P1 IZOArchives of Sexual Behavior pp744-aseb-460154 Februar.docx

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Archives of Sexual Behavior pp744-aseb-460154 February 3,
2003 12:24 Style file version July 26, 1999
Archives of Sexual Behavior, Vol. 32, No. 2, April 2003, pp.
103–114 ( C! 2003)
Handedness, Sexual Orientation, and Gender-Related
Personality Traits in Men and Women
Richard A. Lippa, Ph.D.1
Received April 19, 2002; revision received October 1, 2002;
accepted November 15, 2002
This study assessed large numbers of heterosexual and
homosexual men and women on handedness
andgender-relatedpersonality traits.
Initialanalysesemployedadichotomousmeasureofhandedness
(right-handed vs. non–right-handed). For men and women
combined, homosexual participants had
50% greater odds of being non–right-handed than heterosexual
participants, a statistically significant
difference.Homosexualmenhad82%greateroddsofbeingnon–
right-handedthanheterosexualmen,
astatisticallysignificantdifference,whereashomosexualwomenhad
22%greateroddsofbeingnon–
right-
handedthanheterosexualwomen,anonsignificantdifference.When
participantswereclassified
into five graduated categories of handedness, both men and
women showed significant homosexual–

heterosexualdifferences
inhandednessdistributions.Withingroups,handedness
showedanumberof
weak but statistically significant associations with sex-typed
occupational preferences, self-ascribed
masculinity, and self-ascribed femininity, but not with
instrumentality or expressiveness. Rates of
non–right-handedness were virtually identical for heterosexual
men and women, suggesting that sex
differences in handedness may result from higher rates of
homosexuality in men.
KEY WORDS: handedness; sexual orientation; sex differences;
masculinity; femininity.
INTRODUCTION
Ina recentmeta-analysis,Lalumière,Blanchard,and
Zucker(2000)compiledevidenceonassociationsbetween
handedness and sexual orientation in men and women.
Data from 6,182 homosexual and 14,808 heterosexual
men showed that homosexual men had 34% greater odds
of being non–right-handed than heterosexual men, and
datafrom805homosexualand1,615heterosexualwomen
showed that homosexual women had 91% greater odds of
being non–right-handed than heterosexual women. Both
of these differences were statistically significant. A num-
ber of recent studies have also indicated that gender iden-
titydisorder isassociatedwithnon–right-handedness (see
Green and Young, 2001, and Zucker, Beaulieu, Bradley,
Grimshaw, and Wilcox, 2001, for reviews and new data).
Although there is now considerable evidence for an
association between non–right-handedness and certain
kinds of strong gender-atypicality (e.g., homosexuality,

1Department of Psychology, California State University,
Fullerton,
California 92834; e-mail: [email protected]
gender identity disorder), the evidence is weaker for
associations between handedness and other kinds of
gender-related individual differences. Perhaps the best-
documented finding is that there are slightly higher rates
of left-handedness in males than females. In an interna-
tional survey of over 11,000 participants, for example,
Perelle and Ehrman (1994) reported that 10.6% of male
participantsand8.5%offemaleparticipantsreportedwrit-
ing with their left hands, and in a compilation of data
from over 12,000 children, Zucker et al. (2001) reported
that 11.8% of boys and 9.0% of girls were left-handed.
Finally, a meta-analysis by Seddon and McManus (1991)
compiled results from88studieswithmore thanaquarter
of a million participants and found that 8.5% of men and
6.7% of women were left-handed, with men’s incidence
of left-handedness 27% higher than women’s. Although
a number of theories have attempted to explain the small
but reliablesexdifferences typically foundinhandedness,
these differences remain poorly understood.
A few studies have examined associations between
handedness and gender-related personality traits within
each sex. For example, Nicholls and Forbes (1996)
103
0004-0002/03/0400-0103/0 C! 2003 Plenum Publishing
Corporation
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104 Lippa
reported that 40 left-handed women scored higher on in-
strumentality (i.e., dominance) and lower on expressive-
ness (i.e.,nurturance) thandid40right-handedwomen. In
a study of 340 college women, Casey and Nuttall (1990)
reported a number of significant associations between
“anomalousdominance”(beingnon–right-handedorhav-
ing non–right-handed first-degree relatives) and instru-
mentalityandexpressivenessasassessedbytheBemSex-
Role Inventory and masculinity as assessed by a tomboy
scale. In general, women with “anomalous dominance”
showed more male-typical traits than purely right-handed
women. Santhakumari, Kurian, and Rao (1994) reported
that, among 124 Indian women, non–right-handedness
was associated with higher levels of masculinity as as-
sessed by Blanchard and Freund’s (1983) gender iden-
tity scale.Finally,Coren (1994) reported that left-handers
were higher than right-handers on interpersonal circum-
plex scales that assessed how “arrogant/calculating” and
“coldhearted”participantswere.Theseassociationswere
found both for college men and women, suggesting that
left-handed individuals, whether male or female, show
more male-typical traits, that is, higher dominance and
lowernurturance.Coren (1994) speculated that theremay
be environmental causes for some personality differences
between left and righthanders (e.g., social influences re-
sulting from the minority status of being left-handed).
In sum, several studies suggest that various indices of
masculinity are associated with non–right-handedness
in women. Evidence on links between gender-related
traits and handedness in men is much more
limited.
The study to be reported here extended previous re-

