Women's voice attractiveness varies across the menstrual cycle

Abstract

We investigated ratings of female voice attractiveness as a function of menstrual cycle phase. Women had their voices recorded at four different times during their menstrual cycle. Voice samples were categorized from low to high conception risk based on menstrual cycle phase and empirical pregnancy data. Results showed a significant increase in voice attractiveness ratings as the risk of conception increased across the menstrual cycle in naturally cycling women. There was no effect for women using hormonal contraceptives. Previous research shows that the sound of a person's voice appears to serve as an honest signal of fitness, and our results show perceptual shifts in women's voices that match the predicted output of an independent and well-designed fertility monitoring system. More work is needed to identify the biological mechanisms that underlie these perceptual differences, but growing evidence points to the impact of hormones on the larynx as being the source of these changes.

Full text

Original Article
Women's voice attractiveness varies across the menstrual cycle
R. Nathan Pipitone⁎, Gordon G. Gallup Jr
Department of Psychology, University at Albany, State University of New York, New York, NY, USA
Initial receipt 24 July 2007; final revision received 17 February 2008
Abstract
We investigated ratings of female voice attractiveness as a function of menstrual cycle phase. Women had their voices recorded at four
different times during their menstrual cycle. Voice samples were categorized from low to high conception risk based on menstrual cycle phase
and empirical pregnancy data. Results showed a significant increase in voice attractiveness ratings as the risk of conception increased across
the menstrual cycle in naturally cycling women. There was no effect for women using hormonal contraceptives. Previous research shows that
the sound of a person's voice appears to serve as an honest signal of fitness, and our results show perceptual shifts in women's voices that
match the predicted output of an independent and well-designed fertility monitoring system. More work is needed to identify the biological
mechanisms that underlie these perceptual differences, but growing evidence points to the impact of hormones on the larynx as being the
source of these changes.
© 2008 Published by Elsevier Inc.
Keywords: Voice attractiveness; Conception risk; Hormonal contraceptives; Menstrual cycle; Ovulation
1. Introduction
Research on the human voice has been subject to
increased attention in recent years. Variation in dominance
(Feinberg et al., 2006; Puts, Gaulin, & Verdonili, 2006),
personality attributes (Zuckerman & Driver, 1989), fluctuat-
ing asymmetry (Hughes, Harrison, & Gallup, 2002),
attractive body features (Hughes, Dispenza, & Gallup,
2004) and a host of other behavioral characteristics have
been shown to correlate with variation in the sound of a
person's voice. In other words, independent of the content of
speech, voice appears to be a medium for the transmission of
important biological information.
The human larynx is a hormonal steroid target organ
(Caruso et al., 2000). During puberty, estrogen and
progesterone affect the morphology of the larynx and
shape the mature female voice, while testosterone modifies
and deepens the male voice (Abitbol, Abitbol, & Abitbol,
1999). The same sex hormones that affect the voice at
puberty also influence the development of sex-specific body
configurations (Kasperk et al., 1997; Singh, 1993).
Just as physical characteristics like facial features may be
involved in mate choice (Thornhill & Gangestad, 1999),
vocal cues may also be important, especially since they can
provide information about potential mates when visual cues
are ambiguous or not available, such as at night (Hughes
et al., 2002). Recent evidence shows that the sound of a
person's voice not only provides information about body
morphology, but also about features of their sexual behavior
as well (Hughes et al., 2004).
Cyclic hormones affect the physical properties of a
woman's voice across the menstrual cycle (Abitbol et al.,
1999). Variations in female vocal production that occur
during menstruation, pregnancy and menopause (Caruso
et al., 2000) all coincide with marked hormonal changes.
Epithelial smears from the larynx and vagina show similar
cytology for steroid hormones (Caruso et al., 2000),
particularly estrogen (Fegusson, Hudson, & McCarthy,
1987). Histologic laryngeal changes during the menstrual
cycle mirror those of the endometrium (Abitbol et al., 1999).
The use of hormonal contraceptives also has an effect on
female vocal production. Investigating these changes
Evolution and Human Behavior xx (2008) xxx –xxx
⁎Corresponding author. Tel.: +1 518 442 4786; fax: +1 518 442 4867.
E-mail address: rp2497@albany.edu (R.N. Pipitone).
