Hill and Barton got the idea for their research because of the role that the colour red plays in the animal world. ‘Red seems to be the colour, across species, that signals male dominance,’ Barton says. They thought that ‘there might be a similar effect in humans.’ Setchell, the
primatologist, agrees: ‘As Hill and Barton say, humans redden when we are angry and go pale when we’re scared. These are very important signals to other individuals.’