Menstrual Cycle Effects on Attitudes
toward Romantic Kissing
Rafael Wlodarski & Robin I. M. Dunbar
#Springer Science+Business Media New York 2013
Abstract Hormonal changes associated with the human menstrual cycle have been
previously found to affect female mate preference, whereby women in the late
follicular phase of their cycle (i.e., at higher risk of conception) prefer males
displaying putative signals of underlying genetic fitness. Past research also suggests
that romantic kissing is utilized in human mating contexts to assess potential mating
partners. The current study examined whether women in their late follicular cycle
phase place greater value on kissing at times when it might help serve mate assess-
ment functions. Using an international online questionnaire, results showed that
women in the follicular phase of their menstrual cycle felt that kissing was more
important at initial stages of a relationship than women in the luteal phase of their
cycle. Furthermore, it was found that estimated progesterone levels were a significant
negative predictor for these ratings.
Keywords Menstrualcycle.Romantic kissing.Mateassessment.Relationships
Hormonal changes associated with the human menstrual cycle have been found to
have discernible effects on female sexual and mating behavior. While it has been
known for some time that female sexual desire spikes in the days surrounding
ovulation (Regan 1996), it has recently been discovered that preferences for certain
types of mating partners also co-vary with phases of the menstrual cycle. For
example, women in the late follicular phase of their cycle (in the days immediately
preceding ovulation when risk of conception from a single act of intercourse is at its
peak) report elevated levels of general attraction to men (Garver-Apgar et al. 2006)
and show increased preferences for sexually dimorphic (i.e., “masculine”) faces,
masculine body shapes (Little et al. 2007; Penton-Voak et al. 1999), “typical male
behavioral displays” (Gangestad et al. 2004), for the scents of symmetrical men
(Gangestad and Thornhill 1998) and of men who have greater genetic (MHC)
R. Wlodarski (*):R. I. M. Dunbar
Department of Experimental Psychology, University of Oxford,
South Parks Road, Oxford OX1 3UD, UK
compatibility (Wedekind et al. 1995), as well as for men who are socially dominant
(Havlicek et al. 2005) and high in creative intelligence (Haselton and Miller 2006).
Women in this cycle phase have also been found to be more accurate at judging male
sexual orientation (Rule et al. 2011) and to pay closer attention to cues signaling
status (Lens et al. 2011).
Many of the traits outlined above, including masculinity, dominance, and facial
symmetry, are believed to be acting as signals of underlying genetic competence,
which is in turn responsible for physical health, developmental stability and superior
immune-responsivity (for reviews see Rhodes 2006; Roberts and Little 2008). Mating
with a partner who possesses such a robust gene set increases the odds that resulting
offspring will be endowed with similar genetic advantages. However, a negative
relationship seems to exist between genetic fitness indicators such as these and
behaviors associated with long-term parental investment. For example, higher testos-
terone levels in utero, responsible for the development of masculine features, higher
fluctuating testosterone levels in adulthood, and various male-typical behaviors, have
also been found to correlate with greater relationship infidelity, a larger number of
lifetime sexual partners, higher chances of divorce, lower biological sympathy
responses to crying infants, as well as compromised immune function (Booth and
Dabbs 1993; Fleming et al. 2002; Folstad and Karter 1992; Manning et al. 2000;
Pollet et al. 2011). Choosing a mate of superior genetic health, therefore, may
necessitate a trade-off: genetically fit partners are likely to bequeath offspring with
superior genes but at the same time are less likely to provide long-term parental
investment and support, which has a significant effect on offspring survival (Hill and
It has been proposed that, faced with this dilemma, women may seek to
improve their overall long-term reproductive fitness by pursuing a mixed-
mating strategy: preferring long-term partnerships with males willing to provide
resources and parental support while being open to pursuing short-term sexual
relationships with partners able to contribute superior genes to potential offspring
(Baker and Bellis 1994; Foerster et al. 2003). Such a mating strategy explains
the plethora of data found thus far on subconscious shifts in mate preference
across the menstrual cycle, whereby genetically fit sexual partners are preferen-
tially favored at a time of the cycle when copulation is most likely to lead to
conception (i.e., the late follicular phase), while sexual partners offering the
greatest long-term resource investment potential are favored at times less likely
to lead to conception (i.e., the luteal phase).
Research on female mate preference shifts during luteal cycle phases goes some
way to corroborating theories about mixed-mating strategies. When women are at the
lowest risk of conception from a single sexual encounter, they have been found to
show preferences for men displaying cues associated with kinship, such as phero-
mones indicating a similar MHC genetic makeup and faces with higher levels of self-
resemblance, as well as for cues of present health (for a review see Jones et al. 2008).
