Sandeep Mishra

Androgens and dominance: Sex-specific patterns in a highly social fish (Neolamprologus pulcher)

In most vertebrates, aggression and dominance are tightly linked to circulating testosterone. Fish, however, have two androgens (testosterone, T and 11-ketotestosterone, 11KT) that influence aggression and dominance. To date, few studies have compared the relationship between androgen levels and the outcome of aggressive contests in both females and males of the same species. To investigate sex differences in androgens we staged size-matched, limited-resource (territory) contests with 14 female-female and 10 male-male pairs of the highly social cichlid Neolamprologus pulcher. We then examined androgen levels in recently established dominants, who won the contest and subsequently acquired a territory (for 3h), and subordinates, who lost and did not acquire a territory. Newly dominant females had higher plasma T but similar 11KT levels to newly subordinate females. In contrast, newly dominant males had higher 11KT but similar T levels to subordinate males. The ratio of 11KT to T, which demonstrates physiological importance of T conversion to 11KT, was positively correlated with submissive behavior in female winners, and correlated weakly with aggressive behavior in male winners (p=0.05). These findings provide support for the hypothesis that different androgens play equivalent roles in female versus male dominance establishment, and suggest that relative levels of 11KT and T are implicated in female dominance behavior and perhaps behavior of both sexes.

An Examination of the Relationship Between Gambling and Antisocial Behavior

Problem gambling is significantly more prevalent in forensic populations than in the general population. Although some previous work suggests that gambling and antisocial behavior are related, the extent and nature of this relationship is unclear. Both gambling and antisocial behavior are forms of risk-taking, and may therefore share common determinants. We investigated whether individual differences in personality traits associated with risk-taking, the Big Five personality traits, and antisocial tendencies predicted gambling and antisocial behavior among 180 male students recruited for a study of gambling (35.0% non-problem gamblers, 36.7% low-risk gamblers, 21.7% problem gamblers, and 6.7% pathological gamblers). All forms of gambling and antisocial behavior were significantly correlated. Personality traits associated with risk-acceptance explained a significant portion of the variance in problem gambling, general gambling involvement, and all forms of antisocial behavior. Antisocial tendencies (aggression and psychopathic tendencies) explained a significant portion of additional variance in severe antisocial behavior but not moderate or minor antisocial behavior. When controlling for personality traits associated with risk-acceptance, the relationship between gambling and antisocial behavior was greatly diminished. The results are consistent with the hypothesis that gambling and antisocial behavior are associated because they are, in part, different manifestations of similar personality traits.

Developmental environment affects risk-acceptance in the hissing cockroach, Gromphadorhina portentosa.

Consistent individual differences in the tendency to accept risk have been demonstrated in invertebrates, fish, birds, and mammals, including humans. These individual differences have been associated with size, growth rate, survival, and reproductive success. Little research, however, has investigated the effect of developmental environment on individual differences in risk-acceptance. Competing hypotheses offer different explanations of how variation in the quality of the developmental environment affects risk-acceptance in adults. The first hypothesis states that individuals developing in poor quality environments take risks because such behavior is their only means of obtaining adequate fitness returns. The second hypothesis states that individuals developing in poor environments avoid risk because their poor physical condition makes them especially vulnerable to injury or death. We measured several forms of risk-accepting behavior (exploration, foraging, and recovery after disturbance) in male hissing cockroaches (Gromphadorhina portentosa) that had developed in nutritional and social environments of varying quality. Individuals raised on poor nutrition diets exhibited lower levels of risk-acceptance than those raised on high nutrition diets. Risk-acceptance among individuals that developed on poor nutrition diets was negatively correlated with body size. We conclude that quality of developmental environment affects risk-acceptance across behavioral contexts in male hissing cockroaches. Our findings are consistent with the hypothesis that condition-dependent vulnerability mediates the relationship between developmental environment and risk-acceptance.

Mood and Audience Effects on Video Lottery Terminal Gambling

Little is known about the situational factors associated with gambling behavior. We induced 180 male participants (mean age: 21.6) into a positive, negative, or neutral mood prior to gambling on a video lottery terminal (VLT). While gambling, participants were observed by either a male peer, female peer, or no one. Induced mood had no effect on gambling behavior. Participants induced into a negative mood prior to gambling, however, reported more positive moods after gambling, whereas those with positive and neutral moods reported more negative moods after gambling. Participants observed by either a male or female peer spent less time gambling on the VLT compared to those not observed. Participants observed by a female peer lost less money relative to the other observer conditions. Degree of problem gambling in the last year had little influence on these effects. Some practical implications of these findings are discussed.