Mirror Neurons

Mirror neurons were first observed in the late 1980s and are still the subject of intense scientific study and speculation. Put simply mirror neurons fire in brains when actions are observed or when someone is observed being touched. They allow us to put ourselves in other people's shoes and imagine actions and feelings from their point of view. 

This is ability to tell what another person or animal is up to is very useful as a way of avoiding predators but it is even more useful in promoting empathy. If we can see things from someone else's point of view we are more likely to respond positively to them. Social interactions are also much easier if you have some idea what others are likely to be thinking. Mirror neurons also explain why yawning is contagious.  


There is a very full Wikipedia account of mirror neurons here.