Chimpanzees use observed temporal directionality to learn novel causal relations.

We investigated whether chimpanzees use the temporal sequence of external events to determine causation. Seventeen chimpanzees (Pan troglodytes) witnessed a human experimenter press a button in two different conditions. When she pressed the "causal button" the delivery of juice and a sound immediately followed (cause-then-effect). In contrast, she pressed the "non-causal button" only after the delivery of juice and sound (effect-then-cause). When given the opportunity to produce the desired juice delivery themselves, the chimpanzees preferentially pressed the causal button, i.e., the one that preceded the effect. Importantly, they did so in their first test trial and even though both buttons were equally associated with juice delivery. This outcome suggests that chimpanzees, like human children, do not rely solely on their own actions to make use of novel causal relations, but they can learn causal sequences based on observation alone. We discuss these findings in relation to the literature on causal inferences as well as associative learning.