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The Effect of Eyelash Length on Attractiveness: A Previously Uninvestigated Indicator of Beauty

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Human eyelashes are one of the facial features that contributes to facial attractiveness. While enhancing the appearance of eyelashes has been practiced since antiquity, research investigations that consider the effect of their length on perceived attractiveness are scarce. Length of eyelashes can be an indicator of health, and it has recently been proposed that there is an optimum length for eye protection. In the current article, we investigated if the attractiveness of eyelash length dovetails with these evolutionary and functional proposals. Our results support this proposition, with the preference for eyelash length following an inverted-U function, with the highest ratings peaking at approximately one third of the eyes’ width. Interestingly, there is a difference between male and female faces, suggesting that while in general, eyelashes of an optimum ratio are considered more attractive, this preference is not solely a biologically adaptive phenomenon and is influenced by cultural norms.
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Pazhoohi, F., & Kingstone, A. (2020). The effect of eyelash length on attractiveness: A
previously uninvestigated indicator of beauty. Evolutionary Behavioral Sciences. Advance
online publication. https://doi.org/10.1037/ebs0000243
The effect of eyelash length on attractiveness: A previously uninvestigated indicator of
beauty
Farid Pazhoohi & Alan Kingstone
Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, British
Columbia, Canada V6T 1Z4
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Abstract
Human eyelashes are one of the facial features that contributes to facial attractiveness. While
enhancing the appearance of eyelashes has been practiced since antiquity, research investigations
that consider the effect of their length on perceived attractiveness are scarce. Length of eyelashes
can be an indicator of health, and it has recently been proposed that there is an optimum length
for eye protection. In the current paper, we investigated if the attractiveness of eyelash length
dovetails with these evolutionary and functional proposals. Our results support this proposition,
with the preference for eyelash length following an inverted-U function, with the highest ratings
peaking at approximately one third of the eyes’ width. Interestingly, there is a difference between
male and female faces, suggesting that while in general eyelashes of an optimum ratio are
considered more attractive, this preference is not solely a biologically adaptive phenomenon and
is influenced by cultural norms.
Keywords: eyelash length, eyelash attractiveness, facial attractiveness, evolutionary biology,
adaptation
Public Significance Statements: Eyelashes have evolved to protect eyes from external
contaminations and excessive evaporations, and changes in eyelash length can reflect different
congenitally and noncongenitally diseases. From this evolutionary and biological perspective, we
test, and confirm, that the perceived attractiveness of eyelashes dovetails with their predicted
value to protect the eyes and signal healthiness to others. Contrary to some beliefs that the
attractiveness is increasing with the length of eyelashes on female faces, the preference for
eyelash length follows an inverted-U function. This function is observed for both female and
male faces.
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The effect of eyelash length on attractiveness: A previously uninvestigated indicator of
beauty
My eyes drown in tears, yet thirst for but one chance,
I'll give away my whole life, for Beloved, but one glance.
Be ashamed of Beloved's beautiful eyes and long lashes,
If you have seen what I have, and still deny me my trance.
– Hafez, 1315-1390 A.D.
Human eyelashes are one of several facial features that contribute to facial attractiveness
(Dang et al., 2016). In many cultures, such as old civilizations in Middle East and North Africa,
eyelashes have been used to enhance and modify facial attractiveness and in particular the beauty
of the eyes. Presently such practices are showcased in the use of mascaras and curlers by women,
as possessing long eyelashes is considered beautiful (Patel, Abdul & Joos, 2019). However, the
perceived length of eyelashes needs to be balanced against the fact that long eyelashes can also
be indicators of different congenitally and noncongenitally diseases (for a review see Paus et al.,
2016). For example, children and adolescents with allergic or immunodeficiency diseases have
longer eyelashes than normal cohorts, potentially as a response to these diseases (Graham &
Sires, 1997; Singh & Pawar, 2018; Patrizi et al., 1998; Sharma, Mahajan, Sharma & Sharma,
2002). Such lengthening of eyelashes is suggested to be due to mast cells release of histamine,
prostaglandins, and leukotrienes in response to allergies (Church & McGill, 2002; Singh &
Pawar, 2018), remodelling hair follicle tissue (Paus et al., 1998). On the other hand, the loss of
eyelashes, or when they are very short, may signal disorders of a dermatological or nutritional
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nature, or alternatively, endocrine or systemic diseases (Khong, Casson, Huilgol & Selva, 2006;
Kumar & Karthikeyan, 2012).
