Why you should never short-change a monkey

We humans share an innate sense of fairness – and of righteous grievance – with other primates

In a 2003 experiment, ‘short-changed’ monkeys became upset. Above, a capuchin monkey. Photograph: Thinkstock

In a 2003 experiment, ‘short-changed’ monkeys became upset. Above, a capuchin monkey. Photograph: Thinkstock

 

Humans and other primates have evolved a moral sense of right and wrong, of fairness and unfairness, and are prepared to endure personal sacrifice to uphold moral standards and to inflict discomfort on others who treat us unfairly. This subject is discussed by Michael Shermer in this month’s edition of Scientific American.

In 2003 researchers at Emory University, Atlanta, taught female capuchin monkeys to trade pebbles for treats, mainly slices of cucumber. The monkeys were then grouped in pairs and the experiment continued. Sometimes one member of a pair was given a grape, much nicer than cucumber, in return for the pebble, while their companion monkey received cucumber. Also, some monkeys received grapes or cucumber for doing nothing, while their partners still had to present a pebble to the person doing the experiment in order to receive their treat. As these inequitable trades continued, the “short-changed” monkeys became upset, often refusing to accept the cucumber and even hurling the cucumber back at the person.

Now consider the Ultimatum Game, played in studies of the psychology of human economic motivation. Here the experimenter deals with two subjects, for example two men. The experimenter gives one man €100 and tells him to share it with the other man. He can offer the second man as much or as little as he likes. The rule is, if the second man accepts the offer they can both keep the money, but if the second man rejects the offer, neither man gets to keep any of the money.

A utilitarian view of economics predicts that both men would act in a strictly rational manner. The man with the €100 would offer the second man the lowest possible amount, say €5, and the other man would accept. The first man would thereby maximise his share and the second man would still get €5. The second man might describe the first man as “cheap”, but hey, he is still getting €5 for nothing.

The actual behaviour displayed in the Ultimatum Game is surprising. Firstly, the average money offered by the first man to the second is €40-€50, and secondly, the majority of the receivers turn down offers of less than €30 (Werner Guth and others, Journal of Economic Behaviour and Organisation, Vol 3, 1982).

Why would people behave so irrationally? The answer is our innate sense of fairness, as shown in the Dictator Game, a variation of the Ultimatum Game. Again, one man is given €100 and told he can either split it evenly with the second man or he can offer the second man €10 and keep €90 for himself. But the first man gets to keep the money even if the second man refuses the offer. Of the givers, 76 per cent choose to split the money 50-50 despite knowing that the receiver has to take whatever he is offered.

Our innate sense of grievance is also strong. In a variation of the Dictator Game, the recipient and the dictator swap roles every second round of the game. A former recipient, now turned dictator, gives out an amount strongly correlated with the amount he received in the previous round; in other words, the dictator “sticks it” to the recipient who gave him a low amount in the previous round.

Shermer goes on to generalise about moral behaviour, pointing out that only about 10 per cent of homicides are predatory in nature, for example occurring during a robbery. The other 90 per cent of homicides are a form of capital punishment in which the perpetrator acts as judge, jury and executioner, killing someone they judge to have wronged them grievously.

In most situations, since the Middle Ages, “self-help justice” has been taken over by rational systems of criminal justice. However, where people do not trust the justice system or live in corrupt states, they can still take the law into their own hands. Terrorism is one such example. The specific motives behind terrorism depend on the particular group, ranging from revolutionary Marxism to nationalism to the apocalyptic Islam practised by Islamic State. In order to counter terrorism we must understand its motivation.

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