At bottom: Your brain-stem, near the top of your neck, is also called the "reptilian" brain-because it is similar to the brains of cool-blooded reptiles. It controls many of your body's instinctive functions, such as breathing.

In the center: Your "old mammalian" brain- which is similar to the brains of other warm-blooded mammals. It controls your emotions, your sexuality-and has a key role to play in your memory.

At top: Your "cortex" (bark), which you use for thinking, talking, seeing, hearing and creating.

Not illustrated here: the fourth "brain"or the cerebellum. See illustration, page 124.

The illustration is from Your Child's Growing Mind, by Jane M. Healy, published by Doubleday, 666 Fifth Avenue, New York, NY 10103.