Participants took part in an intergroup negotiation. In the first stage participants recorded their individual preferences (i.e., which of several possible options they should strive to achieve during the negotiation) for each negotiation issue. In the second stage they repeated this process as part of a 3-person cooperative group in preparation for the negotiation task. Our results show that the decision aggregation of negotiation teams is driven by 2 factors: The majority/minority status of the members advocating a given option and the extent to which the option advocated by a member was more hawkish (i.e., advantageous to the ingroup) than that of fellow members.