Humans use subtle sources of information-like nonverbal behavior-to determine whether to act cooperatively or antagonistically when they negotiate. Handshakes are particularly consequential nonverbal gestures in negotiations because people feel comfortable initiating negotiations with them and believe they signal cooperation (Study 1). We show that handshakes increase cooperative behaviors, affecting outcomes for integrative and distributive negotiations. In two studies with MBA students, pairs

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... who shook hands before integrative negotiations obtained higher joint outcomes (Studies 2a and 2b). Pairs randomly assigned to shake hands were more likely to openly reveal their preferences on trade-off issues, which improved joint outcomes (Study 3). In a fourth study using a distributive negotiation, pairs of executives assigned to shake hands were less likely to lie about their preferences and crafted agreements that split the bargaining zone more equally. Together, these studies show that handshaking promotes the adoption of cooperative strategies and influences negotiation outcomes. Word Count: 150