The nose of the fairy-tale puppet Pinocchio may have grown longer with each
lie he told. But what was going on in his head as he lied?
A new study may have the answer. It found a greater amount of prefrontal
white matter in the brains of pathological liars.
"To our knowledge, this study is the first to show a brain
abnormality in people who lie, cheat, and manipulate others," the
investigators said in their study report, which was published in the October
British Journal of Psychiatry.
The study was headed by Yaling Yang, a doctoral student in brain and
cognitive science at the University of Southern California. His team included
Adrian Raine, Ph.D., a professor of psychology at the University of Southern
California and among America's leading scientists when it comes to peering
into the brains of antisocial individuals to learn what is going on
(Psychiatric News, June 17).
Yang and his colleagues recruited subjects by advertising at
temporary-employment agencies. They did not tell people interested in
participating that it had to do with antisocial behavior, and especially with
lying, since they also wanted to include a number of subjects who did not
engage in such behaviors.
They ended up with 49 subjects—21 normal subjects, who had neither
antisocial personality disorder nor a history of pathological lying; 16
subjects with antisocial personality disorder, but no history of pathological
lying; and 12 subjects with a history of pathological lying. Subjects were
defined as pathological liars if they fulfilled criteria for pathological
lying on the Psychopathy Checklist-Revised; criteria for conning/manipulative
behavior on the same checklist; the deceitfulness criterion for
DSM-IV antisocial personality disorder; or criteria for malingering
as indicated by admitting to telling lies to obtain sickness benefits.
None of the groups differed significantly in social class, ethnicity, I.Q.,
handedness, history of head injury, height, head circumference, and
DSM-IV diagnoses of alcohol/drug misuse/dependence.
Yang and his team then assessed the gray-matter and white-matter volumes of
all 108 subjects with structural magnetic resonance imaging.
Compared with both antisocial and normal control subjects, liars had some
25 percent more prefrontal white matter and more than a 33 percent reduction
in the ratio of prefrontal gray matter to prefrontal white matter.
Yang did not expect these results, he told Psychiatric News."
I was surprised by how significantly different the brains of
pathological liars and the brains of controls were," he said. "And
I was surprised that the answer to pathological lying may be in white matter.
To date, neuroscientists still focus more on gray matter, which is the neural
cell bodies of the brain, than on white matter, which is the connection
Indeed, since white matter is pivotal to the connectivity and cognitive
function of the human brain, increased prefrontal white matter might confer a
predisposition to lying, Sean Spence, M.D., a professor of psychiatry at the
University of Sheffield in England and a deception authority, speculates in an
accompanying editorial. On the other hand, he cautioned, "We do not know
whether the findings reflect cause or effect (whether anatomy drives deception
or is driven by its practice)."
Also unknown, he added, is whether the study results apply only to "a
subgroup of unemployed antisocial people who resort to deception for
instrumental gain, but who are not necessarily very good at lying" or
also apply to "those successful social predators who lie and cheat and
yet retain enormous influence in the world."
And as Spence told Psychiatric News, "I don't think the
study changes what a psychiatrist would do in the clinic at the moment, but I
think the scientific study of deception will gradually inform the way people
think about practice that relies so heavily upon subjective
The study was funded by the National Institute of Mental Health and the
An abstract of "Prefrontal White Matter in Pathological
Liars" is posted at<http://bjp.rcpsych.org/cgi/content/abstract/187/4/320>.▪
Br J Psychiatry