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The Biology of Behavior

Neural and Hormonal Systems

Tools of Discovery and Older Brain Structures

The Cerebral Cortex and Our Divided Brain

Genetics, Evolutionary Psychology, and Behavior

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IN 2000, a Virginia teacher began collecting sex magazines, visiting child pornography websites, and then making subtle advances on his young stepdaughter. When his wife called the police, he was arrested and later convicted of child molestation. Though put into a sexual addiction rehabilitation program, he still felt overwhelmed by his sexual urges. The day before being sentenced to prison, he went to his local emergency room complaining of a headache and thoughts of suicide. He was also distraught over his uncontrollable impulses, which led him to proposition nurses.

A brain scan located the problem—in his mind’s biology. Behind his right temple there was an egg-sized brain tumor. After surgeons removed the tumor, his lewd impulses faded and he returned home to his wife and stepdaughter. All was well until a year later, when the tumor partially grew back, and with it the sexual urges. A second tumor removal again lessened the urges (Burns & Swerdlow, 2003).

This case illustrates what you likely believe: that you reside in your head. If surgeons transplanted all your organs below your neck, and even your skin and limbs, you would (Yes?) still be you. An acquaintance of mine [DM’s] received a new heart from a woman who, in a rare operation, had received a matched heart-lung transplant. When the two chanced to meet in their hospital ward, she introduced herself: “I think you have my heart.” But only her heart. Her self, she assumed, still resided in her head. We rightly presume that our brain enables our mind.

Indeed, no principle is more central to today’s psychology than this: Everything psychological is simultaneously biological. Throughout this book, you will find examples of this interplay.

In Modules 3 through 5, we start small and build from the bottom up—from nerve cells to the brain. In Module 6, we consider how our genetic histories predispose our shared human nature, and, in combination with our environments, our individual differences.