Beyond studies examining the relationship between eyelash length and disease, very few
studies have investigated eyelashes from an aesthetic perspective (Shaiek et al., 2018). Recently,
Amador and colleagues (2015) measured eyelashes of twenty-two mammals and showed that the
length of the eyelash is phylogenetically constant and is approximately one-third of the eye
width. They proposed that eyelashes act as air filters for the eyes, and using theoretical models
and simulated eyelashes, they measured the airflow around and through the eyelashes. They
found that the optimum length of eyelashes to width of the eye (L/W ratio) for minimizing
evaporation and contamination at the ocular surface was approximately 0.35 ± 0.15.
The current study reports the first systematic examination of the effect of eyelash length
on perceived facial attractiveness in humans. Assuming the phylogenetically adaptive
functionality of the L/W ratio, we hypothesized that attractiveness would be highest around the
proposed optimum range suggested by Amador et al. (2015). Our hypothesis is based on an
adaptive evolutionary perspective, in which attractiveness is an honest indicator of health and
genetic quality (Gangestad & Scheyd, 2005; Grammar, Fink, Moller & Thornhill, 2003). In other
words, if very short and very long eyelashes are indicators of diseases, such characteristics
should be considered less attractive. Furthermore, our prediction is based on the suggested
evolved functionality of eyelash length, in which shorter than the optimum lengths cannot
effectively protect eye surfaces from contamination, excessive evaporation, and shear stress from
airflow; while longer than optimum lengths impede vision and may signal hyper-sensitivity to
allergic diseases (Amador et al., 2015). Therefore, we asked participants to rank eleven images
of a woman’s face for attractiveness, with the sole manipulation being eyelash length. Lengths
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ranged from zero-length to half the width of the eye (L/W of 0.50). We hypothesize that
preference for eyelashes will show an inverted-U relationship with L/W ratios about 0.35 ± 0.15
being considered the most attractive. From a purely evolutionary-biology perspective, this
inverted-U function should hold for both females and males. However, there is the potential that
the relationship may be modulated by gender cultural norms and the most attractive eyelashes for
a man’s face may be different (e.g., shorter) than for a female face (i.e., men might culturally be
associated with less feminized features, such as shorter eyelashes). Therefore, we also tested the
effect of eyelash length on facial attractiveness using a man’s face.
Material and Methods
Participants
Experimenters randomly tested university students in the Department of Psychology,
asking for either the female or male faces to be rank-ordered in terms of attractiveness. This
resulted in 81 participants (64 women and 17 men; aged 18 to 30 years; M = 20.42 years, SD =
2.48) being tested with the female face, and 51 individuals (38 women and 13 men; aged 18 to
45 years; M = 21.72 years, SD = 5.18) being tested with the male face. (Note that as the majority
of the individuals participating in the study were undergraduate women, reflecting the enrollment
ratio for the Department of Psychology, sex differences were not analyzed.) A total of 79
individuals (62.2%) reported single as their marital status, 34.6% as being in a relationship, and
3.1% as married. In terms of their highest academic degree, 54.3% had a high school diploma,
6.3% had a post-secondary diploma, and 38.6% of the participants had an undergraduate degree.
All participants consented to taking part in the study. The experiment was approved by the Ethics
Committee of the University of British Columbia and was conducted in accordance with the
Declaration of Helsinki as it pertains to research with human participants.
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Stimuli and experiment
The female and male images were each generated using Daz3D software, and using
Photoshop eleven copies of each face varying in eyelash length were created (see Figure 1 for
examples). Eyelash length to eye width ratios were varied by units of .10, with the intervening
value being .04 or .06 (rather than .05) to create some unexpected variation in the different
lengths. Thus, the L/W ratios were: 0, .04, .10, .16, .20, .24, .30, .36, .40, .44, and .50. To avoid
other facial features as potential confounds on the perceived attractiveness, participants were
shown only the female or male face. The eleven female, and male, stimuli were printed
separately in high quality color on US Letter size paper (8" x 11.5") in portrait mode. The female
or male stimuli were stacked randomly and handed to participants. They were asked to order
them on a table from least (1) to most (11) attractive. Then the order of their rating was recorded
by the experimenters.
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Figure 1. Examples of stimuli varying in eyelash length to eye width ratio; left image 0, middle
image .24, and right image .50. Upper row shows examples of the female stimuli, and the lower
row shows examples of the male stimuli.
Results
For female faces, a Kruskal-Wallis H (one-way ANOVA) test was conducted to compare
the perceived attractiveness of eyelashes of different lengths. Results showed a significant main
effect for attractiveness ranking, χ2(10) = 374.95, p < .001. Pairwise comparisons indicated that
eyelashes with .20, .24, .30 and .36 eyelash/eye ratios were ranked as the most attractive
compared to the rest, while .16, .40, and .44 ranked highest in the second order. Images with
eyelash/eye ratios of 0 and .04 were ranked as the least attractive (see Figure 2A).
