Large-scale cooperation is a hallmark of our species and appears to be unique among primates. Yet the evolutionary mechanisms that drove the emergence of humanlike patterns of cooperation remain unclear. Studying the cognitive processes underlying cooperative behavior in apes, our closest living relatives, can help identify these mechanisms. Accordingly, we employed a novel test battery to assess the willingness of 40 chimpanzees to donate resources, instrumentally help others, and punish a culpable thief. We found that chimpanzees were faster to make prosocial than selfish choices and that more prosocial individuals made the fastest responses. Further, two measures of self-control did not predict variation in prosocial responding, and individual performance across cooperative tasks did not covary. These results show that chimpanzees and humans share key cognitive processes for cooperation, despite differences in the scope of their cooperative behaviors.
Rosati_DiNicola_Buckholtz_Donation-task
Trial data from Donation task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_Helping-task
Trial data from Helping task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_Punishment-task
Trial data from Punishment task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_Discounting-task
Trial data from Temporal Discounting task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_GoNoGo-task
Trial data from Go/No-Go task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_SocialResponsivity-task
Trial data from Social Responsivity task; key for variable codes included as a separate tab in the file.
Rosati_DiNicola_Buckholtz_Task-Comparisons
Summary data of performance across tasks; key for variable codes included as a separate tab in the file.
Video_S1_Donation
Movie S1: Resource Donation Task. Chimpanzees chose between a prosocial option that provided food to themself and another individual, and a selfish option that provided food only to themself. Experimenter 1 (E1) sat to the side of the table and distributed the food (with side assignment for the options counterbalanced across trials), whereas E2 (the recipient) sat across from the chimpanzee. E2 could not access the food due to an additional grate between them and table, but they indicated their desire for the prosocial option by reaching for it effortfully through the grate. Here, the chimpanzee first selects the selfish option and then the prosocial option.
Video_S2_Helping
Movie S2: Instrumental Helping Task. E1 plays with a stick when E2 approaches and tries to take the stick; after a struggle, E2 steals the stick and tosses it into the chimpanzee’s room. For up to 30s, E1 reaches for the stick and makes an effortful noise without interacting with the chimpanzee. If the chimpanzee does not give them the object during that time, E1 then switches to directly recruiting the chimpanzee by calling their name and alternating gaze direction between the chimpanzee and stick for up to another 30s. Here, the chimpanzee gives E1 the stick in the first half of the trial.
Video_S3_Punishment
Movie S3: Punishment Task. E1 places a large tray of food on a table in front of the chimpanzees; E2 sits across from the chimpanzee at a collapsible wing of the table held up by a removable leg. E1 previously threaded a rope attached to this leg into the chimpanzee’s room. After 5s, E2 steals the tray of food from the chimpanzee and pretends to eat the food. Here, the chimpanzee collapses the table by using the rope to pull out the removable leg from underneath the table wing.
Video_S4_Discounting
Movie S4: Temporal Discounting Task. The experimenter places the smaller, immediately-available reward (one raw banana slice) on the left and the larger, delayed reward (three raw slices, available after one minute) on the right, with side assignment counterbalanced across trials. Prior to choice trials, chimpanzees experienced the associated quantities and delays in exposure trials with only one option available at a time. Here, the chimpanzee chooses the smaller, immediate reward in the first clip, and the larger, delayed reward in the second clip.
Video_S5_Go-No-Go
Movie S5: Go/No-Go Task. The experimenter places a piece of food on the far end of the table (out of the chimpanzee’s reach) and an object cuing the chimpanzee as to whether it is “go” or “no-go” trial in the center of the table, near the chimpanzee. If chimpanzees emit a response to the “go” object (here, a white overturned cup) by touching it, E gives them the food. In contrast, on trials where E presents the “no-go” option (here an overturned orange container, with cues counterbalanced across chimpanzees), if chimpanzees emit a response, E throws the food away. Here, the chimpanzee emits a response to both cue types, but hesitates before the “no-go” cue.
Video_S6_Social-Responsivity
Movie S6: Social Responsivity Task. Across eight distinct trials, chimpanzees were presented with four social and four non-social stimuli. In each trial, E1 placed a stimulus on a testing table, while E2 initially centered the chimpanzee at a distance 2m away. E2 then left when the trial started, and the chimpanzees’ latency to approach the stimulus was examined (within a trial lasting 30s). Here, the chimpanzee was slower to approach a person and relatively faster to approach a novel object placed on the table.