search on handedness and gender-related traits in two
ways. First, it assessed large samples of both homosexual
and heterosexual men and women. This permitted both
between-sex and within-sex analyses of handedness cor-
relates. Second, this study assessed participants on sev-
eral different kinds of gender-related personality traits,
including male- versus female-typicality of occupational
preferences,self-ascribedmasculinity,self-ascribedfemi-
ninity, instrumentality, and expressiveness. These various
measures of masculinity and femininity permitted a more
componential analysis of which gender-related traits are
and which are not associated with handedness.
Because large numbers of heterosexual and homo-
sexual men and women were assessed, it was possible
to examine associations between handedness and gender-
relatedtraitswithinsexualorientationgroupsaswellasfor
all men combined and for all women combined. Demon-
strating within-group associations between handedness
andgender-related traitswould indicate thatnotonlydoes
handedness differ between gender-atypical and control
populations (e.g., between homosexual and heterosexual
individuals)butalsothathandednesscovarieswithgender-
related traits in largeandrepresentativepopulationsofho-
mosexual and heterosexual men and women. In addition,
the large sample sizes permitted analyses of finer grada-
tions of handedness than have been studied previously.
The results reported here—both on associations be-
tween handedness and sexual orientation and on associ-
ations between handedness and gender-related individual
differences within sexual orientation groups—may help
to test among theories that have attempted to explain as-
sociations between handedness and gender-related traits.
Among the most prominent of these theories are prena-

talhormone theory (e.g.,Geschwind&Galaburda,1985),
pathological left-handedness theory (e.g., Previc, 1996;
Satz, 1972), developmental instability theory (Yeo &
Gangestad, 1998), and maternal immunoreactivity theory
(Blanchard & Klassen, 1997). A brief summary of each
of these theories follows.
Prenatal Hormone Theory
Prenatal hormone theory proposes that both hand-
edness and sexual orientation are influenced by prenatal
androgen levels, with higher androgen exposure hypoth-
esized to produce more male-typical patterns of develop-
ment, including a greater incidence of left-handedness.
One problem with prenatal hormone theory is that male
homosexuality (i.e., a female-typical pattern of sexual
attraction) is associated with the more male-typical
pattern of handedness—left-handedness. In regard to
gender-relatedpersonality traits, themost straightforward
prediction of prenatal hormone theory is that, within sex-
ual orientation groups, non–right-handedness will be as-
sociated with masculine traits both for men and women.
Some theorists have speculated about possible nonlinear
effects of androgens, and they have proposed that the ef-
fectsofandrogensmaybecomplexbecausestress-induced
androgens may abnormally surge at some stages of pre-
natal developmentbut thendeclineat other times, leading
to paradoxical effects (e.g., see James, 1989). The current
predictionsarebasedonasimplelinearversionofprenatal
hormone theory—that prenatal androgens “masculinize”
behaviorwithineachsexandthatmales,onaverage, show
masculinizedpatternsofbehaviorcomparedwithfemales.
Left-handedness isassumed tobe the“masculinized”pat-
tern of handedness, because males show higher rates of
left-handedness than females.

A central piece of evidence motivating the prenatal
hormone theory of handedness is the finding that non–
right-handedness occurs more often in males than in fe-
males. In their meta-analytic review of studies on
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Handedness and Sexual Orientation 105
handedness and sexual orientation, however, Lalumière
et al. (2000) cautioned:
It should be kept in mind that the small sex difference in
handedness may be simply due to the fact that more men
thanwomenarehomosexuals . . . and thatmoremen than
women are affected by conditions associated with hand-
edness, such as autism and dyslexia. . . . There might not
be any sex difference in handedness among “unaffected”
samples. (p. 586)
Because this study assessed large samples of men and
women on sexual orientation as well as on handedness, it
provided data that could be used to test Lalumière et al.’s
hypothesis.
Pathological Left-Handedness Theory
Pathological left-handedness theory proposes that
some cases of left-handedness are caused by patholog-
ical stressors, such as birth traumas and brain injuries.
Considerable evidence shows that left-handedness is, in
fact, associated with a number of neurological and devel-

opmental problems, including learning disabilities, intel-
lectual retardation, autism, schizophrenia, cerebral palsy,
epilepsy, deafness, and strabismus (Previc, 1996). To ap-
ply pathological left-handedness theory to gender-related
traits, one must further assume that gender-atypical traits
andbehaviorsaresometimesalsocausedbystressorssuch
as toxins,birth trauma,andbrain injuries (e.g., seeEllis&
Cole-Harding,2001).CorenandSearleman’s (1990)Rare
TraitMarkerModeladdsastatistical twist topathological
left-handedness theory; see also Coren & Halpern, 1991).
This model proposes that various kinds of developmental
stressorsandtraumasmayswitchanindividual’s“natural”
handedness.Since“natural” right-handers areassumed to
be much more common than “natural” left-handers, de-
velopmental stressors would therefore switch many more
right-handers to non–right-handedness than vice versa.
Thus,statisticalassociationsbetweenleft-handednessand
variouskindsofdevelopmentalpathologymaynotbedue
to the fact that left-handedness is intrinsically associated
withpathologicalprocesses,butrathertothefactthat there
are initially so many more “natural” right-handers than
left-handers.
Developmental Instability Theory
Developmental instability theory argues that biolog-
ical development is influenced by noise-like variations,
which are likely to perturb the organism from optimal de-
velopment (i.e., development leading to optimal fitness).
Such variations may result from mutations, from genetic
variations insusceptibility inenvironmental stressors,and
from environmental variations and stressors (such as in-
fectious agents and toxins). Yeo and Gangestad (1998)
have argued that moderate right-handedness is the opti-
mal evolvedhuman trait and therefore thatdevelopmental

instability leads both to non–right-handedness and to ex-
tremeright-handedness.Developmental instability theory
may be applied to gender-related traits if one makes the
additional assumption that gender-atypical traits, such as
homosexuality and gender identity disorder, may also re-
sult from developmental instability.
According to Yeo and Gangestad’s (1998) theory,
gender-atypical behaviors could be linked either to non–
right-handedness or to extreme right-handedness. How-
ever,giventhemodalmoderateright-handednessproposed
by Yeo and Gangestad and applying reasoning similar to
that of the Rare Trait Marker Model, one could argue that
shifts to non–right-handedness would be more apparent
and frequent in human populations than shifts to extreme
right-handedness.Developmental instability theory there-
fore suggests that non–right-handedness will be linked
to gender-atypical traits in both men and women. It is
worthnoting thatYeoandGangestad’sempirical research
employed behavioral rather than self-report measures of
handedness, and extreme right-handedness may be hard
to detect with the kinds of self-report measures typically
used in large-scale studies of handedness.
Maternal Immunological Theory
Finally, maternal immunological theory proposes
that maternal antibodies to Y-linked minor histocompati-
bility antigens may affect the neural development of male
but not female fetuses. This theory was developed to ex-
plain the empirical finding that older male siblings in-
crease the odds that males but not females will be ho-
mosexual (Blanchard,1997;Cantor,Blanchard,Paterson,
& Bogaert, 2002). To account for links between hand-
edness and gender-related traits, maternal immunological
theory would need to assume further that maternal im-

