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.

The researchers found that each group’s mean testosterone levels and cortisol levels (as measured in their saliva samples) significantly predicted their performance on this computerized lab management task. All measures of group performance showed a trend in which performance was highest when testosterone was high and cortisol was low.

The researchers also checked to see if this hormone interaction remained robust when controlling for dominance and anxiety, two traits that are thought to be associated with testosterone and cortisol, respectively. In this population, however, it turned out that neither self-reported dominance nor anxiety was correlated with either testosterone or cortisol.

Since diverse groups often perform better at tasks like this, the team checked whether high levels of hormonal variability within the groups influenced their performance. A within-group analysis showed that no significant effects of variability in either of these two hormones on a group’s performance.

There’s lots of data on how hormone levels influence individual performance. But scientists hadn’t previously looked into whether a group’s collective hormone profile may affect its functioning. The authors of this study suggest that high levels of testosterone and reduced levels of cortisol are likely to produce greater social rapport within a group and therefore boost the effectiveness of interdependent decision making.

However, plenty of details still need to be worked out. Future directions for this type of research may include investigations of how adding in a group member with markedly high testosterone or markedly low cortisol changes group dynamics. We may also want to examine how an individual’s level of various hormones influences their integration into the group. Regardless, this research presents an intriguing way of looking at organizational behavior.

PNAS, 2016. DOI: 10.1073/pnas.1603443113 (About DOIs).