Have your students work in small groups to demonstrate the ability of their senses of smell.
Fill small jars (baby food jars work well) with a variety of common foods or flavorings (for example, onion, peanut butter, cinnamon, pepper, ginger, lemon, and vanilla). Instruct one student in each group to close his or her eyes and the other student(s) to place a jar under the first student's nose. Students should readily identify many of the odors. Have students switch places and try again.
Again, have your students work in small groups. Pass out toothpicks to each group. Use the toothpicks to determine two-point discrimination on several areas of the body. Have one student operate the toothpicks on a second student whose eyes are closed. A third student can estimate or measure distances between toothpicks. Start with the points of the toothpicks placed on the skin of the back of the hand about one inch apart, then lift the toothpicks and position them slightly closer together. Each time, ask the student who is feeling the toothpicks whether he feels two or one toothpick. At some point, the toothpicks will be close enough together that the student will feel only one toothpick, even though two are there. Repeat the procedure on the palm, the forearm, and the back of the neck. This exercise demonstrates that the number of sensory receptors in the skin varies, depending on the functions of different body parts.