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For male faces, a Kruskal-Wallis H test showed a significant main effect for
attractiveness ranking, χ2(10) = 194.61, p < .001. Pairwise comparisons indicated that eyelashes
with .16 and .20 L/W ratios were ranked as the most attractive compared to the rest, and images
with L/W ratios of .44 and .50 ranked as least attractive (see Figure 2B).
Figure 2. A) Attractiveness ranking means for eleven female images differing in eyelash length
to eye width ratios (L/W); B) Attractiveness means for eleven male images differing in L/W
ratios. Means not sharing the same letters are significantly different (p < .01).
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To investigate if the perceived attractiveness between female and male faces differed as
eyelash length was altered, we ran a series of Mann-Whitney U tests comparing the sex
differences for each ratio. Results showed that the rankings for the ratios 0, .04, .30, .36, .40 and
.50 were significantly different between male and female faces (all Us > 944.5, all ps < .011 after
Bonferroni correction for multiple comparisons). Specifically, individuals ranked males faces as
higher on attractiveness than females at the smaller eyelash length ratios (0 and .04), and they
ranked female faces as higher on attractiveness than males for the larger eyelash ratios (.30, .36,
.40 and .50). No significant difference was observed for intermediate ratios of .10, .16, .20 and
.24 (all ps > .074).
Discussion
The current study tests the perceived attractiveness of eyelash length, and the results
provide support for the proposed evolutionary adaptive length of eyelashes. Perceived
attractiveness rating scores were highest for female faces with L/W ratios of .20, .24, .30 and .36,
and for male faces with ratios of .10, .16, .20 and .24. These highest ratings for males are skewed
toward a shorter ratio than the optimum ratio (0.35 ± 0.15) suggested by Amador et al. (2015).
Collectively, our result shows that contrary to some beliefs and a recent study (Adam, 2020)
finding that attractiveness increases with the length of eyelashes on women faces, our results
indicate that the preference for eyelash length follows an inverted-U function. Moreover, our
results show that female faces with L/W ratios of 0 and .04 (no eyelashes or very short
eyelashes) were considered the least attractive, while for the male faces the least attractive faces
were those with .44 and .50 L/W ratios (very long eyelashes). In other words, there is a
difference in attribution of attractiveness to male and female faces as a function of eyelash
length. The skewed ratings’ in attractiveness peak for male faces towards shorter eyelashes
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relative to those of female faces, suggesting that the preference for eyelash length may be
modulated by gender cultural norms. That is, while in general eyelashes of an optimum ratio are
considered more attractive, this preference is not solely a biologically adaptive phenomenon, and
is influenced by cultural norms. For example, the present result might be different in cultures
where the practice of eyeliners and/or mascara is not limited to women and could also be applied
to children and men (e.g., West and South Asia). Similarly, future studies may wish to combine
eyelash length with other facial features as well as using different ethnicities than the one used in
the current study. Finally, future studies may choose to use larger sample sizes, use ratings rather
than ordinal rankings to enable a direct test of sex differences, and/or assess 3D images, or
stimuli in motion, rather than 2D static images. In sum, although there is much work still to be
done, the present study adds to previously investigated ocular features in the perception of
attractiveness, such as eye color (Kleisner, Kočnar, Rubešová & Flegr, 2010), limbal ring
(Peshek, Semmaknejad, Hoffman & Foley, 2011), pupil size and scleral color (Gründl, Knoll,
Eisenmann-Klein & Prantl, 2012), and in general, to the field of facial attractiveness.
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Declaration of Competing Interest: The authors declare no conflict of interest.
References
Adam, A. (2020). Beauty is in the eye of the beautiful: Enhanced eyelashes increase perceived
health and attractiveness. Evolutionary Behavioral Sciences.
Amador, G. J., Mao, W., DeMercurio, P., Montero, C., Clewis, J., Alexeev, A., & Hu, D. L.
(2015). Eyelashes divert airflow to protect the eye. Journal of the Royal Society Interface,
12(105), 20141294.
Church, M. K., & McGill, J. I. (2002). Human ocular mast cells. Current Opinion in Allergy and
Clinical Immunology, 2(5), 419-422.Dang, J., Cole, J. C., Burgess, S. M., Yang, M.,
Daniels, S. R., & Walt, J. G. (2016). Development and validation of the Eyelash
Satisfaction Questionnaire. Aesthetic Surgery Journal, 36(2), 221-228.
Gangestad, S. W., & Scheyd, G. J. (2005). The evolution of human physical attractiveness. The
Annual Review of Anthropology, 34, 523-548.
Graham, D. A., & Sires, B. S. (1997). Acquired trichomegaly associated with acquired
immunodeficiency syndrome. Archives of Ophthalmology, 115(4), 557-558.
Grammar, K., Fink, B., Moller, A. P., & Thornhill, R. (2003). Darwinian aesthetics: Sexual
selection and the biology of beauty. Biological Review, 78, 385-407.
