Sharon Begley
Interestingly enough, the reverse is apparently true as well, at least in certain circumstances. That is, if there are more females than males in a group, it is detrimental to the females.
See here:
http://infoproc.blogspot.com/2008/07/joy-of-gender-imbalances-on-campus.html
and here for the full article (if you can access it):
http://chronicle.com/weekly/v54/i46/46a02301.htm
I'd be interested to hear what you make of this.