From the publication:
For the study, published in the journal Nature, some 120 test subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything.
[…]
Fairer with testosterone
The study’s results, however, contradict this view sharply. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. “The preconception that testosterone only causes aggressive or egoistic behavior in humans is thus clearly refuted,” sums up Eisenegger. Instead, the findings suggest that the hormone increases the sensitivity for status. For animal species with relatively simple social systems, an increased awareness for status may express itself in aggressiveness. “In the socially complex human environment, pro-social behavior secures status, and not aggression,” surmises study co-author Michael Naef from Royal Holloway London. “The interplay between testosterone and the socially differentiated environment of humans, and not testosterone itself, probably causes fair or aggressive behavior.”
Moreover the study shows that the popular wisdom that the hormone causes aggression is apparently deeply entrenched: those test subjects who believed they had received the testosterone compound and not the placebo stood out with their conspicuously unfair offers. It is possible that these persons exploited the popular wisdom to legitimate their unfair actions. Economist Michael Naef states: “It appears that it is not testosterone itself that induces aggressiveness, but rather the myth surrounding the hormone.”