1. AN EXPOSITION ON HANDEDNESS 1
An Exposition on Handedness
Tehya McGill and Ryan Esplin
Tarrant County Community College
Introduction
Hands can be considered as the instrument of human expression and creation. They’ve
been used to carry out nearly every action that humans have made in their existence, and to even
help them survive. There is so much to look at and understand about what hands have done and
what they can do. This paper will look into what has been collected and understood about
handedness and its significance.
Handedness is the natural or biological preference to use one hand more than the other
for performing special tasks depending on which hemisphere is dominant for the task (Rice,
1998). Annett (2002) went further by defining handedness as not a discrete variable between
right or left, but a continuous one that can be expressed at levels between strong left and strong
right. About 70-90 percent of humans are considered to be strong right-handers, 10 percent are
considered to be strong left, and about 30 percent are considered to be mixed-handed (Holder, M.
K. (1997). On the surface of these observations, there’s not much to see or understand about
hand preference, besides the well-known fact that the brain’s left hemisphere controls the right
side of the body and vise versa. However, when scientists have tried to understand this
phenomenon, there’s some causal mystery as to why left-handers exist in the first place. Studies
have shown that handedness is 24 percent hereditary (Genetic influences on handedness: Data
from 25,732 Australian and Dutch twin families). 24 percent though is hardly a conclusive
percentage and cannot be considered as causality. Also there has been no evolutionary causes
that show the purpose of the existence of left-handed people. A study has shown that apes do not

2. AN EXPOSITION ON HANDEDNESS 2
have the same popular degree of bias for handedness, suggesting that handedness developed
through human lineage (Uomini NT, 2009). To add, studies have shown that right-handedness
dates back over half a million years (Frayer DW, Lozano M, de Castro JMB, Carbonell E,
Arsuaga JL, et al. 2012). To complicate this mystery even more, the existence of left-handedness
has caused some differences in people’s socialization because of the mental disorders that are
often associated with lefties (Sage Open, vol. 3 no. 4). There has been a large accumulation of
interesting trends, characteristics, hypotheses and theories extrapolated from trying to understand
handedness. This exposition will cover the most notable information and how the oddly
occurring phenomenon has affected their socialization.
Literature Review
Through the 20th century, models and studies looking for the causality of handedness
have been similar to one another but have had slightly different conclusions. In Behavior
Genetics (Laland, Kumm, Van Horn, and Feldman, 1995, pg. 433), they go over the differences
and variations of these studies. A common model that has been used assumes genetic basis to
both laterality and hemispheric asymmetry (Levy and Nagylaki, 1972; Annett, 1978, 1985;
McManus, 1985). These studies propose that cerebral dominance (the side of the brain that
determines which hand is most dominant) is controlled by two genes; one gene is responsible for
which side of the brain speech will be placed and the other gene will determine hand dominance
in concordance with contralateral or ipsilateral hemispheres. A similar model developed by
Annett (1978, 1985, and 1994) attempted to explain handedness by only one gene variant. She
concluded that handedness measured by performance tasks continuously distribute handedness,
and variations of handedness are from unknown environmental factors; distribution of
handedness in humans and nonhuman vertebrates have the same standard deviations, and all

3. AN EXPOSITION ON HANDEDNESS 3
humans are equally likely to be left or right handed. McManus (1985) researched a genetic
model that is also similar to the aforementioned models except with a different conclusion on
how to classify handedness. Risch and Pringle (1985) collected family gene-inheritance data
with either a single or two gene model and found it to be consistent. However, they stated that
the results cannot be taken as evidence of genetic causation, and that correlations between
relatives could be a result of environmental factors. To conclude the genetic model: genetic
models assume that the genetic variation is preserved in populations through the heterozygote
advantage (Annette, 1985; Corballis, 1991; McManus and Bryden, 1992). This however has not
been proven, thus we conclude that there are no genetic variations that cause handedness,
variation of handedness is the result of a combination of cultural and environmental factors, and
a genetic influence must still be present because handedness is a facultative trait (Laland, Kumm,
Van Horn, and Feldman, 1995, pg. 433).
The genetic models looking for the causation of handedness are inconclusive, but there is
more to understand about handedness and its effect on people. This phenomenon has affected
humans in many ways throughout history, and there are many characteristics associated with
southpaws which can be significant to their socialization. The very origin of left is defined as
weak, broken, foolish, lameness, worthless, and even “opposite of right” (Online Etymology
Dictionary). In Stanley Coren’s book (The Left-Hander Syndrome: The Causes and
Consequences of Left-Handedness, 1992), he covers even more meanings that have been tied to
left-handers in history such as a nasty habit, a mark of the devil, a sign of neurosis, rebellion,
criminality, and homosexuality. Carl Sagan hypothesized that the cultural link between left-
handedness and badness came from nonindustrialzed nations that used the left hand for hygiene,
however David Wolman pointed out in his book (Left-Hand Turn around the World) that it goes