munological reactions influence handedness as well as
gender-atypical traits. Two kinds of evidence would be
consistent with this theory: (1) if males, but not females,
showanassociationbetweenhandednessandtheirnumber
ofolderbrothers, and (2) if linksbetweenhandednessand
gender-related traitsarestronger formen thanforwomen.
In regard to the second prediction, Lalumière et al.’s
(2000) meta-analysis found that the relationship between
handednessandsexualorientationwasstrongerforwomen
than for men, and this seems to argue against maternal
immunological processes as mediators of the association
between handedness and sexual orientation. It is worth
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106 Lippa
noting, however, that Lalumière et al. compiled handed-
ness data from many more homosexual men (over 6,000)
thanhomosexualwomen(805),andtherefore theiroverall
estimateofnon–right-handed-ness inhomosexualwomen
may be less reliable than their estimate for men.
Lalumièreetal. (2000)speculatedthat therecouldbe
commongenes that influencebothhandednessandmater-
nal immunological mechanisms to male tissue:
. . . perhaps there is some overlap between those MHC
[major histocompatibility complex] alleles that correlate
withnon-right-handednessandthosethatrenderHYanti-
gens lessvisible toneighboringneurons in thefetalbrain,

thus diminishing a signal that contributes to the sexual
differentiation of the brain in the male-typical pattern.
(p. 587)
Onceagain,thishypothesiswouldseemtopredicthanded-
ness and sex-typing associations in males but not
females.
Bryden, McManus, and Bulman-Fleming (1994)
conducted a meta-analysis that showed that left-handed-
ness isassociatedwithvariousautoimmunedisorders,and
Yeo and Gangestad (1998) reported evidence that certain
alleles associated with autoimmune disorders are more
commoninleft-handers(seeGangestadetal.,1996).Such
findingshint that the immunesystemsof left-handersmay
be disregulated in broader ways than those suggested by
maternal immunological theory. If such broader immune
processes are linked to the development of gender-related
traits and handedness, they too might provide a possi-
ble explanation for associations between handedness and
gender-related traits.
In summary, prenatal hormone theory—at least, in
its most straightforward (i.e., linear) version—predicts
thatnon–right-handedness(themoremale-typicalpattern)
will be associated with homosexuality in women but with
heterosexuality in men. It also predicts that non–right-
handedness will be associated with masculinity in both
women and men. Pathological left-handedness theory—
with the added assumption that environmental traumas
and stressors may lead both to left-handedness and to
homosexuality—predicts an association between homo-
sexuality and non–right-handedness in both men and
women. Pathological left-handedness theory does not
make a clear prediction about associations between hand-
edness and measures of masculinity and femininity in

“normal,” nonpathological populations of men and
women. In contrast, developmental instability theory
seemscompatiblewith thenotion thathandednessmaybe
associated with normal within-group variations in mas-
culinity and femininity as well as with sexual orienta-
tion.Thisisbecausevariationsinhandedness,masculinity
and femininity, and sexual orientation may all be due, to
some extent, to perturbations in development. Develop-
mental instability theory may overlap with pathological
left-handedness theory, insofar as extreme kinds of devel-
opmental instability may result in pathological outcomes.
Finally, maternal immunological theory, to the extent that
it applies tohandednessaswell as togender-related traits,
implies thatassociationsbetweenhandednessandgender-
related traits shouldbestronger formales thanfor females
and that handedness will be associated with number of
older brothers for men but not for women. This study
provides data relevant to these hypotheses by assessing
handedness, sexual orientation, gender-related personal-
ity traits,andnumbersofolderbrothersandsisters in large
samplesofhomosexualandheterosexualmenandwomen.
METHOD
Participants
Most homosexual participants were volunteers so-
licited at gay pride festivals in Long Beach and Orange
County, California. The remainder were college students
and university staff. Homosexual participants were
461 men, with a mean age of 37 (SD = 11.18, range =
17–76), and 472 women, with a mean age of 36 (SD =
9.98, range = 17–69). Heterosexual participants were
351menand707women,mostofwhomwerestudentsand
staff at California State University, Fullerton. The mean

age of heterosexual men was 24 (SD = 10.69, range =
12–85; apart from one 12-year-old, all participants were
17 or older), and the mean age of heterosexual women
was 23 (SD = 8.89, range = 15–83).2 Although the ho-
mosexual samples were, on average, significantly older
than the heterosexual samples, none of the results that
followweremuchalteredwhenoldergayand lesbianpar-
ticipants (those over 30) were excluded from analyses,
and so the full sample was included to maximize statisti-
cal power.3 Also, in some analyses, age was treated as a
covariate without changing results.
2The 12-year-old boy who participated in the study was
attending a gay
pride festival with his mother, and he participated in the study
with the
consent of his mother. All participants were informed that they
could
leave questionnaire items blank if they felt uncomfortable
answering
any questions.
3One reviewer of this paper noted that because of their mean
age dif-
ferences, heterosexual and homosexual participants did not
constitute
comparable comparison groups. However, given that previous
research
shows that non–right-handedness tends to decrease with age
(Coren &
Halpern, 1991), the fact that homosexual participants were, on
aver-
age, older than heterosexual participants in this study would, if
any-
thing,decrease thechancesofdemonstratingan increased
frequencyof
non–right-handedness among homosexual participants.

