The science of attraction
‘Beauty’, the philosopher David Hume declared in the mid-18th
century, ‘is no quality in things themselves; it exists merely in the
mind that contemplates them; and each mind perceives a different
beauty.’ Since then, the idea that beauty is in the eye of the beholder
– that standards of attractiveness are arbitrarily defined and rapidly
changing – has become the dominant view in much of philosophy, art,
science and history.
Driven by evolutionary theory, however, many psychologists have argued
that there are certain physical features of the body and face that are
found attractive across all individuals and cultures. The same is true
across the animal kingdom, with most non-human species relying on
external factors such as the sizes, shapes and colour of adornments to
attract mates. Darwin, for example, reasoned that the peacock’s tail
could only have evolved if it conferred an advantage on the animal in
terms of mating, which could compensate for the lowered survival
probability under natural selection. Similarly with humans,
evolutionary psychologists have argued that the attractiveness of
individuals is directly linked to their value as procreative mates
(Buss, 1999). Within this tradition, humans are said to select mates
that will enhance their reproductive success, and there has been a
concurrent emphasis on the importance of certain species-typical
features.
Thus, if the markers of fecundity are known, they may become agreed
criteria of attractiveness in all cultures. Hence we can develop and
test theories in the new science of attractiveness. Much of this work
has converged on facial attractiveness, with research suggesting little
variation in preferences of beauty across cultures (Perrett &
Little, 2002; see tinyurl.com/br5eh). In recent years, however,
attention has focused on the female body (mainly because of the link
with fertility), with researchers identifying two potentially critical
cues for attractiveness: body shape and weight scaled for height, or
the body mass index (BMI). This article looks at the contributions of
both variables to female physical attractiveness.
Body shape
In a series of studies conducted in the early 1990s, Singh (e.g.
1993) identified a particular bodily feature that he claimed reliably
conveys information about female mate value. The waist-to-hip ratio
(WHR) refers to fat distribution regulated by sex hormones
(testosterone in men, oestrogen in women) that primarily sculpt typical
body shape differences. Before puberty, body shape is more or less
similar for both men and women; after puberty, however, women have
greater amounts of body fat deposited in the lower part of the body.
This engenders what is known as gynoid fat distribution, whereas men
have greater amounts of fat in the upper body, or what is known as
android fat distribution. Women typically maintain a lower WHR than men
throughout adulthood, and it is this difference in fat distribution
that engenders a noticeable and typical sex difference. In short, it
gives women their ‘curves’ or hour-glass figure.
Singh also made the point that the WHR reliably signals hormonal
status, susceptibility to endocrinological disorders and, most
importantly, fertility. In particular, a low WHR (typically 0.7) is
said to confer advantages over a high WHR (0.9 and above) in terms of
health and fertility, thus reinforcing the evolutionary assumption that
this feature of the female body conveys information about mate value.
In support of this thesis, Singh (1993, 1994) developed a set of line
drawings with which he amassed evidence for an evolved male preference
for a low WHR (typically 0.7). This ratio happens to correspond closely
to the measurements of supermodels of various sizes, like Anna Nicole
Smith (0.69), Kate Moss (0.66) and Cindy Crawford (0.69).
Although this research is typically framed in terms of the comparison
of low to high WHR, most authors suggest a specific preference for a
WHR of 0.7. Burnham and Phelan (2000), for example, write: ‘Although
subconscious, there’s something about that 0.7 that only a gene could
love.’ Singh’s line-drawing studies have been replicated in a number of
countries (e.g. Furnham et al., 1997; Henss, 1995), and Singh (1993,
p.304) himself argued that the WHR ‘acts as a wide first-pass filter,
which would automatically exclude women who are unhealthy or who have a
low reproductive capacity’. It is only after this ‘culturally
invariant’ filter is passed that other features such as the face, skin,
or weight (which may vary between cultures) become utilised in final
mate selection.
