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Social Psychology. Attractiveness and evolution Christopher Hand Department of Psychology University of Glasgow July 2006. Darwin and evolution. Charles Robert Darwin (1809-1882)

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social psychology

Social Psychology

Attractiveness and evolution

Christopher Hand

Department of Psychology

University of Glasgow

July 2006

darwin and evolution
Darwin and evolution

Charles Robert Darwin (1809-1882)

1859 – publishes On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life (usually abbreviated to ‘The Origin of Species’)

the biological roots of social behaviour
The biological roots of social behaviour
  • Darwin identified that within each species, there are variations from one individual to the next.
  • Many of these variations are a function of the species’ genetic make-up
    • Inherited by their descendants
the biological roots of social behaviour4
The biological roots of social behaviour
  • However –
    • This inheritance will happen only if the animal actually has descendants!
      • Most organisms do not live long enough to reproduce.
  • The issues of who survives and who reproduces are far from random…
the biological roots of social behaviour5
The biological roots of social behaviour
  • A process of selection, if repeated generation after generation, would produce large changes in a species.
  • Therefore, a survival advantage for a genetically-rooted trait will lead, over the generations, to a change in the entire species.
the biological roots of social behaviour6
The biological roots of social behaviour
  • Not all variations within a species are beneficial in this way.
    • Not all variations lead to a reproductive advantage.
  • Evolution should not be thought of as favouring the “better” or “more advanced” organism…
the biological roots of social behaviour7
The biological roots of social behaviour
  • Instead –
    • Evolution merely favours the organism that is better suited to the environment currently in place.
    • If the the environment changes, then the pattern of selective advantages will change as well.
personal and genetic survival
Personal and genetic survival
  • “Survival of the fittest”
    • Misleading
    • Personal survival matters insofar as that survival leads to reproductive success
    • Pass on genes to next generation
personal and genetic survival9
Personal and genetic survival
  • An animal that outlives its competitors, but leaves no offspring, has not flourished.
  • Thus, what really matters for evolution is not personal survival, but the survival of one’s genes.
    • It is via one’s genes that future generations (and so the evolution of the species) will be shaped.
behaviours rooted in genes
Behaviours rooted in genes
  • Many behaviours are rooted in an animal’s genetic makeup
    • these too are inherited by their offspring.
  • If these behaviours contribute to reproductive success –
    • animals with these behaviours will have more offspring
    • a larger proportion of the next generation will inherit the genes that led to the behaviour in the first place
behaviours rooted in genes13
Behaviours rooted in genes
  • In this fashion, natural selection will lead to an evolution of how animals behave just as it leads to an evolution of the animal’s anatomy
social behaviour and reproduction
Social behaviour and reproduction
  • What behaviours are most likely to be shaped by evolution in this way?
    • Social behaviours
  • Particularly those associated with the process central to evolution
    • Reproduction
advertising for a mate
Advertising for a mate
  • First things first
    • Find a mate!
  • Requires the animal to advertise their availability and their sex
    • So that males are noticed by females and vice versa
  • Many animals have anatomical structures whose function seems to be nothing other than this sexual advertising…
andersson 1982
Andersson (1982)

Male widow birds have long

tailfeathers, up to 20 inches long.

The tails of some males were cut, and

extensions were placed on the tails of


Males whose tails were cosmetically

enhanced had more nests than unaltered

males, who in turn had more nests than

males with shortened tails.

advertising for a mate20
Advertising for a mate
  • In humans, structural displays of sex differences are less pronounced.
    • Jordan is the exception to the rule.
  • According to some theorists, the female breast evolved for signalling purposes
    • As we began to walk erect and lose our reliance on smell, members of our species needed some other ways of displaying their sex.
behavioural advertisements
Behavioural advertisements
  • Many animals advertise both their sex and their readiness to mate via their behaviours.
  • Courtship rituals
    • Sometimes elaborate, involving alternating bouts of approach and withdrawal, coy retreat and seductive flirtation.
  • Why this alternation between ‘yes’ and ‘no’?
behavioural advertisements22
Behavioural advertisements
  • Each animal has reason to approach the other,
  • But, each also has reason to fear the other
    • Is the approach amorous or aggressive?
  • This tension between attraction and threat must be resolved
    • Alternating approaches and withdrawals presumably serve this purpose.
  • Humans are biological creatures
    • Our behaviours perhaps including aspects of courtship might well be shaped by our genes.
  • On the other hand
    • Culture-based learning during our lifetime may play a larger role in determining when, how and whom we mate.
  • There is no question that culture does have an influence.
    • It is cultural change, not ultrarapid evolution that has altered the average age of parenting over the last few decades.
    • It is cultural differences, not biological contrast that made people with facial tattoos attractive among New Zealand Maori but not to many Westerners
  • What commonalities are there among the diverse peoples of the world with regard to mate preferences and courtship patterns?
  • No commonality
    • Powerful argument that human mating is not heavily governed by biology.
  • Commonality
    • Is it this part of our biological heritage?
physical attractiveness
Physical Attractiveness
  • Physical appearance is immensely important in determining a person’s attractiveness
    • Or at least their initial attractiveness.
  • US demand for cosmetic and toiletry chemicals is forecast to rise 5.4 percent per year to $7.6 billion in 2010
  • At least £255 million spent in UK in 2005 on cosmetic surgery procedures
walster aronson abrahams rottman 1966
Walster, Aronson, Abrahams, & Rottman (1966)
  • College freshmen were randomly paired at a dance and later how much they liked their partner and whether he or she was someone they

