Waiting for a future benefit, whatever its currency, is hard for all animals, humans included. Studies of rats, birds, monkeys, apes, human children and adults show that individuals perceive future gains as less valuable than immediate, but smaller gains. For example, give any one of these animals a choice between one piece of food and ten, and they will pick the ten. More is better than less, except if you are a dieting human. Now give them a choice between one piece available immediately and ten pieces available after some delay. Virtually every animal shifts to the one piece, with the only comparative difference linked to the length of the delay — a few seconds for rats, birds, most monkeys, young children, and adults with frontal lobe damage, a few minutes for some apes, older children and some adults. Everyone is, to some extent, pulled by the hedonistic now. The future loses its luster when a tasty alternative is just within reach. This is in part due to the uncertainty associated with the future, and in part, the sheer temptation to take what is in front of us.
Unique evolutionary changes in the human brain allowed us to exert much greater patience, overriding the pull of the hedonistic now. These changes didn’t evolve for punishment, but they were readily deployed by this system of justice. We rely on creative strategies to place value on the future, including putting resources away so that we can’t use them — think savings accounts — and making verbal commitments that bind us to the future — think about the social embarrassment of failing in front of friends. These strategies help diminish the emotional pull of taking what is immediately available, allowing future benefits to gain in attractiveness. This is a brain that can wait for the delayed benefits of punishment.
The brain changes that facilitated our capacity to delay gratification were accompanied by others that further offset the costs of punishment: our brains reward us with a feel-good feeling when we pay the costs of punishment. For the first time in evolutionary history, the physical and psychological costs of punishment were at least partially offset by the pleasure of justice served, whether delivered directly or witnessed from afar.
When we punish or get even with those who have acted badly, we feel a hedonic high, an experience captured by the metaphor “revenge is sweet but not fattening.” As demonstrated by the economist Ernst Fehr, this is more than a metaphor. When we hand someone his just deserts, punishing someone for cheating, lying, or breaking a promise, our brain responds as if we handed ourselves just desserts, activating brain circuitry associated with reward. In one study, two subjects played a monetary exchange game in which one player — the donor — decided how much of a pot of money to give to another. A third player observed, out of view, the outcome of the exchange. In some cases, observers witnessed a fair division of the money and in other cases, an unfair division in which the donor kept a disproportionate amount of the total. The observer then faced a difficult decision: leave the two players
with their take-home earnings or use personal funds to take away money from the donor, returning it to
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