The problem with Singh’s line drawings is that they lack ecological
validity (Tassinary & Hansen, 1998). Line drawing stimuli are often
impoverished and unrealistic, relying on a single original image from
which modifications are made. Henss (2000) attempted to overcome this
problem by using photographs of different women with computer-altered
WHR. For each photograph, two versions of the WHR were created using
morphing techniques – in one picture, the waist was tightened and in
the other it was widened. Using these revised techniques, Henss found
support for Singh’s contention that the WHR is an essential attribute
of the attractiveness of the female figure. Whether line drawings or
morphed photographs are used, females with a low WHR of about 0.7 seem
to be judged as most attractive.
Body weight
But not everyone is in agreement that WHR acts as a first-pass
filter for female attractiveness. Using a new set of line drawings,
Tassinary and Hansen (1998) found the weight of the figure to be a more
potent factor than the WHR. Streeter and McBurney (2003) are also quick
to point out that the WHR effect is only evident when body weight is
controlled; when both WHR and body weight are manipulated, it is
evident that weight accounts for more variance than WHR. Other studies
have shown that participants prefer figures that have a WHR around 0.7,
but as body size increases, larger WHRs tend to be preferred (Forestell
et al., 2004). In addition, when photographs of women with WHR
manipulated either by hip or waist changes are used, attractiveness
seems to be more influenced by changes in waist than hip size
(Rozmus-Wrzesinska & Pawlowski, 2005).
Importantly, Martin Tovée and his colleagues (e.g. Tovée &
Cornelissen, 2001; Tovée et al., 1999) have criticised the assumption
held by WHR researchers that the body weight of figures is held
constant when narrowing the waist. When the figures are modified by
altering the width of the torso around the waist, this not only alters
the WHR, but also apparent body mass index (BMI). As the value of WHR
rises, so does that of apparent BMI, and so it is not possible to say
whether changes in attractiveness ratings are made on the basis of WHR
or BMI, or both. This error is intrinsic to most studies that have used
line drawings.
To investigate the relative importance of BMI and WHR in the perception
of female attractiveness, Tovée and his colleagues (1999) used images
of real women in a standard pose and distance from view. By using
images of real women, both BMI and WHR were known precisely, and their
effects on attractiveness ratings could be estimated separately. A
further advantage of these stimuli was the fact that the heads of the
women were obscured, so that facial attractiveness (and racial cues)
would not be a factor in the observers’ ratings. Regressions of
attractiveness ratings for these images suggest that although both WHR
and BMI are significant predictors of female attractiveness, BMI is a
far more important factor than WHR. BMI in these studies account for
more than 70 per cent of the variance, whereas WHR accounts for little
more than 2 per cent. These results also hold when women are presented
in profile, using computer-generated photographic stimuli and using
three-dimensional images (e.g. Fan et al., 2004).
The finding that BMI may be the primary determinant of female
attractiveness is consistent with the fact that successful female
fashion and glamour models all fall within a narrow BMI range (Tovée et
al., 1997). There are advantages to using BMI as a basis for mate
selection, as BMI is strongly correlated with female health (e.g.
Manson et al., 1995) and reproductive potential (e.g. Lake et al.,
1997).
Perhaps, then, a ‘hierarchy of cues’ is used in partner selection.
Features such as the WHR may be used to discriminate between broad
categories, such as male from female or pregnant from non-pregnant.
Discriminating within the category of potential partners, men may use
such cues as BMI and then other cues such as the proportions of the
body to discriminate between women of very similar BMI. Evolutionary
theory suggests that attractiveness is determined by cues linked with
fecundity and that BMI and WHR are both important. However, there are
other ‘third filter’ cues, such as skin quality.
Attractiveness across cultures
A further problem for WHR research is that cross-cultural
replications have not generally supported the notion that there is a
universal preference for low WHRs. Although preferences for a low WHR
have been found in a number of countries, all these studies were
carried out in industrial societies (Swami & Tovée, 2005). What is
clear from the literature is that cultures differ widely in their
attitudes toward such things as obesity and body shape (Furnham &
Alibhai, 1983).
