Hand Preferences in Olive Baboons (Papio anubis) During Cognitive Performance on Match-to-Sample Tasks and Natural Behaviors.

An individual shows handedness when they consistently prefer one hand over the other for tasks that can be performed with either hand. Humans have a population-level right-hand preference, and past research shows that a variety of nonhuman primate species also show hand preferences. More complex manual tasks elicit stronger hand preferences than less complex manual tasks, but not much is known about hand preferences during a cognitive task in nonhuman primates. The current study investigated hand preferences in olive baboons (Papio anubis). Seven baboons participated in a match-to-sample task on a touchscreen computer. We recorded each baboon's hand use as they touched the start box, sample stimulus, choice stimulus, and which hand they used to retrieve the food reward. All 10 baboons in the troop were also observed in their outdoor zoo habitat, where they were carrying out natural behaviors. In the current study, the touchscreen task was cognitively demanding, without being manually complex, as the baboon simply touched the screen. The direction and strength of hand preference were calculated using z-scores and handedness index (HI) scores for each individual baboon. When completing the cognitive task, five baboons were left-handed, and two baboons were right-handed. Five of the baboons had strong preferences (three left-handed and two right-handed) and two had weak preferences. When engaging in natural behaviors, eight baboons were left-handed, one baboon was right-handed, and one baboon was ambiguously handed. Two of the baboons had strong preferences (one right-handed and one left-handed), and eight had weak preferences. Four of the seven baboons had consistent hand preferences when completing the cognitive task and when engaging in natural behaviors in their habitat. These results show that similar to manually complex tasks, a complex cognitive task such as match-to-sample elicits stronger and more directional hand preferences than natural behaviors.