Publication Date


Document Type


First Advisor

Miller, Charles E. (Professor of psychology)

Degree Name

M.A. (Master of Arts)


Department of Psychology


Coalition (Social sciences)


The equal excess and bargaining theories of coalition formation were tested in a study involving 76 five-person groups. The effects of three situational variables assumed by the equal excess model to influence coalition behavior were examined: restrictions on information availability, size of monetary stakes, and bargaining experience. Each group played a multivalued apex game four times, either for low or for relatively high monetary stakes. Information availability was manipulated so that in the complete information condition subjects were given information about the payoff values of all possible coalitions, whereas in the limited information condition subjects were given only information about the payoff values for coalitions of which they could be a part. The bargaining and equal excess models made opposing predictions for the game that was played. Specifically, bargaining theory predicted an increase in the Apex player's share of the payoff in the AB coalition from the initial encounter (low stakes, limited information) to asymptote (high stakes, complete information); whereas the equal excess model predicted a decrease in the Apex player's share of the payoff in the same coalition. As predicted by both theories, the AB coalition formed most frequently. Information availability was found to have a significant effect on coalition frequency, with more groups forming the AB coalition in the incomplete information condition. Both bargaining experience and information were found to play a role in the initial offers made by players. Specifically, Player A was found to become more demanding across games, especially when given complete information. Players C, D, and E, on the other hand, were found to become significantly less demanding across games, particularly when given complete information about payoff values. Information availability also had an effect on actual payoff division, with Player A receiving a higher mean payoff in the AB coalition when given complete information. This finding was contrary to the equal excess model's prediction. In addition, Player A was frequently unable to receive better than an equal split of the payoff when given incomplete information. Experience was also found to have a significant effect on payoff division, with strong players being able to increase their share of the payoff across games. This finding was in opposition to what the equal excess model predicted. Monetary stakes were not found to influence either coalition formation or payoff division. Finally, the accuracy of theoretical predictions was found to depend on information availability. As predicted, the initial predictions of bargaining theory were more accurate for players in the incomplete information condition, whereas the asymptotic predictions were more accurate for players in the complete information condition. Information availability had no significant effect on the accuracy of equal excess predictions, although contrary to expectations, asymptotic predictions seemed to provide a better fit for players in the incomplete information condition. Although the predictions of the equal excess model were more accurate in absolute terms than the predictions of bargaining theory, the equal excess model did not appear to capture accurately the dynamic effects of situational variables such as experience and information availability. Bargaining theory, on the other hand, was able to predict accurately the effects of these variables on both coalition formation and payoff division.


Includes bibliographical references.


v, 55 pages




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