It has been proposed that because mating in the luteal phase of the menstrual cycle
involves little risk of conception, women at this time pursue decision strategies
geared towards affiliating with individuals likely to provide a supportive social
environment, such as kin (DeBruine et al. 2005; Jones et al. 2005). However, it
seems that mate-preference shifts driven by luteal phases of the cycle may not be as
robust as shifts seen during late follicular phases. DeBruine et al. (2005) found that
the cyclic shift for self-resemblance was considerably stronger for female faces than
for male faces, while Jones et al. (2005) found that preference shifts for signs of
health were stronger in pregnant women and women using hormonal contra-
ception than in normally cycling women in the luteal phase, suggesting that
similarity/kin affiliations might be strongest during hormonal profiles associated
The drivers behind a behavioral adaptation such as this are likely to be related to
the steroid hormones which fluctuate in tandem with the menstrual cycle, namely
estrogen and progesterone. Indeed, part of the reason that mate preference shifts seem
to be at their most pronounced between the late follicular and luteal phases of the
menstrual cycle is due to the fact that the two phases are associated with the most
prominent spikes in levels of estradiol (estrogen) and progesterone hormones,
respectively (Durante and Li 2009; Jones et al. 2008; Meston and Frohlich 2000).
Furthermore, menstrual cycle fluctuations in mate choice preferences are typically
only observed among normally cycling women not using any kind of hormonal
contraception (e.g., Penton-Voak et al. 1999), presumably owing to the moderat-
ing effects of such prophylaxes on the conventional fluctuation of estrogen and
Since several studies have already demonstrated menstrual cycle effects on
female preferences for various cues related to mate desirability, it seems worth-
while to examine whether these effects extend to other cues associated with mate
choice. Previous research has found that the cross-culturally prevalent custom of
romantic kissing is one mate cue that can been exploited in the assessment of
potential mating partners (Hughes et al. 2007; Wlodarski and Dunbar 2013). This
research also suggests that females are more reliant on kissing as a mate assess-
ment device and are unwilling to have sexual intercourse with a partner without
first kissing them; rate “bad kissers” as less attractive overall; and tend to base
evaluations of kissing ability on chemical cues (such as breath and taste of mouth).
Though the exact mechanism by which romantic kissing conveys mate information
remains uncertain, these findings suggest that kissing might facilitate assessment
of a mate’s genetic suitability either through the olfactory sampling of auxiliary
gland pheromonal cues (e.g., Wedekind et al. 1995) or via the surreptitious
olfactory/gustatory assessment of semiochemicals found in saliva or skin oils
Based on previous findings that romantic kissing can serve a mate assessment
function, the present study was designed to explore whether menstrual cycle shifts
can be seen in female attitudes towards romantic kissing at different stages of a
relationship. It was predicted that normally cycling women in the late follicular (high
risk of conception) phase of their menstrual cycle would place greater importance on
kissing during the initial stages of a relationship, where it would be most useful as a
preliminary mate assessment device, than women in the luteal (low risk of concep-
tion) phase of their cycle, with these shifts being driven by menstrual hormones.
Furthermore, if this was the case, it was predicted that menstrual hormones would
also affect women’s ratings of various factors associated with a romantic kiss,
particularly kissing factors that might be effectively utilized in the process of mate
An online questionnaire, approved by Oxford University’s Research Ethics Commit-
tee, was distributed on several US and UK public online psychological testing
repository websites, as well as through colleges at the University of Oxford. Partic-
ipants were required to be over 18 years of age to complete the survey; no identifying
personal data were collected and participants were informed that their responses were
completely voluntary and anonymous. Participants were required to provide informed
consent, and were offered the chance to enter a prize draw for an online shopping
voucher upon completion of the questionnaire.
Participants were informed that they were to be completing questions about their
‘attitudes towards kissing with romantic partners.’ In particular, participants were
firstly asked “How important do you think kissing is . . . at the very initial stages of a
relationship/during the established phases of a committed, long-term relationship?”
They were also asked about various attributes of kissing: “In deciding whether
someone is a ‘good kisser,’ how important are the following factors: How pleasant
their breath is/The scent of their body/The taste of their lips/skin/How ‘wet’ the kiss
is/How much touching/physical-contact/caressing is involved/How physically
aroused it makes you/Whether their kissing style is the same as yours?” Responses
to the two questions were collected using 5-point Likert-type scales, with endpoints
ranging from “Not at all important” to “Extremely important” and presented using a
grouped table layout for each of the sub-questions. For menstrual cycle phase
estimation purposes, participants were asked whether they were currently taking
any hormonal contraception, whether they experienced a “regular” menstrual cycle,
the average length of their menstrual cycle, and the date of onset of their last menses.