1090-5138/$ –see front matter © 2008 Published by Elsevier Inc.
doi:10.1016/j.evolhumbehav.2008.02.001
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through spectrogram analysis, Amir, Kishon-Rabin and
Muchnik (2002) found that females using hormonal contra-
ceptives had significantly lower jitter and shimmer in their
voices than naturally cycling females. Chae, Choi, Kang,
Choi and Jin (2001) showed that females experiencing
premenstrual syndrome (PMS), which corresponds to
hormonal aberrations, were also more prone to vocal changes
(e.g., more jitter, lower frequency) compared to other times
during the menstrual cycle. G. Bryant and M. Haselton
(unpublished data) have also recently reported preliminary
evidence for an increase in voice pitch at ovulation compared
to other times during the menstrual cycle.
Progesterone increases the viscosity and acidity levels
of glandular laryngeal cells, which leads to a decrease in
volume, causing vocal cord edema. Estrogen has a
hypertrophic effect on laryngeal mucus and increases
glandular cell secretion (Abitbol et al., 1999; Amir et al.,
2002). Abitbol (1989) and Abitbol et al. (1999) have
identified vocal characteristics such as hoarseness, fatigue
and decreases in range as being clinical signs of vocal
PMS. In summary, the larynx and genitals clearly seem
to be targets for the same sex hormones, and both seem
to be affected by hormonal fluctuations across the
menstrual cycle.
A number of adaptive behaviors vary across the
menstrual cycle that correspond to changes in conception
risk. Sexual risk-taking behaviors (Chavenne & Gallup,
1998), reactions to the scent of more symmetrical males
(Gangestad & Thornhill, 1998) and preference for more
masculine facial features (Penton-Voak & Perrett, 2000)
have all been shown to vary as a function of cycle phase.
It is reasonable to suppose that the cyclic hormones
driving these behaviors could also affect women's voices
as well.
In the present study, we investigated attractiveness ratings
of female voices collected at different points during the
menstrual cycle.
2. Methods
2.1. Voice participants
A total of 51 female undergraduates from the State
University of New York at Albany were recruited to provide
voice samples. Students were recruited through the research
subject pool and by advertisements posted around campus.
Participants recruited through the research pool were given
course credit; those recruited by posters were paid US$2.50
for each voice session they participated in. The study was
approved by the university Institutional Review Board.
Using a coded anonymous survey, participants were
asked about their age, number of committed partners and
number of lifetime sexual partners. There were no significant
differences between females using hormonal contraceptives
and naturally cycling females for number of committed
partners (t
35
=.24, p=.81), or number of sexual partners
(t
36
=−.86, p=.39). Naturally cycling females were between
17 and 30 years of age (mean=21.12, S.D.=3.16), and their
cycle length ranged from 19 to 48 days (mean=29.59,
S.D.=7.12). All females were asked to report whether their
menstrual cycle was regular, somewhat regular, somewhat
irregular or very irregular (regularity was defined as the
number of days between periods being the same from cycle to
cycle, e.g., every 28 days). The majority of females reported
having either somewhat regular or regular cycles. All females
except three met the criterion of reporting somewhat regular
or regular cycles and were included in the analyses. Two
females had atypical cycle lengths but reported having
regular cycles. Upon returning for follow-up voice samples,
we were able to verify that menstruation did happen on the
days predicted for these females; therefore, they were
included in analyses. One naturally cycling female had
used a form of hormonal contraceptive 3 months prior to the
study. All other naturally cycling females indicated not
having used hormonal contraceptives for more than 3 months
prior to this study.
Females taking hormonal contraceptives ranged from 18
to 26 years of age (mean=20.19, S.D.=2.09), and their cycle
length ranged from 24 to 34 days (mean=27.86, S.D.=1.8).
One participant started using hormonal contraceptives 2
months prior to the study. All others had been using
hormonal contraceptive for longer periods of time. Partici-
pants were not included in the analysis if they were not fluent
in English, had speech impediments, were chronic smokers
(more than a pack a week), had a cold or illness on the day of
voice recording, had very irregular menstrual cycles, were
pregnant or used any form of morning-after pill within the
last 3 months. Thirteen women were excluded for these
reasons, leaving 17 naturally cycling females and 21 females
using hormonal contraceptives.
2.2. Voice raters
An additional 34 males and 32 females were recruited
through the university research subject pool to rate the voice
recordings. Raters ranged from 17 to 25 years of age. All
raters reported being heterosexual. Raters all reported having
normal hearing. Six raters handed in incomplete rating forms
and were not included in the analysis, leaving 30 male and 30
female raters.
