[Former Harvard economics professor Terry Burnham] recruited 26 male graduate school students to play the low ultimatum game. Each subject started out with $40 and could anonymously offer either $5 or $25 of this sum to another player.According to Burnham, men with higher testosterone levels refuse the $5 because the hormone is linked with dominance-seeking behaviors. Burnham says accepting the $5 is akin to being put in a subordinate position, which would likely have been an evolutionary disadvantage for our ancestors.
Burnham also took saliva samples from all the volunteers and measured their levels of testosterone. This revealed considerable variability in the levels of the hormone. While the subject with the most testosterone had 497 picomoles per litre of saliva, the one with the least only had 30% of this amount – 153 picomoles per litre.
Comparing the hormone data with the results of the money game showed a correlation between high testosterone levels and an increased likelihood of refusing the low, "unfair" offer of $5. . . . Men who rejected the deal had an average testosterone count of 380 picomoles per litre of saliva, whereas those who accepted it had an average of almost 40% of that figure.