How do children learn empathy?

Empathy, the ability to understand others and feel compassion for them, is arguably the most defining human quality – setting us apart from smart machines and even other animals. Without it, we couldn’t function in social areas such as the schools, court rooms and office workplaces that are the cornerstones of our society.

But babies and toddlers are generally poor at showing sensitivity to other people’s feelings. So how do they develop this crucial skill – do they learn it gradually or is it just an innate ability that kicks in at a certain age?