IT鈥橲 not love, affection or even blatant self-interest that binds human
societies together. It鈥檚 anger. Swiss researchers made the unsettling discovery
while trying to fathom what makes people cooperate.
Traditional explanations, such as kinship and reciprocal altruism, rely on
genetic relationships or self-interest. These work for animals, but fail for
humans because people cooperate with strangers they may never meet again, and
when the pay-off is not obvious.
Such cooperation can be explained if punishment of freeloaders or
鈥渇ree-riders鈥濃�攖hose who do not contribute to a group but benefit from
it鈥攊s taken into account. However, in real life, punishment is rarely
without cost to the punisher. So why should someone punish a free-rider? Because
of emotionally driven altruism, says Ernst Fehr, an economist at the University
of Zurich in Switzerland.
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To test this 鈥渁ltruistic punishment鈥� hypothesis, Fehr and his colleagues
played an experimental game with six groups of four students each, in which real
money was at stake. Each member was given 20 monetary units (MUs) to keep or
invest in a group project. For every MU invested, the return for the group was
1.6 MUs, which was divided equally among the four members. So if only one person
chose to invest, putting in 1 MU, she got back only 0.4 MU. But if everyone
invested the full 20 MUs, they each ended up with 32 MUs, making total
cooperation worthwhile.
Investment, therefore, was always in the interests of the group, but never in
the interest of the individual doing the investing. A free-rider would benefit
from not investing. She could just gain from the money invested by others. After
a series of six games, in which members鈥� investments were anonymous and everyone
invested simultaneously, Fehr found that members contributed an average of 10
MUs in the first game. But cooperation quickly unravelled, says Fehr.
Contributions dropped to 4 MUs by the sixth game.
So Fehr decided to allow members to punish free-riders in their group, but at
a cost. If a member punished another, it cost the punisher 1 MU and the punished
3 MUs. In six such games the average investment was always higher than in those
without punishment, increasing to over 16 MUs. The threat of punishment
sustained cooperation.
Crucially, the punishment was an altruistic act, as the punisher would never
encounter the same free-rider again. To understand the motive behind altruistic
punishment, the researchers questioned the students about their emotions. They
found that anger appeared to be the cause. 鈥淎t the end of the experiment, people
told us that they were very angry about the free-riders,鈥� says Fehr. 鈥淥ur
hypothesis is that negative emotions are the driving force behind the
辫耻苍颈蝉丑尘别苍迟.鈥�
鈥淚t鈥檚 a great experiment,鈥� says Herb Gintis, an expert on human cooperative
behaviour at the University of Massachusetts in Amherst. Social policies which
do not provide an outlet for such emotions will fail, he says. In the 1980s, for
instance, people revolted against the welfare state in the US because they felt
that perceived freeloaders were not being taken to task.
More at: Nature (vol 415, p 137)