Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.     

The burden of social proof: shared thresholds and social influence

Social influence rises with the number of influence sources, but the proposed relationship varies across theories, situations, and research paradigms. To clarify this relationship, I argue that people share some sense of where the "burden of social proof" lies in situations where opinions or choices are in conflict. This suggests a family of models sharing 2 key parameters, one corresponding to the location of the influence threshold, and the other reflecting its clarity--a factor that explains why discrete "tipping points" are not observed more frequently. The plausibility and implications of this account are examined using Monte Carlo and cellular automata simulations and the relative fit of competing models across classic data sets in the conformity, group deliberation, and social diffusion literatures.     

Calibration trumps confidence as a basis for witness credibility

Confident witnesses are deemed more credible than unconfident ones, and accurate witnesses are deemed more credible than inaccurate ones. But are those effects independent? Two experiments show that errors in testimony damage the overall credibility of witnesses who were confident about the erroneous testimony more than that of witnesses who were not confident about it. Furthermore, after making an error, less confident witnesses may appear more credible than more confident ones. Our interpretation of these results is that people make inferences about source calibration when evaluating testimony and other social communication.     

Cheap talk and credibility: The consequences of confidence and accuracy on advisor credibility and persuasiveness

Is it possible to increase one’s influence simply by behaving more confidently? Prior research presents two competing hypotheses: (1) the confidence heuristic holds that more confidence increases credibility, and (2) the calibration hypothesis asserts that overconfidence will backfire when others find out. Study 1 reveals that, consistent with the calibration hypothesis, while accurate advisors benefit from displaying confidence, confident but inaccurate advisors receive low credibility ratings. However, Study 2 shows that when feedback on advisor accuracy is unavailable or costly, confident advisors hold sway regardless of accuracy. People also made less effort to determine the accuracy of confident advisors; interest in buying advisor performance data decreased as the advisor’s confidence went up. These results add to our understanding of how advisor confidence, accuracy, and calibration influence others.     

The effects of jury size and polling method on the process and product of jury deliberation

The U.S. Supreme Court has repeatedly assumed the functional equivalence of different sized juries (at least in the range of 6- to 12-person groups). Several formal models of jury decision making predict that larger juries should hang more often, particularly for very close cases. Failures to confirm this prediction in several previous studies were attributed to inadequate sample sizes or to insufficiently close cases. An experimental simulation study that minimized these problems was undertaken to test the models' prediction. Social decision scheme and social transition scheme analyses permitted comparisons of the decision-making processes of the different-sized mock juries. The effect of the method used to poll group members' verdict preferences was also examined. As group size increased, the observed probability of a hung jury increased significantly. No process differences between 6- and 12-person groups were detected, but 3-person groups did exhibit several process differences from the larger groups. When cases were very close, the likelihood of a hung jury for typically sized juries was found to be lower when the group was polled by secret ballot than when a show-of-hands polling method was used.     

Asymmetric influence in mock jury deliberation: jurors' bias for leniency

Investigators have frequently noted a leniency bias in mock jury research, in which deliberation appears to induce greater leniency in criminal mock jurors. One manifestation of this bias, the asymmetry effect, suggests that proacquittal factions are more influential than proconviction factions of comparable size. A meta-analysis indicated that these asymmetry effects are reliable across a variety of experimental contexts. Experiment 1 examined the possibility that the leniency bias is restricted to the typical college-student subject population. The decisions of college-student and community mock jurors in groups beginning deliberation with equal faction sizes (viz., 2:2) were compared. The magnitude of the asymmetry effect did not differ between the two populations. We hypothesized that the asymmetry effect was caused by an asymmetric prodefendant standard of proof--the reasonable-doubt standard. In Experiment 2, subjects received either reasonable-doubt or preponderance-of-evidence instructions. After providing initial verdict preferences, some subjects deliberated in groups composed with an initial 2:2 split, whereas other subjects privately generated arguments for each verdict option. A significant asymmetry was found for groups in the reasonable-doubt condition, but group verdicts were symmetrical under the preponderance-of-evidence instructions. Shifts toward leniency in individual verdict preferences occurred for group members, but not for subjects who performed the argument-generation task. The theoretical and applied significance of these findings is discussed.