I had an interesting discussion with my just-turned-4 year old yesterday about saying sorry and putting yourself in someone else's shoes. She said that she would say sorry if she'd done something naughty like hitting her sister but only if she was found out - and if she had gotten away with it she would feel happy. So far, so 4-year-old. However, she doesn't at all understand the concept of empathy or guilt, as we talked further about how her sister would feel sad when she was hit and she just didn't 'get' it.
Is this normal? When does this start to develop?