might want to date.

  • The main determinant of

each person’s desirability as

a future date was their

physical attractiveness.

green buchanan heuer 1984
Green, Buchanan, & Heuer (1984)
  • Studied clients of a video-dating service who selected partners based on files that included a photograph, background information, and details about interests, hobbies and personal


  • When it came down to actual

choice, the primary determinant was

the photograph.

physical attractiveness30
Physical Attractiveness
  • Physically attractive individuals also benefit from the common belief that what is beautiful is good.
  • People tend to associate physical attractiveness with a variety of positive personality traits
    • Dominance
    • Good social skills
    • Intelligence
    • Happiness
    • Good mental health
      • Dion, Bersheid, & Walster, 1972
physical attractiveness31
Physical Attractiveness
  • Attractive people are:
  • Judged as less maladjusted or disturbed (Cash et al., 1977; Dion, 1972)
  • Judged as more likely to be hired after a job interview (Dipboye et al., 1977)
  • Rated as happier, more successful, having a better personality and more likely to get married (Dion et al., 1972)
  • Given an easier time by jurors, if the defendant was female (Sigall & Ostrove, 1975)
  • Evaluated more highly on their written work, if they were female students (Landy & Sigall, 1974)
physical attractiveness32
Physical Attractiveness
  • People often assume that individuals who are more attractive will also be more intelligent than average.
  • In truth, there is no correlation between attractiveness and intelligence
    • Eagly, Ashmore, Makhijani, & Longo, 1991; Feingold, 1992; Jackson, Hunter, & Hodge, 1995.
matching for attractiveness
Matching for attractiveness
  • Physical attractiveness is clearly desireable
    • But if we set our sights on only the most desireable, the world would soon be depopulated
      • There aren’t enough supermodels to go around : (
  • We seek partners who are roughly the same level of attractiveness that we are
    • This will ensure that we reach as high as we can, while simultaneously minimising the chance of rejection.
matching for attractiveness34
Matching for attractiveness
  • Much evidence favours this matching hypothesis
    • There will be a strong correlation between the physical attractiveness of the two partners
      • Berscheid, Dion, Walster, & Walster, 1971
  • Everyday observations confirm this hypothesis
    • “They make such a good couple” etc
  • As do many empirical studies
    • Berscheid & Walster, 1974; Feingold, 1988; White, 1980.
what is physically attractive
What is physically attractive?
  • To some extent, this is a matter of personal taste
    • “Beauty is in the eye of the beholder”
  • However, there is more agreement about attractiveness than this bit of common wisdom would suggest.
what is physically attractive37
What is physically attractive?
  • People of different cultures, by and large, seem to agree about which faces are attractive, as do people of different generations
    • Cunningham, Roberts, Barbee, Druen, & Wu, 1998.
  • Evidence also indicates that infants prefer to look at faces that adults consider attractive, suggesting that the allure of faces is not learned
    • Langlois et al., 1987.
what is physically attractive38
What is physically attractive?
  • Across ages, generations and cultures, attractive people are almost always those with:
    • Clear skin
    • Shiny hair
    • No visible deformities
what is physically attractive39
What is physically attractive?
  • Faces that are symmetrical are usually considered more attractive than those that are not.
  • Generally, “average faces” (those of average width, eye size, and so on) are more attractive than faces that deviate from average
    • Grammer & Thornhill, 1994; Fink & Penton-Voak, 2002; Mealey et al., 1999; Rhodes et al., 1998; Rhodes et al., 1999; Thornhill & Gagestad, 1999.
what is physically attractive40
What is physically attractive?
  • However, some departures from average increase attractiveness
    • These seem to be the ones that exaggerate important features found in the average face.
    • The average female has big eyes, full lips, and a small chin
    • A female face will be more attractive if it has slightly larger than average eyes, fuller than average lips, and so on…
what is physically attractive42
What is physically attractive?
  • The average male face has a strong chin, a large jaw, and prominent brows.
  • Therefore, a male face will be more attractive if these features are slightly exaggerated.
what is physically attractive45
What is physically attractive?
  • As with faces, symmetry and being near average contribute to the attractiveness of someone’s body.
  • This is probably why individuals who are symmetrical in the size of their hands and feet begin to have sex at an earlier age and have more sexual partners in their lifetime
    • Thornhill & Gangestad, 1994.
what is physically attractive46
What is physically attractive?
  • Body size
