To arrive at their conclusions, the researchers conducted studies at MIT's Center for Collective Intelligence and Carnegie Mellon, in which 699 people were placed in groups of two to five. The groups worked together on tasks that ranged from visual puzzles to negotiations, brainstorming, games and complex rule-based design assignments. The researchers concluded that a group's collective intelligence accounted for about 40 percent of the variation in performance on this wide range of tasks.
Moreover, the researchers found that the performance of groups was not primarily due to the individual abilities of the group's members. For instance, the average and maximum intelligence of individual group members did not significantly predict the performance of their groups overall.
"We didn't design this study to focus on the gender effect," Malone says. "That was a surprise to us." However, further analysis revealed that the effect seemed to be explained by the higher social sensitivity exhibited by females, on average.
http://www.sciencedaily.com/releases/2010/09/100930143339.htm