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Frontiers in Behavioral Neuroscience www.frontiersin.org March 2011 | Volume 5 | Article 9 | 1
BEHAVIORAL NEUROSCIENCE
GENERAL COMMENTARY
published: 08 March 2011
doi: 10.3389/fnbeh.2011.00009
The essential implications of gender in human behavioral
endocrinology studies
Steven J. Stanton1,2*
1 Department of Psychology and Neuroscience, Duke University, Durham, NC, USA
2 Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
*Correspondence: steven.stanton@duke.edu
A commentary on
Power posing: brief nonverbal displays
affect neuroendocrine levels and risk
tolerance
by Carney, D. R., Cuddy, A. J. C., and Yap,
A. J. (2010). Psychol. Sci. 21, 1363–1368. doi:
10.1177/0956797610383437
Carney et al. (2010) recently published a
study in which they examined the effect
of assuming “high- and low-power” body
postures on changes in testosterone levels in
men and women. To do so, they randomly
assigned participants to two groups (high-
power and low-power), and then placed
them in two successive 1-min poses appro-
priate for their group. They reported that
“high-power” poses produced testosterone
increases in participants and “low-power”
poses produced testosterone decrements,
while collapsing over gender in their analy-
ses. This study tested an important hypoth-
esis regarding the effects of dominance
posturing on endocrine changes that may
be critical precursors to dominance compe-
tition, in which dominance posturing could
lead to pre-competition changes in testoster-
one that influence the impending domi-
nance competition (Mazur, 1985; Salvador
et al., 2003; Gleason et al., 2009; Edwards and
Kurlander, 2010). While Carney et al. (2010)
asked an important research question, there
are a number of methodological and analyti-
cal factors regarding gender and testoster-
one that must be considered in greater detail
before their data can be fully understood and
used to motivate future research.
Gender differences in
testosterone responses to
dominance situations
Before commenting on specific aspects of the
work of Carney et al. (2010), it is informative
and relevant to consider gender differences
in testosterone responses to dominance situ-
ations (e.g., sports, laboratory competitions)
found in past studies. Generally, across many
studies, men’s testosterone levels change in
response to dominance competitions by
rising after a dominance victory and falling
after a defeat (reviewed in Mazur and Booth,
1998; Archer, 2006; e.g., Stanton et al., 2009).
Although, recent studies have also suggested
that individual differences and context are
relevant in accurately predicting men’s tes-
tosterone responses (e.g., Schultheiss et al.,
2005; Carre, 2009) and others have shown
null results of competition (e.g., Carre et al.,
2009). In contrast, women do not have dif-
ferential testosterone responses to winning
or losing a dominance contest (Mazur and
Booth, 1998; Archer, 2006; Stanton and
Schultheiss, 2007), but a single recent study
has challenged this conclusion (Oliveira
et al., 2009).
The commonly observed gender differ-
ence in testosterone responses to dominance
situations is likely due to the different source
glands for testosterone in men and women.
In men, the vast majority of testosterone
comes from the testes (and the adrenal
glands to a lesser extent). In women, testo-
sterone is principally released by the adrenal
glands (and the ovaries to a lesser extent).
This difference in testosterone source glands
makes symmetrical testosterone responses in
both genders unlikely1. Even if the adrenals
were the source of testosterone change in
both genders, one would then expect corti-
sol changes (also produced by the adrenals)
to be in the same direction as testosterone
changes. Yet, Carney et al. (2010) report that
cortisol changes in the same participants
moved in the opposing direction to testo-
sterone changes, such that “high-power”
poses were associated with decrements in
cortisol and “low-power” poses were associ-
ated with increases in cortisol2. This suggests
that the testosterone changes were not driven
by the adrenals and makes it less likely that
the testosterone responses would have been
the same in each gender since the adrenals
are the main testosterone-producing gland
shared between the genders.
It is notable that Carney et al. (2010) do
not discuss the gender-specific mechanisms
of testosterone production and release or
the empirical history of gender differences
in testosterone responses. The gender dif-
ference in testosterone source glands and
lack of prior positive findings in women do
not mandate that testosterone responses to
“power poses” would also differ between the
genders, but greater consideration of the
effects of gender are essential due to these
fundamental neuroendocrine differences
between the genders.
collapsinG over Gender
Carney et al. (2010) collapsed over gender
in all testosterone analyses. Testosterone
conforms to a bimodal distribution when
including both genders (see Figure 13;
Sapienza et al., 2009). Raw testosterone
cannot be considered a normally distrib-
uted dependent or independent variable
1Another potential confound: Carney et al. (2010)
provided no information on oral contraceptive use
by the female participants, which significantly alters
endogenous testosterone levels (e.g., Schultheiss et al.,
2005) and may alter hormone × behavior associations
(Josephs, 2009; Stanton and Edelstein, 2009).
2Mean cortisol levels for all participants were reported
as 0.16 ng/mL pre-posing and 0.12 ng/mL post-posing,
thus showing that for all participants there was an
average decrease of 0.04 ng/mL from pre- to post-
posing, regardless of condition. Yet, Figure 4 of Carney
et al. (2010) shows that low-power posers had mean
cortisol increases of roughly 0.025 ng/mL and high-
power posers had mean cortisol decreases of roughly
0.03 ng/mL. It is unclear given the data in Figure 4 how
the overall cortisol change for all participants could
have been a decrease of 0.04 ng/mL.
3The University of Michigan’s Institutional Review
Board and Duke University’s Institutional Review Board
approved all of the experiments in which the saliva
samples were collected and testosterone was assayed.
