In this activity (12th activity on the page), learners conduct an experiment to demonstrate how muscles are constantly feeding information to the brain about what they are doing. Two identical containers, labeled "A" and "B" are filled halfway with same amount of water (or dry substance). When a blindfolded learner holds the containers in each hand, they should feel the same weight. Then, more water is added to the containers until the blindfolded learner can detect a difference between container weights. Use this activity for a lesson on the sense of touch and/or detection threshold.