    • Seems to be an area where preferences vary between cultures and time periods.
    • Even so, there may be consistency in preferred proportions.
  • Waist-to-hip ratio
    • Waist circumference divided by hip circumference.
what is physically attractive47
What is physically attractive?
  • Numerous studies indicate that women are perceived to be more attractive if their ratio is approximately 7:10.
    • Therefore, if a culture favours slender women, someone with a 241/2 inch waist and 35 inch hips will be considered attractive.
    • If a culture favours larger women, then someone with a 32 inch waist and 46 inch hips might be ideal.
    • In both cases, the 7:10 ratio is preserved
      • Furnham et al., 1997; Henss, 2000; Singh, 1993; Singh & Luis, 1995.
the biological basis for attractiveness
The biological basis for attractiveness
  • Why symmetrical faces and a certain hip-to-waist ratio?
    • Evolutionary explanation is that the 7:10 waist-to-hip ratio indicates mature pelvis and adequate supply of fat
      • Readiness for pregnancy, signals fertile partner
    • Relatively low ratio indicates higher oestrogen levels = better overall health and greater fertility
      • Singh 1993; 1994.
  • Any male with a preference for this shape maximises his chances for reproductive success
    • Natural selection favours individuals with this preference.
the biological basis for attractiveness51
The biological basis for attractiveness
  • The preference for symmetrical faces may too have evolutionary roots.
    • A number of health problems will lead to asymmetrical faces
      • Proximity to the average indicates absence of these problems
      • Attraction to these features would be more likely to result in healthy offspring (Thornhill & Gangestad, 1999)
  • Natural selection favours an organism that finds average and symmetrical faces attractive
the biological basis for attractiveness52
The biological basis for attractiveness
  • Scepticism about evolutionary claims
    • Is facial attractiveness an indicator of health?
      • Kalick, Zebrowitz, Langlois, & Johnson, 1998
    • If not, we must rethink the evolutionary argument just offered.
    • It is possible that our preference for average and symmetrical faces derives from another source
      • A general preference for balance
      • We prefer average watches and birds over peculiar ones
      • Halberstadt & Rhodes, 2000
  • More data is required…
  • “What does she see in him?”
  • A number of surprisingly simple factors play a large role in making someone attractive.
  • One of the most important of these is sheer proximity.
  • 1949 - Columbus, Ohio
    • Of all couples who took out marriage licenses, more than half lived within 16 blocks of one another when they first started dating
      • Clarke, 1952
  • Proximity also predicts who will stay engaged and get married
    • The farther apart the two live, the greater the chance the engagement will be broken
      • Berscheid & Walster, 1978
  • The results of proximity are not always positive
    • Study of a condo complex showed that people who lived there developed most of their friendships with others who lived there.
    • However, the people they disliked also lived there
      • Ebbesen, & Kjos, & Kohecni, 1976.
  • Proximity allows familiarity to develop
    • People tend to like what is familiar
      • Brickman & D’Amata, 1975; Moreland & Zajonc, 1982; Zajonc, 1968
    • People shown photographs of strangers’ faces judged the strangers to be more likeable the more often they saw them
      • Jorgensen & Cervone, 1978
  • Comparison of faces and mirror images
    • If familiarity is what is critical, our frineds should prefer an unaltered view of our face to its mirror image, whereas we ourselves should prefer the mirror image
    • Experimental data confirm this to be the case
      • Mita, Dermer, & Knight, 1977.
  • Do “birds of a feather flock together” or do “opposites attract”?
  • People tend to be attracted to others who are like themselves on attributes such as
    • Race
    • Ethnic origin
    • Social and educational level
    • Family background
    • Income
    • Religion
    • Behavioural patterns, such as drinking habits
burgess wallin 1943
Burgess & Wallin, 1943
  • Widely cited study showing that engaged US couples tended to be similar along all of these dimensions.
  • These findings provide strong evidence for homogamy
    • A powerful tendency for like to choose like.
  • Has been shown to influence a couple’s stability
    • Couples who remained together after 21/2 years were more similar to those that had broken up.
      • Hill, Rubin, & Peplau, 1976
  • Married couples tend to be similar on nearly all personality dimensions
      • Caspi & Herbener, 1990
what produces homogamy
What produces homogamy?
  • One possibility is that similarity really does lead to liking.
  • Another is that similarity is a by-product of proximity
    • We don’t really meet, interact become attracted to, and marry someone hugely dissimilar from ourselves
      • Berscheid & Walster, 1978

