You probably noticed early on in life that other people see the world differently to you. They must do, because most of them do different things to you.
However, they have broadly the same equipment and the same world to observe, so where's the variation?
The variation is, of course, internal. As Hume suggested over 300 years ago, humans develop by noticing patterns in their surroundings, they form useful habits as time goes by so that they don't have to concentrate on the detail of everything they do.
For example, when you learn to drive you have to concentrate loads at first, but then it comes naturally and you can drive almost without consciously thinking about it at all. In the same way you learn to walk and a thousand other things. The same is true of not just physical skills, but anything you habitually do, such as basic conversation and how to react to certain events.
The way in which the mind learns is by significance and repetition. Thus if something happens that you consider important enough and it happens often enough then you will form a new habit or change an existing one.
For example, if your boss is rude to you every morning for a week, you'll form a habit related to that, perhaps to avoid them.
Maybe you get a new boss; trouble is, old habits die hard and your interactions with this new boss will be (at least initially) coloured by your old habits until a new habit is established.
Now if you spent fifteen years at school being bullied then you have habits (e.g. defensiveness, aloofness) that will be much more difficult to shake, simply because the repetition ingrained the habit more deeply.
The effects this has are both positive and negative. We know from 'How you see the world: representative realism' that your mind interprets the world, so if you change your mind by learning something new you can change your perspective of the world (recall how your perspective of relationships was changed once you learnt about sex! Imagine being able to revolutionise your outlook on anything in the same way).
The negative is that other people literally see the world differently to you. You cannot see it how it is from their perspective, because although you share similar sense organs, you do not have their history with which they make sense of the world. This isolates you to a certain extent from everyone else.
