Over the next year, Kenneth’s testimony was remarkably consistent, even in the face of attempts to lead him astray: he remembered nothing of the incident. Moreover, while all parties agreed that Kenneth had undoubtedly committed the murder, they also agreed that he had no motive. His defense attorneys argued that this was a case of killing while sleepwalking, known as homicidal somnambulism.

Although critics cried “Faker!,” sleepwalking is a verifiable phenomenon. On May 25, 1988, after lengthy consideration of electrical recordings from Kenneth’s brain, the jury concluded that his actions had indeed been involuntary, and declared him not guilty.

As with Tourette’s sufferers, split-brain patients, and those with choreic movements, Kenneth’s case illustrates that high-level behaviors can take place in the absence of free will. Like your heartbeat, breathing, blinking, and swallowing, even your mental machinery can run on autopilot. The crux of the question is whether all of your actions are fundamentally on autopilot or whether some little bit of you is “free” to choose, independent of the rules of biology.

This has always been the sticking point for philosophers and scientists alike. After all, there is no spot in the brain that is not densely interconnected with—and driven by—other brain parts. And that suggests that no part is independent and therefore “free.” In modern science, it is difficult to find the gap into which to slip free will—the uncaused causer—because there seems to be no part of the machinery that does not follow in a causal relationship from the other parts.

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.

The study of brains and behaviors is in the midst of a conceptual shift. Historically, clinicians and lawyers have agreed on an intuitive distinction between neurological disorders (“brain problems”) and psychiatric disorders (“mind problems”). As recently as a century ago, a common approach was to get psychiatric patients to “toughen up,” through deprivation, pleading, or torture. Not surprisingly, this approach was medically fruitless. After all, while psychiatric disorders tend to be the product of more-subtle forms of brain pathology, they, too, are based in the biological details of the brain.

What accounts for the shift from blame to biology? Perhaps the largest driving force is the effectiveness of pharmaceutical treatments. No amount of threatening will chase away depression, but a little pill called fluoxetine often does the trick. Schizophrenic symptoms cannot be overcome by exorcism, but they can be controlled by risperidone. Mania responds not to talk or to ostracism, but to lithium. These successes, most of them introduced in the past 60 years, have underscored the idea that calling some disorders “brain problems” while consigning others to the ineffable realm of “the psychic” does not make sense. Instead, we have begun to approach mental problems in the same way we might approach a broken leg. The neuroscientist Robert Sapolsky invites us to contemplate this conceptual shift with a series of questions:

Is a loved one, sunk in a depression so severe that she cannot function, a case of a disease whose biochemical basis is as “real” as is the biochemistry of, say, diabetes, or is she merely indulging herself? Is a child doing poorly at school because he is unmotivated and slow, or because there is a neurobiologically based learning disability? Is a friend, edging towards a serious problem with substance abuse, displaying a simple lack of discipline, or suffering from problems with the neurochemistry of reward?

Acts cannot be understood separately from the biology of the actors—and this recognition has legal implications. Tom Bingham, Britain’s former senior law lord, once put it this way:

In the past, the law has tended to base its approach … on a series of rather crude working assumptions: adults of competent mental capacity are free to choose whether they will act in one way or another; they are presumed to act rationally, and in what they conceive to be their own best interests; they are credited with such foresight of the consequences of their actions as reasonable people in their position could ordinarily be expected to have; they are generally taken to mean what they say.



Whatever the merits or demerits of working assumptions such as these in the ordinary range of cases, it is evident that they do not provide a uniformly accurate guide to human behaviour.

The more we discover about the circuitry of the brain, the more we tip away from accusations of indulgence, lack of motivation, and poor discipline—and toward the details of biology. The shift from blame to science reflects our modern understanding that our perceptions and behaviors are steered by deeply embedded neural programs.