Stanton Gender in human behavioral endocrinology
Frontiers in Behavioral Neuroscience www.frontiersin.org March 2011 | Volume 5 | Article 9 | 2
tion of dominance situations that was noted
above.
maGnitude of testosterone
chanGe
Men tend to have baseline testosterone lev-
els three to seven times greater than women
on average (Dabbs, 1990; Liening et al.,
2010). Despite reporting that testosterone
levels were significantly higher in men than
women via a t-test, Carney et al. (2010) do
not report the mean testosterone levels sep-
arately for each gender at baseline or post-
manipulation, which are essential for the
interpretation of magnitude of testosterone
change. Without reporting the testosterone
changes separately for each gender, we sim-
ply cannot deduce the real magnitude of
the effect for men and women, since their
baseline testosterone levels are so different.
In conclusion, Carney et al. (2010) used
a novel manipulation to ask an important
question, but the degree to which their find-
ings can be fully understood and imple-
mented into future research is questionable
without more complete analyses.
references
Archer, J. (2006). Testosterone and human aggression:
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Carney, D. R., Cuddy, A. J. C., and Yap, A. J. (2010).
Power posing: brief nonverbal displays affect neu-
roendocrine levels and risk tolerance. Psychol. Sci.
21, 1363–1368.
Carre, J. M. (2009). No place like home: testosterone
responses to victory depend on game location. Am.
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Carre, J. M., Putnam, S. K., and McCormick, C. M. (2009).
Testosterone responses to competition predict future
aggressive behaviour at a cost to reward in men.
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Dabbs, J. M. Jr. (1990). Salivary testosterone measure-
ments: reliability across hours, days, and weeks.
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Edwards, D. A., and Kurlander, L. S. (2010). Women’s
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Gleason, E. D., Fuxjager, M. J., Oyegbile, T. O., and Marler, C.
A. (2009). Testosterone release and social context: when
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Josephs, R. A. (2009). Moving beyond dichotomies
in research on oral contraceptives: a comment on
Edwards and O’Neal. Horm. Behav. 56, 193–194.
Liening, S. H., Stanton, S. J., Saini, E. K., and Schultheiss, O. C.
(2010). Salivary testosterone, cortisol, and progesterone:
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very low testosterone level would be hard
to identify because he could fall within the
normal range when including women.
In their statistical analyses, the Carney
et al. (2010) reported “participant sex was
included as a covariate in all analyses.” But,
they did not report whether or not partici-
pant sex accounted for a significant portion
of the variance in any analyses, which leaves
open the possibility that the effects are driven
principally by one sex, or that the sexes might
have exhibited divergent patterns of testo-
sterone response. Ideally for such analyses,
it would be best to report the effect size and
p-value for the main effect of gender as well
as a potential gender × power pose condition
interaction. While the authors use residual
change in their statistical tests of testoster-
one change (which is a valid, well-chosen
technique) and include gender as a covariate,
again, the bimodal distribution of raw testo-
sterone is a statistical issue, since raw post-
competition testosterone is their dependent
variable and raw pre-competition testoster-
one is their covariate, both collapsing over
gender. Additionally, Carney et al. (2010)
had a small sample size for a human behav-
ioral endocrinology study (N = 42) that
was predominantly composed of women
(N = 26), which makes the reported effects
of power posing on testosterone change even
more surprising given the common lack of
testosterone changes in women as a func-
when including both genders. Thus, Carney
et al. (2010) violated a basic assumption of
the statistical analyses that they reported,
because they used raw testosterone from
pre- and post-power posing as independent
and dependent variables, respectively, with
all subjects (male and female) included.
Additionally, Carney et al. (2010)
excluded a single subject (presumably of
the 16 men) for having testosterone levels
above 3 SD from the mean. But, was this
the mean and SD for all subjects? Such
exclusions should only occur when com-
puting means and SDs within each sex.
This is because when considering the
exclusion of high-testosterone cases (likely
men), the mean and SD for the whole sam-
ple (including men and women) would
be artificially low and small, respectively,
as compared to the mean and SD for just
men. Using the whole sample mean and
SD would make it easy to exclude a high-
testosterone male subject that is not really
an outlier within their own sex, which is
what is most important to identify for tes-
tosterone analyses. As an additional cau-
tionary note, using the mean and SD for
the whole sample would also mean that a
woman who is a significant high outlier
would likely not be excluded, since she
could easily fall within the normal range
when including men. The same is true for
low values in men, such that a man with a
FIGURE 1 | Shown is a depiction of the bimodal distribution of raw, baseline salivary testosterone
values (in pg/mL) when including both men (N = 360) and women (N = 407). All saliva samples were
collected and assayed by the present author using radioimmunoassay (Schultheiss and Stanton, 2009). The
displayed testosterone data were aggregated from several past studies by the author, and for graphical
purposes only, exclude eight male participants with testosterone levels between 150 and 230 pg/mL.
Stanton Gender in human behavioral endocrinology
Frontiers in Behavioral Neuroscience www.frontiersin.org March 2011 | Volume 5 | Article 9 | 3
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(2009). Testosterone responsiveness to winning
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Received: 28 September 2010; accepted: 21 February 2011;
published online: 08 March 2011.
Citation: Stanton SJ (2011) The essential implications of
gender in human behavioral endocrinology studies. Front.
Behav. Neurosci. 5:9. doi: 10.3389/fnbeh.2011.00009
Copyright © 2011 Stanton. This is an open-access arti-
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