General demographic information was also collected.
Estimations of Menstrual Cycle Phase and Risk of Conception
For all analyses, data were only used from women who reported having a regular
menstrual cycle whose length fell within the normal ranges of 22 to 36 days (Chiazze
et al. 1968), were not on any form of hormonal contraception, and provided the
information required to make cycle phase calculations. To estimate the menstrual
cycle phase at the time of answering the survey, information was used about the last
date of menses onset and typical cycle length to estimate day of ovulation using the
reverse cycle day method—approximated as 15 days prior to next estimated onset of
menses (see Pillsworth et al. 2004; Thornhill and Gangestad 1999). This method is
preferable to forward-counting methods because previous research has found that the
follicular phase of the menstrual cycle accounts for much of the variation in average
cycle length (Fehring et al. 2006; Lenton et al. 1984).
For analyses involving a binary measure of cycle phase, participants undertaking
the experiment on the estimated day of ovulation or within 5 days prior to ovulation
were classed as being in the late follicular phase of their cycle (i.e., at “high risk of
conception”) and participants within 10 days of the next onset of menses were classed
as being in the luteal phase (i.e., at “low risk of conception”) (Jones et al. 2005a;
Pillsworth et al. 2004; Wilcox et al. 2001). These cycle days represent the largest
differences in progesterone and estradiol levels throughout the menstrual cycle
(Durante and Li 2009; Jones et al. 2005; 2008; Meston and Frohlich 2000).
For analyses investigating the hormonal mechanisms driving menstrual-cycle-shift
behavior effects, estradiol and progesterone levels on any given day of the cycle were
estimated using mean serum estradiol and progesterone reference values derived from
normally cycling women within 15 days of ovulation (Stricker et al. 2006).
For analyses involving the binary variable of women in their late follicular and luteal
cycle phases only, participants consisted of 50 women in the luteal phase and 34
women in the late follicular phase of their menstrual cycle at the time of completing
the survey. These participants’ ages ranged from 18 to 47 (M=24.7, SD=0.6), their
menstrual cycle length varied from 23 to 35 days (M=28.9, SD=2.2), and the sample
was predominantly made up of North American (33%), British (28%), and Western
(8%) and Eastern (6%) European nationals.
Analyses using the continuous variables of estimated estradiol and progesterone,
which utilized data from women in all phases of their menstrual cycle, incorporated
173 women aged 18 to 51 (M=24.7, SD±6.5) with menstrual lengths varying between
23 to 36 days (M=28.9, SD±2.1) and included primarily North American (39%),
British (25%), and Western (10%) and Eastern (5%) European nationalities.
Participants’ responses to questions about the importance of kissing at both initial
and established relationship stages can be seen plotted against the estimated day of
their menstrual cycle in Fig. 1.
A 2×2 mixed design ANOVAwas carried out on answers to this question, with the
binary variable of follicular/luteal cycle phase as a between-subject factor and stage
of the relationship (initial stage/established phase) as a within-subject factor. Al-
though no significant main effect of cycle phase on ratings of the importance of
kissing (F1,82=3.55, p=0.063, partial η2=0.041) and no main effect of relationship
stage on ratings of kissing importance (F1, 82=1.83, p=0.180, partial η2=0.022) were
found, a significant interaction effect existed between cycle phase and relationship
stage (F1, 82=5.58, p=0.021, partial η2=0.064). That is, during the initial stages of a
relationship, participants in the follicular phase of their cycle (M=4.10, SD±0.97)
believed that kissing was more important than participants in the luteal phase did (M=
3.86, SD=1.03), while at established stages of a relationship both follicular and luteal
phase participants stated that kissing was equally important (follicular phase M=4.00,
SD±0.78, luteal phase M=3.98, SD±0.92).
To determine if key hormones associated with the menstrual cycle might be acting
as underlying drivers of participant responses, linear regression analyses were carried
out, regressing estimated levels of estradiol and progesterone onto answers to the
same questions. As can be seen in Table 1, progesterone levels were found to be a
significant negative predictor for ratings of the importance of kissing only during the
initial stages of a relationship.