4. AN EXPOSITION ON HANDEDNESS 4
much further back because of how deep the etymology roots go in association with badness to
left-handedness. Even in modern days left-handedness is still clouded in misconceptions, as
David Wolman explains
Most people presume the hand used for writing is the litmus test for
determining whether someone is lefty or righty, and for anyone content to live with a
pedestrian level of knowledge on the subject, this narrow reading will serve well enough.
[And yet] everyday tasks, like throwing and eating, also influence the popular
understanding of hand dominance, sometimes nearly as strongly as writing. These
different behaviors lead immediately to a quintessential problem of handedness inquiries:
how to define handedness itself. The definition of lefty or righty varies, sometimes to a
frustrating degree, and that variation has troubled researchers who want to get a better
handle on why it is that humans have hand preference and performance discrepancies in
the first place, where these discrepancies come from, and why as a population we usually
favor the right hand.
To reflect Wolman’s points and the results of the genetic models, this complicates the
understanding and comprehension of handedness and remains a mystery because of how the
history of unknown influences and variables of genetic and environmental causes resulted in
differences and variations of a person’s performance that ultimately effected people’s
socialization.
In the Journal of the Indian Academy of Applied Psychology (Vol. 33, No. 1, 2007), they
found that there is no doubt that left-handedness is associated with a lot of disadvantages, but
various studies have shown that left-handedness is also associated with enhanced abilities. For
example, left-handers can produce a corresponding intellectual advance and leap in the number

5. AN EXPOSITION ON HANDEDNESS 5
of mathematical sporting or artistic geniuses. McManus (1997) proposed that the reason for this
is that right-hander’s brains have genes that force their neural activity into a slightly more one
sided structure, whereas left-hander’s brains have neural activity that is more symmetric in each
hemisphere which enhances a person’s abilities. If lefties have enhanced abilities, it’s usually
mathematics, art, architecture, music, or high levels of IQ. Papilia (1993) conducted a study
trying to understand these highly skilled and intelligent people. The study suggested that they
required less glucose energy while performing cognitive tasks, and also found they absorbed
information more quickly and showed faster brain-wave response times to simple stimuli such as
a flash of light. However, Cole (1997) thoroughly reviewed the research on handedness and
intelligence and concluded that there was no consistent link. Needleman (2001) added to Cole’s
findings by finding that left-handed people as a whole are not more or less intelligent than right-
handed people and on average are both equal.
Methodology
Method of research consisted of a list of activities that required hand operation to
perform. The participant filled in the preferred hand for the activity for a total of ten activities.
Each activity had three options to choose for hand preference: left, right, or either. Every mark
indicated ten percent toward left, right, or either handed. For example, if an individual chose nine
activities as either hand and one activity with the right hand, they would be considered as ninety
percent ambidextrous and ten percent right handed. After finding the percent of handedness, a
questionnaire would be filled out by the participant asking a total of three questions: What is
your sexual preference? Have you been diagnosed with or noticed symptoms of ADHD,
schizophrenia, disorganized thinking (speech), dyslexia, and speech dysfluency (stuttering)? &
how old was your mother when you were born? The purpose of the questionnaire was to gather

6. AN EXPOSITION ON HANDEDNESS 6
symptoms and associations that are often attributed to left-handers, then to relate that person’s
handedness to their answers.
Conclusion
At the beginning of this research it was mentioned that hands could be considered as the
instruments of human expression and creation. It may possibly be that handedness is a direct
representation of the way the brain processes abstract information into an abstract construct that
is then interfaced and expressed with motor functions. If so, how would that be proven? That is
ultimately a question for a neuroscientist to answer, which is far behind in completely explaining
it, but while the answers for that are put on hold, what is the lesson we can draw from
handedness? With everything that has been put forward, the lesson to learn from handedness is
understanding how a seemingly random biological occurrence can cause random results, which
then can affect people’s social integration by the way they are innately different from this
random occurrence.
References
Wolman, D. (2005). Left-hand Turn around the World: Chasing the Mystery and Meaning of All
Things Southpaw: Cambridge, MA:
Da Capo Press
Coren, S. (1992). The Left-Hander Syndrome: The Causes and Consequences of Left-
Handedness: Detroit, MI:
Free Press.
Annett, M. (1985). Left, Right, Hand and Brain: The Right Shift Theory: London:
Psychology Press. 488 p. p.
McManus, C. (2004). Right hand, left hand: The origins of asymmetry in brains, bodies, atoms
and cultures:
Harvard University Press

7. AN EXPOSITION ON HANDEDNESS 7
Mcgrew, W.C. Marchant, L.F. (1997). On the other hand: Current issues in and meta-analysis of
the behavioral laterality of hand function in nonhuman primates:
Yearbook of Physical Anthropology, Vol. 40 - 1997 40: 201–232
Uomini, N.T. (2009). The prehistory of handedness: archaeological data and comparative
ethology.
J Hum Evol. 57: 411–419
Ghayas, S. Adil, A. (2007). Effect of Handedness on Intelligence Level Students: Sargodha,
Pakistan:
Journal of the Indian Academy of Applied Psychology, Vol. 33, No.1, 85-91
Rice, (1998). Effect of Handedness on Intelligence Level Students: Sargodha, Pakistan:
Journal of the Indian Academy of Applied Psychology, Vol. 33, No.1, 85-91
Neuropsychologia, (2009). Genetic influences on handedness: data from 25,732 Australian and
Dutch twin families: Queensland Institute of Medical Research, Australia:
10.1016/j.neuropsychologia.2008.09.005. Epub. 2008, Sep 9.