Men put on their best behaviour when attractive ladies are close by. When the scenario is reversed however, the behaviour of women remains the same. These findings were published February 2, 2012, in the British Psychological Society's British Journal of Psychology via the Wiley Online Library.

The research, which also found that the number of kind and selfless acts by men corresponded to the attractiveness of ladies, was undertaken by Dr Wendy Iredale of Sheffield Hallam University and Mark Van Vugt of the VU University in Amsterdam and the University of Oxford.

Two experiments were undertaken. For the first, 65 men and 65 women, all of an average age of 21, anonymously played a cooperation game where they could donate money via a computer program to a group fund. Donations were selfless acts, as all other players would benefit from the fund, whilst the donor wouldn't necessarily receive anything in return.

Players did not know who they were playing with. They were observed by either someone of the same sex or opposite sex -- two physically attractive volunteers, one man and one woman. Men were found to do significantly more good deeds when observed by the opposite sex. Whilst the number of good deeds made by women didn't change, regardless of who observed.

For the second experiment, groups of males were formed. Males were asked to make a number of public donations. These increased when observed by an attractive female, where they were found to actively compete with one another. When observed by another male, however, donations didn't increase.

Dr Iredale said: "The research shows that good deeds among men increase when presented with an opportunity to copulate. Theoretically, this suggests that a good deed is the human equivalent of the peacock's tail. Practically, this research shows how societies can encourage selfless acts."