2.3. Procedures —female voice recordings
The initial session consisted of two parts: completion of a
background survey (menstrual cycle length and regularity,
use of hormonal contraceptives, etc.), and a voice sample.
To preclude the possibility that the content of what
participants said could influence the perception of their
voices, subject's voices were only recorded while they
counted from 1 to 10. This procedure has been used
previously to hold the content of recordings constant and to
obtain speech samples that are cognitively and affectively
neutral (Hughes et al., 2002, 2004). Voice recordings were
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taken using an Altec Lansing AHS515 headset, with the
microphone placed approximately 8 cm from the subject's
mouth. Voices were recorded onto computer software at 48
kHz, 16 bit, mono (Microsoft Sound Recorder 5.0). After the
initial voice recording, participants were scheduled to return
for three follow-up voice recording sessions depending on
their menstrual cycle length. For example, if a female
indicated having a cycle length of 28 days, she would be
instructed to return every 7 days, but if she indicated having
a 35-day cycle, she would be asked to return every 9 days.
Thus we attempted to obtain a total of four equally spaced
voice recordings across every female's menstrual cycle.
Other studies investigating behavior across the menstrual
cycle have often dichotomized females into high and low
conception groups (i.e., Feinberg et al., 2006; Haselton &
Gangestad, 2006; Penton-Voak & Perrett, 2000). With the
average menstrual cycle length being around 28 days, we
chose four, weekly spaced follow-up voice sessions that
would enable us to map effects within groups, but would not
burden the participants with excessive requirements for
return visits.
All participants provided information about the first day of
their last menstruation and their average cycle length. Since our
subjects returned to give follow-up voice samples, we were able
to verify whether they did begin menstruation on the day
calculated from the initial voice recording session. As evidence
that our estimates were accurate, menstruation began within 1
or 2 days of our calculations for the majority (87%) of females.
If subjects had a shortened or delayed onset of their next
menstrual flow (meaning shorter or longer cycle length), we
adjusted the projected length of the subject's cycle in order to
provide a more accurate estimate of where they were in their
menstrual cycle when voice samples were obtained.
2.4. Procedures —voice ratings
The entire stimulus set was too large to have each rater
listen to all 152 voice samples from the 38 females. Raters
were divided into two groups: one group (14 males, 14
females) listened to each of four different voice recordings
from 20 females (10 naturally cycling and 10 taking
hormonal contraceptives), the other group (16 males, 16
females) listened to the four different voice recordings from
the remaining 18 females (7 naturally cycling and 11 taking
hormonal contraceptives). Raters were asked to rate the level
of voice attractiveness on a 100-point unlabelled scale, with
1 being the least attractive and 100 being the most attractive.
The presentation of voice recordings was randomized and
each voice was presented only once unless a rater asked to
hear the voice again. Subjects were instructed not to rate any
voices they thought they recognized. After the completion
of the study, raters were informed that they heard four
different versions of each female's voice. Only two raters
indicated being aware of this, suggesting that for the most
part raters were oblivious to hearing repeated versions of the
same voice.
2.5. Conception risk calculations
Since each voice sample coincided with a particular day
in the subject's menstrual cycle, we calculated conception
risks for each of the four voice samples obtained from each
female using empirical pregnancy rates derived from
Wilcox, Dunson, Weinberg, Trussell and Baird (2001).
Conception risk is the probability of conceiving from a
single act of unprotected sexual intercourse. The closer a
female is to ovulation, the greater the risk of conception
(obviously females who were taking hormonal contra-
ceptives would not be subject to changes in conception
risk, but for purposes of comparison their data were
organized according to their cycle phase as though they
were normally cycling). For instance, according to Wilcox
et al., a regularly cycling female has a 9.3% chance of
conceiving from having unprotected sexual intercourse on
Day 13 of her menstrual cycle and a 0.5% chance on Day
28. With the Puts (2006) methodology, females who had
cycle lengths other than 28 days were standardized into a
28-day cycle and conception risks were calculated accord-
ing to the variation that occurred during the follicular phase
of the menstrual cycle.
