The threat of group extinction proves a powerful motivator to cooperation

A new study has suggested that groups enjoy an advantage if their members are "ready to aid one another and to sacrifice themselves for the common good", in keeping with one of Charles Darwin's theories regarding cooperation and competition.

The researchers from Rice University, the University of East Anglia and Texas A&M University showed, using variations of the 'public goods game', that when no other mechanism is present to reinforce group cooperation, the threat of group extinction is powerful enough to motivate and increase cooperation within a group.

"The finding is stunning for what it says about group extinction," said Professor Rick Wilson of Rice University, one of the authors of the paper which was published this week in the journal PLOS ONE. "People respond to threats to their group. They're willing to forego opportunities to free ride on the efforts of their group members."

The authors said that the study provides insight into the origins of group conflict and "supports the notion that competition between groups is part of what has cultivated human cooperation."

"History seems to support the idea that a group working together can overcome another group and drive them to extinction," said Wilson. "But it had not been clear whether this was due to groups cooperating when in competition or to pressure of extinction through selection."

The research centred on an experiment which was used to determine whether competition or extinction drives increased cooperation within groups. The experiment was based on the public goods game in which participants in groups are each given a set amount of money. Then each group member secretly chooses how much money to put into a group account and how much to retain for their own account. The amount in the group account is multiplied by a set factor, with the payoff equally divided among the members of the group at the end of the game. Participants also keep any money they did not contribute to the group account.

For the latest study, 168 undergraduate students were randomly assigned to groups of four. No participant had any knowledge of who their fellow group members were, and all interactions took place anonymously over a computer network.

The game consisted of two blocks of 10 periods. In each period every participant was given 50 monetary units and decided how much to keep in their private account and how much to put in to the group account. The private account was paid out at a rate of one to one whereas the group account contributions total was doubled and then divided equally among each member of the group.

"This basic experimental design has been used hundreds of times, and free riding is common," Wilson said. "We wanted to know whether competition or extinction works to eliminate free riding in the way that Darwin suggests."

The researchers split the experiment into four different versions:

The first version adhered to the standard public goods game in which, at the end of each period, subjects found out how much was contributed by others into the group account but were told nothing about the contributions of participants in the other groups.

In the second version, group competition was introduced. Participants were given the same information as the first version, however, they were also told that at the end of the first 10 periods their group would be ranked in terms of total earnings against the other groups in the experiment.

The concept of 'extinction' was introduced in the third version. Subjects were told that that at the end of 10 periods their earnings would be compared with the earnings of all the other subjects. One third of the lowest earners would be removed from the experiment and would subsequently not be allowed to participate in the second block of 10 periods.

In the fourth and final version of the experiment, 'extinction' was applied to groups rather than individuals. Participants were told that at the end of the first 10 periods, their group's earnings would be compared with the earnings of the other groups. Any groups that found themselves in the bottom third of earners would be removed from the experiment and would not participate in the second block of 10 periods.

The team found that in versions one to three of the experiment, average contributions declined steadily over the first 10 periods. "Over time, people contribute less to the public good and favour their private investments," Wilson said.

"But when we introduce group extinction, we see a remarkably different result," he said. "At the outset, individuals contribute almost everything to the group account. The pressure of group extinction results in individuals cooperating within the group."

In the fourth version, members contributed about 92% of the total amount of money into their group accounts, compared to 35%, 42% and 36% for the first, second and third versions respectively.

The authors noted that "group extinction leads to enhanced cooperation as long as the selection mechanism is present. Once it is removed, contributions remain higher for a time, but fall quickly toward ... zero contributions. The culture of cooperation engendered by the group extinction mechanism has only a brief longer-term carryover after the mechanism is removed."