Fig. 1 Importance of kissing during initial relationship stages (grey markers, dashed line) versus
established relationship phases (black markers, solid line) across the menstrual cycle. Day 0 represents
reverse-day-count estimated day of ovulation, trend curves fitted using Loess curve estimation, 65% points
fit, Epanechnikov kernel
Table 1 Linear regression analyses of estimated estradiol and progesterone levels regressed onto ratings of
the importance of kissing at initial and established stages of a relationship
B SE B
Importance of kissing at initial stages
Estimated Estradiol Levels
Estimated Progesterone Levels
Importance of kissing at established stages
Estimated Estradiol Levels
Estimated Progesterone Levels
Next,answers givenbywomenatdifferentphases oftheircycle toquestions aboutthe
importance of factors contributing to a good kiss were examined. It was initially found
that women in late follicular phases of the cycle believed that “pleasant breath” was a
more important component of a good kiss than women in luteal cycle phases did
(follicular M=4.15, SD±0.82, luteal M=3.70, SD±0.91, t82=2.34, p=0.022), with no
significant differences found between participants ratings of other factors associated with
kissing. Similarly, initial linear regression analyses found that estimated progesterone
levels were a negative predictor when rating “pleasantness of breath” as an important
component of a good kiss (constant B=3.867, SE B=0.131; Estradiol B=0.000, SE B=
0.000; β=0.111 p=0.174; Progesterone B=−0.011, SE B=−0.005; β=−0.189, p=0.022;
R2=0.032), whereas similar regression analyses did not find progesterone or estradiol
levels to be significant predictors for importance ratings of other factors associated with
kissing (scent of body, taste of their lips/skin, wetness of kiss, amount of touching,
physical arousal, and similarity of kissing style) (0.29<t<1.91, 0.056<p<0.875).
However, after these initial analyses were corrected for multiple comparisons, the two
significant findings were edged out of the range of statistical significance.
A principal components analysis (PCA) with orthogonal (varimax) rotation was
the results of the PCA, with factor loadings for the three main extracted factors shown
after rotation, and coefficients over 0.5 displayed in bold. Linear regression analysis
indicated that neither estimated estradiol nor progesterone levels were significant
predictors for any of the three PCA extracted factors (0.01<t<1.80, 0.075<p<0.990).
This study found that when asked about the importance of kissing at initial stages of a
relationship, women in the late follicular phase of their menstrual cycle (i.e., at high
Table 2 Principal components analysis on factors contributing to a “good” kiss
Scent of body
Taste of lips/skin
Wetness of kiss
Amount of arousal
Same kissing style
Sampling adequacy verified by the Kaiser-Meyer-Olkin technique (KMO=0.585), with Bartlett’s test of
sphericity indicating significantly large correlations (χ2
suggested a clear inflection point at 3 components, with all components displaying eigenvalues over 0.989
and combining to explain 63.6% of the variance
21=156.4, p<0.001). Inspection of the scree plot
risk of conception) rated it as more important than women in the luteal (low
conception risk) phase of their cycle. Furthermore, estimated levels of progester-
one were found to be a significant negative predictor for women’s ratings of
kissing importance at this relationship stage. When it came to kissing at the more
established phases of a relationship, women in the late follicular and luteal phases
of the menstrual cycle considered kissing equally important, and neither estimated
estradiol nor estimated progesterone levels were associated with ratings of kissing
Previous research indicates that women in late follicular phases of their menstrual
cycle, who are at the highest risk of conception, show an increased preference for men
possessing cues signaling underlying genetic superiority or compatibility, including
masculinized faces, facial symmetry, social dominance, and MHC compatibility
(Gangestad and Thornhill 1998; Havlicek et al. 2005; Penton-Voak et al. 1999;
Wedekind et al. 1995). It has also previously been found that romantic kissing is
used in assessing a mating partner’s desirability (Hughes et al. 2007; Wlodarski and
Dunbar 2013). The results of the current study synthesize these findings by showing
that attitudes towards romantic kissing vary across the menstrual cycle and are
significantly associated with the fluctuation of menstrual hormones. Since women
in the late follicular phase of their cycle are more attracted to, and motivated to find,
genetically fit/compatible males, it follows that they would place greater value on
devices which aid the assessment of genetic qualities—in this case, romantic kissing.
That no cycle phase shift was found for ratings of kissing importance at established
relationship phases, a situation in which the initial assessment of a mate is no longer
pertinent, supports the premise that romantic kissing may play a particularly useful role
in the earliest stages of a relationship, when preliminary partner evaluation is most
likely to take place. The fact that progesterone was significantly negatively associated
with ratings of kissing importance at initial relationship stages insinuates that it may be
acting as a driver of this particular attitude shift. Progesterone is one of the candidate
mechanisms thought to be responsible for various menstrual cycle behavioral changes
(Haselton and Gangestad 2006) and has previously been implicated in cyclic shifts in
mate preference for healthy faces (Jones et al. 2005), self-resemblance (DeBruine
et al. 2005), feminine faces (Jones et al. 2005), and vocal masculinity (Puts 2005).
