The effects of group size and communication availability on coalition bargaining in a veto game

Examined the effects of manipulating the size of groups of 250 male undergraduate negotiators and their ability to communicate with one another in a game in which 1 player held veto power (i.e., had to be included in any winning coalition). The predictions of 3 models (core, value, and weighted probability) were tested. The game, in which the veto player could form a winning coalition with any other single player, was repeated for a series of 10 winning coalitions (trials). The effects for group size indicate significant differences between 3-person groups and 4-, 5-, and 6-person groups, and between all of these groups and 7-person groups. The increasing payoffs over trials were significant in the no-communication conditions, but no significant increases occurred in the conditions in which communication was available. The increasing payoffs for the veto player when communication opportunities were not available yielded the only support for the predictions of the core model; the overall payoffs consistently supported the predictions of the value and the weighted probability models.