How little we notice things that don't don't directly affect us.


For example, my left handed daughter tells me that when people attach a pen to a 'sign up' sheet with a string, it is almost always too short for left handlers.


Until my wife developed an arthritic hip, I was embarrassingly ignorant of how difficult many buildings can be to enter. Even if they have a ramp for wheelchairs - which may still don't - it is often very much further to walk if ou are on foot. Getting on and off trains can be difficult, and if there is a ramp it is usually far too steep. And so on.


And I was positively ancient when I realised how different art galleries are if you are colour blind.