Only in Hollywood movies is homogamy violated

who chooses whom
Who chooses whom?
  • In most animal species, the two sexes play very different roles in seeking and selecting a partner.
  • Usually the female makes the final decision of whether to mate or not.
    • The reason for this is simple
    • The female shoulders the major cost of reproduction
who chooses whom65
Who chooses whom?
  • In birds
    • The female supplies the ovum as well as the food supply for the developing embryo.
  • In mammals
    • The female carries the embryo within her body and later provides it with milk.
  • Either case
    • Her biological burden is vastly greater than the male’s.
who chooses whom66
Who chooses whom?
  • This burden can be measured in many ways, including the sheer amount of time that each sex must invest in its offspring
interesting exceptions
Interesting exceptions
  • Seahorses

males exhibit greater

sexual discrimination

  • Phalaropes

greater sexual choosiness

human mate choice
Human mate choice
  • In humans, both males and females are selective in choosing their sexual partners
    • Mating only happens when both partners consent
  • However, the two sexes differ in the criteria they use in making their choices…
human mate choice69
Human mate choice
  • According to studies:
  • Physical attractiveness of partner seems more attractive to men than to women
  • Men generally prefer younger women
  • Women prefer older men
  • Social and financial status of partner matters more to women than to men
human mate choice71
Human mate choice
  • Male-female differences are not unique to our society
    • China, India, France, Nigeria and Iran
      • Buss, 1989, 1992; Buss & Barnes, 1986
  • Interestingly, both sexes agree on one point
    • Both men and women value intelligence and kindness in their prospective mates
      • Buss, 1992
practical exercise
Practical Exercise
  • Read through these selections of adverts from the Financial Times (15/07/06) magazine
  • Look for differences between “Men seeking women” and “Women seeking men” on whether they
      • State their age / State the age (or range of ages) of their preferred partner
      • Advertise their physical features
      • Height, signs of youthfulness, facial features
      • Advertise their height / desired height of partner
      • Advertise their social / professional status / desired status of partner
human mate choice73
Human Mate Choice
  • According to Buss
    • The best explanation for these preferences is evolutionary
    • If our male ancestors preferred attractive women, this would have increased their reproductive success, as attractive women are likely to be healthy and thus likely to be fertile.
    • Natural selection would favour males with this preference, and this preference would thus become widespread among the males of our species
human mate choice74
Human Mate Choice
  • Likewise for a woman’s age
    • The younger she is, the more reproductive years she is likely to have ahead of her
    • Therefore, a male selecting a younger partner could plausibly look forward to more offspring.
    • Again, this would increase the male’s reproductive success, be favoured by natural selection, and so become common for the species
human mate choice75
Human Mate Choice
  • Female’s preferences easy to understand from this perspective
    • High investment in each child means it is better to have just a few and do all she can to ensure survival of each
    • A wealthy, high-status male would help her achieve this goal
      • Able to provide food and other resources needed
  • Reproductive advantage associated with such a preference
    • gradual evolution toward all females in the species having this preference
human mate choice76
Human Mate Choice
  • Other explanations
    • Possible that human females prefer wealthy, high-status males because of learning across their lifetimes the advantages they gain from such a mate
      • In many cultures, women’s professional and educational opportunities are limited, and so “marrying wealth” is their best resource-gathering strategy
human mate choice77
Human Mate Choice
  • Some evidence consistent with the cultural account
    • Women seem less concerned with their potential mate’s status if they live in a culture that provides more opportunities for women
      • A potential husband’s resources become less important in mate selection
      • (Kasser & Sharma, 1999; Eagly & Wood, 1999)
mating systems
Mating Systems
  • Polygamy
    • Several members of one sex mating with one individual of another.
    • Polygyny
      • Several females mating with one male
    • Polyandry
      • Several males mating with one female
  • Monogamy
    • Reproductive partnership based on a more or less permanent tie between one male and one female
mating systems79
Mating Systems
  • Mammals vs. Birds
    • 90% of all birds are monogamous
      • Through a breeding season
    • In contrast, more than 90% of all mammals are polygynous
  • Evolutionary economics
    • What can an organism do to maximise its reproductive success?
mating systems80
Mating Systems
