Trust and group size in a social dilemma

In social dilemma experiments, the positive effect of trust on the level of cooperation has been repeatedly demonstrated. However, the effect of trust is expected only when the members behave strategically. Since strategic considerations are less relevant in larger groups, the effect of trust is hypothesized to diminish as the group size increases. The hypothesis was clearly supported in an experiment using 3-person and 7-person groups: The trust by size interaction was significant with the simple main effect of trust being significant only in 3-person groups, but not in 7-person groups.