“How many bad apples does it take to spoil the whole barrel?”: Social exclusion and toleration for bad apples

In social dilemmas, where personal welfare is in con?ict with collective welfare, there are inherent incentives

to act non-cooperatively. Moreover, there is evidence that the example of a few uncooperative

group members ("bad apples”) is more in?uential than the example of comparable numbers of cooperative

members (a bad apple effect). Two studies are reported that examine the functional relationship

between the number of likely bad apples and individual cooperation, and whether and when the threat

of social exclusion for uncooperative behavior may effectively counter the temptation to follow the

example of such ‘‘bad apples”. It is shown that (a) the threat of exclusion is suf?cient to counter the temptation

to follow a few bad apples’ example, (b) such threats cannot, however, overcome the cooperation degrading

effects of large numbers (e.g., a majority) of bad apples, and (c) the effectiveness of such threats

may be greater in relatively smaller groups.