Growing up, your parents and teachers probably reminded you to "play fairly" and share with others. Mantras like this often get repeated to children so they know the right way to behave upon reaching adolescence.
However, reminding children of these tenets could not only be a waste of breath but it could also have the opposite effect on them.
Children naturally develop the tendency to behave fairly, Rachel L. Kendal, a senior lecturer in anthropology at England's Durham University, wrote in The Washington Post. When authority figures tell children to "be fair," the motivation for the child becomes these externally imposed rules, which they're less likely to follow than rules they personally believe in.
The issue of how animals react to fairness has made the news lately due to a recent review of the evolution of fairness published in the journal Science by Sarah Brosnan of Georgia State University and Frans de Waal of Emory University. Brosnan and de Waal analyzed studies on how species of primates, dogs, birds and fish reacted to equity and non-equity when completing the same tasks.
The results show that responding to someone getting more than you for doing the same task is common among many different species. However, it seems that noticing when you receive more and trying to make things equitable is much less widespread. It is something that only humans and their closest ape cousins seem to do. Brosnan and de Waal believe that humans and chimpanzees splitting off from other primates during evolution may have sparked their unique view of fairness.
This latter response might be because animals would rather avoid any negative outcomes, such as conflict and the loss of cooperation, by having a happy partner. It also might be a way to save one's reputation so that future cooperation remains intact.
However, Brosnan told NPR's Shots blog that "fairness is a social ideal" and animals "don't have social ideals in the same sense" as humans. For animals, this behavior may be based more on emotion such that when cooperative partners get upset, giving them something makes them more satisfied, which makes for a more pleasant experience for everyone.
There's a reason the phrase "The squeaky wheel gets the grease" is so well known.
