Working collaboratively in small groups is one of the primary ways that modern humans accomplish anything. But what explains whether a group succeeds? Previous research on group dynamics has considered things like the demographic and psychological characteristics of individual group members. But a recent study published in PNAS indicates that their biology matters, too. Groups with collectively high testosterone and low cortisol (a stress hormone) show the highest performance in group tasks.

To examine the effects of hormones on group performance, the researchers collected saliva samples from 370 MBA students, then assigned them into groups of three to six members. The groups were then given a group decision-making task, and their performance was evaluated in light of the testosterone and cortisol levels in their saliva samples.

The decision-making task was a computerized exercise that asked the group to manage a fictional computerized laboratory for seven days, with the goal of maximizing profitability. The groups competed against each other to devise the most profitable management scheme. Since the lab required 24-hour monitoring and was too complicated for one person to manage on their own, the task required members to be interdependent and rely on each other to maximize their performance. However, team members were allowed to use any decision-making process they preferred to complete the task.