How information is sent from the muscles to the brain. Your muscles are pretty good, but they can't detect small differences. This experiment shows "threshold detection" — a fancy name for the point at which your muscles can detect a enough of a weight difference to say to the brain: "Hey, this one is heavier!"
- A friend
- A blindfold
- Two large cups (16 oz. or greater)
- A marker
- Enough marbles, beans, or rice to fill both cups
- Label one cup "A" and one cup "B."
- Fill each cup exactly halfway.
- Blindfold your friend.
- Have your friend hold one cup in each hand. They should feel of equal weight.
- Take the cups back and add a small amount of marbles, beans, or rice to cup A. ("A" for add!)
- Return the cups to your friend's hands. Ask which weighs more.
- If your friend says one is heavier, ask which one. Is your friend right?
- If your friend says they weigh the same, take the cups back again and add a little more to cup A.
- Keep taking the cups back and adding to cup A until your friend notices a difference. When he or she does, how much extra weight was needed for the muscles to send that message to the brain?