Elevation and reduction of plasma tryptophan and their effects on aggression and perceptual sensitivity in normal males

Data from experimental animals suggest that 5-hydroxytryptamine (5HT) may have an inhibitory effect on aggression, while clinical studies have found a correlation between pathological aggression and low brain 5HT. To investigate this relationship further we used amino acid mixtures designed to raise or lower the levels of the 5HT precursor, tryptophan. Normal male subjects were given tryptophan-depleted, balanced, or tryptophan-supplemented ammo acid mixtures and tested for aggression 5 hours later. The balanced amino acid mixture served as a control for the tryptophan depletion and supplementation. Testing for aggression was done using the Buss paradigm in which subjects deliver electric shocks to a (nonexistent) partner in response to stimulus tones. Duration and intensity of shock delivered were the measures of aggression, while responsivity to the stimulus tones was the measure of perceptual sensitivity. Neither tryptophan supplementation nor tryptophan depletion had any effect on these measures of aggression or perceptual sensitivity. We conclude that raising or lowering the synthesis of brain 5HT through alterations in tryptophan availability does not influence aggression in normal males as measured by the Buss task.     

The relationship between STD locus of control and STD acquisition among adolescent girls

This longitudinal study examined adolescent girls' perception of control over sexually transmitted disease (STD) acquisition. Participants were asked questions regarding their perception of their STD locus of control (internal control; control by parents, partners, peers, and health care providers; and chance) at two waves of data collection. Of the 116 participants (mean age = 17 years), 82% were African-American and 18% were Caucasian. Responses to the measure of locus of control were significantly correlated across a 6-month interval. The responses regarding internal control, control by partner, and chance were not related to the acquisition of an STD in the next 6 months. Further, they were not influenced by an STD in the preceding 6 months. These results indicate that responses to a locus of control measure were stable over a 6-month period, and internal, partner, and chance locus of control perceptions seem to be neither determined by STD experience nor directly related to future STD acquisition. However, understanding an individual's locus of control may be helpful in providing appropriate counseling. Future research could examine how adolescent girls form their perceptions of control over STD acquisition.     

The relationship between personality,anger expression,and perceived family control among incarcerated male juveniles

The literature suggests that a multitude of psychological and social factors can interact to place adolescents at risk for aggression and violence. This study examined three of these factors: personality, affect, and family. Using a heterogeneous sample of male adolescents at risk for violence, a hierarchical, agglomerative cluster analysis was conducted to categorize these adolescents in terms of personality characteristics. Results of the analysis suggested three clusters of at-risk adolescents. Examination of the three cluster types found distinctions between groups on anger expression, trait anger, and trait anxiety, but not family control. It was concluded that, among male delinquents, elevated psychopathology is associated with higher anger and anxiety, but not higher family control.     

List of Contributors

Authors Index

List of Contributors     

Retaking ability tests in a selection setting: implications for practice effects,training performance,and turnover

This field study investigated the effect of retaking identical selection tests on subsequent test scores of 4,726 candidates for law enforcement positions. For both cognitive ability and oral communication ability selection tests, candidates produced significant score increases between the 1st and 2nd and the 2nd and 3rd test administrations. Furthermore, the repeat testing relationships with posthire training performance and turnover were examined in a sample of 1,515 candidates eventually selected into the organization. As predicted from persistence and continuance commitment rationales, the number of tests necessary to gain entry into the organization was positively associated with training performance and negatively associated with turnover probability.     

Temperamental differences between healthy,asthmatic, and allergic children before onset of illness: a longitudinal prospective study of asthma development

The authors investigated the link between children's temperament and the development of asthma and allergies. Prospective longitudinal data on children at the ages of 3-5 months, 3-5 years, and 7-9 years were collected. At age 7-9 years, analyses were performed on data for 3 groups of children (n = 42): those with asthma (no allergies), those with allergies (no asthma), and those with neither asthma nor allergies (the control group). Data for children who developed asthma or allergies prior to age 7-9 years were not analyzed. Differences were found in the premorbid period between the control group and the children who later developed asthma or allergies as well as between the asthma and allergy groups. After onset of illness, no temperamental differences were observed between the 3 groups. The study shows the importance of longitudinal design for asthma research.     

