High testosterone levels may affect behaviour in men: study

Increased levels of male hormone testosterone can cause men to engage in both social and antisocial behaviours, a new study has found.
Modern society has taken a less-than-positive view of testosterone, blaming it for aggressive, boorish or simply bad behaviour in men - but there may be more to the impact the steroid hormone has on men than has been suspected.
The researchers, including those from Trinity College Dublin in Ireland, concocted a game called the Ultimatum Game, which involved a pot of money that was spilt and shared with the aim of maximising the amount participants would get in the end.

The experiment enlisted the assistance of 40 male volunteers - half were given an injection of testosterone while the other half were given a placebo.
The men where then asked to play the Ultimatum Game in two ways - one group played by responding to predetermined proposals, while another group played in pairs against one another.
In both versions, volunteers were presented with a proposal of accepting money from a split pot of cash. If they accepted the cash, they got to keep it; if not, the other person did not get to keep their share, either.

Afterwards, the volunteers were allowed to reward or punish their opponents for being fair or not by using their own winnings to reduce or increase the amount their opponent got.

By watching and comparing player behaviour of those that had received the testosterone shots versus the placebo, the researchers found that those that received the shots tended to be more likely to reject proposals and to punish opponents they found unfair - which was expected behaviour.
However, surprisingly, those operating on heightened levels of testosterone were also found to be more generous with opponents they deemed fair.
The researchers suggest this form of ultraism was likely due to what they described as a "status display" - a move meant to make the player seem more impressive to their peers.
The research was published in the journal Proceedings of the National Academy of Sciences.