Contrasting effects of social stress and foot-shock on acute cardiovascular response in salt-sensitive rats

Repeated defeat by an aggressive resident attacker rat produces a large decrement in systolic blood pressure (SBP) in male S/JR rats. The present experiments compared the cardiovascular (CV) response of male S/JR rats exposed either to repeated defeat, or to a common laboratory stressor, electric foot-shock. Using the tail-cuff method of determining SBP, the results of Experiment 1 replicated the previous finding that on the second and subsequent exposures, repeated defeat is followed by an acute decrement in SBP (30-40 mm Hg in magnitude). In contrast, repeated exposures to foot-shock were followed by acute increases in SBP (20-40 mm Hg) and in heart rate (HR). In Experiment 2, mean arterial blood pressure (MAP) and HR were measured directly from chronically cannulated male S/JR rats after defeat or exposure to foot-shock: again, defeated males exhibited an acute decrease in MAP, whereas the MAP of rats exposed to foot-shock tended to increase. In Experiment 3 we varied the parameters of shock intensity and the social context of shock exposure. Male S/JR rats exposed to more intense foot-shock than in the previous experiments or to foot-shock while paired with one of the resident attacker rats all exhibited acute increases in SBP. The results of these experiments indicate that CV response to defeat may be qualitatively different from CV response to foot-shock.     

Sex differences in a simulated classroom economy: Children's beliefs about entrepreneurship

The purposes of this study were (1) to measure sex differences in children's perceptions of entrepreneurship and occupational sex-stereotyping and (2) to assess sex differences in children's risk taking, persistence, and economic success. For 10 weeks 938 children in grades 3–6 participated in Mini-Society, an experience-based economics education instructional program. Child self-report measures and teacher ratings were utilized. Before Mini-Society children reported entrepreneurship to be primarily a male domain. There was less entrepreneurial stereotyping after Mini-Society, especially in favor of girls. Children's occupational sex stereotyping also decreased following Mini-Society. Finally, there were no sex differences in the children's risk taking, persistence, or economic success during the Mini-Society experience.     

Memory search: When does semantic analysis occur?

This study was addressed to the determination of the stage at which semantic analysis occurs during a STM recognition task. A list of exemplars (memory set), drawn from 13 different categories, was presented at a rate of 11/2 sec/item, followed by a category name probe. Ss then indicated whether any of the exemplars in the memory set belonged to that category. List length was varied from 5 to 7, with each memory set containing items from either two or three categories. It was found that RT was independent of list length, but did increase by 60 msec as the number of categories represented in the list increased from two to three. From this, it was concluded that activation of a superordinate category representation occurred upon presentation of each memory-set item, and that the memory scan was done on these superordinate categories.     

Factors in the modification by isolation of electroconvulsive shock-produced retrograde amnesia in the rat.

It has been demonstrated that placing rats in a sensory-restricted environment during the electronconvulsive shock- (ECS) retention interval following 1-trial appetitive learning will prevent or eliminate ECS-produced retrograde amnesia. The first study replicated this finding with a 1-trial aversive learning task, indicating that this effect is not task specific. The second study attempted to determine whether illumination or the restricted environment was the crucial factor in this penomenon. Rats placed in the light during the ECS-retention interval, whether restricted or in the colony, demonstrated retrograde amnesia after ECS. However, rats left in the dark during this interval demonstrated little, if any, retention deficit particularly if this condition was combined with sensory isolation. These studies further indicate that manipulation of the general environment of the animal after ECS can alter ECS-produced retention losses.     

Competitive fighting in the rat.

Competitive fighting was obtained in pairs of like-sexed laboratory rats by placing a single piece of food into the food hopper following 48 hr. of food deprivation. The fighting was characterized by offensive sideways posture, full aggressive posture, and bite and kick attack. Tests were conducted at 110-120 days of age on pairs of animals that had been housed together since weaning. Fighting was more frequent in pairs consisting of nonlittermates than in pairs of littermates, and it was equally frequent in male and female pairings. Probability of fighting was enhanced by prior experience with food deprivation, and attack was most often initiated by the heavier animal of the pair.     

Post-cueing after erasure of the icon: Is there a set effect?

Recognition accuracy in a tachistoscopic identification task typically declines as the size of the set from which the target was selected increases. To determine whether this effect is due to selective encoding from iconic store, a masking stimulus, intended to erase the icon, was presented following the stimulus. Information about the set was then presented. It was found that subjects' performance in this post-cueing situation did not differ from performance in a pre-cueing condition, where the set was presented prior to the stimulus. It was concluded that set size does not have its effect through selective encoding from iconic store. Results were discussed in terms of the fragment theory.