The results revealed that when taking the placebo, 51% of the time women chose to share the money, while for men the figure was lower, at 40%. But after taking the amisulpride, women were less keen to share, while men became more prosocial, opting to split the cash 45% and 44% of the time respectively.
In the second study, the team looked at data from 40 men and women who had undergone brain imaging while undertaking decisions on whether to share money, focussing on the activity of a value-processing region of the brain that relies on dopamine signalling.
The team found that when making prosocial choices, activity in this brain region was stronger for women than men, suggesting a greater dopamine response.
The researchers say that, taken together, the studies support the idea that the dopamine-based reward system is geared towards sharing behaviour in women and more selfish behaviour in men.