The relations among laterality, cortisol, and approach-avoidance behavior in Garnett's bushbaby (Otolemur garnettii)
Many studies to date have demonstrated that approach and avoidance behaviors are processed asymmetrically in the brain and may be reflected in measures such as handedness. The purpose of this study was to extend work in primates on this topic to Garnett's bushbaby, a prosimian species. Furthermore, to determine whether measures in addition to handedness relate to approach-avoidance behavior, lateralized differences in tympanic membrane temperature were assessed. Cortisol measures were also obtained to determine whether it was related approach-avoidance behavior and handedness. Eleven captive-born Garnett's bushbabies ( Otolemur garnettii ) were evaluated for handedness and responsiveness to novelty. Moreover, the bushbabies were exposed to a sociality paradigm in which tympanic membrane temperature and cortisol were tested before and after social interaction. In line with a theory proposed by Davidson (1992), right-handed (left-hemisphere dominant) bushbabies were expected to show more approach behaviors and left-handed bushbabies more avoidance-related behavior in a novel-objects paradigm. In the sociality paradigm, patterns of prosocial and agonistic behaviors were expected to follow the same pattern, respectively. It was further hypothesized that prosocial behavior would be associated with decreases in left ear temperature while decreases in right ear temperature were expected to be associated with agonistic behavior. Regarding cortisol, it was expected that bushbabies in the sociality phase with higher cortisol would be left handed and show higher levels of agonistic behavior. None of the hypotheses implicating handedness or cortisol were supported. However, increases in left-ear temperature were associated with grooming and approach. The present study suggests the need for further consideration of models integrating the right hemisphere hypothesis with that of Davidson (1992) regarding the processing of approach-avoidance behaviors.