Gamma-range oscillations in backward-masking functions and their putative neural correlates

Backward-masking functions have been hitherto categorized into two types, commonly named Type A and Type B. The analysis of a model of Retino-Cortical Dynamics produces the prediction that spatially localized stimuli should reveal an oscillatory metacontrast function. The predicted new type of metacontrast masking function was investigated in a psychophysical experiment. The results show oscillatory metacontrast functions with significant power in the gamma range (30-70 Hz). A marked decrease in the oscillations is observed when the spatial extent of the stimuli is increased. The theoretical basis of the study relates the oscillations found in the metacontrast function to gamma-range oscillations observed in scalp and intracerebral recordings. The qualitative agreement between the model and data provides support for this putative relationship.     

On the relationship between locus of control, level of ability and gender

In a sample of Norwegian 14- and 15-year-old students no significant relationship was found between total externality-internality score and level of ability. However, a significant relationship was found between ability and a subscale of locus of control related to degree of belief in the impact of school effort. The analyses of gender differences showed that girls had significantly higher total internal locus of control scores than boys. Boys were, however, significantly more internally oriented than girls on a subscale related to the respondents' general belief in luck, while girls were significantly more internally oriented than boys on a school effort scale. The present study does not support the notion that girls develop an attributional pattern which is more closely related to their abilities while boys may develop a broader attributional pattern.     

Individual postdecision processes in group settings

In two experiments Differentiation and Consolidation Theory (Diff Con) (Svenson, 1992) was used to investigate individual postdecision making processes in three-member groups. It was predicted that in groups in which the subjects preferred different alternatives (conflict groups), subjects would consolidate their own preferred alternative, and not the group's final decision. A second hypothesis was that no consolidation would be indicated in groups in which all members preferred the same alternative (non-conflict groups). The results showed that in conflict groups, the members who gave up their preferred alternative (minority members) consolidated their own preference, thereby significantly regretting the group decision. In contrast, members who got their own will through in the majority decision (majority members) showed no consolidation of the group decision. The corresponding pattern of results was replicated in a second experiment, using a different decision situation. The results indicated that perceptions of social support, agreement in a group and decreasing responsibility for a group's decision, could all partly substitute consolidation by attractiveness restructuring.     

Postdecision consolidation in a trend prediction task

To be able to learn from experience it is necessary to correctly apprehend experienced feedback and the situation in which it is provided. The results indicate how post-decision consolidation in complex domains may affect learning. The problem may be particularly pertinent in recurrent decision making where considerable risk is involved. The study explores the changes in aspect (signal) importance from pre- to postdiction as a function of outcome information. By postdiction we mean the remembering of an earlier prediction (cf. Hawkins & Hastie, 1990). Subjects were asked to decide on which of four alternative future price developments would follow a historical price trajectory for different commodities, and to rate the importance of each of the chosen alternative's corresponding aspects. The subjects revealed a bias in their support ratings of aspects--seeing support in aspects that traditionally (by themselves and in many contexts) would be seen as neutral or even counter-indicative of the alternative chosen. After an intermission, the subjects were also given information about what was indicated to be the actual development of the market. One group was told that their decisions were correct (irrespective of what the decisions were), another group that they were incorrect but close, a third group that they were incorrect by far, while a fourth group served as a control. Following this information the subjects were again asked to judge the importance of the aspects for their own prior decision on the most likely future development. The results indicated that outcome feed-back had an effect on post decision restructuring of facts. Subjects in the correct condition showed an average consolidation that increased the support, while the wrong conditions lead to negative consolidation (in retrospect indicating that they never found as much support for their decision in the past as they actually did). Thus, in a choice between consolidating their own initial prediction and the price trajectory they would have to live with, the decision makers consolidated the outcome. Therefore, the results of the study were related to the hindsight bias phenomenon (Fischhoff, 1975) and to Kahneman and Miller's (1986) mutability concept.