Effects of early adverse experiences on behavioural lateralisation in rhesus monkeys (Macaca mulatta).

In the past 15 to 20 years, evidence of population-level handedness in non-human primates has emerged from a plethora of studies, although considerable inconsistency is also apparent. The study reported here examined two factors that may contribute to the expression of hand preference: early rearing history and sex differences. Handedness was assessed in rhesus monkeys (Macaca mulatta) using a task that measures coordinated bimanual actions and is referred to as the TUBE task. Nursery-reared monkeys demonstrated greater left-hand bias in the TUBE task when compared to their mother-reared counterparts. Females showed greater right-hand preference and stronger bias on the TUBE task compared to males. These results provide evidence that early rearing experiences significantly influence the development of lateralisation in nonhuman primates.