Recently, Wetsman and Marlowe (1999) elicited preferences from a
hunter-gatherer tribe called the Hadza, in Tanzania, who subsist almost
exclusively from foraging wild foods. They found that the size of the
WHR does not affect judgements of attractiveness. Instead, the Hadza
prefer heavy over medium and medium over lightweight line drawings when
selecting for attractiveness, health and desirability as a wife,
regardless of WHR. Marlowe and Wetsman (2001) recently returned to
Tanzania with a new set of line drawings in which only the WHR was
varied. With no weight variation, Hadza men preferred high WHRs, which
the authors argue is nevertheless an artefact of the preference for
heavier women.
These results are strikingly similar to that of a previous study
conducted among the isolated Matsiengka of southern Peru (Yu &
Shepard, 1998). They tested three groups of the same population,
differing in their degree of contact (and, therefore, their degree of
‘Westernisation’). The least Westernised group, like the Hadza, ranked
figures first by weight (high preferred to low) and then high WHR over
low WHR, once again opposing findings from industrialised societies.
The second, moderately Westernised group differed in that they rated
low WHR females as being more attractive and more desirable as spouses,
but not more healthy. The third and most Westernised group (first
contacted 20 to 30 years previously) did not differ from male
participants in the US. For Wetsman and Marlowe (1999) this conclusion
suggested to them that a first-pass filter would consist of partner
preferences based on body weight. Individuals in environments where
food scarcity is a constant threat might make mate choice decisions
based solely on the weight of a potential partner. The influence of WHR
may only become relevant when food resources are plentiful enough that
the risk of women’s starvation during pregnancy and lactation is
minimal, thereby acting as a second-pass filter.
Explaining cross-cultural differences
Tovée and Cornelissen (2001) have argued that the reported
difference in preferences for WHR across culture may instead be based
on BMI. Combined with the argument that WHR and body weight are
confounded in line drawings, they suggest that the same ideal BMI
should not be expected for all ethnic groups and environments.
Epidemiological evidence suggests that different ethnic populations may
have differing risk for negative health consequences with changing BMI
(e.g. Kopelman, 2000), and so there may be a different optimal BMI for
health and longevity in different racial groups.
As a consequence, there will be a preferred optimal BMI for each group,
which will balance environmental and health factors, but this optimal
BMI may differ between groups and environments. This is reflected in
the observation that in economically poor societies a high BMI is
regarded as attractive whereas the opposite is true in wealthy
societies. Thus, while some cultures attempt to ‘fatten up’ young women
to make them more desirable mates, other attempt ‘radical slimming’ to
achieve the same end.
A series of recent studies sought to test this hypothesis by examining
preferences for female attractiveness in different cross-cultural
settings (e.g. Knight et al., 2004; Swami, Caprario et al., 2006).
Swami and Tovée (in press), for example, examined preferences for
female attractiveness along a socio-economic gradient in Malaysia and
Britain, from rural to semi-urban to urban. Their results show that,
regardless of the cultural setting, BMI is the primary predictor of
physical attractiveness, whereas WHR failed to emerge as a strong
factor. The authors also found that preference for physical
attractiveness varied with socio-economic status, with rural observers
preferring larger figures than semi-urban observers, who in turn
preferred larger figures than urban observers.
