fb-pixel Skip to main content
Opinion | Daniel J. Levitin

Forget the tax returns; show me his brain scans

AP/Globe staff

In Princeton philosopher Harry Frankfurt’s 2005 essay “On Bullshit,’’ he makes a distinction between lies and B.S. that is perhaps more important right now than ever before.

A lie occurs when someone has the intent to deceive, that is, the misrepresentation is not merely inadvertent. On the other hand, B.S. occurs when the speaker doesn’t even care what is true or not, and is just making things up. These are clearly separate cases. The B.S.-er shows a blatant disregard for facts and figures and, to him or her, they hold no value. The liar may well be a very methodical collector of facts, who uses them or lies about them in order to advance an agenda.

As Frankfurt writes, “Telling a lie is an act with a sharp focus. It is designed to insert a particular falsehood at a specific point in a set or system of beliefs, in order to avoid the consequences of having that point occupied by the truth. This requires a degree of craftsmanship, in which the teller of the lie submits to objective constraints imposed by what he takes to be the truth. . . . [A] person who undertakes to [B.S.] his way through has much more freedom. His focus is panoramic rather than particular. He does not limit himself to inserting a certain falsehood at a specific point, and thus he is not constrained by the truths surrounding that point or intersecting it.” For the B.S.-er all bets are off: “[H]e is neither on the side of the true nor on the side of the false. His eye is not on the facts at all, as the eyes of the honest man and of the liar are.”

The B.S.-er can be more dangerous than the liar because he or she won’t even agree, as the liar does, that facts exist. This places the entire conversation into a bizarro alternate world in which up is down and lies are truth.


There has been much talk about our living in a post-truth era — an era in which facts don’t matter. President Trump, when challenged on facts, says that many people feel the way he does. But feelings should not take the place of reason in matters of public policy. If we are to appropriate money for roads, we need statistics on how bad our roads really are and moreover, where more roads will be beneficial — it would be irresponsible to just build them where our gut tells us to.


Research in cognitive neuroscience since Frankfurt’s time reveals something that was not then known about how the brain generates B.S. The human brain is made up of two hemispheres, the familiar left and right. The old story that the left is for language and the right for art is outdated. But the hemispheres do specialize in two important ways. The left brain is responsible for making order out of chaos, for making sense of things in the world that don’t always add up. To do this, it often makes up stories, fantastic confabulations in some cases, just to be able to explain what we’re experiencing. The right brain, however, contains a powerful B.S. detector, the won’t-take-no-guff fact-checking system. The right brain keeps track of what is actually going on, while the left brain is busy spinning stories and theories. The left tries to explain not just external events, but our own mood shifts.

Suppose you walk across a shaky, unstable bridge, something that raises your physiological arousal levels. At the other end of the bridge you encounter a potential love interest. You’re more likely to rate that person as highly attractive than if you walked across a stable bridge or no bridge at all — psychologists call this misattribution of arousal. Your left brain notices that your heart is beating quicker, you feel a bit of adrenaline, and then — voilà! — a person standing at the other end, giving our left brain something to work with. It provides a plausible, though incorrect, explanation for what we observed about our bodies. If no person is there, we instead infer that our arousal must be due to the shaky bridge and nothing else.


The left-brain fudges things to put the observed information into a story that makes sense. The fact-checking right brain allows mild white lies to pass through. But go too far off the rails and it springs into action.

But what happens if the fact-checking right brain becomes damaged, or disconnected from the left brain? The left just goes on and on, making stuff up without being checked. Brain scans can potentially reveal right-brain atrophy or damage, or even hyperactive left-brain circuits that overpower their right-brain gatekeepers. Todd Feinberg, from the Albert Einstein School of Medicine, has shown that people who confabulate are likely to have right-brain damage. This converges nicely with a host of studies, including those by Michael Gazzaniga at the University of California, Santa Barbara, showing that people with a damaged corpus callosum – the mass of fibers that connects the two hemispheres — are unable to stop themselves from lying when information is presented to the confabulating left brain.


The next time you hear a politician answering a question about evidence by saying “I feel,” or dismissing actual evidence as irrelevant or “fake,” you’re probably dealing with a B.S.-er, not a pathological liar. If a politician says that our country’s gross domestic product (GDP) is less than zero, or that unemployment may be as high as 42 percent, you’re probably not dealing with a liar. These are not the sort of razor-sharp lies that a manipulator of the truth might employ in order to get his way. There are so many ways that unemployment can be measured, for example, that there is no need to make up numbers – one can simply choose the number that best makes one’s point. At least then we the public can engage in an evidence-based discussion about whether that was the appropriate number to use or not, and what to do about unemployment.

Telling a pathological liar apart from a B.S.-er is not that difficult once you know what to look for. Maybe instead of asking political candidates to submit tax returns, we really should be asking to see their brain scans.

Politicians have always lied, or (more generously), they speak inconsistently to different audiences in order to build consensus and get things done. But lies threaten to crumble the very foundation of our democracy. We, the public, can’t exercise our rights of free speech and elections if we don’t know what we’re speaking and voting for or against. We have a right to the facts. Marijuana, gun control, abortion, immigration, trade — these are all emotional issues that can be informed by statistics and facts. Different people may disagree about what to do about those data, and that is the basis of democracy. As the late Senator Daniel Patrick Moynihan quipped, you are entitled to your own opinion, but not your own facts.


Daniel J. Levitin is the author of “Weaponized Lies: How To Think Critically in the Post-Truth Era.” He is founding dean of arts and humanities at the Minerva Schools at KGI and distinguished faculty fellow at the Haas School of Business, UC Berkeley.