A study that has found auditory mirror neurons in people (mirror neurons activate when an activity is observed, rather than performed by the person himself) has also found that how empathetic we are is linked to the activity of these mirror neurons -- those whose mirror neurons are more strongly activated are more empathic.

Some people are extreme 'larks' -- they go to bed at 6 or 7pm and get up at 4am. Their circadian rhythm runs fast. A German study has now found that this sort of behavior is linked to the mutation of a particular gene.