PY2 Core Studies: 9 – Buss (1989)
Study 9 - Buss (1989)
Sex differences in human mate preferences (pg 116-121)
Field of psychology: Individual Differences
1. CONTEXT AND AIMS
Context

You have to pick one of the following to marry.
Who do you pick? Why?
Recapping the Evolutionary Approach
The last study we looked at was Bennett-Levy and
Marteau, where we explained the development of animal
phobias as being an adaptation that our ancestors evolved
as a way of surviving long enough to reproduce. This core
study is also based on the assumption that human behaviour
has evolved and that behaviour shown by modern humans
would have given our ancestors an advantage in the “survive
and reproduce” stakes. However, whereas Bennett-Levy
and Marteau investigated how humans react to other
animals, Buss is more interested in how humans react to
other humans. Specifically, we are looking at sexual
selection or mate selection; how do humans decide who to
breed with?
If we assume that human behaviour evolved, we should
be able to predict what behaviour would lead to more
successful reproduction. For example, the behaviour “avoid
the opposite sex” would prevent that organism from
reproducing. Therefore that characteristic would soon
become extinct as it would not be passed on. However, the
characteristic “have sex with as many members of the
opposite sex as you possibly can” would lead to increased
reproduction, meaning that characteristic or gene would be
passed on to the offspring, who would pass it to their
offspring and so on. However, as we will see, this is a very
simplistic view, and human mate selection is much more
complex than this! Successful reproduction is not just about
quantity, but quality. It would be little use to have 20 children
who all died before they could reproduce themselves. Also,
men and women have different agendas for reproduction,
leading to an evolutionary “battle of the sexes”! Hence the
title of this study Sex differences in human mate
selection.
If we accept that human behaviour has evolved, characteristics, behaviour or genes that increase the
success of reproduction should appear more often in the general population. Thornhill & Thornhill (1983)
propose that individuals lacking preferred characteristics will not be selected to mate and therefore will not
be able to become people’s ancestors. This is why current mate preference is of interest to evolutionary
psychologists because they reflect prior selection pressures, thus allowing us to learn about humans’ past
reproductive history. They also demonstrate the current direction of sexual selection by showing us who is
likely to be selected as a mate.
Despite the importance of mate preferences, little is known about which characteristics are valued by
human males and females. There are three possible arguments that predict particular sex differences in
mate preferences.
1. Prediction based on parental investment and sexual selection
theory (Trivers, 1972): This theory states that sexual selection is
driven in part by the different levels of investment males and females
make in their offspring. Biologically, in mammals, male investment is
minimal, whereas the female investment is much greater. The female
has to carry the child, and also has to produce milk to feed the child,
as well as generally care for and look after it, all of which require a
great deal of the female’s biological resources as well as physical
resources and time.
1
PY2 Core Studies: 9 – Buss (1989)
Prediction: If we follow this through, we would predict that women are likely to be
choosier when selecting a mate. In particular, they may choose a partner who can offer
resources (food, territory, and protection). This will enhance the female’s reproductive
success, as any child she bears will have a greater chance of survival (and
consequently, passing these genes on). In modern times, this need for resources might
not necessarily be food and shelter, but might be translated into money and status, and
men with ambition and industriousness.
2. Prediction based on reproductive value (Symons, 1979) and fertility
(Williams 1975): Fertility refers to the probability of reproducing now (short
term), whereas reproductive value is the probability of reproducing in the
future (long term). A 10 year old girl would have high reproductive value, but
low fertility, whereas a 25 year old woman may have high fertility, but a
lower reproductive value. Youthfulness would be an indicator of both
reproductive value and fertility. This could be signalled by physical
characteristics such as smooth skin, good muscle tone, full lips and healthy
hair, or by behaviour such as high energy levels or a sprightly gait (Symons
1979). Males who select females with youthful characteristics will therefore
father more offspring than men who chose females without.
Prediction: As female fertility is closely related to age, we would predict that men would show a preference
for younger, physically attractive women, or women who showed signs of youthfulness. As men are fertile
their whole life, and so their fertility is less closely related to age, this preference for youth and physical
attractiveness should be much more pronounced in men than in women.
3. Prediction based on paternity probability (Daly et al, 1982): In humans, while the bulk of
parental investment is shouldered by females, males do contribute, and so they want to ensure that
any time and effort invested is directed towards their own offspring rather than those of another
male. Paternity probability refers to the probability that the offspring that a male is investing in is
actually his own. Sexual jealousy is a means of increasing paternity probability as it “guards” their
mate and dissuades male competitors. Daly goes as far as to state that in humans many murders
and much violence stem from male sexual jealousy. Another means would be a preference for
chastity in a mate. Males who desire females who have no other lovers would raise his paternity
probability.
Prediction: males should show a preference for women who are chaste, and should
also show greater sexual jealousy than women. Because women can be certain that
any child they produce is theirs, they should have less need for chastity in males.
However, it is possible that male sexual experience may signal that the male has to
share resources between a number or females and/or children. Therefore, chastity
might be important for females.
Aims
Buss aimed to investigate if evolutionary explanations for sex differences in human mate preferences are
found in cultures with varying ecologies, locations, ethnic compositions, religious orientations and political
inclinations. Cross-cultural studies provide an opportunity for testing evolution-based hypotheses
because we would expect behaviours that are innate to be the same in all cultures.
Buss predicted that regardless of culture women would prefer
______________________________________
_____________________________________________________________________________________
________________ while men would prefer
____________________________________________________________________________
_____________________________________________________________________________________
________________
2
PY2 Core Studies: 9 – Buss (1989)
2. PROCEDURES (pg117)
Who were the participants?

