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Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Research into the origins of our own social behavior begins with understanding how environmental elements lead to complex social interaction. Social structure emerges from these interactions as a bottom-up process, whose patterning constitutes the very framework of a society. Studies of behavioral mechanisms are important in determining the full repertoire that results in the social and dominance structures of a species. Hormones such as oxytocin and cortisol facilitate and fluctuate in response to social interactions and measuring their relative values among individuals is a valuable tool in testing functional hypotheses of behavioral mechanisms. The objective of this dissertation is to investigate several fundamental, under-, or previously unstudied behavioral mechanisms and hormonal correlates that shape the unique social system of bonobos. The first study describes the pattern of expression of harassment behavior among immatures and tests predictions generated by the Exploratory Aggression and Rank Improvement hypotheses. Results demonstrate that immatures use harassment to test the nature of existing inter-individual relationships and to explore the parameters of aggressive behaviors and furthers our understanding of juvenile development of aggression and integration into the dominance hierarchy. The second study describes the pattern of occurrence of infant handling and tests predictions generated by several functional hypotheses, including examining the relationship between oxytocin and handling behaviors. Results show a significant sex difference in expression of handling where, during adolescence, male interest in infants sharply declines whereas females continue to handle infants, the expression of which was correlated with oxytocin. These results primarily support the Learning-to-Mother hypothesis and provide insight into the role oxytocin may play in facilitating care-giving behaviors in young females. The final study explores the patterning of female sexual behavior and male aggression, and investigates whether male constraint of female choice imposes a cost to females through induction of a stress response. Results show that while females exercise unconstrained mate choice through proceptive behaviors, males influence female receptivity through aggression and sexual coercion, shedding light on the degree to which rank related asymmetry in male mating success reflects female choice vs. constraint of choice. This dissertation includes previously published and unpublished co-authored material.

Made available in DSpace on 2014-12-17T15:37:20Z (GMT). No. of bitstreams: 1 MarianaCP.pdf: 340646 bytes, checksum: 7b38e8b3f11facf027891302ba389354 (MD5) Previous issue date: 2006-10-23 / Contrary to what is recorded for Callithrix jacchus females, the social interactions and hormonal profiles of males are less studied, and mainly in wild groups. The goal of this study was to investigate the behavioral and endocrine profiles of reproductive (RMs) and non-reproductive (NRs) common marmoset adult free-ranging males living in two natural groups (GC1 and GR2). The groups inhabited the area of the Escola Agr?cola de Jundia?/UFRN, located in Maca?ba, Brazil. Fecal collection for cortisol and androgen measurement and behavioral monitoring was carried out during the active phase from April to September, 2005. For behavioral data collection the focal instantaneous method was used every 5 min, for a total of 11.563 records. Statistical analysis was performed using non parametric tests and p < 0.05. Besides showing diurnal variation, the frequency of affiliative behaviors was significantly higher for RMs toward reproductive females than for NRs. Affiliative interactions of RMs with both reproductive females and NRs were similar, probably related to pair bond formation and helper recruitment, respectively. Parental care was also similar for both RMs and NRs. Both androgen and cortisol levels increased after the birth of the infants, mainly in RMs. The longitudinal profile of androgens fluctuates more in response to agonistic encounters and sexual behavior than that of cortisol. The mean basal excretion of both hormones was significantly higher in RMs and seems to reflect their higher participation in territorial vigilance and mate guarding behaviors. Significant positive correlations were found between agonism and cortisol and androgen hormones. These results describe, for the first time, the behavioral and hormonal profiles of common marmosets living in free-ranging groups and suggest that reproductive males are more responsive both behaviorally and hormonally to social group dynamics / Ao contr?rio do que ocorre para as f?meas da esp?cie Callithrix jacchus, as intera??es sociais e perfis hormonais de machos s?o pouco estudados, principalmente em grupos naturais. O objetivo desse estudo foi estabelecer os perfis comportamental e end?crino de machos adultos reprodutores (MRs) e n?o reprodutores (MnRs) vivendo em ambiente natural em dois grupos silvestres (GC1 e GR2). Os grupos habitavam a ?rea da Escola Agr?cola de Jundia?/UFRN, localizada no munic?pio de Maca?ba. A coleta de fezes para dosagem de cortisol e andr?genos e o monitoramento comportamental foram feitas uma vez por semana durante a fase de atividade no per?odo de abril a setembro de 2005. A coleta de dados comportamentais foi feita usando o m?todo focal instant?neo a cada 5 minutos para cada animal, em um total de observa??o de 11.563 registros. Para a an?lise estat?stica, foram utilizados testes n?o param?tricos e p < 0,05. Al?m de apresentarem varia??o diurna significativa, a freq??ncia de comportamentos afiliativos foi maior entre os pares reprodutores, comparado aos registros entre os MnRs e as f?meas reprodutoras. As intera??es afiliativas dos MRs com as f?meas reprodutoras foram semelhantes a freq??ncia de intera??es entre os focais (MRs e MnRs), possivelmente em fun??o da liga??o do par e recrutamento de ajudantes, respectivamente. O comportamento de cuidado com o infante tamb?m foi semelhante entre os MRs e MnRs e os n?veis de cortisol e andr?genos se elevaram ap?s o nascimento dos filhotes, principalmente nos MRs. O perfil longitudinal dos andr?genos flutuou mais em resposta aos encontros agonistas e contextos de c?pulas do que o cortisol. A excre??o basal m?dia de cortisol e andr?genos foi significativamente maior nos MRs e parecem refletir o maior envolvimento destes em contextos de territorialidade, vigil?ncia e guarda da parceira no grupo social. Correla??es positivas significativas foram detectadas entre a freq??ncia de comportamentos agon?sticos e os horm?nios cortisol e andr?genos. Estes resultados descrevem pela primeira vez o perfil comportamental associado ao perfil hormonal de machos de C. jacchus vivendo em grupos silvestres e sugerem que o macho reprodutor ? mais responsivo tanto comportamental como hormonalmente a din?mica do grupo social

Do endocrine systems influence personality and social behavior? Although animal research has identified several hormone-behavior relationships and the mechanisms that give rise to them, much less is known about hormones and social functioning in humans. This dissertation used three large data sets to investigate whether testosterone and cortisol were related to variation in personality constructs (Study 1), leadership behaviors (Study 2), and economic decision making (Studies 3 and 4). Study 1 revealed that basal testosterone was negatively associated with conscientiousness, basal cortisol was negatively associated with extraversion but positively associated with social dominance orientation, and the interaction between testosterone and cortisol was associated with the implicit power motive. Study 2 found that the testosterone-cortisol interaction predicted leadership behaviors, and Study 3 showed that basal testosterone as well as change in cortisol predicted economic decisions in the Hawk-Dove Game. Finally, Study 4 demonstrated that aggression predicted decisions to punish unfair monetary offers in the Ultimatum and Third Party Punishment Games. Aggression was also related to women's changes in testosterone from before to after the games. Taken together, these studies provide important evidence that testosterone and cortisol are related to personality, leadership, and social decision making. More broadly, this dissertation lays the empirical foundation for further inquiry on the complex biological systems that regulate personality and social behavior.