April 6, 2006
People agree freeloaders must be punished: study
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - People's ideas of a happy,
cooperative society in which no one gets punished fall apart as
soon as a few freeloaders show up, researchers reported on
group that did not use punishment, most eventually left for a
group that fined transgressors, the team at the University of
Erfurt in Germany and the London School of Economics in Britain
"Our results show that the sanctioning institution is the
undisputed winner in a 'voting-with-one's-feet' competition
with a sanction-free institution," the researchers wrote in
their report, published in the journal Science.
The study can help in understanding how to make society
work more smoothly and can help in designing policies aimed at
ensuring cooperation, Joseph Henrich, an anthropologist at
Emory University in Georgia, wrote in a commentary.
"Even if nearly everyone is initially cooperative and
contributes, free-riders can profit and proliferate, leading to
the eventual collapse of cooperation," Henrich wrote.
For example, if most people in society are brave, conserve
gas and donate blood, he explained, others benefit by evading
military service or driving gas-guzzling cars.
In the study, researchers asked 84 students from Erfurt
University to join one of two groups to play a game with
tokens. One group of players punished members who did not share
freely, while the other group did not.
The students could choose which group to join.
"Each player is endowed with 20 money units (tokens) and
may contribute between 0 and 20 (tokens) to a public good," the
researchers wrote. "Each group member equally profits from the
public good, independent of his or her own contribution."
In the punishment group, members could choose to fine other
members three tokens, but it cost them one of their own tokens
to do so.
Two-thirds of the students initially chose the group in
which members could not punish others, but many abandoned that
group when they saw those in the "punishment" group were
And former freeloaders were some of the most enthusiastic
converts to the punishment mode, the researchers found.
"You can't explain this dramatic change in behavior by
saying that people are just looking for the best payoff. People
gave up payoff to follow the cooperative norm," Erfurt
researcher Bettina Rockenbach said.
Bernd Irlenbusch of the London School of Economics added,
"I was surprised so many of the freeloaders exerted punishment
on others when they entered the sanctioning institution."
When the game ended after 30 rounds, the people in the
punishment group had donated an average of 18 tokens per round,
while the live-and-let-live group had almost no members and
those who remained donated three tokens to the public good on
average per round.
Little actual punishment was applied during the later
rounds of the game, apparently because the threat of punishment
was enough to ensure cooperation, the researchers said.