The Boyd-lead team found that small groups are usually made up of people who know each other. They maintain coordination through a system of mutual help.
Each member wants to help each other because they don't want to disappoint other friends (members) and they, themselves, might need help from other members in the future.
The Boyd team suggests that these small groups have a 'personal connection' and are able to maintain the ability to cooperate among one another through this familiarity with one another.
However, in larger groups everyone doesn't always know each other. And, some members become, what the researchers call, 'free-riders,' or people who benefit from the group without adding to it.
For instance, they are able to eat the food produced by the group, without actually having to help produce the food.
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When this happens, the group must resort to punishment in order to maintain cooperation among members. And, this punishment is coordinated and conditional.
In the April 29, 2010 National Science Foundation's article 'Coordinated Punishment Leads to Increased Cooperation in Large Groups' states that 'The finding challenges previous cooperation/punishment models that argue punishment is uncoordinated and unconditional.'
Dr. Boyd and his team report their research's findings in the April 30, 2010 issue of the journal Science. The article's title is "Coordinated Punishment of Defectors Sustains Cooperation and Can Proliferate When Rare" (DOI: 10.1126/science.1183665).
The NSF article adds, ''¦ it turns out that most members of large groups cooperate. Why? Boyd and his colleagues suggest cooperation is maintained by punishment, which reduces the benefits to free riding. There are tribes, for example, that punish free-riders who do not participate in warfare by not allowing them to take a bride. Thus, there is the threat of losing societal benefits if a member does not cooperate, which leads to increased group cooperation.'
And, 'Previous models of cooperation assumed that punishment of free-riders was uncoordinated and unconditional. One problem with these models was that the costs associated with punishment were often higher than the gains of cooperation. Thus, the cost of one group member's punishing a free-rider would be substantial and would not overweigh the gains achieved through increased cooperation.'
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Thus, the researchers conclude that punishment of so-called free-riders in large groups is coordinated and conditional. And, that it occurs in three steps: (1) one or more members signal that punishment may be performed on a free-rider (or free-riders), (2) other members decide to join or not to join in the act of punishment, and (3) members punish the free-rider (or free-riders).
The NSF article states that the ''¦ results of their [researchers'] model look a lot like what is seen in most human societies, where individuals meet and decide whether and how to punish group members who are not cooperating."
And, "This is coordinated punishment where group members signal their intent to punish, only punish when a threshold has been met and share the costs of punishing.'
Louis Putterman, also in the Science magazine, comments on the Boyd study in his article "Cooperation and Punishment." Dr. Putterman is from the Department of Economics at Brown University, in Providence, Rhode Island.