Furthermore,
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Measures
Sexual Orientation
Participants were asked to check “true” or “false”
to whether they used each of the following labels to de-
scribe themselves: “heterosexual (straight),” “gay,”
“lesbian,” and “bisexual.” Men and women were classi-
fied, respectively, as “gay” or “lesbian” (i.e., homosex-
ual) if they checked “true” to using these labels to de-
scribe themselves. Men and women were classified as
“heterosexual” if they checked “true” to using this la-
bel to describe themselves and they checked false to us-
ing the label “gay” (for men) or “lesbian” (women) to
describe themselves, or if they did not respond to these
items.
Handedness
Handednesswasassessedvia three self-report items.
The first item “Are you left- or right-handed?” asked par-
ticipantstorespondbycirclinganumberona5-pointscale
thatrangedfrom1(completelyleft-handed) through3(use
both hands equally) to 5 (completely right-handed). Two
additional items asked “Which hand do you usually write
with?” and “Which hand do you normally use to throw

a ball?” Participants responded to each of these items by
circling one of five responses: exclusively use left; mostly
use left,equallyuseboth;mostlyuseright; andexclusively
use right.
Continuous and categorical handedness measures
were computed from self-report handedness items. The
continuous measure was simply the mean of the three
handedness items (! = .90, mean = 4.44, SD = 1.03,
range = 1–5). The categorical measure was based on re-
sponses to the first item, “Are you left- or right-handed?”
Participants who responded 1, 2, or 3 in response to this
item (completely left-handed to use both hands equally)
wereclassifiedasnon–right-handed,whereasparticipants
who responded 4 or 5 (responses on the right-handed side
of the 5-point scale) were classified as right-handed. Us-
ing this system, 14.5% of participants were classified as
non–right-handed and 85.5% as right-handed.
theincidenceof left-
handednessinthisstudy(i.e.,participantsrespond-
ing 1 or 2 to the overall handedness item; see Table II) was
6.8% for
heterosexual men and 8.1% for heterosexual women, which is
well
within the range of rates observed for men and women in
previous
studies. Thus, the incidence of left-handedness in heterosexuals
seems
unexceptional in this study, and thedata
fromheterosexualparticipants
would therefore seem to provide reasonable comparisons to the
data
from homosexual participants.
Number of Older Brothers and Sisters

Participantsrespondedtotwoquestions thatassessed
their number of older brothers and sisters: “How many of
the babies that your biological mother carried before you
were boys (girls)?” Participants responded by circling a
number that ranged from none to 10, or by circling a final
response of more than 10.
Gender-Related Personality Traits
Participants completed the Bem Sex-Role Inventory
(BSRI), a measure of instrumental and expressive traits
(Bem, 1981), and a section that asked participants to rate
their degree of preference for 40 occupations on a 5-point
scalethatrangedfromstronglydislike tostronglylike.Par-
ticipants also completed a 6-item scale by Storms (1979),
which assessed their self-ascribed masculinity and femi-
ninity (Items: “Howmasculine (feminine) isyourperson-
ality?” “How masculine (feminine) do you act, appear,
and come across to others?” “In general, how masculine
(feminine) do you feel you are?”).
Occupational preference ratings were used to com-
pute gender diagnosticity (GD) scores, which assessed
the male- versus female-typicality of participants’ occu-
pationalpreferences.Genderdiagnosticprobabilitieswere
computed by applying multiple discriminant analyses to
eight nonoverlapping subsets of participants’ 40 occupa-
tional preference ratings (see Lippa, 1995, 2001, 2002a;
Lippa & Connelly, 1990). Because of the large number of
gay and lesbian participants, the heterosexual sample was
multiplied by a factor of 10 when computing gender di-
agnostic probabilities. The reason for this procedure was
to guarantee that gay and lesbian participants constituted
a minority of the sample used to compute GD scores (see
Lippa, 2000, 2002b, and Lippa and Tan, 2001, for similar

procedures).4
GD measures give the probability that an individ-
ual is predicted to be male or female an the basis of his
or her pattern of occupational preference ratings. High
scores(closer to1.0)aremoremale-typicalandlowscores
(closer to 0.0) are more female-typical. The reliabilities
4The reader may wonder, as did one reviewer, why a factor of
10 was
chosen.Thegoalherewas tomakehomosexualparticipantsa
relatively
small minority and heterosexual participants a relatively large
major-
ity when computing GD scores. Experimentation with various
factors
of multiplication (5, 10, 15) shows that GD scores computed in
the
variously augmented samples correlate very strongly with one
another,
regardlessofthefactorofmultiplication.ThecomputationofGDscor
es
therefore is a robustprocess thatyields reliableandvalid scoresas
long
as thenumberofheterosexualparticipants inasample isat least
several
times the number of homosexual participants.
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108 Lippa

of GD probabilities for all participants, men, and women
were .80, .76, and .79, respectively. Previous research
has shown that GD scores correlate strongly (.95 and
above) with a sex-typed occupational preference index
computed by simply adding all items that males prefer
significantly more than females and subtracting all items
that females prefer significantly more than males (Lippa,
2002b).
BSRI short-form instrumentality and expressiveness
were computed in standard ways (with scale items av-
eraged rather than summed), and their reliabilities were
.85 and .87, respectively. The three items assessing self-
ascribed masculinity were averaged from Storms’ scale
(Storm, 1979), as were the three items assessing self-
ascribedfemininity.Thereliabilitiesof self-ascribedmas-
culinity were .80 for men and .87 for women, and the
reliabilities of self-ascribed femininity were .85 for men
and .90 for women.
RESULTS
Handedness and Sexual Orientation
Categorical Handedness
Table I presents 2 (sexual orientation) " 2 (hand-
edness) contingency tables for men, for women, and for
bothsexescombined.Therewasasignificantdifferencein
handedness frequencies for heterosexual and homosexual
men ("2[1, N = 808] = 8.58, p = .003), with 11.4% of
heterosexual men and 19.0% of homosexual men classi-
fied as non–right-handed. Lalumière et al. (2000) recom-
mended computing the odds ratio, which in this case was
homosexual participants’ increased odds of being non–
right-handed compared with heterosexual participants.

