Psychologists point out that defining empathy as the act of stepping into someone's mind to experience their feeling can lead to some tricky moral dilemmas.

• We are moved to open our hearts (or wallet) when presented with a case such as a charity campaign where a single story of a named, suffering child is showcased to the exclusion of other suffering children. Psychologists call it the "identifiable victim effect."
• This can also help explain why many people become numb to the deaths of strangers, but be up in arms about the minor loss of personal freedoms they more directly experience.

We naturally have more empathy for people closer to us. Our empathy and affinity for others decline the further people are from us.

But our natural empathy for those closer and more similar to us can be used to provoke antipathy towards those who are not like us. Politicians and activists often play to the idea of "us and them," deploying empathy and identifiable victims to make a political case.

While shared happiness is a very pleasant state, sharing someone's suffering, such as a loved one, can be very difficult.

Our brain activity in the regions associated with pain is partially mirrored. At worst, people feel "empathic distress," which leads to apathy, withdrawal, and feelings of helplessness. It can even be bad for your health.

• Empathy is about stepping into someone's shoes.
• Compassion is a feeling of concern for another person's suffering, which moves the person to help.

To be compassionate, you don't have to share somebody's feelings. It's the idea of extending kindness towards others.