  • In many bird species, successful incubation requires both parents
    • One to sit on the eggs, one to forage for food.
    • After hatching, finding food may still require the efforts of both birds
    • Monogamy makes reproductive sense for both the male and female
      • Each needs its partner’s help, otherwise no chicks, and therefore no genes, survive
mating systems81
Mating Systems
  • Situation is different for mammals
    • No issue of tending the nest
    • After birth, only the mother can secrete milk to the young
    • Mother can still forage for food during gestation
    • The young can often survive under the mother’s care alone, and the male’s genes will be carried into the next generation nonetheless
mating systems82
Mating Systems
  • How should a male behave?
    • In evolutionary terms, a successful organism is one that perpetuates its genes through successive generations
    • The most successful organism therefore is the one that has the greatest number of thriving and fertile offspring
mating systems83
Mating Systems
  • If the young can survive without his care
    • The male maximises his reproductive success by mating with as many females as possible.
  • End result
    • Polygyny, with each male looking to mate with a number of females.
mating systems84
Mating Systems
  • Anatomical consequences
    • Polygynous males must be physically distinctive
      • To attract a female
      • To win in competition with other males
  • Polygyny is almost always accompanied by sexual dimorphism
    • Pronounced differences is the size or bodily structures of the two sexes
mating systems85
Mating Systems
  • The more polygynous the species, the more dimorphic it tends to be.
mating systems86
Mating systems
  • In polyandrous species, females are larger, more aggressive etc…
mating systems87
Mating Systems
  • In monogamous species, there is no such dimorphism
human mating systems
Human Mating Systems
  • Are humans biologically inclined towards monogamous relationships?
    • Humans are moderately dimorphic
      • On average the human male is about 10% larger and 5 inches taller than the female.
      • Suggests a tendency towards polygyny.
human mating systems89
Human Mating Systems
  • Most traditional cultures do allow polygyny
    • Only 16% of those studied require monogamous marital arrangements
      • Ford & Beach (1951).
  • Most modern societies frown on polygamy
    • Nonetheless, some evidence suggests that men desire a greater number of sexual partners than women do
      • Symons, 1979
human mating systems90
Human Mating Systems
  • Evolutionary theorists believe that these differences between the sexes are ultimately rooted in our biological nature
    • Men wanted greater sexual variety because for them it is reproductively adaptive.
    • Their investment in each child (in terms of time or resources) is small
      • They can afford to have many children
      • More children = more genes in next generation
      • More women they mate with = more children likely to be fathered
human mating systems91
Human Mating Systems
  • Women need to evaluate sexual partners more cautiously
    • More interested in stable familial relationship
    • Women cannot afford (biologically) to have child after child after child
    • Huge stake in finding the best possible father for their young
      • One who’ll provide resources and support
human mating systems92
Human Mating Systems
  • Again, controversy over evolutionary account
    • Sexual attitudes reflect cultural values rather than biological preprogramming
      • Male’s attitudes shaped by social conditions in which boys are taught that sexual conquests prove their “manliness”
      • Girls are taught to value home, family and a single dependable partner
human mating systems93
Human Mating Systems
  • The data surrounding the evolutionary explanation are also controversial
    • Pedersen et al, 2002
      • Men desired 7.7 sexual partners over the next 30 years; women desired 2.8 over the same time period.
      • However, on other measures, men and women were highly alike.
      • Almost half the men indicated their ideal number of partners was 1; and 98.9% of men indicated that they hoped to settle down with one mutually exclusive sexual partner at some time in their life, ideally the next 5 years.
      • 99.2% of women expressed the same wish.
human mating systems94
Human Mating Systems
  • Overall
    • We can find a difference between men and women in the direction predicted by an evolutionary account
  • However,
    • Other results run contrary to evolutionary predictions
      • Cultural values and expectations play at least as strong a role as biology
essay question
Essay Question
  • Discuss evidence for evolutionary causes of attractiveness judgements.
  • Sources of information
    • Gleitman, H., Fridlund, A.J., & Reisberg, D. (2004). Psychology (6th Ed.) Chapter 11.
    • Hogg, M.A., & Vaughan, G.M. (2002). Social Psychology (3rd Ed.) Chapter 13.
    • Web of Knowledge / Web of Science
    • ScienceDirect -
contact details
Contact Details
  • E-mail
  • Website