This statistic is independent of sample base rates of hand-
edness. For men, the computed odds ratio was 1.82, in-
dicating that being homosexual increased a man’s odds
of being non–right-handed by 82%. The 95% confidence
interval for this odds ratio, using the formula provided
by Haddock, Rindskopf, and Shadish (1998, p. 342), was
(1.21, 2.72).
The corresponding contingency table for women
yieldedanonsignificantdifferenceinhandednessfrequen-
cies forheterosexual andhomosexualwomen("2[1, N =
1174] = 1.29, p = .255), with 12.0% of heterosexual
women and 14.3% of homosexual women classified as
non–right-handed. The odds ratio for women was 1.22,
with a 95% confidence interval of (.87, 1.72), indicating
thatbeinghomosexual increasedawoman’soddsofbeing
non–right-handed by 22%.
Table I. Cross-Tabulation of Sexual Orientation by Two-
Category
Handedness for Males, Females, and Both Sexes Combined
Handedness
Sexual orientation Non–right-handed Right-handed
Males
Heterosexual (N = 350) 40 (11.4%) 310 (88.6%)
Homosexual (N = 458) 87 (19.0%) 371 (81.0%)
Females
Heterosexual (N = 706) 85 (12.0%) 621 (88.0%)
Homosexual (N = 468) 67 (14.3%) 401 (85.7%)
Combined
Heterosexual (N = 1, 056) 125 (11.8%) 931 (88.2%)

Homosexual (N = 939) 157 (16.7%) 782 (83.3%)
Note. There are 13 more participants in the table for males and
females
combined than in the summed totals from the tables for males
only and
femalesonly.This resulted fromasmall
numberofparticipantswhodid
not report their sex, but who did report their sexual orientation.
When
these participants were excluded from the table for males and
females
combined, the results were virtually unchanged.
Finally, the contingency table for men and women
combined yielded a significant difference in handedness
frequencies forheterosexual andhomosexualparticipants
("2[1, N = 1995] = 9.76, p = .002), with 11.8% of het-
erosexuals and 16.7% of homosexuals classified as non–
right-handed. The odds ratio for men and women com-
bined was 1.50, with a 95% confidence interval of (1.16,
1.93), indicating that being homosexual increased an in-
dividual’s odds of being non–right-handed by 50%.
Five-Category Handedness
Table II presents 2 (sexual orientation) " 5 (5-
category handedness) contingency tables for men and for
women.Thefivehandednesscategorieswerebasedonthe
fivescalepoints thatparticipantsused in rating theirover-
allhandedness.Therewasasignificantdifferenceinhand-
edness frequencies across the five handedness categories
forheterosexualandhomosexualmen("2[4, N = 808] =
13.21, p = .01). Similarly, for women, and in contrast to
the2 " 2contingencytablepresentedinTableI, therewas
a significant difference in handedness frequencies across

the five handedness categories for heterosexual and ho-
mosexualwomen("2[4, N = 1174] = 11.95, p = .018).
The results for both men and women indicated that for
homosexual participants, handedness was shifted away
from complete right-handedness. However, homosexual
men and women seemed to show somewhat different pat-
terns of a leftward shift.
Included in Table II are odds ratios (homosexual to
heterosexual) computed for each category of handedness
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Table II. Cross-Tabulation of Sexual Orientation by Five-
Category Handedness for Males and Females
Five-category handedness
Sexual orientation 1 (Completely left-handed) 2 3 (Use both
hands equally) 4 5 (Completely right-handed)
Males
Heterosexual (N = 350) 12 (3.4%) 12 (3.4%) 16 (4.6%) 109
(31.1%) 201 (57.4%)
Homosexual (N = 458) 36 (7.9%) 27 (5.9%) 24 (5.2%) 109
(23.7%) 262 (57.2%)
Odds ratio (homosexual 2.40 1.76 1.15 0.69 0.99
to heterosexual) for each
handedness category vs. all
other categories

Females
Heterosexual (N = 706) 26 (3.7%) 31 (4.4%) 28 (4.0%) 164
(23.2%) 457 (64.7%)
Homosexual (N = 468) 25 (5.3%) 22 (4.7%) 20 (4.3%) 143
(30.6%) 258 (55.1%)
Odds ratio (homosexual 1.48 1.07 1.08 1.45 0.67
to heterosexual) for each
handedness category vs. all
other categories
versus all the other categories combined. Interestingly,
both the data for men and for women show anomalous
odds ratios for the moderate right-handedness category.
However, the direction of effect was opposite for men
and women. For men, moderately right-handed individ-
uals showed the lowest odds of being homosexual
(odds ratio = .69),whereas forwomen,moderately right-
handed individuals showed elevated odds of being
homosexual (odds ratio = 1.45), which were virtually
indistinguishable from the similarly elevated odds of
completely left-handed women (odds ratio = 1.48). Par-
ticularly for men, the moderately right-handed group
seemed to mark an inflection point in odds ratios—i.e.,
odds ratios steadily decreased from the completely left-
handed to the moderately right-handed groups, but then
rebounded somewhat for the completely right-handed
group.
Continuous Handedness
A2(sex) " 2(sexualorientation)ANOVAoncontin-
uoushandedness formenandwomencombinedyieldeda
significant main effect for sexual orientation (F[1, 1987]
= 9.80, p = .002), and a marginally significant interac-
tion between sex and sexual orientation (F[1, 1987] =

