Overconfidence is a disadvantage in war, finds study

From the New Scientist - Overconfidence is a disadvantage in war, finds study:

"A further analysis showed that people with higher self-rankings ended up worse off at the end of the game. “Those who expected to do best tended to do worst,” the researchers say. “This suggests that positive illusions were not only misguided but actually may have been detrimental to performance in this scenario.”

Men tended to be more overconfident than women. But the study found nothing to back up the popular idea that high testosterone causes confidence and aggression. Saliva tests showed that, within each gender group, testosterone level did not correlate with how participants expected to perform in the game."