On January 20, Barack Obama was sworn in as president of the United States.
It was a triumphant day not just for Democrats, African Americans, and
Americans who wanted a leadership change, but for left-handed Americans. The
reason? Only 10 percent of the American population is left-handed, and Obama
is one of this minority group.
In fact, four of the past six presidents—Gerald Ford, Ronald Reagan,
George H.W. Bush, and Bill Clinton—were also left-handed, demonstrating
that in spite of the age-old prejudice and discrimination against left-handed
individuals, "lefties may have the right cerebral stuff."
Moreover, many other famous people have been, or are, left-handed—the
Roman general Julius Caesar, the Renaissance painter Michelangelo, American
novelist Mark Twain, Beatle Paul McCartney, television mogul Oprah Winfrey,
and Supreme Court Justice Ruth Bader Ginsberg.
Some scientific studies also attest to the positive mental aspects of being
left-handed or ambidextrous.
Two Pakistani researchers explored the effect of handedness on the
intelligence level of students. The sample included an equal number of
left-handed and right-handed students drawn from various universities in
Pakistan, altogether 150 subjects. Subjects were assessed for both handedness
and intelligence. The researchers found no significant difference in
intelligence between subjects from various educational levels, but they did
find that left-handed subjects were significantly more intelligent than
right-handed subjects. Results were published in the January 2007 Journal
of the Indian Academy of Applied Psychology.
In a study of 250 healthy undergraduate students, ambidextrous individuals
were found to engage in more magical ideation than either left-handed or
right-handed persons were. Such ideation, the researchers proposed, may
reflect heightened creativity. Study results appeared in the January 2002
Laterality: Asymmetries of Body, Brain, and Cognition.
Then Johns Hopkins economists determined, in a nationally representative
sample of 5,000 men and women, that left-handed college-educated men earned 15
percent more than right-handed college-educated men did, even after possibly
confounding factors such as age, race, IQ, level of education, and marital
status were considered.
"Our findings are quite contrary to expectations," they
acknowledged in their study report, which was published by the National Bureau
of Economic Research in 2006. However, they did not find the same wage
differential for women in the sample.
Nonetheless, some studies reported in the psychiatric research literature
suggest that being left-handed or ambidextrous has another side—that
left-handed or ambidextrous persons are more likely to have certain mental
disorders than right-handed persons are. Moreover, the number of these
studies, as well as their quality, intimate that the links they have made
between left-handedness or ambidexterity and mental disorders are not simply
related to chance.
During the 1970s and 1980s, for instance, some studies noted what appeared
to be an unusually large percentage of left-handed or ambidextrous people
among those with autism, dyslexia, stuttering, or neurodevelopmental
disorders. Much more recently, DSM-IV developmental coordinational
disorder (DCD), which can impair both large and fine motor skills and make
everyday activities such as getting dressed, writing by hand, and
participating in sports difficult, has also been coupled with left-handedness.
In the February 2008 Journal of Child Neurology, two Israeli
scientists reported that out of 98 children with DCD, 31 percent were
left-handed, and 13 percent were ambidextrous. In the October 2008
Canadian Journal of Psychiatry, Canadian researchers reported that
out of 19 children with DCD, 37 percent were left-handed.
An unusually large number of persons with schizophrenia also appear to be
left-handed. In one study, some 400 subjects with schizophrenia, major
depression with psychosis, bipolar psychosis, or no psychiatric illness were
evaluated on handedness. The schizophrenia subjects were left-handed
significantly more often than the other groups were, the researchers reported
in the May 1994 Journal of Abnormal Psychology.
Tyrone Cannon, Ph.D., a professor of psychiatry at the University of
California at Los Angeles, and coworkers have since discovered, while
comparing the childhood neurocognitive test results of individuals with
schizophrenia with those of their siblings or controls—altogether 258
subjects—that 32 percent of those with schizophrenia were left-handed,
compared with only 12 percent of their siblings and only 9 percent of the
controls. These results were published in the November 2003 American
Journal of Psychiatry.
Further, Clyde Francks, Ph.D., of the University of Oxford in England, and
his team reported something intriguing in the July 31, 2007, Molecular
Psychiatry—that they had found a gene that increases the odds of
being left-handed. The gene, dubbed LRRTMI, appears to be the first gene
discovered that has an effect on handedness. They also found that the gene
might slightly increase the risk of developing schizophrenia.