2.43, p = .119), which reflected larger heterosexual–
homosexual handedness differences for men (means of
4.54 vs. 4.31) than for women (4.50 vs. 4.42). When age
was entered into this analysis as a covariate, the results
werevirtuallyunchanged.Therewasasignificantmainef-
fect forsexualorientation(F[1,1939] = 7.61, p = .006),
and a marginally significant interaction between sex and
sexual orientation (F[1, 1939] = 2.53, p = .112).
Handedness and Gender-Related Traits
in Men and Women
Tables III and IV present correlations between con-
tinuoushandednessandvariousgender-related traits (GD,
self-ascribedmasculinity, self-ascribedfemininity, instru-
mentality, and expressiveness). These correlations were
computed separately for all men, heterosexual men,
and homosexual men (Table III) and for all women, het-
erosexual women, and homosexual women (Table IV).
Because continuous handedness was a decidedly skewed
measure, nonparamentric correlations (Spearman’s rho)
are presented as well as Pearson product–moment
correlations.
Tables III and IV show that the gender-related traits
ofGD(male-vs. female-typicalityofoccupationalprefer-
ences), self-ascribed masculinity, and self-ascribed fem-
ininity sometimes showed significant associations with
handedness, but instrumentality and expressiveness did
not. For all men, non–right-handedness was associated
with female-typical occupational preferences, self-
ascribednonmasculinity,andself-ascribedfemininity.For
all women, non–right-handedness was associated with
male-typicaloccupationalpreferences, self-ascribedmas-
culinity, and self-ascribed nonfemininity. GD was associ-
atedwithhandedness forheterosexualwomen,butnot for

homosexual women, with non–right-handedness weakly
associated with more male-typical occupational prefer-
ences. GD and self-ascribed masculinity were associated
with right-handedness in gay men, and self-ascribed fem-
ininity was associated with non–right-handedness in het-
erosexual men.
The data in Tables III and IV suggest that, to the de-
gree that correlations were significant, right-handed men
P1: IZO
110 Lippa
Table III. Correlations Between Continuous Handedness and
Gender-Related Personality Traits for All
Males, Heterosexual Males, and Homosexual Males
All males Heterosexual males Homosexual males
(N = 818–842) (N = 345–350) (N = 444–461)
Gender-related traits Pearson Spearman Pearson Spearman
Pearson Spearman
GD .12### .07# .06 .06 .11# .07
Self Masc .12## .10## .08 .08 .11# .08†
Self Fem $.08# $.10## $.11# $.15## $.05 $.06
BSRI I .02 $.01 $.03 $.03 .03 $.02
BSRI E $.05 $.04 $.06 $.04 $.02 $.03
Note. Higher handedness scores indicate greater right-
handedness. Higher GD scores indicate more male-

typicaloccupationalpreferences.SelfMasc = Self-
AscribedMasculinity.SelfFem = Self-AscribedFem-
ininity. BSRI I = Bem Sex-Role Inventory Instrumentality.
BSRI E = Bem Sex-Role Inventory Expres-
siveness. Pearson = Pearson product–moment correlation.
Spearman = Spearman’s rho.
† p < .10, two-tailed. # p < .05, two-tailed. ## p < .01, two-
tailed. ### p < .001, two-tailed.
tended to be more masculine and less feminine than left-
handed men, whereas right-handed women tended to be
more feminine and less masculine than left-handed
women. Partial correlations that controlled for age were
also computed between handedness and gender-related
traits, and these partial correlations were quite similar to
the raw correlations presented in Table II.
Handedness and Number of Older Brothers
and Sisters
The variables “number of older brothers” and “num-
ber of older sisters” generally took the values 0, 1, and 2.
However, there were a small number of outlier values for
participantswithvery largenumbersofolderbrothersand
sisters. To reduce the impact of these outlier values, vari-
ableswere transformedtoreflect just threecategories:“no
olderbrother (orsister),”“oneolderbrother (orsister),”or
Table IV. Correlations Between Continuous Handedness and
Gender-Related Personality Traits for All
Females, Heterosexual Females, and Homosexual Females
All females Heterosexual females Homosexual females
(N = 1212–1227) (N = 697–707) (N = 464–470)
Gender-related traits Pearson Spearman Pearson Spearman

Pearson Spearman
GD $.06# $.12### $.11## $.15### .03 $.05
Self Masc $.03 $.06# $.01 $.05 $.02 $.01
Self Fem .03 .07# .04 .06 $.01 $.01
BSRI I .03 .02 .05 .01 .00 .03
BSRI E .00 .01 .02 .01 $.02 $.02
Note. Higher handedness scores indicate greater right-
handedness. Higher GD scores indicate more male-
typicaloccupationalpreferences.SelfMasc = Self-
AscribedMasculinity.SelfFem = Self-AscribedFem-
ininity. BSRI I = Bem Sex-Role Inventory Instrumentality.
BSRI E = Bem Sex-Role Inventory Expres-
siveness. Pearson = Pearson product–moment correlation.
Spearman = Spearman’s rho.
# p < .05, two-tailed. ## p < .01, two-tailed. ### p < .001, two-
tailed.
“two or more older brothers (or sisters).” The percent of
participants in each of the three categories of number of
olderbrotherswas55,27,and18%,respectively.Theper-
centage of participants in each of the three categories of
numberofolder sisterswas57,27, and16%, respectively.
One-way ANOVAs examined whether continuous
handedness scores differed across the three “older broth-
ers” or “older sisters” groups. These analyses were con-
ducted for all men, heterosexual men, homosexual men
and similarly, for all women, heterosexual women, and
homosexualwomen.Noneof theseANOVAsshowedsig-
nificant effects for number of older brothers or sisters.
Contingency tables, created separately for men and
women, examined the frequency of right- and non–right-
handed individuals in each of the three “number of older

brother” (or “number of older sister”) groups. The only
categorical handedness analysis that showed a significant
relationship was that for handedness and number of older
P1: IZO
sisters in men ("2[2, N = 801] = 6.44, p = .04). This
significant effect reflected the fact that, for men, the per-
centage of non–right-handed individuals increased with
number of older sisters (the percent of non–right-handed
menwithno,one,ormore thanoneolder sisterswas14.1,
17.6, and 23.3%, respectively).
SexDifferencesinHandednessAmongHeterosexuals
Sex differences in handedness were examined first
for just heterosexual participants. A t test contrasting het-
erosexual men’s and women’s continuous handedness
scores showed no sex difference (t[1056] < 1, ns; male
mean = 4.54 and female mean = 4.50). Similarly, a 2
(sex) " 2 (categorical handedness) contingency table for
heterosexual participants showed no evidence for a rela-
tionship between participant sex and handedness ("2[1,
N = 1056] < 1, ns), with the percentage of non–right-
handed males and females 11.4 and 12.0%, respectively.
In contrast, homosexual participants showed a ten-
dencytosexdifferencesinhandedness.A t testcontrasting
homosexual men’s and women’s continuous handedness
scores yielded a marginally significant result (t[931] =

