Our genes can influence our behaviour in delicate ways, and these effects, while subtle, are not undetectable. Scientists can pick them up by studying large groups of people, but individuals can sometimes be sensitive to these small differences.

Consider the OXTR gene. It creates a docking station for a hormone called oxytocin, which has far-ranging effects on our social behaviour. People carry either the A or G versions of OXTR, depending on the “letter” that appears at a particular spot along its length. People with two G-copies tend to be more empathic, sociable and sensitive than those with at least one A-copy. These differences are small, but according to a new study from Aleksandr Kogan at the University of