Friday, September 26, 2003

Monkey business

Something for the phil of biology / phil of mind / evolutionary ethics geeks: a recent experiment seems to indicate that monkeys have a sense of fairness

Individuals were drawn from two large, well-established social groups of captive brown capuchins from colonies at the Yerkes National Primate Research Center and paired with a partner. Pairs were placed next to each other and trained to exchange with human handlers a small granite rock within 60 seconds to receive a reward, in most cases, a piece of cucumber.


Partners of capuchins who made the swap either received the same reward (a cucumber slice), or a better reward (a grape, a more desirable food), for the same amount of work or, in some cases, for performing no work at all.

Brosnan said the response to the unequal treatment was astonishing: Capuchins who witnessed unfair treatment and failed to benefit from it often refused to conduct future exchanges with human researchers, would not eat the cucumbers they received for their labors, and in some cases, hurled food rewards at human researchers.

Those actions were significant. They confirmed that not only did capuchins expect fair treatment, but that the human desire for equity has an evolutionary basis.

It's easy to see how reciprocal altruism would create evolutionary pressure for both "cheater detectors" (for which there is apparantly some evidence) and mechanisms to ensure you're not getting a crap deal and being played for a sucker (of which the above is a great example). And the existence of such detectors in monkeys would suggest that they evolved fairly early on (though we'd need further experiments with other primates to confirm that).

Of course, we can't draw any sort of moral conclusion from this (that would violate Hume's principle of "no ought from is"). But what it is useful for is

  • adding more evidence to the growing pile that suggests that humans are not rational utility maximisers, as presupposed by economists; and
  • pointing out that unfairness makes people unhappy. If we independently value happiness in our moral scheme, then this gives us added reason to value equity.

Crooked Timber has some typically thoughtful comments as well.