You’ll need three bowls. Fill one with ice water. Fill one with water that’s hot—but not too hot! Fill the third bowl with room temperature water.

To catch any spills, place the bowl of hot water and the bowl of cold water on a plate. Hide the third bowl.

Have your child place one hand in the hot water and one in the cold water. Wait about a minute. Tell your child to close his eyes.

Have him take his hand out of the hot water. Replace that bowl with the hidden bowl of room temperature water. Ask “Is the water hot or cold?” After he answers, do the same thing to the “cold water hand.” Ask the same question.

Your child’s “hot water hand” will feel cold. The “cold water hand” will feel hot, even though the water in the bowl was room temperature. Why? Our skin has tiny sensors that send messages to the brain. These are called nerve receptors. Other sensors sense pressure or pain.

The receptors are best at noticing change. When the hand goes in water, these receptors send a message to the brain. The message says “Hey, that’s hot” or “Wow, that’s cold.” When your child’s hand went from the hot water to the cooler water, the nerve sensors sent a message that the water was cooler.

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