Ignore the Daily Mail’s headline, but read the report, since the contents are important.
The Virginia Tech Carilion Research Institute in the U.S.A. found that being in a group can lower intelligence, albeit on a temporary basis. This apparently affects women more than men.
Irrespective of gender, this phenomenon may certainly help explain some bad political decisions over the years!
The importance for leaders and managers is that they need to minimise or bypass this effect. In part this is another reason to limit the number of small group meetings. It is also a reason for whoever is running a meeting to be constantly aware of group dynamics, taking care to encourage those who may be affected.