Eyewitness accuracy and confidence: within- versus between-subjects correlations

Previous researchers using between-subjects comparisons have found eyewitness confidence and accuracy to be only negligibly correlated. In this study, we examined the predictive power of confidence in within-subject terms. Ninety-six subjects answered, and made confidence ratings for, a series of questions about a crime they witnessed. The average between-subjects and within-subject accuracy-confidence correlations were comparably low: r = .14 (p less than .001) and r = .17 (p less than .001), respectively. Confidence is neither a useful predictor of the accuracy of a particular witness nor of the accuracy of particular statements made by the same witness. Another possible predictor of accuracy, response latency, correlated only negligibly with accuracy (r = -.09 within subjects), but more strongly with confidence (r = -.27 within subjects). This pattern was obtained for both between-subjects and within-subject comparisons. The theoretical and practical implications of these results are discussed.     

Patients' perceptions of treatment for kidney failure: The impact of personal experience on population predictions

Estimates of the probability of various outcomes associated with treatment for kidney failure were made by chronic dialysis patients, dialysis patients awaiting transplant, successful transplant patients, and unsuccessful transplant patients back on dialysis. The latter two groups can be considered a natural experiment testing the impact of personal experience on population predictions. Consistent with the law of small numbers and the availability heuristic, successful transplant patients gave higher estimates of the population success rate for transplantation than unsuccessful transplant patients gave.     

Characteristics of dropouts, remainers, and refusers at a psychosocial rehabilitation program for the chronically mentally disabled

Thirty-eight chronically mentally disabled patients who were invited to join a newly established, vocationally oriented, day treatment program in Raleigh, North Carolina, served as subjects. We attempted to determine whether demographic and psychosocial characteristics significantly differed among groups of clients who dropped out of, remained in, or refused membership in this community-support program. A variety of demographic, expectancy, psychological, and psychosocial measures were administered to each subject. Most significant was the finding that the subjects' perceived level of help and support from friends was a significant determinant of the level of program participation. Those subjects who refused to participate (refusers) perceived themselves as receiving proportionately less support than did members of the other two groups (dropouts and remainers).     

Alternation behavior, spatial discrimination, and reversal disturbances following 6-hydroxydopamine lesions in the nucleus accumbens of the rat

The effects of dopaminergic depletion of the nucleus accumbens was tested in various behavioral tasks such as alternation, spatial discrimination, and reversal learning, and in an extinction paradigm in a T maze. Animals with lesions showed impairment of spontaneous alternation behavior, disturbances in the acquisition of spatial discrimination, and great difficulty in reversing previously learned habits. In the extinction phase, experimental animals are unable to adjust their behavior, and continue to choose the previously reinforced arm of the T maze. It is suggested that the nucleus accumbens plays an important role in the transition of motivation into action, and that dopamine has a facilitatory influence on the mediation of these processes.     

Aggressive behavior inhibition by serotonin and quipazine injected into the amygdala in the rat

The effects on aggressive behavior, open-field activity, and pain threshold of bilateral microinjections of serotonin (20 micrograms) and quipazine (20 micrograms), the direct serotonergic receptor agonist, into the cortico-medial amygdala were investigated in Wistar rats. Both drugs significantly prolonged the attack latency in isolated killer rats (predatory aggression model), and suppressed the incidence of aggressive postures/attacks in shock-induced fighting test (affective aggression). The only difference in the open-field behavior was the lower number of central square entries in drug-treated compared to saline-injected rats. None of the substances produced any significant change in jump threshold. It is concluded that stimulation of serotonin receptors within the amygdala produces inhibition of affective and muricidal behavior in isolated rats. The effect does not seem to be dependent on changes in general activity and pain sensitivity.     

Selective attention and priming: Inhibitory and facilitatory effects of ignored primes

The priming effects of ignored information have been studied in Stroop displays (Neill, 1977) and with spatially superimposed drawings (Tipper, in this issue); naming of probes related to ignored primes is delayed in these experiments (“negative priming”). This negative priming effect is confirmed in a list reading task in Experiment 1, which used partially superimposed letters, and Experiment 2, which used spatially separated letters. Furthermore, Lowe (1979) using Stroop colour words observed that changing the nature of the probe such that it did not require selection from a competing word reversed the priming effects of the ignored word from inhibition to facilitation. Experiment 3 confirmed this observation when subjects selected a red letter from a green letter. Two models are suggested to account for this result. In the first, negative priming is a product of the ignored prime and subsequent probe being encoded both as a stimulus to be ignored and one to be named (Allport, Tipper and Chmiel, in press; Lowe, in press). This dual encoding is ambiguous, requiring further processing before response can be output. The other model suggests that negative priming reflects inhibition of response to ignored information, slowing naming latencies to probe stimuli that require the same response. Experiment 4 attempts to differentiate between the models, and the latter inhibition view is preferred.     

Co-occurrent use of cigarettes, alcohol, and coffee in healthy, community-living men and women

Previous studies have examined intra-individual aggregation in the use of cigarettes, alcohol, and coffee by examining the co-occurrent use of any pair of these three substances. A recent literature review failed to find a single investigation that studied use of all three in the same sample. In the present study, co-occurrent use of all three of these substances was examined in crossvalidated subsamples of 226 male and 245 female healthy, community-living, middle-class Americans. A log-linear analysis was used to compare the proportion of smokers, ex-smokers, and nonsmokers categorized as users of more or less amounts of coffee and alcohol. Although most of the intercorrelations were not strong, the results indicate that for both sexes, smokers and ex-smokers were more likely than nonsmokers to drink greater amounts of alcohol and coffee. Furthermore, for smokers, ex-smokers, and nonsmokers, a majority of individuals who reported drinking more alcohol also reported drinking more coffee. Interestingly, the coffee and alcohol consumption levels of ex-smokers resembled those of smokers more than those of nonsmokers. Also, ex-smokers reported drinking more wine and decaffeinated coffee than either smokers or nonsmokers. Finally, the number of cigarettes smoked per day (daily quantity) was positively related to total alcohol and coffee consumption in men, but not in women. Further studies are recommended to examine the role of individual differences in the development, maintenance, and modification of these three appetitive habits and their co-occurrence.