Take the case of a fourty-year-old man we'll call Alex. Alex's wife, Julia, began to notice a change in his sexual preferences. For the first time in the two decades she had known him, he began to show an interest in child pornography. And not just a little interest, an overwhelming one. He poured his time and energy into visiting child pornography websites and collecting magazines. He also solicited prostitution from a young woman at a massage parlor, something he had never previously done. This was no longer the man Julia had married, and she was alarmed by the change his his behavior.
At the same time, Alex was complaining of worsening headaches. And so Julia took them to the family doctor, who referred them on to a neurologis. Alex underwent a brain scan, which revealed a massive brain tumor in his orbitofrontal cortex. The neurosurgeons removed the tummor. Alex's sexual appetite returned to normal.
Alex's story highlights a deep central point: when tour biology changes, so can your decision making, your appetites, and your desires. The drives you take for granted ("I'm a hetero/homosexual," "I'm aggressive/not aggressive," and so on) depend on the intricate details of your neural machinery. Although acting on such drives is popularly thought to be a free choice, the most cursory examination of the evidence demonstrates the limits of that assumption; we will see further examples in a moment.
The lesson of Alex's story is reinforced by its unexpected follow-up. About six months after the brain surgery, his pedophiliac behavior began to return. His wife took him back to the doctors. The neuroradiologist discovered that a portion of the tumor had been missed in surgery and was regrowing -- and Alex went back under the knife. After the removal of the remaining tumor, his behavior returned to normal.
Alex's sudden pedophilia illustrates that hidden drives and desires can lurk undetected behind the neural machinery of socialization. When the frontal lobe is compromised, people become "disinhibited," unmasking the seedier elements in the neural democracy. Would it be correct to say that Alex was "fundamentally" a pedophile, merely socialized to resist his impulses? Perhaps, but before we assigned labels, consider that you probably would not want to discover alien subroutines that lurk under your own frontal cortex.
A common example of this disinhibited behavior is seen in patients with frontotemporal dementia, a tragic disease in which the frontal and temporal lobes degenerate. With he loss of the brain tissue, patients lose the ability to control hidden impulses.