Although our study design assesses temporary cognitive changes associated with
variation in menstrual cycle hormone levels, tapping into “state” rather than “trait”
effects, it seems that these state changes are substantial enough to influence partici-
pants’ attitudes towards kissing at other times.
Our results also suggest that menstrual cycle phase and estimated levels of
progesterone across the cycle might be related to ratings of the importance of
“pleasantness of breath” as a contributing factor to a “good kiss.” However our
findings at this stage are only suggestive since adjustments for multiple compar-
isons nudged the observed differences out of the range of statistical significance.
If one of the major functions of kissing is to assist individuals in assessing the
quality of a mate via olfactory or gustatory cues, then women at high conception
risk (and low progesterone levels) should place greater value on components of
kissing which might aid them in assessing the genetic suitability of potential
mates. Since it has been previously suggested that semiochemicals found in skin
oils and pheromonal secretions might convey information about underlying health
and genetic quality (Durham et al. 1993; Nicholson 1984; Wedekind et al. 1995),
women at high risk of conception should be particularly interested in utilizing
cues found in breath odor to assess mate quality. It is interesting to note than
women in the late follicular phases of their cycle also show increased sensitivity
to odors and display faster odor processing times (Doty et al. 1981; Pause et al.
1996). This increased sensitivity would be particularly useful in assessing mate
olfactory cues at the most reproductively critical time of the menstrual
cycle—when sexual intercourse is most likely to lead to conception.
It was predicted that hormones associated with the menstrual cycle may also
be related to other facets of kissing which could be conveying mate quality
information (such as scent of body or taste of lips). However, none of the other
traits sampled suggested significant relationships, implying that kissing may be
useful in assessing cues related primarily to breath. When responses to this
question were analyzed using PCA, the three factors that were extracted
coincided with several previously proposed theories on possible functions of
romantic kissing. The first component, relating to “sensory factors,” implies that
sensations involving smell contribute in a similar way to making someone a
good kisser, possibly because these cues can be used to make inferences about
the underlying mate quality or genetic suitability using pheromonal cues or on
signals of general health (Durham et al. 1993; Wedekind et al. 1995). The second
PCA factor related to contact/arousal themes, which have been proposed as
another possible function of kissing promoting partner arousal and the initiation
of sexual relations (Hughes et al. 2007). The final PCA factor appears to be
related to kissing technique and may also be indicative of mate quality in certain
situations, as research in related fields suggests that the quality of execution of
complicated behavioral rituals (such as dancing) may be a cue to underlying
genetic quality (Hugill et al. 2010). It might be that physical awkwardness or
poor coordination during intimate courtship behaviors such as kissing may act as
a signal of substandard fitness. None of these extracted factors, however, were
significantly related to estimated levels of progesterone or estradiol, suggesting
that they may not confer the same level of mate-quality information as pleasant-
ness of breath alone does.
The findings from this study indicate that women in the late follicular stages of
their menstrual cycles place greater value on kissing in the early stages of a
relationship, and that this behavioral shift seems to be related to menstrual cycle
fluctuations in the hormone progesterone. Furthermore, women with low estimated
levels of serum progesterone seemed to state that pleasantness of breath was a more
important component of kissing than did women with high estimated levels of
progesterone. These findings extend previous research on shifts in mating partner
preferences across the mating cycle, while also building on previous evidence that
romantic kissing may be utilized in the process of assessing the suitability of
potential mates. At this point, investigations into the menstrual cycle and romantic
kissing as a mate assessment device are still in their infancy, and future research in
this field would benefit from study designs based on more methodologically
challenging experimental designs in which subjects rated actual kissing experi-
ences, and where measures of fluctuating menstrual hormones were taken using
more direct measures.
RD are both supported by a European Research Council Advanced Grant to RD.
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Rafael Wlodarski BBus, BA(Hon) is a PhD research student at Oxford University’s Department of
Experimental Psychology. His research interests revolve around evolutionary approaches to the study of
human behavior, particularly human courtship and pair-bonding.
Robin I. M. Dunbar MA, PhD, FRAI, FBA, is a professor of evolutionary psychology at the University of
Oxford. His principal research interests are in social evolution in mammals, with particular reference to
ungulates, primates and humans, and the ways in which ecology, behavior, cognition and neurobiology