[paul.fr]

when i am writing, say this post, i think what i am writing and the spelling as i type. Why is it that sometimes (most times), what i actuall write is not what im thinking or spelling in my head?

[another_someone]

Thinking with which part of your brain.

Your brain is a massively parallel processor (it has to be massively parallel, because each processor of itself is actually very slow), so there are lots of calculations going on - and often they don't exactly match up, so what one part of the brain is thinking is not exactly the same as another part of the brain (bear in mind that the brain is good at fuzzy logic, which means mostly it is better at getting things approximately right quickly, and often with incomplete knowledge, than getting it exactly right).