Sharing is a prosocial behaviour, one that individuals do to benefit others. Living Links researchers and others from American institutes have recently published a paper looking at how these three species compare.
The main aims of the research were to;
1 – Compare the ability to be prosocial in chimpanzees, capuchins and humans of various ages by using the same method across all three species.
2 – Investigate if experiencing prosocial behaviour will then in turn influence individuals to be more prosocial.
The apparatus that was used in the study has been nick named the ‘Shelfish Apparatus’. The device has two sliding shelves with rewards on them of varying levels (i.e. some high food rewards and some low food rewards). One primate has the power to pull the shelf where the other will just receive what the other primate has chosen in the pull.
Note: Stickers were used in the human test scenarios instead of food items.
In the first part of the study where the species were compared against each other they tested various scenarios. In all cases the puller was always given 2 shelves with rewards of the same value, the receiver side had the varying levels of rewards.
Some of the scenarios they tested were;
Empty control - They could pull the shelf towards them to receive a reward with no one next to them.
Prosocial option – They could pull the shelves with a neighbour there to also receive a reward.
The results showed the most significant prosocial behaviours occurred in separated chimpanzees when they received a more preferred food reward.
Adult humans would still pull the shelf with a more preferred reward for their partner even if they received a less preferred reward themselves.
Finally like the chimpanzees, the older human children were only significantly prosocial when they received a more preferred reward.
As for our capuchins…well when they were tested in the prosocial condition they only gave the receiver a more preferred food reward by chance.
In the second part of the study our researchers wanted to find out if experiencing prosocial behaviour would then encourage and individual to then become more prosocial.
They tested this in a very clever way that took out the chances of the prosocial behaviour just being reciprocal. The experiments were run in three phases with chimps, children and capuchins.
In the first phase was done the same as the prosocial condition in the above tests. The second phase let them experience another primate that was always prosocial to them and then third they were retested with their original partner.
In this study chimpanzees were significantly more likely to be prosocial after they experienced someone being prosocial to them. This was also true for the children aged 7 and older. Both the capuchins and younger children were still only demonstrating prosocial behaviour by chance.
So what do these results mean in terms of the evolution of prosocial behaviours?
One of the authors on the paper, Professor Whiten states:
“We believe our study is the first to demonstrate that the prosocial behaviour of humans and non-human primates is shaped by the everyday social actions of those around them. Kindness may thrive, evolve and inspire when helping, sharing or donating are part of the cultural experience.”
To read the full article click on the reference link below.
Claidiere, N., Whiten, A., Mareno, M.C., Messer, E.J.E., Brosnan, S.F., Hopper, L.M. Lambeth, S.P., Schapiro, S.J. & McGuigan, N. (2015). Selective and contagious prosocial resource donation in capuchin monkeys, chimpanzees and humans. Scientific Reports, 5: 7631. DOI: 10.1038/srep07631