The Gray Areas of Gray Matter
Neuroimaging is pretty cool, but it can't do what its most enthusiastic boosters claim.
Brainwashed: The Seductive Appeal of Mindless Neuroscience, by Sally Satel and Scott O. Lilienfeld, Basic Books, 256 pages, $26.99.
Toward the end of the Reagan administration, the Partnership for a Drug-Free America created a widely mocked public service announcement that showed an egg frying in a hot skillet as the narrator declared, "This is your brain on drugs." A quarter of a century later, the frying pan has been replaced by pictures produced through impressive-sounding technologies such as functional magnetic resonance imaging (fMRI). "This is your brain on drugs," say the government's favored researchers, pointing to the areas of enhanced blood flow highlighted by color-coded fMRI scans. Their seemingly scientific pronouncements usually inspire credulous concern rather than laughter.
But as Sally Satel and Scott Lilienfeld explain in Brainwashed: The Seductive Appeal of Mindless Neuroscience, suggesting that computer-generated brain images capture the underlying reality of complex patterns of behavior such as addiction is only slightly less simplistic than portraying the seat of human consciousness as a sizzling egg. These images "are not photographs of the brain in action in real time," Satel and Lilienfeld write. "Those beautiful color-dappled images are actually representations of particular areas in the brain that are working 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 of faces. The powerful computer located within the scanning machine transforms changes in oxygen levels into the familiar candy-colored splotches indicating the brain regions that become especially active during the subject's performance. Despite well-informed inferences, the greatest challenge of imaging is that it is very difficult for scientists to look at a fiery spot on a brain scan and conclude with certainty what is going on in the mind of the person." Or as an expert interviewed by my colleague Brian Doherty for a 2007 article about the insanity defense put it, "You can't see why on an fMRI."
Satel, a practicing psychiatrist in Washington, D.C., who is a resident scholar at the American Enterprise Institute, and Lilienfeld, a professor of psychology at Emory University in Atlanta, do not dismiss the potential value of neuroimaging, but they persuasively argue that its current capabilities have been greatly exaggerated by overenthusiastic researchers, entrepreneurs, and journalists. "With its implied promise of decoding the brain," they write, "it is easy to see why brain imaging would beguile almost anyone interested in pulling back the curtain on the mental lives of others: politicians hoping to manipulate voter attitudes, marketers tapping the brain to learn what consumers really want to buy, agents of the law seeking an infallible lie detector, addiction researchers trying to gauge the pull of temptations, psychologists and psychiatrists seeking the causes of mental illness, and defense attorneys fighting to prove that their clients lack malign intent or even free will. The problem is that brain imaging cannot do any of these things—at least not yet." Satel and Lilienfeld lucidly explain why, offering a skeptical but fair-minded review of the field that carefully distinguishes between wild hopes and actual accomplishments.
One major limitation of neuroimaging is that the pictures it produces are ambiguous because the areas of the brain it tracks have more than one function. Satel and Lilienfeld note that the insula is commonly said to be associated with disgust, but it also plays a role in experiences such as trust, empathy, and sudden insight. Activity in the amygdala might indicate fear, or it might indicate happiness, anger, excitement, sexual arousal, or exposure to a novel stimulus. A subject whose amygdala or insula "lights up" in response to a photograph of Mitt Romney, John Edwards, or Mahmoud Ahmadinejad therefore could be experiencing positive or negative emotions.
Even when the response is pretty clearly positive, the ability to see evidence of emotional states in brain scans does not tell us how those experiences should be judged. The sight of white powder may stimulate an addict's nucleus accumbens (part of the brain's reward sytem), but so might a picture of his girlfriend or the prospect of a great deal on a big-screen TV. "The fact that addiction is associated with neurobiological changes," Lilienfeld and Satel observe, "is not, in itself, proof that the addict is unable to choose." Yet what they call "the brain-disease fallacy" permeates supposedly enlightened and scientific discussions of addiction, where it is used to justify coercion as well as compassion.
Neuroimaging also suffers from what the University of Montreal researcher Eric Racine calls "neurorealism," which Satel and Lilienfeld define as "the misbegotten propensity to regard brain images as inherently more 'real' or valid than other types of behavioral data." A study reported this year in the journal Socioaffective Neuroscience and Psychology illustrates this tendency. UCLA researchers solicited 52 subjects who said they had trouble controlling their consumption of pornography and hooked them up to an electroencephalograph while they looked at sexually explicit images. Based on electrical activity in the subjects' brains, the researchers concluded that hypersexuality should be understood as "high desire, rather than disordered." Or as The Huffington Post put it, "Sex Addiction Does Not Appear to Be a Disorder."
The UCLA press release added another level of confusion. "If [the subjects] indeed suffer from hypersexuality, or sexual addiction," it said, "their brain response to visual sexual stimuli could be expected to be higher, in much the same way that the brains of cocaine addicts have been shown to react to images of the drug in other studies." According to this gloss, sexual addiction not only is not a disorder; it is not even an addiction. Thus does neurorealism, based on a white-coated scientist's squiggly lines, discount the actual experiences of people who believe they have a problem. The flip side would be insisting, based on a brain scan, that someone who believes his life is better thanks to drugs is in fact an addict in need of treatment, whether he wants it or not.
In addition to misconceptions about addiction, Satel and Lilienfeld critically examine overblown claims about the relevance of neuroimaging to consumer behavior, criminal justice, and moral responsibility. They draw instructive parallels with earlier attempts to reveal the secrets of human motivation and behavior that did not live up to their promises, ranging from Franz Joseph Gall's phrenology to Vance Packard's unveiling of The Hidden Persuaders. While brain scans may have a stronger scientific basis, they are the latest prop wielded by biological reductionists who see human experience as an incidental byproduct of deterministic processes beyond our control. According to this view, addicts are slaves, consumers are pawns, and criminals are puppets. While those portraits are hardly flattering, they do offer a benefit: relief from responsibility. To collect, all you have to do is surrender your freedom.