NEW YORK (Reuters Health) - A concern with one's reputation can help counter humanity's inherently selfish instincts, according to research published in the latest issue of the journal Nature.

``There are a lot of interactions where reputation is very important for the decision finding of an individual,'' study co-author Dirk Semmann, a biologist in the department of evolutionary ecology at the Max Planck Institute of Limnology in Plon, Germany, told Reuters Health.

Lead author Manfred Milinksi and colleagues were concerned with mechanisms that encourage people to cooperate with one another when natural instincts often place self-interest over group interest.

In one well-known experiment of cooperation, players are put into a group where they can benefit greatly by collectively contributing money to a common pot, but have an incentive to opt out for a greater personal gain. Researchers typically find that without checks or rewards to keep self-interest in line, the tendency to cooperate with others steadily declines.

In this study, researchers had students play two monetary games, the public goods game in which they publicly donated to the common pot, and a second game called indirect reciprocity, in which players publicly donated money to other people in the group, but never received direct donations back from those particular people.

As expected, when the players simply played the common goods game, cooperation within the group steadily declined. However, when the players alternated between the two games, their levels of cooperation remained high, motivated by their reputation developed in the public goods game.

The researchers hypothesize this was because players who were ``stingy'' in the public goods game developed a negative reputation and were ``punished'' by their fellow players in the subsequent indirect reciprocity games. These players were then more motivated to cooperate when they returned to the public goods game.

The investigators found that the impetus to cooperate was fragile: when the players did not expect to continue the indirect reciprocity game, their cooperation in the public goods game lapsed.

Overall, though, the players who alternated games had high levels of cooperation in the public goods game--leading to higher profits for all the players involved.

``Cooperation in the public goods game paid off,'' the authors note. ``Groups that alternated rounds...and thus were more cooperative in the public goods game earned significantly more money.''

``This result will not change human society,'' noted Semmann. ''But it may help understanding why under certain conditions people will not cooperate.''

SOURCE: Nature 2002;415:424-426.

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