Innocent Until Proven Free? The Question of Neuroscience and Moral Responsibility

By: Kristina Madjoska

“Plead insanity!” you might have heard Detective Cohle say to some of his interrogees in the show True Detective. Even if you have not watched True Detective, chances are you have heard of the term insanity plea. The idea that moral and legal responsibility is alleviated when a person cannot control their impulses or reason through ethically meaningful situations is fundamentally embedded in our legal understanding of insanity. This logic certainly makes intuitive sense: if someone has acted under a compulsion and hasn’t been able to choose their course of action freely, then they shouldn’t be blamed for having bad intentions. After all, it was not their choice. Neuroscience has consistently provided support for this reasoning, as evidence of abnormal brain structures and neurotransmitter actions in mentally ill patients has piled up. Yet in an essential way, modern neuroscience also problematizes this logic. If increasing evidence shows that our brain biochemistries are responsible for the choices we make, then are we allowed to talk about free choice? And if free choice cannot be argued for, can we rightfully assign blame to anyone?

These questions suggest that a ‘pledge to insanity’ should not be an exclusive privilege of the mentally ill. In certain ways, all criminal acts are a result of some malfunction of our brains, or simply said, we are all in some small ways insane. This is important to our concepts of law and morality because, when assigning blame, we typically consider whether a person has freely chosen to act in a way that deserves this negative judgment. If it is true that we have no control over our actions, then blame might be assigned purely to those who happen to have gotten the wrong combination of genes and environmental conditions which have prompted them to act contrary to the rules. There are multiple thoughtful approaches that neuroscientists have taken to study this issue. Neuroscientific literature on the topic is broad, yet two especially salient questions emerge: Does our brain biochemistry cause our behavior? And if this is true, then is it still smart or rightful to regard ourselves as responsible for our actions?

The Moral Compass

Before we begin delving into the intricacies of these two questions, it is first important to discern which parts of our brain participate in our moral decision-making. Refined neuroimaging techniques like fMRI (functional magnetic resonance scanning) have allowed us to inspect in real-time where brain activity is localized and what cognitive and behavioral responses it corresponds to. Two scientists from the University of California, Santa Barbara give an extensive overview of the current understandings of the neurobiology of ethical reasoning (1). Synthesizing multiple findings, they posit that morality in the human brain works by a mechanism of parallel processing. This means that there are several different regions in the brain that work simultaneously to produce any ethical thought, value or conclusion. Such a division of labor reflects the plurality of human moral thought. For example, a study from the National Institute of Health has shown that social emotions, particularly disgust, play a critical role in our evaluations of morally meaningful situations. Our basal ganglia and amygdala, parts of our brain that are also associated with disgust elicited by stimuli like spoiled food, are significantly active when people are asked to think about statements that frequently elicit moral reprehension, like incestuous relationships or murder (2). At the same time, our emotional moral responses also depend on feelings of compassion and admiration. Observed activity in the anterior cingulate cortex, a region in the frontal part of our brain involved with empathy, showed that these feelings depend on our ability to imagine ourselves in someone else’s shoes (3). However, it is critical to note that emotion is not the only important medium through which we come to understand morality. Human capacity to reason abstractly is also a crucial aspect of this process. A specific type of abstract reasoning is our belief attribution system. This system is responsible for our ability to imagine other people’s intentions, even if their actions do not explicitly demonstrate them. Functional belief attribution would help us to, for example, see behind a dubious smile or party invitation. The right temporoparietal lobe, a module on the surface of our right brain, is involved in our performance of belief attribution (4).

To date, there is no convincing evidence of centralized command integrating these multiple parallel processes. In most cases, the parallel neural mechanism manages to (at least somewhat) coherently inform our moral evaluations. Nevertheless, how effectively we act upon these evaluations also depends on how well we can control our impulses. Impulse control is the means through which we postpone momentary pleasure-seeking for long-term, objective benefits. In a significant way, impulse control affects whether we act on immediate threats or desires when they contradict our more nuanced understanding of the moral thing to do. A paper published by the International Journal of Law and Psychiatry identifies the prefrontal cortex, the part of our brain found just behind our foreheads, as the vital center for impulse control (5). Evidence from multiple studies shows that people who have diminished gray matter in their prefrontal cortices behave more rashly, are more often violent and are more likely to have trouble with the law. Our ability to roughly correctly evaluate hypothetical moral situations is mostly independent from our ability to hold on to these considerations in the heat of the moment.

