The activity of the emotion centres in the brain – the amygdalae – is influenced by motivation rather than by the emotions themselves. This can be concluded from research carried out into the hormone testosterone. Testosterone increases amygdala activity in a person who is approaching a socially threatening situation and decreases the activity when such a situation is avoided. It was already known that the amygdala response to images of angry faces was stronger in a person who had received testosterone. This new study shows that this only happens when people approach angry faces and not when they avoid them.