Chimpanzees and bonobos reinstate an interrupted triadic game

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 a 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. Yet data are inconsistent for triadic games with objects. We addressed this issue by engaging N=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 exhibited more reengagement attempts, including 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, although this capacity might develop only later in life. We discuss this finding in relation to evolutionary and developmental theories on joint commitment.