A universal preference for animate agents in hominids

When conversing, humans instantaneously predict meaning from only fragmentary and ambiguous speech, long before utterances are completed. They do this by integrating priors, i.e., assumptions about the world before evidence is taken into account, with novel contextual evidence to rapidly decide on the most likely meaning. One powerful prior is attentional preference for agents as the instigators of events. This biases sentence processing across languages, but universally so only if agents are animate. Here, we investigate the evolutionary origins of this preference, by allowing chimpanzees, gorillas, orangutans, as well as human children and adults to freely choose between agents and patients in still images, directly following video clips depicting their dyadic interaction. All participants showed an agent preference when agents were animate, although the effect was attenuated if patients were also animate. The preference occasionally extended to inanimate agents but never to animate patients. Our findings suggest that a preference for animate agents evolved prior to language and is not reducible to a more general interest in self-propelled entities or other widely attested perceptual biases in animals. To conclude, both humans and great apes prefer animate agents in decision tasks, echoing a universal prior in human language processing.