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Free will and determinism

What neuroscience tells us about moral responsibility

Neuroethics is an interdisciplinary field of research that centers two general topics: the ethics of neuroscience, and the neuroscience of ethics. This dual definition refers to research which either critically questions the role of neuroscience in society or employs neuroscience to explain human moral behaviour. This application raises the concern that understanding how brains cause behaviour may undermine notions of free will and, consequently, absolve us of moral responsibility.

We make thousands of decisions every day. We wake up, decide what to wear, choose what we eat, and decide which route we will take to get to school or work. It seems that we are consciously guiding our bodies in a purposeful way; we think that our thoughts and actions are freely chosen.

Psychologists Dan Wegner and Thalia Wheatley published a paper almost twenty years ago that altered popular conceptions  of free will. They proposed that the experience of intentionally willing an action is often nothing more than a post hoc causal inference that our thoughts caused some behavior.

A dominant view of the relationship between free will and moral responsibility is that if an agent does not have free will, then that agent is not morally responsible for their actions. Free will, as the name suggests, means that an agent has the capacity to choose their course of action. Our action entails responsibility — how we choose to act is our fault — because our actions are self-determined. We must be responsible, because we are in control. Therefore, some insist that free will is necessary for a person to be morally responsible for their actions.

Joshua D. Greene, an assistant professor of psychology at Harvard, says that “to a neuroscientist, you are your brain; nothing causes your behavior other than the operations of your brain.” He continues, “If that’s right, it radically changes the way we think about the law. Often those who do not support free will are said to be determinists. A determinist says that the causal mechanisms in a person’s brain, for example, a genetic predisposition to violence, makes someone less culpable for their actions.” The rationale is: if there are rules that govern the universe which exist outside of ourselves, and if before we are born, these rules anticipate our actions, how can we be responsible for those actions? If our behaviours are governed by chemical interactions in the brain, then they are a result of predictable interactions governed by laws of classical physics.

How far can we take determinism?

There have been several legal cases in which neuroscientific evidence has had an impact on the outcome of the trial. Lie detector tests, and other neuroimaging results, have been used to indicate abnormalities in the brain which caused the aberrant behavior of the defendant. In the early 1990s, 68 year-old Herbert Weinstein was charged with murder of his wife. Weinstein’s lack of emotion while discussing the crime, and his apparent lack of remorse for his actions, led his legal team to question whether he might be suffering from a neurological impairment which might have caused such an uncharacteristic act of aggression. Physicians who consulted with Mr. Weinstein’s defense attorneys suggested that Mr. Weinstein undergo neuropsychological testing and brain scanning that could reveal potential structural and/or functional deficits in his brain. And those tests showed Weinstein’s brain had an abnormal cyst. Weinstein’s lawyers argues that his actions were because of this abnormality in his arachnoid membrane, which surrounds the brain like a spider web. Can we excuse Weinstein’s behaviour with the discovery of a cyst?

Stephen J. Morse, professor of law and psychiatry at the University of Pennsylvania, maintains that “brains do not commit crimes; people commit crimes” — a conclusion, he suggests, that has been ignored by advocates of determinism. He believes that often, those who support determinism are “infected and inflamed by stunning advances in our understanding of the brain . . . [and] all too often make moral and legal claims that the new neuroscience . . . cannot sustain.” He calls this “brain overclaim syndrome.” Morse is referring to the use of neuroscientific evidence to distinguish between “normal” and “abnormal” brains. “There’s nothing new about the neuroscience ideas of responsibility; it’s just another material, causal explanation of human behavior,” says Morse, “How is this different than the Chicago school of sociology?”

Morse does not believe that using scientific evidence to identify an “abnormal brain” should mitigate responsibility. Neuroscience could hypothetically reveal that reason actually plays no role in determining human behavior: without our conscious participation, all actions are simply determined. If determinism is taken at face value, humans are automatons in this respect. But if all behavior is caused by our brains, this mean all behavior could potentially be excused. This may mean we have to abandon current ideas about responsibility and seek other ways of protecting society.

Neither free will nor determinism are proven, but remain controversially debated. Determinism is inconsistent with societal views of responsibility, self-control, and moral obligation. When neuroscientific evidence is introduced in trials, questions about moral responsibility waver and are strongly debated on a case-by-case basis.

Perhaps it is not necessary to equate free will with non-determinism at all. Just because our choices are predictable it does not mean that we do not consciously make those choices. Regardless of whether you believe in free will or determinism, it seems that the two oppositional philosophical explanations for human behaviour cannot individually determine moral responsibility. Even if neuroscience is able to disprove any trace of free will in human behaviour, determinism alone fails to justify the absolution of moral responsibility for actions.