“Make sure you play fairly,” often say parents to their kids. In fact, children do not need encouragement to be fair, it is a unique feature of human social life, which emerges in childhood. When given the opportunity to share sweets equally, young children tend to behave selfishly but, by about eight years of age, most prefer to distribute resources to avoid inequalities, at least among members of their own social group.
Biologists are surprised by this tendency to behave fairly. The
theory of evolution by natural selection predicts that individuals
should behave in ways to maximise their inclusive fitness. So behaviours
are only selected, and hence evolve, if they ensure the survival and
reproduction of the actor or kin whom contain copies of the actor’s
genes. However, the behaviour displayed by children seems to be at a
detriment to themselves, especially when those who benefit from their
selfless behaviour are not the children’s kin.
A child’s sense of fairness, egalitarianism, or aversion to
inequality can actually be hampered by instruction to “be fair” and
rewarding of this behaviour. That is because what is the child’s
intrinsic motivation, becomes a need to follow externally imposed rules.
And, as we all know, following rules we believe in is far easier than
following rules that are imposed upon us, despite attendant punishments
for not doing so.
Humans are pro-actively prosocial. We are often motivated to help
others without those others signalling their need, such as begging, or
displaying signs of need, such as crying.
As cultural practices are not responsible for children developing
their initial pro-social tendencies, it is thought that a sense of
fairness must have been under strong positive selection during human
In a new review published in the journal Science,
Sarah Brosnan of Georgia State University and Frans de Waal of Emory
University explore this topic by trying to explain how our response to
fairness, and unfairness, evolved. Their review is based on a large
number of studies with non-human animals regarding their responses to
receiving more or less (inequity), rather than the same (equity), reward
as others for undertaking the same task.
Species of primates, dogs, birds and fish have been studied. The
overall results indicate that responses to disadvantageous inequity,
say, protesting when another receives more banana pieces than you for
pulling the same rope, are strongest in species that co-operate with
others outside of mating and kinship bonds. This includes capuchin
monkeys, chimpanzees and the ancestors of dogs. In other words, animals,
including humans, that cooperate with non-kin have evolved sensitivity
to detrimental unfairness so that they can avoid being taken advantage
However, what is less common in the animal kingdom, is sensitivity to
advantageous inequity, or protest when you receive more reward than
another for the same task. Such inequity aversion, at a cost to oneself,
has only been recorded in humans and chimpanzees.
Brosnan and de Waal propose that the motivation to seek equal
rewards, despite disadvantaging oneself, is to prevent dissatisfaction
of the co-operative partner and avoid any negative outcomes that may
follow. The main negative outcomes are the likelihood of conflict and
loss of future advantageous co-operation with the partner.
Also, one’s reputation is tainted, reducing the chances of forming
future beneficial partnerships. When we humans “play fair” we are doing
so, according to Brosnan and de Waal, not due to a motivation for
“equality for its own sake but for the sake of continued cooperation”.
Humans have enlarged brains, which enhance our ability to understand
the benefits of self-control in dividing resources. We also have
language, which allows for enhanced reputation building. Because
responsiveness to advantageous inequity is only seen in humans and
chimpanzees, Brosnan and de Waal hypothesise that its evolution, since
the split from other primates, was the starting point for the eventual
development of the advanced sense of fairness displayed by humans.
The many heroic and selfless actions of individual humans, for
example rescuing strangers in mortal danger and money or blood donation,
are inspiring and admirable. Yet, however distasteful to contemplate,
it is likely that these individuals gain in terms of their reputation
and future cooperation from others, known as indirect reciprocity. If
extreme prosociality is a “costly signal” indicating ones worth to
future mates, it makes sense that highly visible individuals, such as
celebrities, may feel the most pressure to act charitably.