Gründl, M., Knoll, S., Eisenmann-Klein, M., & Prantl, L. (2012). The blue-eyes stereotype: do
eye color, pupil diameter, and scleral color affect attractiveness?. Aesthetic Plastic
Surgery, 36(2), 234-240.
12
Hoss, R. A., Ramsey, J. L., Griffin, A. M., & Langlois, J. H. (2005). The role of facial
attractiveness and facial masculinity/femininity in sex classification of faces. Perception,
34(12), 1459-1474.
Khong, J. J., Casson, R. J., Huilgol, S. C., & Selva, D. (2006). Madarosis. Survey of
Ophthalmology, 51(6), 550-560.
Kleisner, K., Kočnar, T., Rubešová, A., & Flegr, J. (2010). Eye color predicts but does not
directly influence perceived dominance in men. Personality and Individual Differences,
49(1), 59-64.
Kumar, A., & Karthikeyan, K. (2012). Madarosis: a marker of many maladies. International
Journal of Trichology, 4(1), 3-18.
Patel, B. C., Abdul, W., & Joos, Z. P. (2019). Anatomy, Head and Neck, Eyelash. In: StatPearls
[Internet]. Treasure Island (FL): StatPearls Publishing. Available from:
https://www.ncbi.nlm.nih.gov/books/NBK537278/
Patrizi, A., Neri, I., Trestini, D., Landi, C., Ricci, G., & Masi, M. (1998). Acquired trichomegaly
of the eyelashes in a child with human immunodeficiency virus infection. Journal of the
European Academy of Dermatology and Venereology, 11(1), 89-91.Paus, R., Burgoa, I.,
Platt, C. I., Griffiths, T., Poblet, E., & Izeta, A. (2016). Biology of the eyelash hair
follicle: an enigma in plain sight. British Journal of Dermatology, 174(4), 741-752.
Paus, R., Van Der Veen, C., Eichmüller, S., Kopp, T., Hagen, E., Müller-Röver, S., & Hofmann,
U. (1998). Generation and cyclic remodeling of the hair follicle immune system in mice.
Journal of Investigative Dermatology, 111(1), 7-18.
13
Peshek, D., Semmaknejad, N., Hoffman, D., & Foley, P. (2011). Preliminary evidence that the
limbal ring influences facial attractiveness. Evolutionary Psychology, 9(2),
147470491100900201.
Shaiek, A., Flament, F., François, G., Vicic, M., Cointereau‐Chardron, S., Curval, E., ... &
Idelcaid, Y. (2018). Morphological criteria of feminine upper eyelashes, quantified by a
new semi‐automatized image analysis: Application to the objective assessment of
mascaras. Skin Research and Technology, 24(1), 135-144.
Sharma, R. C., Mahajan, V. K., Sharma, N. L., & Sharma, A. (2002). Trichomegaly of the
eyelashes in dermatomyositis. Dermatology, 205(3), 305-305.
Singh, M., & Pawar, M. (2018). Eyelash length for the diagnosis of atopic dermatitis and
ichthyosis vulgaris in children—a case control study. European Journal of Pediatrics,
177(6), 955-960.
Walter et al. (2020). Sex Differences in Mate Preferences Across 45 Countries: A Large-Scale
Replication. Psychological Science. https://doi.org/10.1177/0956797620904154
... A similar example that has recently received empirical attention is eyelash length. Eyelash length may be a visual cue to health, with males expressing a stronger preference for longer lashes on females (Pazhoohi & Kingstone, 2020). Eyelash vigor and length can be modified with eyelash conditioners and serums (e.g., RevitaLash®), curling, extensions, and with mascara. ...
... Collectively, these findings suggest that digital visual appearance enhancement involves culturally unique modern technologies, applications, and websites that appear to be governed by motivations, dynamics, and outcomes that are similar to those observed with traditional face-to-face visual self-presentation modification. It will be fruitful for future researchers to study the motivations and effectiveness of using digital means to augment various aspects of physical appearance often regarded as attractive, such as using virtual makeup apps (e.g., Perfect365©) to increase the prominence of limbal rings (Lewis & Buss, 2021), eyelash length (Pazhoohi & Kingstone, 2020), and youthfulness (Jones et al., 2021). ...
... Since the writing of the target article, research on the diverse ways in which humans alter and modify their appearance from an evolutionary perspective has continued to grow (e.g., Jach & Moroń, 2020;Kellie et al., 2021;Pazhoohi & Kingstone, 2020;Wang et al., 2021). This demonstrates the timely nature of a comprehensive review of human visual selfpresentation modification to provide scholars with insight into the complementarity of sociocultural and evolutionary approaches (i.e., a socioevolutionary framework), pertinent theoretical and methodological considerations, and avenues in need of future empirical attention. ...
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