2.6. Data organization and analysis
After all of the voices had been rated, the dataset was
organized for planned comparison contrasts. Female's voice
samples were arranged in order from lowest to highest risk of
conception. Phase 1 represents voices that were recorded at
the lowest risk of conception, and Phase 4 represents those
obtained at the highest risk of conception, with Phases 2 and
3 corresponding to intermediate levels of conception risk. In
the initial analysis, we collapsed across voices, yielding four
composite scores for all of the voices that each rater heard at
each of the four different phases. This was done separately
for the naturally cycling females and those using hormonal
contraceptives. In a subsequent analysis, we collapsed across
raters rather than voices in order to conduct additional
analyses on voice attractiveness, yielding average ratings
across raters for each female voice. The average risk of
conception for all females across the four phases was 0.25%
(S.D.=.25%), 0.97% (S.D.=.68%), 3.04% (S.D.=1.37%) and
7.84 % (S.D.=1.83%), respectively.
A 2×4 repeated measures MANOVA was used to
analyze the data. The first factor was hormonal contra-
ceptive use: naturally cycling or hormonal contraceptives.
The second factor was phase: the four different voice
samples from females collected at different times across the
menstrual cycle.
3. Results
Initial data screening revealed no univariate Zscore
outliers among the voice samples. With a critical chi-square
value of 24.32 (df =7, pb.001) for Mahalanobis distance
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(Tabachnick & Fidell, 2007), no multivariate outliers were
found. For Cook's distance (Tabachnick & Fidell, 2007), all
cases fell within the acceptable range of 0 and 1. Before
collapsing across voices, there were several missing data
points in both groups for five raters. In order to include their
ratings in subsequent analyses, the mean attractiveness rating
that other raters gave the same voice was substituted for the
missing data.
The Contraceptive Use by Phase interaction was signi-
ficant (Wilks' F
3,56
=12.14, pb.001). As shown in Fig. 1,
ratings of voice attractiveness for naturally cycling females
increased as the risk of conception increased. However, there
was no effect of voice attractiveness and menstrual cycle
phase for females taking hormonal contraceptives. No other
omnibus tests were considered since planned comparisons
were the focus of interest (Tabachnick, & Fidell, 2007).
A priori trend analysis contrasts were conducted to
identify trends in vocal attractiveness ratings in each of the
simple main effects of phase, moving from lowest to highest
conception risk. Trend analysis was used because of the
quantitative nature of conception risk as an independent
variable. Since conception risk for females was not the same
when moving from low to high conception risk across the
groups, the polynomial coefficient weights matched the
varying, monotonic increases in conception risk. The voice
attractiveness rating trend as a function of conception risk
among naturally cycling females was significant
(F
1,58
=41.95, pb.001). The partial eta
2
(η
2
), which is a
measure of effect size in MANOVA, showed that 42% of the
variance in the ratings of vocal attractiveness could be
explained in an increasing fashion moving from low to high
conception risk in females who were naturally cycling.
The trend among females who were using hormonal
contraceptives was not significant (F
1,58
=1.48, p=.229,
partialη
2
=.02) (see Fig. 1). Since we predicted a priori the
best-fitting weights for the trend derived from calculated
conception risks, the higher order polynomial contrasts such
as quadratic and cubic functions were not of interest (Myers
& Well, 2003, p. 280). There were no significant sex
differences between male and female raters (F
1,58
=1.15,
p=.289). Naturally cycling females had higher voice
attractiveness ratings than those using hormonal contra-
ceptives when collapsed across phases, but the difference
was not significant (F
1,58
=.69, p=.409).
We also conducted stepwise post hoc comparisons on
each of the mean voice attractiveness ratings using
Hochberg's step-up method, which organizes mean compar-
ison pvalues from largest to smallest, then adjusts error rates
sequentially to keep the familywise error rate constant, in this
instance .05 (see Myers & Well, 2003, p. 247). The results
are presented in Tab l e 1 and show that none of the phase
comparisons for women using hormonal contraceptives was
significant, while five out of the six phase comparisons for
naturally cycling females were significantly different.
As further evidence that the perceptual features of female
voices vary as a function of cycle phase, the correlation
between conception risk and the average rank-ordered voice
attractiveness ratings from each rater was significant for
naturally cycling females (r=.41, pb.01), but not for those
taking hormonal contraceptives.