$1.53, one-tailed p = .064; male mean = 4.31 and fe-
male mean = 4.42). Similarly, a 2 (sex) " 2 (categori-
calhandedness)contingencytableforhomosexualpartici-
pants showed a marginally significant relationship
between participant sex and handedness ("2[1, N =
926] = 3.66, p = .056),withthepercentageofnon–right-
handed homosexual males (19.0%) greater than the per-
centage of non–right-handed homosexual females
(14.3%). Unlike heterosexual participants, homosexual
participants tended to show the commonly reported sex
difference,withmendisplayinghigher ratesofnon–right-
handedness than women.
DISCUSSION
The current results replicated previous findings of
an association between handedness and sexual orienta-
tion, with homosexual participants showing higher rates
of non–right-handedness than heterosexual participants.
Incontrast to the resultsofLalumièreet al.’s (2000)meta-
analysis, however, this study found that sexual orienta-
tion differences in handedness tended to be larger for
men than for women. If the current results for men were
added to Lalumière et al.’s (2000) meta-analysis, they
would alter its conclusions for men only modestly, given
that the sample studied here (N = 460) was consider-
ably smaller than their meta-analyzed sample of homo-
sexual men (N = 6,182). However, the current results
for women would likely have a more dramatic impact,
for the current sample of homosexual women (N = 461)
was quite large in comparison to the combined sample
of homosexual women reviewed by Lalumière et al.
(N = 805).
Complicating the current results, however, was the

finding that gradations of handedness made a difference
in observed links between handedness and sexual orien-
tation. Although this study did not find a significant dif-
ference between heterosexual and homosexual women’s
handedness when using a dichotomous handedness clas-
sification, it did find significant differences when using a
5-category classification of handedness. In a recent study
of 205 homosexual men and 149 homosexual women,
Mustanski, Bailey, and Kaspar (2002) found larger as-
sociations between handedness and sexual orientation in
women than in men, as did the Lalumière et al. meta-
analysis; however, theseassociations resultedparticularly
from sexual orientation differences in the number of am-
bidextrous women. Additional studies will likely be
needed to determine how the association between hand-
edness andsexualorientationdiffers formenandwomen.
It is worth noting that this study employed a short
3-item measure of continuous handedness and a 1-item
measure of dichotomous handedness. In their examina-
tion of possible moderators of the relationship between
handednessandsexualorientation,Lalumièreetal. (2000,
p.584) reported that thenumberofhandedness itemsused
inagivenstudydidnotmoderate therelationshipbetween
handedness and sexual orientation. However, the specific
handednessmeasureusedinastudydidshowamoderating
effect, with the link between handedness and sexual ori-
entationstronger instudiesusing theEdinburghInventory
than in studies using the Annett questionnaire for partic-
ipants’ writing hand. The Edinburgh Inventory, like the
measure of handedness used in this study, includes items
that ask which hand is used for writing and throwing.
However, theEdinburghInventory includesother itemsas
well, and its items are rated and scored differently than
those in this study.Given itsgreater length, theEdinburgh
Inventorymayhavegreater reliability than the1-itemand

3-item measures used here. If this is so, then the current
results may have somewhat underestimated the relation
between handedness and sexual orientation.
This study demonstrated a number of significant,
albeitweak,associationsbetweenhandednessandgender-
relatedpersonality traitswithin sexualorientationgroups.
Specifically,non–right-handednessinmenwassometimes
associated with more female-typical occupational
preferences, self-ascribed femininity, and self-ascribed
nonmasculinity. However, men’s handedness was not
associated with their levels of instrumentality or expres-
siveness. Among women, there was a tendency for
P1: IZO
112 Lippa
non–right-handedness sometimes to be associated with
moremale-typicaloccupationalpreferences,self-ascribed
nonfemininity, and self-ascribed masculinity. As was the
case for men, women’s handedness was not associated
with their levels of instrumentality or expressiveness.
The current results provided little support for the
simple version of prenatal hormone theory (for more di-
rect evidence against the theory, see Grimshaw, Bryden,
& Finegan, 1995). Consistent with previous studies, the
current research found thatnon–right-handednesswasas-
sociated with homosexuality (contrary to prenatal hor-
monetheory’spredictionformen)andalsothatnon–right-
handednesswasslightlyassociatedwithfemininityinmen

and masculinity in women (again, contrary to prediction
for men).
Furthermore, the current results call into question
oneof thecentralunderlyingassumptionsofprenatalhor-
mone theory—that sex differences in handedness result
from sex differences in exposure to prenatal androgens.
This assumption motivated the hypothesis that associa-
tionsbetweenhandednessandsexualorientationmayalso
be due to hormonal mediators. The current data showed
no sex differences in handedness among heterosexuals,
despite certain and large sex differences in their prena-
tal exposure to androgens. Thus, the reasoning of prena-
tal hormone theory may be backward. Rather than sex
differences in handedness suggesting a simple hormonal
explanationforassociationsbetweenhandednessandsex-
ual orientation, the greater non–right-handedness of ho-
mosexual individuals and the greater prevalence of male
homosexuality may help explain sex differences in hand-
edness. However, this explanation for sex differences in
handednessleavestheassociationbetweenhomosexuality
and non–right-handedness unexplained.
Likeprenatalhormone theory,maternal immunolog-
ical theory was not consistently supported in this study.
There was no evidence that men’s handedness was asso-
ciated with their number of older brothers. However, con-
sistent with maternal immunological theory, the current
data showeda tendency for associationsbetweenhanded-
ness and gender-related traits to be stronger for men than
women. As noted before, the current finding that hand-
edness and sexual orientation was more strongly linked
in men than women was at odds with the findings of
Lalumière et al.’s (2000) meta-analysis, and the issue of
sex differences in links between handedness and sexual
orientation is best regarded as unresolved.

