And....
Because when your brain is only partially engaged in a task, it's easier to make errors--vs. when you are working in "zone of proximal development" where the work is just difficult enough to require complete attention.
Because when you "know" the answer but have to show your work, you can become very confused (try swinging a baseball bat in little tiny steps instead of one fluid swing--you'll probably miss the ball).
Because when you're used to "knowing" and you are presented with something unknown, you are likely to say "I don't know" rather than to make the guess and risk being wrong.
Because you might not finish your work if you can't keep your mind on it, and it's hard to keep your mind on something that doesn't take you anywhere "new".
Because maybe the other kids are good linear, step by step learners and you think your way must be "wrong" because no one else does it that way--and because when you try to do it their way it doesn't make sense (it's routine based, not concept based) and so you make a lot of mistakes or say you can't do it.
Because you don't know that you are supposed to elaborate on your answer and no one asks you to--they just take it at face value. But students who have been working in zpd have gotten feedback as they've made errors along the way, and they have learned to elaborate/explain what they mean.
(sigh)