In a subsequent analysis, we collapsed attractiveness
ratings across raters and ran trend analyses among females
who were naturally cycling and those using hormonal
contraceptives, focusing on individual female voices as the
level of analysis, not raters. Comparable effects were found
whether collapsing on voices or raters. The Contraceptive
Use by Phase interaction was significant [Wilks' F
3,14
=4.72,
Fig. 1. Mean voice attractiveness ratings as a function of conception risk in
naturally cycling women and those taking hormonal contraceptives (females
taking hormonal contraceptives are not at risk of conception, but for
purposes of comparison their voices were analyzed according to comparable
points in the menstrual cycle). Means and standard errors for naturally
cycling women (from lowest to highest likelihood to conceive) were
42.45±1.56, 44.1±1.18, 46.12±1.2 and 48.39±1.38; for women who were
taking hormonal contraceptives, they were 43.4±1.2, 45.15±1.13, 44.89±1.42
and 43.41±1.2.
Table 1
Hochberg's step-up post hoc comparisons in naturally cycling females and
those taking hormonal contraceptives
Phase
comparisons
Mean
difference
Adjusted
error rate
Pvalue Cohen's d
Natural cycling
1–2−1.645 .05 .076 −.23
3–4−2.265 .025 .016 ⁎−.32
2–3−2.031 .0167 .007 ⁎−.36
1–3−3.676 .0125 .001 ⁎−.43
2–4−4.296 .01 b.001⁎−.66
1–4−5.94 .008 b.001⁎−.79
Hormone contraceptives
1–4−.012 .05 .987 b−.01
2–3 .26 .025 .756 .04
3–4 1.487 .0167 .064 .24
1–3−1.499 .0125 .057 −.25
1–2−1.759 .01 .021 −.31
2–4 1.747 .008 .011 .34
⁎Indicates significant effect compared to adjusted error rate.
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pb.05 (since there were more females using hormonal
contraceptives, in order to compute the interaction with equal
n's we randomly excluded four females in the hormonal
contraceptive group)]. The trend was also significant for
naturally cycling females (F
1,16
=9.18, pb.01, partial
η
2
=.36), but not for females using hormonal contraceptives
(F
1,16
=.82, p=.38, partial η
2
=.05).
4. Discussion
Students listening to women count from 1 to 10 at
different times during the menstrual cycle rated the voices as
being more attractive as the speaker's risk of conception
increased. This increase in vocal attractiveness was only
found for females who were naturally cycling. There were no
menstrual cycle effects on voice attractiveness ratings for
those taking hormonal contraceptives.
Consistent with the findings of Hughes et al. (2002)
concerning voice and fluctuating asymmetry where there
were no sex differences in ratings of voice attractiveness, we
also found no differences in how males and females rated
voices as a function of where the speakers were in their
menstrual cycle. Had more targeted questions been asked
such as, “rate this voice for sexual attractiveness,”or “how
likely would you be to date or have sex with this person,”it is
possible that sex differences might have emerged. For
example, the correlations between voice attractiveness
ratings by members of the opposite sex and different aspects
of the speaker's sexual behavior are higher than same sex
ratings (Hughes et al., 2004). Females also rate feminized
voices of other females as more attractive than masculinized
voices (Feinberg et al., 2006). When rating male voices,
females prefer those lower in pitch (Collins, 2000),
especially when they are near ovulation (Feinberg et al.,
2006; Puts, 2005). Males, on the other hand, judge male
voices that are lower in pitch as being more dominant (Puts
et al., 2006; Puts, Hodges, Cárdenas, & Gaulin, 2007).
However, both sexes rate male and female voices as more
attractive if they are collected from speakers who have
pronounced sex-specific body configurations (Hughes et al.,
2004). Clearly under certain circumstances both sexes are
discerning of same/opposite sex vocal cues, albeit for
different reasons. Puts et al. (2006) argue that males can
distinguish vocal dominance cues from other males because
of male–male intrasexual competition.
Although raters preferred voice samples taken from
females who were closer to ovulation, the physical properties
of voice that mediate these effects remain unclear. Abitbol
et al. have identified physical features of women's voices
that change with the PMS (Abitbol et al., 1989; Abitbol et al.,
1999). Collins and Missing (2003) found that female voices
higher in frequency were rated as more attractive and
younger, whereas lower frequency voices were rated as
being less attractive and older. Chae et al. (2001) found that
vocal parameters in most of the women in their study who
experienced PMS showed an increase in jitter and slightly
lower frequency compared to other times during the
menstrual cycle. Vocal cord edema produces a decrease in
vocal frequency, causes antiproliferative effects on mucosa
and increases the viscosity and acidity of cellular secretions
which frequently occur around menstruation and are
thought to be driven by higher progesterone and lower
estrogen levels (Abitbol et al., 1999; Amir et al., 2002).
