Testosterone makes people more self-centered and less cooperative, a finding that may explain why group decisions can be affected by dominant individuals, researchers report. Their study included 34 females who had never met. The women were divided into 17 pairs and asked to complete a series of tasks designed to assess their levels of cooperation. The tests were conducted on two separate days. On one day both women received a testosterone supplement. On the other day, they were given a placebo.
