Prior research has shown that an individual's hormonal profile can influence the individual's social standing within a group. We introduce a different construct-a collective hormonal profilewhich describes a group's hormonal make-up. We test whether a group's collective hormonal profile is related to its performance. Analysis of 370 individuals randomly assigned to work in 74 groups of three to six individuals revealed that group-level concentrations of testosterone and cortisol interact to predict a group's standing across groups. Groups with a collective hormonal profile characterized by high testosterone and low cortisol exhibited the highest performance. These collective hormonal level results remained reliable when controlling for personality traits and group-level variability in hormones. These findings support the hypothesis that groups with a biological propensity toward status pursuit (high testosterone) coupled with reduced stress-axis activity (low cortisol) engage in profit-maximizing decision-making. The current work extends the dual-hormone hypothesis to the collective level and provides a neurobiological perspective on the factors that determine who rises to the top across, not just within, social hierarchies.umans have always worked collaboratively in small groups to accomplish goals. In modern organizations, group work is increasing because of the growing competitive and technological demands placed on organizations and the belief that a greater variety of perspectives and approaches will lead to more innovative solutions (1-3). As a result, decades of research have focused on understanding the factors that can enhance group performance and allow some groups to outperform others. Not surprisingly, groups with structures, processes, and norms that facilitate collaboration and coordination tend to perform well (4, 5). Additionally, group composition can influence performance; groups composed of members that vary in diversity, skills, and intelligence outperform others when the appropriate structures, processes, and norms are in place (3,(6)(7)(8)(9)(10).Past research on the effects of group composition on performance has focused primarily on the demographic and psychological characteristics of group members without taking into consideration the biological make-up of groups. This omission is particularly surprising because there is evidence that hormonal profiles can influence performance among individuals within a group. Indeed, past research has found that a hormonal profile characterized by high testosterone and low cortisol predicts an individual's performance and status attainment (11). Just as individuals have a hormonal profile that affects their individual performance and social status, we suggest that groups likewise can be characterized by a particular hormonal profile-their collective hormonal profile-which will influence group performance. We define a collective hormonal profile as the hormonal make-up of a group of individuals. Here, we test the hypothesis that groups with a collective...