The Brain Imaging Fallacy in Neurolaw and Neuroeconomics

The New York Times Magazine for last Sunday (March 11)has an article on "neurolaw" by Jeffrey Rosen. Advances in the technology for brain-imaging seem to allow us to look into the brain as it's working and thus to literally read the minds of human beings as they think. "Neurolaw" is the use of such brain-imaging in the courtroom and in legal discussions of human behavior. Similarly, "neuroeconomics" is the use of the same technology to study economic behavior.

This research suffers from a fundamental fallacy, which I will call the brain-imaging fallacy. The brain-imaging fallacy is the false assumption that brain-imaging techniques explain and predict human thoughts, actions, and consciousness.

One of the most commonly used techniques is functional magnetic resonance imaging (fMRI). A fMRI machine uses a magnetic field to detect increases in blood oxygenation that show increased blood flow to active areas of the brain. Computer analysis can generate colored pictures showing patterns of blood flow that presumably indicate which parts of the brain are most active at some point in time. As Rosen's article indicates, it is easy to jump to the conclusion that fMRI allows us to read the human mind. But in fact, all that fMRI shows us is patterns of blood flow in the brain. To infer that these patterns of blood flow explain thoughts, actions, and consciousness requires speculation that goes beyond the evidence of the brain imaging.

For example, Rosen refers to the famous experiments conducted by Elizabeth Phelps who used brain scans to detect unconscious racism. Individuals were shown pictures of white and black faces. When they saw unfamiliar black faces, the fMRI scans showed high activation in their amydalas, which is associated with fear and other strong emotions. But when they saw pictures of familar black faces (such as Denzel Washington or Martin Luther King, Jr.), there was no increase in amygdala activity. This was interpreted as a sign of unconscious racism. If so, this would have legal implications, because we could identify such unconscious racism as a propensity to illegal racist behavior.

But notice how speculative this is. All that the fMRI scan shows us is patterns of blood flow. Increased blood flow to the amydala can be identified as emotional arousal only if we assume that we know exactly how emotion is localized in the amydala and how exactly specific emotions are activated there. We cannot see racist emotions directly. We can only infer such emotions based on elaborate speculation about the underlying neural circuitry. Do we really understand exactly how blood flow to the amydala causes specific emotions? Aren't emotions likely to arise from complicated interactions of many elements of neural circuitry that are not well understood?

Can we be sure that this amydala activity shows racist emotions? As indicated in Rosen's article, some researchers doubt this. The amydala activity in response to seeing black faces might indicate our awareness that black people are socially disadvantaged.

Moreover, even if we could be certain that we could locate specific emotions in specific brain areas like the amygdala, we still could not be sure that this would predict actions. People might often have racist emotions without ever acting on those emotions.

It is also false to assume that we can see human consciousness in these brain scans. We all have direct access to our own consciousness. But none of us has direct access to the consciousness of others. When people come out of the fMRI machines, they are interviewed. We need their verbal reports about what they were consciously doing, because the machines cannot record consciousness. The machines can only record brain activity that might be correlated with conscious experience. But this correlation is not identity.

Rosen makes a lot of the claim that brain imaging throws doubt on the traditional belief in moral responsibility. If people's thoughts, actions, and consciousness are determined by their brains, then we might conclude that human beings are not capable of free choice.

But as I have argued in Darwinian Conservatism, brain imaging shows that human beings have the power to make choices that actually change their brain circuitry. In the book, I cite the work of Jeffrey Schwartz. Working with patients suffering from obsessive-compulsive disorder, Schwartz has showed them how to use "directed mental force" to change their brains. Those with this disorder can be locked into repetitive behavior--such as washing their hands over and over again--that they cannot control because the brain's neuronal circuits for this behavior are overactive. Dr. Schwartz has helped these people by training them to concentrate their minds to divert their attention away from the obsessive-compulsive behavior. So when they feel compelled to wash their hands, for example, they might concentrate on an alternative behavior such as tending the flowers in their garden. As this mental exercise becomes habitual, it becomes easier to resist their obsessive-compulsive behavior. Using brain-imaging, Dr. Schwartz has discovered that this therapy actually changes the neuronal activity of the brain so that the activity of the frontal cortex exerts a mental force to activate one circuit rather than another. So it seems that the mind that emerges from the human brain can change the brain itself. This emergent power of the brain for mental attention is the natural ground for human freedom and moral responsibility. Here we see the emergent evolution of the human soul in the human brain.