Buss used 37 samples from 33 different countries, located on six
continents and five islands, creating a total number of participants
of _____________. The samples varied in size from 55 in
____________ to 1670 in ___________. Apart from
_____________ all samples were greater than 100.

The average sample size was 272 participants

_______________ were male, ________________ were female

The average age of participants was __________________
Research method used?
Questionnaire (cross cultural comparison)
Variables
IV: sex of participants, DV: factors effecting mate preference

Complete the table below to show how the sampling techniques varied widely across countries:
Sampling method:
In Estonia one sub sample consisted of couples applying
for a marriage licence
In Venezuela the sample consisted of every fifth household
in a series of neighbourhoods that varied in socioeconomic
class
In South Africa the Zulu sample consisted of a rural
population some of which had the questions read aloud to
them
In West Germany the sample was selected through
newspaper ads
In New Zealand the sample consisted of high school
students taken from three schools

The data was collected in most cases by native residents of each country and mailed to the USA for
analysis. The research collaborators were unaware of the aims of the study.
The Questionnaire
Buss used two methods to assess the participants’ views on mating preferences
Instrument 1: Rating
 Part 1 Biographical data: this was information about the participant themselves e.g. age, sex,
religion, marital status, number of brothers and sisters.

Part 2 Mate preferences: the questions were
general questions regarding choosing a mate e.g.
questions about the age at which they would prefer
to get married, what age difference (if any) would
they prefer between themselves and their spouse,
how many children they desired etc.

