Hand preference predicts behavioral responses to threats in Barbary macaques

The structure and functioning of the brain are lateralized – the right hemisphere processes unexpected stimuli and controls spontaneous behavior, while the left deals with familiar stimuli and routine responses. Hemispheric dominance, the predisposition of an individual using one hemisphere over the other, may lead to behavioral differences; particularly, an individual may be programmed to act in a certain way concerning hemispheric dominance. Hand preference is a robust estimator of hemispheric dominance in primates, as each brain hemisphere controls the opposing side of the body. Studies have found links between hand preference and the exhibition of different behaviors in contexts such as exploring and manipulating objects. However, little is known about whether hand preference can predict behavioral variations in other ecologically relevant contexts like, for example, predation. We investigated the relationship between hand preference and the behavioral responses to two types of predator models in captive Barbary macaques ( Macaca sylvanus ) (n=22). Hand preference was determined by observing unimanual foraging, whereas focus and tension behaviors were quantified during experimental exposure to predator models. We found 91% of the macaques to be lateralized with no group-level bias. In contrast to their right-hand counterparts, individuals with a strong left-hand preference elicited frequent focus and tension behavior. Additionally, the behavioral response varied with predator type. We also found an interaction effect between hand preference and the predator type. Our study suggests that hand preference can reliably predict behavioral variations in the context of potential predation. While these results are consistent with the lateralized brain function, indicating lateralization as a potential neural mechanism of behavioral variation, the interaction effect between hand preference and predator type elucidates the importance of context-specificity when investigating laterality non-invasively. Future research on other non-human primates using the current framework may shed light on the evolution of laterality and underlying behavioral predispositions.