Summary of bonobo prosociality.

1. Prosociality driven by selfish motivation (i.e. self-regarding preferences): experiment 1–2 of current study; [12]; [47] also confirmed the groupmate results. 2. Prosociality driven by selfish motivation (i.e. self-regarding preferences): The current series of experiments does not examine this type of prosociality since it does not require sharing. Given the results of experiment 1–2, this low-cost, high-benefit context does not allow us to examine the presence of any unselfish motivation. In a setup similar to experiment 1–2, [47] showed that when there was no food to share bonobos in a zoo opened a door for a groupmate, although they also opened the same door at similar rates in a non-social control (i.e. this suggests for groupmates, opening is probably not driven by social reward). We predict in the same contexts bonobos would open the door more frequently for a stranger than in a nonsocial control or for a groupmate since they do this in the current study when it results in the loss of food. 3. Prosociality driven by unselfish motivation (i.e. other-regarding preferences): experiment 3 of current study. 4. Prosociality driven by (stronger) unselfish motivation: experiment 4 of current study; [48] also confirmed the groupmate results.