To test Tovée and Cornelissen’s (2001) hypothesis that the same ideal
BMI should not be expected for all groups, this study also examined
people of different racial origin from the same environment (Malay,
Chinese and Indian in Kuala Lumpur). Studies have indicated that ethnic
Malays, Chinese and Indians in Southeast Asia have different optimal
BMIs for risk factors for morbidity and mortality (e.g. Deurenberg et
al., 2002), which would suggest that these ethnic groups should have
different preferences for body weight. However, this was not the case:
Malays, Chinese and Indians in Kuala Lumpur all have a similar
preference for slender figures, lending credence to the view that
physical attractiveness may be linked less to ethnicity than to
modernity or socio-economic status. Elsewhere, this group of
researchers have shown that attractiveness preferences can be modified,
as attested by the changing preferences of migrants . For example, in
Swami, Tovée et al. (in press) we reported significant changes in the
attractiveness preferences of South African Zulus who had moved to
Britain, showing that attractiveness preferences are malleable, and can
change with exposure to different environments
A symptom of resource scarcity
The finding that preference for body weight varies according to
socio-economic status is in line with earlier ethnographic reports
(e.g. Brewis & McGarvey, 2000). Until recently, this pattern
linking resource availability (as indicated by socio-economic status)
and female body weight lacked an obvious psychological mechanism.
Nelson and Morrison (2005), however, proposed an explanation based on
the situational influence of environmental conditions, which does not
require the invoking of any evolved mechanism. They argue that the
affective and physiological states associated with the resources
available to an individual provide implicit information about
collective resource availability, and that this information then plays
a role in the construction of preferences.
In a series of imaginative studies, Nelson and Morrison (2005) tested
this hypothesis by manipulating people’s financial satisfaction or
hunger (both these being proxies for personal resources in
industrialised societies) and measuring their preferences for potential
romantic partners. Their studies confirmed that financially
dissatisfied and hungry men preferred a heavier mate than did
financially satisfied men or satiated men respectively. We have since
confirmed the finding by manipulating hunger using photographic
stimuli, with hungrier men preferring larger figures than satiated men
(Swami & Tovée, in press).
These studies provide evidence that temporary affective states can
produce individual variation in mate preferences that mirrors patterns
of cultural differences. In this sense, ratings of attractiveness vary
over time. The mood or state of the rater can subtly but significantly
influence his or her ratings of the physical attractiveness of a
possible mate. This helps explain why preferences for body weight
should vary according to socio-economic status, as individual
preferences depend on situational feelings of resource scarcity. In
rural contexts, where resource scarcity is more likely to be prevalent,
affective and physiological states associated with individual-level
resource availability provide implicit information about collective
resource availability, and this information then plays a role in the
construction of preferences for a heavier body weight. This hypothesis
appears to have firm grounding in the psychological literature:
feelings not only often serve as ‘information’ about the environment,
but can also influence behaviour without the engagement of complex
cognitive processes.
Biology as destiny
Evolutionary theory has proved to be a powerful theoretical tool in
exploring female bodily attractiveness. Slogans like ‘biology is
destiny’ have been used by both supporters and critics of evolutionary
theory, which always attracts both philosophic and socio-political
criticism. Certainly, some aspects of attractiveness seem to be
ingrained in our biology: characteristics associated with evolutionary
advantages (e.g. a low WHR) seem to be perceived as attractive.
The cross-disciplinary research in this area has led to the beginning
of a new science of attractiveness, and has had implications for our
understanding of body image and eating disorders. Through experimental
studies we are beginning to understand how, when and why beauty is not
only in the eye of the beholder, but can also be determined in the
facial and bodily characteristics of human beings.
- Viren Swami and Adrian Furnham
are at the Department Psychology, University College London. E-mail: [email protected] or [email protected].
Next month
Look out for another article by Viren Swami and Adrian Furnham, this time in collaboration with a computer scientist offering a new way of investigating attractiveness and related psychological areas.
Discuss and debate
Is facial attractiveness a separate entity, or does it interact with or influence bodily attractiveness?
BMI and WHR are both static measures of bodily attractiveness. Does body motion affect attractiveness?
What role does behaviour/personality play in physical attractiveness?
Is beauty merely skin deep?
What is driving the contemporary obsession with being thin, especially among young women?
Have your say on these or other issues this article raises. E-mail
Letters on [email protected] or contribute to our forum via
www.thepsychologist.org.uk.
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(Please note that some pictures may have been removed for copyright reasons)
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