Why the Insanity Defense is Un-scientific

In his class book Emotional Intelligence, Daniel Goleman presents a very compelling case for studying individual differences in social and emotional skills. Since people who are less empathic — less aware of others’ thoughts and feelings — are apparently more likely to commit crime, Goleman argues that this raises the issue of what to do about criminals who are biologically limited in their empathic abilities:

If there are biological patterns at play in some kinds of criminality — such as a neural defect in empathy — that does not argue that all criminals are biologically flawed, or that there is some biological marker for crime … Even if there is a biological basis for a lack of empathy in some cases, that does not mean all who have it will drift to crime; most will not. A lack of empathy should be factored in with all other psychological, economic, and social forces that contribute to a vector toward criminality.

This may seem like a reasonable, middle-of-the road take on the issue, but I would argue that it is actually an extremely radical, non-scientific statement. (Since it is such a common sentiment, I realize this means I may be calling most of the public crazy radicals. So be it. Sometimes, that’s the case.)

The Fundamental Axiom of Cognitive Science

It is the scientific consensus that all human behavior is the result activity in the brain. Like gravity and the laws of thermodynamics, this cannot be proven beyond a doubt (in fact, there’s a good argument that nothing can be proven beyond a doubt). However, it is the foundation upon which modern psychology and neuroscience is built, and there is no good reason to doubt it.

In fact, many of the world’s events cannot be understood otherwise. Classic examples are people who, as a result of brain injury, are unaware of the fact that they can see or that the left half of the world exists or think their leg is a foreign entity not part of their own body. The oddest fact about such syndromes is that such patients sometimes are completely unaware of their problem and cannot understand it when it is explained to them (Oliver Sacks is a great source of such case histories).

The Problem for the Insanity Defense

Back to Goleman. He writes “Even if there is a biological basis for a lack of empathy in some cases…”

I hope that the fundamental problem with the quote is now clear. The consensus of the scientific community is that for any behavior, personality trait or disposition, there is always a biological basis. There are fundamental brain differences between Red Sox fans and Yankees fans, or between those attracted to Tom Cruise or Nicole Kidman. There is some brain state such that it is being a Red Sox fan.

So whenever somebody says, “My brain made me do it,” they are telling the truth.

The Soft Bigotry of Medical Evidence

As matters currently stand, however, certain brain differences are privileged over others. Say Jane and Sally are both accused of a similar crime, but Jane has a known brain “abnormality” that correlates with criminal behavior, but Sally has no such brain data to point to. They may likely face different sentences.

However, the difference between Jane and Sally may have more to do with the state of our scientific understanding than anything else. If Sally is predisposed to crime in some way, then it must be because of some difference in her brain. At the very least, if you were able to take a snapshot of her brain during the moments leading up the crime, there would be some difference between her brain and the brain of Rebecca, who had the opportunity to commit the crime but chose not to, because the act of choosing is itself a brain state.

The effect is to discriminate between people based, not on their actions or on their persons, but based on current medical knowledge.

A problem without an easy solution

I think that most people prefer that the legal system only punish those who are responsible for wrongdoing. If we exclude from responsibility everybody whose actions are caused by their brains, we must exclude everybody. If we include even those who clearly have little understanding or control of their own actions, that seems grossly unfair.

I don’t have any insight into how to solve the problem, but I don’t think the current standard is workable. It is an exceptionally complex problem, and many very smart people have thought about it very hard. I hope they come up with something good.


After writing this I noticed wilcoxclynn’s very relevant recent post.

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