In choosing between the two remaining theories—
pathological left-handedness theory and developmental
instability theory—the current findings nod slightly in
the direction of the latter theory. One intriguing finding
that seems consistent with Yeo and Gangestad’s (1998)
developmental instability theory is the finding that, for
both men and women, moderately right-handed partici-
pants showed anomalous results, with moderately right-
handed men showing the lowest odds of homosexual-
ity and moderately right-handed women showing high
odds. The findings for men seem the most consistent with
YeoandGangestad’s (1998) theory—thatmoderate right-
handednessmaybeassociatedwith the leastdevelopmen-
tal instability. The findings for women are more puzzling.
At the very least, they suggest that associations between
handedness and sexual orientation and their mediating
processes may differ for men and women. Given that gra-
dations of handedness seem to be significant, the current
findings lead to thefollowingrecommendation:Future re-
searchers should use more finely graduated measures of
handedness when possible, and they should assess suffi-
ciently large numbers of participants so that analyses on
graduated handedness categories yield statistically reli-
able results.
Although the current findings lend some support to
developmental instability theory over pathological left-
handedness theory, it is important to note that these two
theories may not be independent. This study found some
associationsbetweenhandednessandgender-relatedtraits
in large, representative populations of men and women
as well as associations between handedness and sexual
orientation. As noted before, developmental instability
theory seems compatible with the notion that sexual ori-

entation, other gender-related traits, and handedness may
all be influenced by perturbations in development. Patho-
logical left-handedness theory, however, does not make
strong predictions about associations between handed-
ness and individual differences in gender-related person-
ality traits in “normal” populations. Of course, it may
be the case that “normal” populations include individu-
als with various kinds and various degrees of pathology,
and it may also be the case that developmental stressors
and their developmental sequelae represent a continuum
rather thanan“either–or” (pathological vs. nonpathologi-
cal)phenomenon.The“continuous”viewofstressorsand
their developmental outcomes is consistent with develop-
mental instability theory.
The finding that handedness and gender-related per-
sonality traits showed associations for men as well as
for women is significant, given that most previous re-
search has focused on women. The current results lead
to the recommendation that future research study men
as well as women. This study found some evidence that
the association between handedness and sexual orienta-
tionwasstronger formen than forwomen. If this reported
sex difference is replicated, how might it be explained
by each of the four theories discussed earlier? Maternal
P1: IZO
immunological theory directly predicts that certain asso-
ciations (e.g., betweennumberofoldermalebrothers and

sexual orientation) will be stronger for men than women,
and thus it hints that other correlates of gender-related
traits may also show sex differences.
To account for sex differences in the strength of as-
sociations between handedness and gender-related traits,
prenatal hormone theory might assume that there is more
variabilityinexposuretoprenatalandrogensamongmales
than females. This hypothesis is consistent with the as-
sumptionthat femaledevelopment is thehuman“default,”
whereasmaledevelopment requireshormonallymediated
departures from the female “default” (Collaer & Hines,
1995). The multistage hormonal processes that lead to
male rather than female development could be hypothe-
sizedtoresult inmorevariableoutcomesformalesthanfor
females. Pathological left-handedness theory might try to
account for sex differences by proposing that male births,
perhaps for both genetic and environmental reasons, are
more stressed than female births. Finally, developmental
instability theorymightpropose that, in regard tohanded-
ness and gender-related traits, there is more developmen-
tal instability in male than in female development. These
various theoretical approaches are not necessarily inde-
pendent. For example, variations is hormonally mediated
processes may result from developmental instability and
environmental stressors, and some kinds of pathological
outcomes may be linked to developmental instability.
All of the hypotheses just proposed suggest ques-
tions that are amenable to further empirical investigation.
For example, are putative markers of prenatal androgen
exposure more variable in males or in females, and are
such markers linked to handedness? Are male births in
factmorestressed thanfemalebirths, anddocertainkinds
of birth stress affect both handedness and sexual orien-
tation? Do males show more or less evidence of devel-

opmental instability (e.g., fluctuating asymmetry, minor
physical anomalies) than femalesdo?Given thatdevelop-
mental instability theory (e.g., Yeo & Gangestad, 1998)
hasproposed thatmoderate right-handedness is theevolu-
tionarily optimal human trait and given that research gen-
erated by developmental instability theory has assessed
handednesswithperformancerather thanself-reportmea-
sures, it would be of interest to examine whether sexual
orientation and other gender-related traits are related to
performanceaswell as to self-reportmeasuresofhanded-
ness. Such research could study whether gender-atypical
traitsareassociatedwithextremeright-handednessaswell
as with non–right-handedness.
It is worth noting that in this study not all gender-
related personality traits were equally associated with
handedness. GD measures (i.e., male- vs. female-typical
occupational preferences), self-ascribed masculinity, and
self-ascribed femininity showed some significant associ-
ations with handedness, but instrumentality and expres-
sivenessdidnot.Thesefindingsareconsistentwith recent
research showing that GD, self-ascribed masculinity, and
self-ascribed femininity show much stronger links to sex-
ualorientation thandoinstrumentalityandexpressiveness
(Lippa, 2000, 2002b).
At the same time, the current findings seem to con-
tradict some previous studies on handedness and gender-
related traits in women. As described earlier, a number
of studies have found that non–right-handedness is asso-
ciated with various kinds of masculinity in women, in-
cluding higher instrumentality and lower expressiveness.
However, these earlier studies differed from the current
one in a number of ways. One study preselected par-
ticipants on handedness (Nicholls & Forbes, 1996), an-

other used a nonstandard measure of handedness (Casey
& Nuttall, 1990), and various studies used different
measures of gender-related traits (e.g., Coren, 1994;
Santhakumari et al., 1994).This study is thefirst toassess
various kinds of gender-related traits in the same large
samples of men and women. As a result, the current data
are probably the most complete to date on links between
handedness and various kinds of gender-related personal-
ity traits.
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