Men may have developed a psychology that makes them particularly able to engage in wars, a scientist said.

New research has shown that men bond together and cooperate well in the face of adversity to protect their interests more than women, which could explain why war is almost exclusively a male business, according to Professor Mark van Vugt of the University of Kent in southern England.

"Men respond more strongly to outward threats, we've labeled that the 'man warrior effect'," he told the British Association for the Advancement of Science meeting.

"Men are more likely to support a country going to war. Men are more likely sign up for the military and men are more likely to lead groups in more autocratic, militaristic ways than women," he added.

Van Vugt said the finding is consistent with results from different behavioral science disciplines.

In experiments with 300 university men and women students, Van Vugt and his team gave the volunteers small sums of money which they could either keep or invest in a common fund that would be doubled and equally divided. None of the students knew what the others were doing.

Both sexes cooperated in investing in the fund. But when the groups were told they were competing against other universities, the males were more eager to invest rather than keep their money while the number of women contributing remained the same.

"We all know males are more aggressive than females," Van Vugt said, adding that co-operation is needed to establish institutions and governments and to wage wars.

"Male co-operation is a double-edged sword," he added.