACTIVITIES: A MULTIPLE INDICATOR MODEL

This study examines the effects of certain communication variables (member integration, boundary communication, environmental uncertainty, and system autonomy) on organizational effectiveness. While often discussed in the literature, these variables have not been precisely defined. As a result, a multiple indicator model using maximum likelihood estimates for each variable was created. Interviews with managers from 82 different organizations from a variety of industries are used to test the model. The results suggest that member integration and environmental uncertainty, when the latter is mediated by boundary communication, provide an excellent predictor of organizational effectiveness (R= .64). The results are discussed in light of the proposed theory along with implications for future research using intertypical sampling methods and LISREL analysis.     

The epistemological objection to modal primitivism

Modal primitivists hold that some modal truths are primitively true. They thus seem to face a special epistemological problem: how can primitive modal truths be known? The epistemological objection has not been adequately developed in the literature. I undertake to develop the objection, and then to argue that the best formulation of the epistemological objection targets all realists about modality, rather than the primitivist alone. Furthermore, the moves available to reductionists in response to the objection are also available to primitivists. I conclude by suggesting that extant theories of the epistemology of modality are not sensitive to the question of primitivism versus reductionism.