Why do you spill coffee when looking at it and not when not looking at it while walking with a cup of it?!
Why do you spill coffee when looking at it and not when not looking at it while walking with a cup of it?
When you have a cup of coffee in your hand and you are looking at it to make sure you don't spill you spill and when you don't look at the cup in your hand and you are walking you don't spill it?
Answers:
Your wrists respond to a small set of sensations when you don't have your eyes on the cup. The sensations felt are directly read and responded to. The reaction loop is very short-- therefore fast enough to hold the cup steady. No thinking is involved.
When you're looking at it, you have to appreciate the situation more indirectly--you do some little thinking about the situation--and when a decision to adjust is made, the motor impulses have a longer way to go.