Part 3 Rating Scale: these questions aimed to
investigate what characteristics a participant looked
for in a mate (see right). Participants had to rate 18
characteristics on a four point scale from 3
(indispensable) to 0 (unimportant). Mixed in with
these 18 were the four target variables: good
financial prospects, good looks, chastity (no
previous sexual intercourse) and ambition and
industriousness.
3
2
1
0
Good cook and housekeeper
Pleasing disposition
Sociability
Similar education background
Refinement, neatness
Good financial prospects
Chastity
Dependable character
Emotional stability/maturity
Desire for home and children
Favourable social status
Good looks
Similar religious background
Ambition and industriousness
Similar political background
Mutual attraction – Love
Good health
Education and intelligence
3
PY2 Core Studies: 9 – Buss (1989)
Instrument 2: Ranking
Participants were asked to place 13 characteristics in rank order based on their
desirability in someone they may want to marry. Rank 1 was given to the most
desirable characteristic, rank 2 to the second most important and so on down to rank
13. Among these 13 characteristics were the two target variables: good earning
capacity and physical attractiveness. Other variables included being religious,
being kind and understanding, and having an exciting personality.
Translations
Research collaborators had the task of employing three bilingual speakers: one translated the
questionnaire from English into their native language, the second translated the answers back into English,
and the third resolved any discrepancies. The translators were instructed to make sure all the terms were
neutral rather than using words that might be linked to a specific sex. For example
‘physically attractive’ is neutral, whereas ‘handsome’ and ‘beautiful’ are sex-linked.
Occasionally, questionnaires needed to be amended to reflect the cultural
differences. In Sweden, many couples do not get married, but just live together, so
the questions had to be modified to reflect this cultural difference. In Nigeria, men
often have more than one wife (polygyny), and so the questions had to be altered
to reflect the possibility of multiple wives.
3. FINDINGS AND CONCLUSIONS (pg118-119)
Findings
Significance recap: some of the results below talk about ‘statistical significance’. If a result is statistically
significant, it means that there is a less than 5% probability that the results came about by chance. If a
finding is reported, but is not statistically significant, it means that the probability of the results having come
about by chance are more than 5%. In psychology, we do not draw conclusions from such results.
Good financial prospects
In 36 of the 37 samples (97%) females valued ‘good financial prospects’ in a mate
more highly than did males. The sole exception was Spain, where there was a
difference in the predicted direction, but it was not significant.
There was considerable variation in how much this mate characteristic was valued.
In general, Western European samples valued earning capacity less than South
American, North American, Asian and African samples, although there were
variations among samples within countries.
Ambition and Industriousness
In 34 of the 37 samples (92%), females expressed a higher valuation for ambition and industriousness in a
mate than males did. In 29 samples (78%), this difference was statistically significant providing more
support for the theory of sex differences.
In three samples, (Columbia, Spain and South African Zulus) the opposite sex difference was found - males
rated ambition and industriousness more highly than females did, although it was only significant in the
South African Zulu sample. The research collaborator for the Zulu sample suggested that this may be
because physical tasks, such as building the house are considered
to be woman’s work. Males in this culture usually commute from
rural to urban centres to work.
Both sexes in the Nigerian, Zulu, Chinese, Taiwanese, Estonian,
Palestinian, Columbian and Venezuelan samples placed a high
value on this mate characteristic. This characteristic was not rated
low in any sample, although samples in The Netherland and Great
Britain, West Germany and Finland expressed the least amount of
preference for it.
Age Difference
4
PY2 Core Studies: 9 – Buss (1989)
In all 37 samples, males preferred mates who were younger. The mean age
difference preferred by males was 2.66 years younger, and the mean age at which
men prefer to marry is 27.49 years. This therefore suggests an ideal age for females
of 24.83 years, which is closer to the peak female fertility rather than the peak
female reproductive value.
Across all countries, females preferred mates who were older. The
mean desirable age difference was 3.42 years older, and the mean age
that females prefer to marry is 25.39. Therefore ideal mate age is 28.81
years.
In cultures where polygyny was substantial, male preference for being
older was at its largest: 6.45 (Nigeria) and 7.38 (Zambia). This could be
because males tend to be older when they acquire wives in polygynous
systems compared with monogamous (one partner) mating systems.
Good Looks
All of the 37 samples showed that males rated ‘good looks’ in their mate more important than
females did. This differences was statistically significant in 34 (92%) of the samples. Good looks
were particularly important to males in the Bulgarian, Palestinian, Nigerian and Zambian populations.
Chastity
Samples varied tremendously in the value placed on chastity. In 23 (62%) of the samples, males
preferred chastity in their mates, whereas there was no significance in the remaining 14 samples. Samples
from China, India, Indonesia, Iran, Taiwan and Israel (Palestine) attached a high value to chastity in a
potential mate. Chastity was viewed as irrelevant or unimportant in most of the Western European samples.
Conclusions
Five evolution-based predictions received support from the data.
1. Females valued the financial capacity of potential mates more than males did. This supports the
hypothesis that women seek cues related to resources (supporting __________________ from the
aims and context)
2. Females valued ambition and industriousness more than males did, again, supporting the hypothesis
that women seek cues related to resources (again supporting __________________ from the aims
and context)
3. Males value physical attractiveness and relative youth more than females did, supporting the
hypothesis that males seek cues related to high reproductive capacity (supporting
5
PY2 Core Studies: 9 – Buss (1989)
____________________ from the aims and context). The fact that males sought partners around the
age of 25 suggest that they look for cues related to fertility rather that reproductive value. However,
the ideal age preference was actually a few years beyond the peak female fertility, suggesting that
non evolutionary factors may also be involved, such as compatibility and maturity.
4. Females preferred somewhat older mates. This was not specifically predicted at the outset, but
supports the importance of resources because older men would be likely to have greater resources
(supporting __________________ from the aims and context).
5. Males valued chastity more than females did, supporting the importance of paternity probability
(supporting __________________ from the aims and context) although only modestly as large
numbers of samples showed no difference. These less impressive results could be that chastity
(unlike physical attractiveness and age) is not directly observable.

How do Buss’s findings support the general notion of mating behaviour being innate?

Buss also concluded that mating behaviour differs by gender, and that
these differences reflect the differences in the reproductive capacities of
males and females.

Buss also concluded that, unlike other animals, human mate preference
is not simply about female choosiness. Human males and females both
express preferences and there are evolutionary reasons for doing so.

However, while he showed the importance of evolutionary explanations
for mating behaviour, Buss also highlighted that there are cultural
influences as well. This is demonstrated by the large differences in
preferences for chastity between cultures.
4. EVALUATING THE METHODOLOGY (pg 120)
Method:
 Buss used a questionnaire to gain his data. What are the strengths and weaknesses of using a
questionnaire in this study? (use your notes on questionnaires)
 Are there any issues with the questionnaire itself? What types of questions were used, and could
these present problems?
Reliability:
 Could this study be replicated?
 The participants were only given the questionnaire once. How could this affect reliability?
 Buss used two different measures/instruments with the participants. How does this improve
reliability?
Validity:
 Efforts were made to ensure that all participants fully understood the questions asked. The questions
were translated into local languages, the questionnaire was read out to those who could not read, and
questions were tailored to match local customs. To what extent do you think the answers provided
accurately reflected the true thoughts and feelings of the participants?
 Could the fact that some participants received slightly different versions of the questionnaire, or had it
read to them instead of reading it themselves affect the validity of the results?
 Could the results have been affected by a social desirability bias?
 Can we be certain that the responses that the participants gave actually reflect their real mate
choice?
6
PY2 Core Studies: 9 – Buss (1989)

