Por Fabrizio Dell’Anna, alumno del Máster en Primatología UdG – Fundació Mona, convocatoria 2016-18
A wise man once said: «Be the change you want to see in the world». But that mantra really works? Well, accordingly to a recent study, it could. Even among chimpanzees, but restrictions may apply.
But first, a little introduction: what are prosociality and prosocial behaviours? Broadly speaking, we can call «prosocial» a voluntary behavior intended to benefit another individual or a social group as a whole. These kinds of selfless actions are common and easily observable among humans, you can find them even at the foundations of one of the most followed religion in the world. But until now, there were not so much evidence that our closest relatives, the chimpanzees (Pan troglodytes), were keen to this kind of behaviour. Even human children usually don’t show prosocial behaviour until they reach the age of 7 and that’s probably due to the time needed to learn it and to be exposed to social influence.
So French researcher Nicolas Claidière and his colleagues wanted to test if prosocial behaviour can be affected by social learning. To put it simply: will I be more kind, generous or altruistic if I observe somebody being kind to someone else or to me?
Researchers designed a new experiment to test this hypothesis and they performed it on humans (children aged 5 and 7, and adults), chimpanzees and capuchin monkeys. Participants were paired with a conspecific and assigned a rather simple task: to choose a food reward while facing a pair of shelves, each baited with two rewards. The chosen shelf was connected to another one that delivered a reward to the partner, too. The quality of the rewards was the same for the individual that made the choice but different for the partner, one food reward was of higher quality than the other. In this way, researcher could test the presence of potential prosocial tendencies, for example if a participant always choose the shelf with the best rewards for the partner (see image below for a visual example).
That was just the first phase of the study, needed to understand the basic levels of prosociality in the participants: in this part only adult humans showed a clear tendency to also give the partner the high quality food reward, taking into account the partner condition and needs.
During the second phase of the study the tested individuals went under the social learning part of the study: a conspecific (a different individual from phase 1!) was trained to always exhibith a prosocial choice. In this way, participants were the recipient of an altruistic behaviour and researcher could test if there were any change between the first phase of the study and the Phase 3, which was structured in the same way as the first one, with the same first partner, except it happened after the “social-learning” Phase 2.
What about the results?
Human adults were not even tested in Phase 2 and 3, results were already clear in the first part of the study. Older children and chimpanzees showed a significant increase in prosocial behaviour after being exposed to the second phase, under some conditions: children showed prosocial tendencies only when they could choose the high quality reward for themselves. On the contrary, chimpanzees were more prosocial and did not care about their reward so much, showing an overall tendency to prosociality. Capuchin monkeys and younger children did not show any sign of prosocial tendencies after being tested in the third phase.
What does this study tell us about our species and our closest relatives?
Well, the first thing is that prosociality, even when present, is slow to develop: young children don’t show it but older ones do, even in a conditional and not fully developed form, meaning that time and experience are needed to learn these kinds of behaviours. And even more importantly, that it can be acquired or could be influenced by social learning and experience: doing good and being nice to someone can effectively teach others to behave in the same way.
Claidière, Nicolas, et al. “Selective and contagious prosocial resource donation in capuchin monkeys, chimpanzees and humans.” Scientific reports 5 (2015).
Images for Arkive.org