Effects of Acute Stress or Centrally Injected Interleukin-1beta on Neuropeptide Expression in the Immune System

Acute stress stimulates the expression and release of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus, and the pro-opiomelanocortin products beta-endorphin and ACTH from the anterior pituitary. These neuropeptides are also expressed in immune tissues, and it has been proposed that they may modulate immune responses to stress through paracrine mechanisms. We subjected rats to restraint stress or central injection of interleukin (IL)-1beta to determine whether these acute stimuli can alter the expression of neuropeptides in the spleen and thymus. Restraint stress significantly increased the contents of all these neuropeptides in thymic, but not splenic, extracts. A single icv injection of IL-1beta increased contents of CRH, AVP, ACTH and beta-endorphin in the spleens of both sham-operated and adrenalectomised (ADX) rats. IL-1beta increased thymic contents of CRH and ACTH in sham-operated rats but these increases were not observed in ADX rats. These results suggest that the effects of IL-1beta on neuropeptide expression in the spleen are independent of glucocorticoids, whereas IL-1beta stimulation of neuropeptide expression in the thymus is dependent on circulating glucocorticoids. There were significant correlations between increases in CRH, ACTH and beta-endorphin in the spleen, and between CRH and ACTH in the thymus, consistent with the suggestion that IL-1beta-induced increases in ACTH and beta-endorphin may be mediated through CRH. These results provide evidence that stressors can directly influence neuropeptide expression in immune tissues. Thus stress may influence immune functions through paracrine mechanisms involving locally synthesised neuropeptides as well as through activation of the hypothalamo-pituitary-adrenal axis.     

Sexual victimization in relation to perceptions of risk: mediation, generalization, and temporal stability

There is evidence that personal experience with trauma is associated with increases in both personal and comparative risk perception. This study investigates this relation in terms of sexual victimization among women, focusing on three potential mediators: perceived control over sexual assault, perceived similarity to a typical sexual assault victim, and psychological distress. Mediational analyses were investigated using structural equation modeling. Although victimization experience was not related to comparative risk perception, it was associated with greater personal risk perception. This relation was mediated by perceived similarity to a typical sexual assault victim. Prospective analyses indicated that personal risk perception does change in response to sexual victimization but also indicated that heightened risk perception may be an accurate assessment of risk that actually precedes victimization experience. Implications for the meaning of perceived similarity and perceptions of risk for sexual assault victims are discussed.     

Coordination success and interpersonal perceptions: matching versus mismatching

Coordination is an essential part of social functioning. The authors distinguish 2 types of coordination: matching and mismatching. In matching, coordination is successful if parties choose the same action. In mismatching, coordination is successful if people choose different actions. In 3 studies, the authors investigated the downstream social consequences of tacit coordination for interpersonal perceptions. In all studies, participants repeatedly choose between 2 bets with equivalent expected values, and payoffs increased either when they choose the same bet or when they choose different bets. In the 1st 2 studies, coordination success increased the perceptions of interpersonal similarity and liking when matching was required but not when mismatching was required. The authors' interpretation is that matching responses and coordination success had countervailing effects in the mismatching task. Also, percentage of matched responses did not affect perceptions when coordination was not required (Experiment 2). In 4 person teams, a frequently matching partner was viewed more favorably (smarter, more similar to self, and more liked) than were other teammates, even when mismatching increased payoffs (Experiment 3).     

The sampling of critical,unshared information in decision-making groups: the role of an informed minority

A collective information sampling model and observations of discussion content suggest that decision-making groups often fail to disseminate unshared information. This paper examines the role that a fully-informed minority may play in facilitating the sampling and consideration of unshared information. University students read a mystery and then met in four-person groups to discuss the case. When critical clues were unshared among three members before discussion, a fully informed fourth member (informed minority) promoted the discussion of these critical clues when participants thought the mystery had a demonstrably correct answer (solve set) but not when they thought the clue may have been insufficient to solve definitively the case (judge set). None the less, under both solve and judge sets, the informed minority increased the likelihood that the group would identify the correct suspect. Social combination, information sampling, and minority influence interpretations of the results are discussed. © 1998 John Wiley & Sons, Ltd.     

Use of social knowledge in tacit coordination: Social focal points

Social focal point theory predicts that, in matching, people search for a shared characteristic that makes one decision option salient whereas, in mismatching, they search for complementary characteristics that make different options salient for each of the coordinating parties. In two studies, participants learned about a partner’s activity preferences and then tried to either match or mismatch choices on a series of pictures that were remotely associated with one of these preferences. Being the same on a relevant preference facilitated matching whereas being different facilitated mismatching. In the second study, participants also used overall perceived similarity to supplement specific trait information. Coordination performance also affected interpersonal impressions: successful matching increased interpersonal attraction whereas successful mismatching did not. These downstream effects were obtained even when participants had considerable prior social information about their partners. Tacit coordination is compared with mimicry and synchrony, and the implications for coordinated team performance are discussed.     

Differential access to information and anticipated group interaction: impact on individual reasoning

Two studies examined the impact of relative differences in access to information and anticipated group interaction on individual reasoning. On 2 different reasoning tasks (P. C. Wason's [1966] selection task and D. Kahneman & A. Tversky's [1973] lawyer-engineer problem), participants sensing that they knew more in anticipation of group interaction or knew less when not anticipating interaction were less susceptible to typical cognitive biases demonstrated by these tasks. Study 2 also showed that the effect of these social contexts was contingent on the task presentation format. Thus, knowing more in anticipation of group interaction and knowing less when not anticipating group interaction seemingly compensated for task features that enhance suboptimal reasoning strategies. These results illustrate the importance of the social context in which reasoning is situated and are discussed in terms of cognitive tuning, social comparison, and social motivations.     

The effects of consensus requirements and multiple decisions on mock juror verdict preferences

After watching a simulated rape trial, prerecorded on videotape, mock jurors either did or did not expect to sentence a defendant following deliberation with or without a group verdict required. Both sentencing expectation and verdict requirement significantly elevated jurors' preference for conviction (and average ratings of guilt likelihood). Closer analyses of personal changes (before and after deliberation) in the distribution of opinions suggested that majorities favoring not guilty were more influential than guilty-favoring majorities; and, somewhat unexpectedly, minorities in juries which deliberated without a verdict required were more likely to change personal opinions than minorities in juries required to render a verdict. The overall social decision scheme confirmed earlier observations about the importance of the initial majority in determining the verdict; but the majority did not always prevail and there was a marked asymmetry (“defendant protection”) in its action.