Posttraumatic stress disorder (PTSD), too, has been coupled with
left-handedness. Two Scottish researchers—Carolyn Choudhary, Ph.D., and
Ronan O'Carroll, Ph.D., of the University of Stirling—screened a general
population sample of some 600 people for handedness and PTSD. They found that
11 percent of the sample was left-handed, that 9 percent of the sample met all
DSM-IV criteria for PTSD, and that significantly more left-handers
than right-handers comprised the PTSD group. Results were reported in the June
2007 Journal of Traumatic Stress.
PTSD has likewise been associated with ambidexterity. A study of some 2,500
U.S. Army veterans found that veterans who were extremely ambidextrous (about
3 percent of the study sample) were twice as likely to have developed PTSD
after combat as were veterans who were not extremely ambidextrous. Veterans
who were extremely ambidextrous and who experienced especially high combat
exposure were nearly five times as likely to have developed PTSD after combat
as were those who were not extremely ambidextrous and who experienced
especially high combat exposure. Study results, published in the May 17, 2007,
Psychosomatic Medicine, held firm even when some possibly confounding
factors such as age, race, intelligence, and age at entry into the Army were
But perhaps the greatest surprise is that left-handedness has been linked
with a mental disorder considered more psychosocial than biological in
origin—pedophilia. James Cantor, Ph.D., an assistant professor of
psychology at the University of Toronto in Canada, and colleagues found, in a
study of some 400 sexual offenders, that the odds of being left-handed were
about two times greater among pedophiles than among sexual offenders targeting
adults as their victims. In fact, more than 30 percent of the pedophiles were
left-handed, that is, three times the rate in the general population. Results
were published in the August 2005 Archives of Sexual Behavior.
So, since left-handedness and ambidexterity have been linked with certain
neurodevelopmental disorders, schizophrenia, PTSD, and pedophilia, what might
that link be?
Left-handedness and ambidexterity may share some underlying biological
origins with them, some researchers contend.
For example, Choudhary and O'Carroll do not believe that the reason why
left-handed persons are more likely to develop PTSD is because they are more
at risk of trauma in a right-handed world than are right-handed people. The
reason why is because they found no significant difference between the number
of traumas experienced by left-handed subjects and by right-handed ones.
However, the researchers do suspect that the reason that left-handed
individuals may be more likely to develop PTSD is because their brains are
responding to, or processing, emotional events differently from the brains of
Francks suspects that the gene LRRTMI might set the stage for both
left-handedness and schizophrenia by influencing the development of brain
asymmetry. Asymmetry is an important feature of the human brain, with the left
side usually controlling speech and the right side controlling emotion. In
left-handers, this pattern is usually reversed. Iris Sommer, M.D., Ph.D., of
the University of Utrecht in the Netherlands, agreed with Francks. In fact,
she has found that, just as speech often originates in the right side of the
brain in left-handed persons, it is also the case for persons with
And as for why left-handed persons may be disproportionately represented
among known pedophiles, Cantor believes that the answer may lie in brain
characteristics common to both conditions.
In any event, even if left-handedness and ambidexterity share common
biological pathways with some mental disorders, left-handed individuals should
not conclude that they will necessarily develop these mental disorders,
authorities on the subject stress.
For example, regarding the finding that Francks and his colleagues have
made—that the gene that predisposes to left-handedness may also increase
the risk of schizophrenia—"People really should not be concerned
by this result," he said. "There are many factors which make
individuals more likely to develop schizophrenia, and the vast majority of
left-handers will never develop the problem."
As for Choudary and O'Carroll's finding that left-handers are significantly
more at risk of PTSD, Choudhary said, "The development of PTSD is
multi-factorially determined and incompletely understood. In this context,
left-handedness seems to be an important part of the jigsaw and one previously
neglected, but though apparently important, is only one determinant of who
might develop PTSD following trauma."
All in all, Choudhary stressed, "The majority of left-handers are not
going to develop mental health problems because of their
Cantor agreed: "The association between left-handedness and disease
is very complex.... Being left-handed does not make a person appreciably more
likely to have any given disease."
So being left-handed or ambidextrous, like virtually everything in life,
has both its pluses and minuses. And if you are left-handed or ambidextrous,
why not try to capitalize on your mental strengths—say, exceptional
intelligence, economic shrewdness, or creativity? Who knows, you might even
become president! ▪