Consistent with this, recent evidence suggests that funda-
mental frequency in female voices may be higher at
ovulation compared to other times during the menstrual
cycle (Bryant, G., & Haselton, M., unpublished data),
suggesting that fundamental frequency may be one
component of attractiveness.
Puberty (Abitbol et al., 1999) and menopause (Caruso et
al., 2000) affect vocal production. The evidence suggests that
the impact of hormones across the menstrual cycle might
drive vocal changes and perceptual features of voice, but
more research is needed. Premenstrual syndrome and the
more psychologically detrimental premenstrual dysphoric
disorder occur during the luteal phase just before menstrua-
tion, when progesterone is highest. These disorders are
thought to be dependent on the menstrual cycle and are
disabling both behaviorally and emotionally (Indusekhar,
Usman & O'Brien, 2007). Because of potential hormonal
influences on mood, female voices recorded close to
ovulation might actually seem more prosocial or interactive
compared to voice recordings that were closer to menstrua-
tion, which in turn could be driving the perceptual
differences obtained in our study.
Our data interpretation is limited to perceptual effects. We
did not perform acoustic analyses (i.e., spectrogram analysis)
on our voice data. From the perspective of evolutionary
theory, we were principally interested in whether people
could detect differences. In trying to pinpoint the physical
parameters of voice attractiveness using spectrogram
analysis, Hughes, Pastizzo and Gallup (in press) have
recently failed to find a substantial number of parametric
differences between attractive and unattractive voices.
Hughes et al. attribute the lack of acoustical correlates in
their study as evidence for highly evolved modules in the
human brain that conduct a more complicated and/or more
efficient assessment of voice than what contemporary
acoustic computer software provides.
A number of behaviors vary across the menstrual cycle in
relationship to conception risk (e.g., Chavenne & Gallup,
1998; Gangestad & Thornhill, 1998; Penton-Voak & Perrett,
2000). Most studies focus on how females may be affected
by their menstrual cycle (e.g., Feinberg et al., 2006; Puts,
2005, 2006), and less attention has focused on how people's
judgments vary as a function of the target female's cycle
phase. Recent evidence, however, suggests that men may
adjust their mate guarding strategies depending on their
partner's cycle (Haselton & Gangestad, 2006), and our data
suggest that the sound of a woman's voice may also change
as a function of her menstrual cycle phase.
5R.N. Pipitone, G.G. Gallup Jr / Evolution and Human Behavior xx (2008) xxx–xxx
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Consistent with our findings, it has been shown that male
macaque monkeys distinguish and prefer female vocal calls
made in estrus, compared to nonfertile calls (Semple &
McComb, 2000). The basic underlying anatomy, acoustics
and central control over vocal tracts are similar between
humans and other mammals (Fitch, 2000) implying that our
findings may not be unique to humans.
Unlike visual cues, vocal communication is light inde-
pendent (Gallup & Cameron, 1992). Patterns of nocturnal
copulation are common among humans the world over (Ford
& Beach, 1951). During daylight, vocal cues probably
compliment other sensory domains when it comes to mate
selection and the timing of copulation relative to changes in
the probability of conception. Collins and Missing (2003) and
Johnstone (1995) refer to this as “back up signaling”or
“multiple messages”of overall fitness. How important vocal
cues are compared to other sensory domains remains unclear,
but in the absence of other cues the evidence suggests that the
human vocal tract is a medium that provides cues about many
biologically/reproductively relevant features. Not only are
fluctuating asymmetry and body configuration conveyed
through voice, but significant differences in sexual behavior
can also be accounted for by the sound of someone's voice
(see Hughes et al., 2002, 2004).
In support of the hypothesis that voice is a medium for
conveying important fitness and mate assessment cues, our
data show that voice varies as a function of fertility in
females and ratings of voice attractiveness peak during the
ovulatory phase. These results showing that ratings of female
voices vary as a function of menstrual cycle-induced changes
in fertility may, along with other changes, help explain recent
findings showing that lap dancers make significantly more
tip revenue when they are in midcycle (Miller, Tybur, &
Jordan, 2007).
Acknowledgments
The authors thank Holly Krohel and Nicole Miklos for
assistance in data collection, and members of the Human
Behavior and Evolution Laboratory for suggestions through-
out this project. We also thank Barbara Wilkinson for
assistance with design and analysis, and the editor for helpful
comments on an earlier draft of this paper.
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