Great Apes Reinstate an Interrupted Triadic Game: A Comparison Across Age and Species

When humans engage in joint action, they do so with an underlying sense of joint commitment, a feeling of mutual obligation towards their partner and the shared goal. Whether our closest living relatives, the great apes, experience and understand joint actions in the same way is subject to debate. Crucial evidence concerns how participants respond to interruptions of joint actions, particularly if they protest or attempt to reengage their reluctant or distracted partners. During dyadic interactions, great apes appear to have some sense of joint commitment, according to recent studies, but data are inconsistent for triadic games with artefacts. We addressed this issue by engaging <em>N</em>=23 apes (5 adult chimpanzees, 5 infant bonobos, 13 adult bonobos) in a “tug-of-war” game with a human experimenter who abruptly stopped playing. Adult apes readily attempted to reengage the experimenter, with no species differences. Older bonobos showed more reengagement attempts with more game-related behaviours than younger bonobos, which might explain negative results of earlier research. Great apes may thus have motivational foundations for joint commitment experienced by humans, but this capacity might develop only later in life. We discuss this finding in relation to evolutionary and developmental theories on shared intentionality.