when they arise.

Group decision making obviously involves members interacting with each other. Casting a vote requires a minimum amount of communication for the individual (only to inform other group members about his or her choice). However, other group decisions allow for extensive communication and negotiations of the decision. Our questions are: 1) which forms of communication are most likely to facilitate an improved outcome, and 2) what is actually being communicated in successful groups? Recent experiments by @Bahrami2010 have shown that cooperation can be beneficial, even in simple task, and that this benefit is best explained by the participants communicating their relative confidences. In their study, dyads (pairs) performed a perceptual two-choice discrimination task. On every trial participants had to decide which of two consecutive stimuli (sets of Gabor patches) contained a patch with higher contrast. First, decisions were collected from both persons; then, if the decisions were different, the participants were allowed to communicate to reach a joint decision.

The decision data obtained from each person was used to fit a psychometric function, i.e., the probability of that person giving a specific answer, as a function of the difference of the contrast between Gabor patches. These functions describe 