Don’t Read Too Much Into Brain Scans

We cannot read minds (yet.) And we shouldn't be making reverse inferences from pictures of brain activity

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For several years now, the phrase “brain scans show” has become ubiquitous in news stories. But what does it mean when the media tell us that “Brain Scans Show Vegetarians and Vegans More Empathic than Omnivores” or “Rejection Really Hurts, Brain Scans Show”? Less than we may think.


First, bear in mind that Technicolor brain scans are not anything remotely like photographs of the brain in action in real time. Scientists can’t just look “in” the brain and see what it does. They cannot “read” minds. More accurately, scans produced by functional magnetic resonance imaging (fMRI) tell us which areas in the brain are working the hardest, as measured by increased oxygen consumption, when a subject performs a task such as reading a passage or reacting to stimuli, such as pictures or sounds. The problem is that almost all regions of the brain have not just one but several job descriptions, which can make interpretation of scans a challenge.

For example, according to marketing consultant Martin Lindstrom, people “love” their iPhones. He concluded this based on the fact that brain scans of smart phone users listening to their personal ring tones showed a  “flurry of activation” in the insula, a prune-sized area of the brain. But in another study, researchers at UCLA claimed that photos of former presidential candidate John Edwards provoked feelings of “disgust” because they “lit up” the…insula.

The insula plays a role in a broad range of psychological experiences, including empathy and disgust, but also sudden insight, uncertainty, and the awareness of bodily sensations, such as pain, hunger, and thirst. With such a broad physiological portfolio, it is no surprise that the insula is activated in many fMRI studies. The same holds true for other brain areas. The amygdala, for instance, shows increased activation when one experiences fear, but it also springs to life when one encounters novel or unexpected stimuli.

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The multi-functionality of most brain areas renders reasoning backwards from neural activation depicted by a scan to the subjective experience of the brain’s owner a dubious strategy. Formally, this logically suspect approach is called “reverse inference,” and when crudely applied it functions much like a high-tech Rorschach test, inviting interpreters to read what they want into largely ambiguous findings. In fact, researchers are now using techniques that measure the nature of brain activity in more informative ways. Increasingly, they are moving away from the time-honored approach of examining which discrete brain areas “light up” and toward the study of the brain as it operates in nature:  as the electrical crackling of crosstalk among numerous regions as they are strung together in specialized neural circuits that work in parallel to produce our thoughts and feelings.

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Brain imaging is surely the most mediagenic of neuroscientific tools – and, indeed, it is an invaluable part of a technological arsenal aimed at discovering the workings of the brain. Through these tools, scientists will develop next-generation treatments for crippling illnesses, such as schizophrenia and Alzheimer’s Disease. Novel insights into the biology of memory, learning, decision-making and emotion are also forthcoming. But we must remember that brain images have their limits. Since they are better suited for generating promising hypotheses than for confirming them, they should be a starting point, not a finish line. Unless we are careful, pretty pictures of the brain can seduce us into drawing simplistic conclusions, leading us to ask more of these images than they can possibly deliver.