On Being Unpredictable and Winning

Empirically, it remains open whether and how competitors make themselves unpredictable, why they do so, and how this conditions conflict dynamics and outcomes. We examine these questions in interactive attacker-defender contests, in which attackers invest to capture resources held and defended by their opponent.

Study 1, a re-analysis of nine (un)published experiments (total N=650), reveals significant cross-trial variability especially in pro-active attacks and less in re-active defense. Study 2 (N=200) shows that greater variability makes both attacker’s and defender’s next move more difficult to predict, especially when variability is due to occasional rather than (in)frequent extreme investments in conflict. Studies 3 (N=27) and 4 (N=106) show that pre-contest testosterone, a hormone associated with risk-taking and status competition, drives variability during attack which, in turn, increases sympathetic arousal in defenders and defender variability (Study 4).