Tuesday, October 18, 2011

Mind:  The Brain on Trial

After Charles Whitman shot 45 people from the top of the University of Texas Tower, ...

[his] body was taken to the morgue, his skull was put under the bone saw, and the medical examiner lifted the brain from its vault. He discovered that Whitman's brain harbored a tumor the diameter of a nickel. This tumor, called a glioblastoma, had blossomed from beneath a structure called the thalamus, impinged on the hypothalamus, and compressed a third region called the amygdala. The amygdala is involved in emotional regulation, especially of fear and aggression. By the late 1800s, researchers had discovered that damage to the amygdala caused emotional and social disturbances. In the 1930s, the researchers Heinrich Kl├╝ver and Paul Bucy demonstrated that damage to the amygdala in monkeys led to a constellation of symptoms, including lack of fear, blunting of emotion, and overreaction. Female monkeys with amygdala damage often neglected or physically abused their infants. In humans, activity in the amygdala increases when people are shown threatening faces, are put into frightening situations, or experience social phobias. Whitman's intuition about himself—that something in his brain was changing his behavior—was spot-on.
When your biology changes, so can your decision-making and your desires. The drives you take for granted (I'm a heterosexual/homosexual, I'm attracted to children/adults, 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.
Many of us like to believe that all adults possess the same capacity to make sound choices. It's a charitable idea, but demonstrably wrong. People's brains are vastly different.

Who you even have the possibility to be starts at conception. If you think genes don't affect how people behave, consider this fact: if you are a carrier of a particular set of genes, the probability that you will commit a violent crime is four times as high as it would be if you lacked those genes. You're three times as likely to commit robbery, five times as likely to commit aggravated assault, eight times as likely to be arrested for murder, and 13 times as likely to be arrested for a sexual offense. The overwhelming majority of prisoners carry these genes; 98.1% of death-row inmates do. These statistics alone indicate that we cannot presume that everyone is coming to the table equally equipped in terms of drives and behaviors.

Free will may exist (it may simply be beyond our current science), but one thing seems clear: if free will does exist, it has little room in which to operate. It can at best be a small factor riding on top of vast neural networks shaped by genes and environment. In fact, free will may end up being so small that we eventually think about bad decision-making in the same way we think about any physical process, such as diabetes or lung disease.

For much more about how the law should be changed due to this, see The Brain on Trial by David Eagleman, July, 2011 at The Atlantic.

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