Although the questionnaire was translated and adapted for various cultures, it was still made by a
Western scientist, who would have his own preconceived notions about relationships. Could this
affect the validity of the questionnaire? Might there be things missing from the questionnaire that would
not apply to Western relationships, but might in other parts of the world?
Sampling:
 Buss’s sample size was 10,047. What is the advantage of this?
 The mean age of all participants was 23.49 for males and 22.52 for females. Could this have affected
the results? Would the results have been different with different age groups? Considering that he was
interested in mate selection would it have been appropriate to use other ages?
 The sampling methods varied drastically from one culture to another. Could this act as an extraneous
variable?
 Buss acknowledged that many of the samples were unrepresentative of the target population, in
particular rural and less educated people were less represented. How could this affect the results?
 Buss aimed to have samples of as many different types of people as possible. However, over 77% of
the participants were from westernised industrialised nations. How might this affect the validity?
Ethical issues:
 Can you see any ethical issues in Buss’s research?
5. CRITICALLY ASSESS WITH REFERENCE TO ALTERNATIVE EVIDENCE
Buss found that physical attractiveness was rated as important by the vast majority of males. However, his
research is limited in its explanation of what particular factors are considered to be attractive. We would
assume that if mate selection has been shaped by evolution, then all people should agree on what is
attractive. If each culture had a different idea of what defines physical attractiveness, it would be unlikely to
be due to evolution.
Cunningham et al (1995) found very close agreement across cultural groups
when rating female physical attractiveness. In this study, recently arrived
native Asians and Hispanic students and white Americans rated the
attractiveness of Asian, Hispanic, black and white women in photographs. The
mean correlation between groups in attractiveness ratings was +0.93.
Evolutionary explanations would also predict
that the traits that are seen as physically attractive give cues about health
and fertility. Singh (1993) found that waist to hip ration (WHR) was related to
physical attractiveness across many cultures. Men prefer women who have a
low WHR (the ideal being around 0.7). A woman with this WHR is likely to
have a large bottom, indicting good fat reserves for pregnancy, and a narrow
waist, indicating that she is not pregnant. Thus the reason that a low WHR
would be attractive is that it is a sign of youthfulness and fertility.
It has been proposed that facial symmetry is a sign of genetic
strength, as a number of genetic disorders cause asymmetrical faces.
Therefore, we should find symmetrical faces more attractive as it
would lead to more successful reproduction. Little et al (2007)
examined preferences for symmetry in both the UK and the Hadza, a
primitive hunter gatherer society in Tanzania. Both groups preferred
symmetrical faces, and this was the strongest in the Hadza.
What did Schmitt (2003) find? What does this suggest about Buss’s study?
7
PY2 Core Studies: 9 – Buss (1989)
One potential issue with Buss’s research is the extent to which people’s stated preferences actually reflect
their real mating decisions; how can we be sure that his results were not just a product of social desirability
bias? Lonely hearts adverts are an easy to access source of quantifiable data on human mate choice. Such
ads let us see what specific traits men and women seek in a mate.
Waynforth and Dunbar (1995) performed a content analysis on 900 ads from four American newspapers.
The ads were sorted into 10 year age groups (20-29, 30-39, etc) and scored the frequency with which they
mentioned certain key terms related to the following categories; physical attractiveness,
wealth/status/family commitment, sexual fidelity, tolerance of children, and age requirements. They found
the following differences in the ads posted by men and women:




More men than women sought a youthful mate
More men sought a physically attractive mate
More women used physically attractive terms to describe
themselves
More men reported their economic status/earning power when
describing themselves.
An issue with Buss is that he focused exclusively on heterosexual relationships. This
means that his results may not be applicable to gay and lesbian relationships. In a later
study Dunbar (1995) looked at gay personal ads, and found that heterosexual women
were three times more likely to seek resources and status then lesbians, and gay men
offered resources about half as often as heterosexual men. This supports the
evolutionary explanation because we would not expect lesbian and gay mate choice to
be related to reproductive criteria.
Dunbar also notes that times have changed, and that many women have their own
economic security, and are less interested in a partner’s resources. They therefore seek
a caring and sharing partner rather than one with resources. This still makes
evolutionary sense because that kind of partner should still enhance reproductive
success.
Use three colours to highlight research that supports, contradicts, or develops Buss’s research.
8