Body fat distribution and hemodynamic stress responses in premenopausal obese women: a preliminary study.

To examine the relationship between body fat distribution and hemodynamic stress responses, cardiovascular responses to a speech task and a forehead cold pressor task were evaluated with 24 premenopausal women classified a priori as either centrally or peripherally obese. Results showed that women with central adiposity exhibited greater stress-related increases in diastolic blood pressure and total peripheral resistance, whereas women with peripheral adiposity exhibited greater stress-related increases in cardiac output. Depression, self-consciousness, hostility, and mood scores did not explain significant variance in the stress response differences between regional adiposity groups. The findings suggest that central adiposity may increase the risk of cardiovascular disease in women at least in part by enhancing vascular responses to stress.     

Early communication in dyads with visual impairment

The ability of dyads with restricted access to the visual channel of communication to establish a reliable pre‐linguistic communicative signalling system has traditionally been viewed as problematic. Such a conclusion is due in part to the emphasis that has been placed on vision as central to communication by traditional theory. The data presented in this paper question these assertions. The results of a longitudinal study exploring the nature of early dyadic interactions in dyads with visual impairment are presented. The dyads' use of three types of non‐visual behaviour—touch, vocalizations and facial orientation—were investigated in terms of their potential as alternatives to visual communication. It is argued that the results are evidence that visually impaired dyads engage in sophisticated communicative exchanges prior to infants' acquisition of language. Copyright © 2005 John Wiley & Sons, Ltd.     

Instrumental learning as a result of omission training on wheel running

The present experiment sought to provide unequivocal evidence of instrumental learning under omission training. Hungry rats received free food reinforcement while spontaneously running in a wheel. For an omission group, running postponed or cancelled reinforcers in the presence of a discriminative stimulus (SD) requiring subjects to reduce responding to earn food. Background food presentations were then yoked to reinforcement delivered in the presence of the discriminative stimulus. For a control group, which received the same stimulus presentations, reinforcement delivery was yoked to the experimental group at all times. The procedure allowed both within- and between-subject comparisons between omission and response-independent schedules. The response-reinforcer delay under the omission contingency was adjusted so as to equate reinforcement frequency in the presence and absence of the SD. As the SD was not correlated differentially with reinforcement and the running response did not involve approach or withdrawal to the site of food delivery, the successful discrimination performance observed in this experiment cannot be accounted for by appeal to implicit classical conditioning. Instead, it is suggested that decreased running in the presence of the discriminative stimulus was based on the animals' veridical representation of the negative contingency between the response and reinforcement.     

Predictive accuracy and not reduction in uncertainty influences responding during serial autoshaping

Two experiments with pigeons employed a serial autoshaping design in which food was presented on every trial, and the initial element was of variable duration. When the first element was followed randomly by one stimulus of fixed short duration and another stimulus of fixed long duration, then it elicited a relatively high rate of responding. But when the second elements were of equal mean durations, whether fixed or variable, then responding during the first element was relatively slow. Two explanations for these findings were considered. One stipulates that the rate of responding during a stimulus is related to its predictive accuracy, the other stipulates that responding is influenced by the reduction in uncertainty that follows the offset of a stimulus. It is argued that the evidence favours the first of these alternatives.