Agent Preference in Chasing Interactions in Guinea Baboons (Papio papio): Uncovering the Roots of Subject-Object Order in Language.

Languages tend to describe "who is doing what to whom" by placing subjects before objects. This may reflect a bias for agents in event cognition: Agents capture more attention than patients in human adults and infants. We investigated whether this agent preference is shared with nonhuman animals. We presented Guinea baboons (Papio papio; N = 13) with a change-detection paradigm on chasing animations. The baboons were trained to respond to a color change that was applied to either the chaser/agent or the chasee/patient. They were faster to detect a change to the chaser than to the chasee, which could not be explained by low-level features in our stimuli such as the chaser's motion pattern or position. An agent preference may be an evolutionarily old mechanism that is shared between humans and other primates that could have become externalized in language as a tendency to place the subject first.