Sex, Lies, and the Brain

Men, women, and the lies we tell

Posted Nov 10, 2012

It’s often said that everyone lies.  Psychologists have data to back up this statement. According to Robert S. Feldman, a University of Massachusetts Amherst social psychologist, men lie to impress other people, and women lie to preserve someone else’s feelings. By virtue of the nature of the subject matter, though, it’s not always easy to tell even if a research participant is telling the truth. This is a big problem in an experimental setting, where participants know they’re being monitored. If you want to look good to a psychologist, you’ll probably try to minimize the extent to which you intentionally deceive.  On the other hand, you may be even more motivated to hide your deepest personal secrets.

Lie detectors have their place in understanding the psychology of lying, but they clearly have their limitations. Good liars can defeat most of these instruments by controlling their breathing and other indicators of their stress levels.  Another way to detect lying is to observe a person’s “micro-expressions”. Again, a good liar (or actor) can easily exert control over those mini-muscles of the face and sail through even the most grueling cross-examination.

Enter the fMRI. A brain scanning method increasingly being used to watch your brain as you solve problems, answer questions, remember nonsense words, or look at pictures depicting various situations, the fMRI may hold promise as a way to examine the brain’s reaction as we decide to tell the truth or lie.  Researchers who use this and other brain scanning methods claim that our brains make decisions about half a second before we “know” we do. Such findings certainly raise questions about the nature of free will and consciousness. However, without getting into these thorny philosophical debates, there may be some practical applications. The technology of brain scanning may mean that someone can see what you’re thinking before even you know it yourself.

Lying takes more cognitive effort than telling the truth.  Brain scan results reflect this fact.  When people lie, they need to keep information in working memory (to remember what they’ve said) while also suppressing or inhibiting the actual truth. Liars also have to use up more mental energy to switch between truth-telling (such as stating their names) and fibbing (such as stating their whereabouts or actions).  The only way that liars can avoid being caught is if their stories are consistent. Even if the truth of something you’ve done involves complicated facts, there is only one story that you have to tell.  No matter how many times you’re questioned, your answers will come out the same. The only exceptions occur during confessions under duress, when a truth-teller finally gives up in confusion, fatigue, or misdirection from the questioner.

Presumably, the same cognitive effort should be involved in lying about your personal qualities or lying to preserve someone else’s feelings, the areas in which gender differences have been identified.  This was the basis for an fMRI study by Polish researcher Artur Marchewka and his colleagues, who compared the brain scans of men and women while lying and telling the truth about either personal or factual material. They brought in a sample of young adult men and women (ages 21-28) and asked them a series of questions while conducting fMRI scans.  Half the questions involved personal information that participants had earlier shared about themselves (such as their names) and the other half involved general knowledge that participants stated that they knew (such as historical facts). The participants were given an incentive, as they were promised rewards for being the best “truth-tellers” or “liars.”  Their task was to say “yes” on half the trials and “no” the other half. They also were told that a lie expert was watching their faces while they responded (which was actually a lie) and that their stress levels were being monitored through a fake device placed on one of their fingers (also a lie).  To measure their “psychological” gender, the participants also completed a questionnaire that tests masculine and feminine sex roles.

The experimenters compared men and women in both the length of time it took participants to respond “yes” or “no” to the questions and their brain activation patterns.  Men showed greater difficulty (i.e. took longer) when they lied about their personal information than when they lied about general information. More to the point, their brain scans showed that these personal lies swallowed up more neural energy in their frontal lobes, which is the part of the brain involved in executive control and decision-making.  Women showed no differences in their brain activation or response time between the general and personal lying questions.  Taking into account the person’s psychological gender role didn’t change the findings. From these results, the authors concluded that male-female differences in lying are due to biology, not socialization. Women, they maintain, just find it biologically easier to lie about personal information or at least find it no easier to lie about personal vs. non-personal information.

We might question this last conclusion about the role of socialization. Claims about biologically caused sex differences in, for example, sexuality, are often attributed to evolution’s differential pressures on men and women.  We can bicker with these claims, which may be as much political as factual, though the facts tend to favor lack of biologically-caused differences.  When it comes to the brain, however, there are many reasons to reject biologically-based claims. The brains we’re born with aren’t necessarily the brains we keep throughout our lives. Experience shapes and reshapes our neurons as they adapt and grow with our experiences. Women may learn that it’s important and even necessary to tell lies about themselves, such as their age, given the negative attitudes in our society toward older women.  In many situations, women may also have to lie about other attributes to avoid seeming “better” than the men in their lives.  Our brains rewire themselves constantly based on the experiences we feed them.  The more often we have to (or feel we have to) lie about ourselves, the easier it gets, and the less effort our brains must exert.

Apart from what the study tells us about sex differences, the findings point to fascinating new ways we may be able to separate the liars from the truth-tellers in all kinds of situations. I doubt if you’re ready to purchase a portable MRI to check out your next potential date, employee or employer, or friend.  However, you may be able to perform your own virtual checks of those in your social world by using other more readily available cues. Response times, tiny furrows in the forehead, and general inconsistencies in stories are your best bets for spotting a social liar.   When it comes to your own lies, obviously, you are better off being honest than lying. Not only is it more ethical to tell the truth, but will also save your brain for more important, and productive uses, of its energy. 

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Copyright Susan Krauss Whitbourne, Ph.D. 2012


Marchewka A, Jednorog K, Falkiewicz M, Szeszkowski W, Grabowska A, et al. (2012) Sex, Lies and fMRI—Gender Differences in Neural Basis of Deception. PLoS ONE 7(8): e43076. doi:10.1371/journal.pone.0043076