Can't say your observation is true for everyone - it is not true for me.
Whenever I feel watched, I feel just that, observed and ready to be judged. This thought makes me more prone to silly mistakes I wouldn't have made if working alone, unwatched.
Might be a side-effect of being the youngest (both in terms of employment and age) member of our staff that has to listen to everybody's advice of everybody, no matter how stupid it might be