The Causation Effect

New and elegant neuroimaging technologies and the studies they have propelled have certainly contoured our understanding of how our brain thinks about and acts on right and wrong. Yet, the more we learn about these relationships, the more deeply they begin to problematize the idea of our moral responsibility. If our morally relevant actions are determined by our amygdalas and prefrontal cortices, then should we be held responsible for them? A meticulous way in which scientists have tried to study this question is through DBS, or deep brain stimulation.6 Although DBS is not typically used to study moral behavior, it has been extremely useful in clarifying the brain-behavior relationship. The technique essentially involves a surgical transplantation of a pacemaker, which transmits electrical signals to local brain regions to stimulate activity. Given that neurons, the cells that make up our brains, communicate through electrical signals, the pacemaker can simulate this type of communication. DBS has seen some success in the treatment of depression, Parkinson’s, aggressive behavior and addiction. Experiments with DBS demonstrate that, when electrical activity is altered (in this case through DBS), altered behavior follows. This evidence indicates that the brain-behavior rapport is possibly not only correlational, but also causal. An older study supporting that idea found that brain activity in regions correlated with a certain behavior preceded the conscious awareness of that behavior being initiated7 . This means that the participants may not have exercised conscious control over their own actions. Although definitive proof of causation is still not available, these studies open up the possibility that free will may not, in fact, be as free as we would have thought.

The Question of Responsibility

Because of ethical considerations, causation experiments have not been performed specifically for moral decision-making and criminal behavior. However, if we extend the logic of DBS studies to our moral processing system, then it seems like there might not be much that we can do to control our moral behavior either. The neural determinism suggested by neuroscientific literature invites a discussion of whether freedom of choice is necessary for assigning moral blame. Two philosophical intuitions, compatibilism and incompatibilism, argue opposing sides of the issue. On the one hand, compatibilists maintain that even if our behaviors are primarily guided by the structures of our brain, the choices we make can still be called our own, because it is our brains that have initiated them (8). Therefore, we should be held responsible for their consequences. On the other hand, incompatibilists argue that our choices must be made freely if we are to assign any sort of blame to them. Perhaps, the truth is a more nuanced version of both, and a sliding scale between what we consider insanity and health may be a better representation of it.

However, it is just as pressing to consider how neuroscience has already affected the practicalities of the justice system. Brain scans and images are increasingly finding their way to attorneys’ briefs and judges’ benches; they have been used to argue for juvenile criminal offenders (their prefrontal cortices and impulse control are underdeveloped) and for mentally ill patients, among others (1). One of the most precise insights on the issue has been provided by the writers of the University of California, Santa Barbara paper. In discussing the implications of neurological determinism, they say: “The biggest threat to our taking seriously the idea that many who commit bad, even criminal acts, are less free, less rational, less responsible, and less blameworthy than we have been thinking all along may be the following: if we take seriously that these individuals are impeded in nontrivial ways in their ability to make good choices and therefore don’t deserve to be punished as harshly as they have been up until now, then what do we do with them? One answer is that we stop using the criminal justice system solely to levy punishment on wrongdoers and use it more to prevent subsequent harm from occurring” (1).

Even though it is an already existing concern in legal systems globally, this consideration may need to make its way into legal thought more quickly and more fundamentally than it has so far.


Although neuroscience is a vibrant and fertile field that requires much more work to be done, the implications of its findings already widely and deeply challenge our social relationships and structures. Realizing that we do not control our own actions as much as we often assume may be a little disheartening. Hopefully, however, in studying ourselves more closely, we can begin to more thoughtfully and more compassionately respond to others. Hopefully, neuroscience can inspire us to approach anyone from a substance-abusing neighbor to a lying friend not as a blameworthy criminal, but as a human in need of our help and care. Just as importantly, to begin adjusting our legal thought to the nuance of neuroscience may help our society deal with criminal behavior in a more effective and meaningful way.


Kristina Madjoska ’19 is a sophomore in Lowell House concentrating in Neurobiology.


Works cited

[1] Funk, C. M.; Gazzaniga, M. S. Curr. Opin. Neurobiol. 2009, 19, 678-681.

[2] Borg, J. S. et al. J. Cogn. Neurosci. 2008, 20, 1529-1546.

[3] Immordino-Yang M. H. PNAS. 2009, 106, 8021-8026.

[4] Young, L. et al. PNAS. 2007, 104, 8235-8240.

[5] Penney, S. Int. J. Law Psychiatry 2012, 35, 99-103.

[6] Sharp, D.; Wasserman, D. Neuroethics 2016, 9, 173-185.

[7] Libet, B. et al. Brain 1983, 106, 623-642.

[8] McKenna, M.; Coates, D. J. Compatibilism. Stanford Encyclopedia of Philosophy. https://plato. (accessed Feb. 19, 2017).

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