Every single person is different.

We all have different backgrounds, views, values and interests.

And yet there is one universal feeling that we all experience at every single moment.

Call it an "ego", a "self" or just an "I" – it's the idea that our thoughts and feelings are our own, and no one else has access to them in the same way.

This may sound a bit like post-war French existentialism or psycho-analysis, but it's actually a topic that's being increasingly addressed by neuroscientists.