Presentation on theme: "Social Psychology Attractiveness and evolution Christopher Hand"— Presentation transcript:
1 Social Psychology Attractiveness and evolution Christopher Hand Department of PsychologyUniversity of GlasgowJuly 2006
2 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’)
3 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-upInherited by their descendants
4 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…
5 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.
6 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…
7 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.
8 Personal and genetic survival “Survival of the fittest”MisleadingPersonal survival matters insofar as that survival leads to reproductive successPass on genes to next generation
9 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.
12 Behaviours rooted in genes Many behaviours are rooted in an animal’s genetic makeupthese too are inherited by their offspring.If these behaviours contribute to reproductive success –animals with these behaviours will have more offspringa larger proportion of the next generation will inherit the genes that led to the behaviour in the first place
13 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
14 Social behaviour and reproduction What behaviours are most likely to be shaped by evolution in this way?Social behavioursParticularly those associated with the process central to evolutionReproduction
15 Advertising for a mate First things first Find a mate!Requires the animal to advertise their availability and their sexSo that males are noticed by females and vice versaMany animals have anatomical structures whose function seems to be nothing other than this sexual advertising…
19 Andersson (1982) Male widow birds have long tailfeathers, up to 20 inches long.The tails of some males were cut, andextensions were placed on the tails ofothers.Males whose tails were cosmeticallyenhanced had more nests than unalteredmales, who in turn had more nests thanmales with shortened tails.
20 Advertising for a mateIn 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 purposesAs we began to walk erect and lose our reliance on smell, members of our species needed some other ways of displaying their sex.
21 Behavioural advertisements Many animals advertise both their sex and their readiness to mate via their behaviours.Courtship ritualsSometimes elaborate, involving alternating bouts of approach and withdrawal, coy retreat and seductive flirtation.Why this alternation between ‘yes’ and ‘no’?
22 Behavioural advertisements Each animal has reason to approach the other,But, each also has reason to fear the otherIs the approach amorous or aggressive?This tension between attraction and threat must be resolvedAlternating approaches and withdrawals presumably serve this purpose.
23 Attraction Humans are biological creatures On the other hand Our behaviours perhaps including aspects of courtship might well be shaped by our genes.On the other handCulture-based learning during our lifetime may play a larger role in determining when, how and whom we mate.
24 Attraction 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
26 AttractionWhat commonalities are there among the diverse peoples of the world with regard to mate preferences and courtship patterns?No commonalityPowerful argument that human mating is not heavily governed by biology.CommonalityIs it this part of our biological heritage?
27 Physical Attractiveness Physical appearance is immensely important in determining a person’s attractivenessOr 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 2010At least £255 million spent in UK in 2005 on cosmetic surgery procedures
28 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 theymight want to date.The main determinant ofeach person’s desirability asa future date was theirphysical attractiveness.
29 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 personalideals.When it came down to actualchoice, the primary determinant wasthe photograph.
30 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 traitsDominanceGood social skillsIntelligenceHappinessGood mental healthDion, Bersheid, & Walster, 1972
31 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)
32 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 intelligenceEagly, Ashmore, Makhijani, & Longo, 1991; Feingold, 1992; Jackson, Hunter, & Hodge, 1995.
33 Matching for attractiveness Physical attractiveness is clearly desireableBut if we set our sights on only the most desireable, the world would soon be depopulatedThere aren’t enough supermodels to go around : (We seek partners who are roughly the same level of attractiveness that we areThis will ensure that we reach as high as we can, while simultaneously minimising the chance of rejection.
34 Matching for attractiveness Much evidence favours this matching hypothesisThere will be a strong correlation between the physical attractiveness of the two partnersBerscheid, Dion, Walster, & Walster, 1971Everyday observations confirm this hypothesis“They make such a good couple” etcAs do many empirical studiesBerscheid & Walster, 1974; Feingold, 1988; White, 1980.
36 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.
37 What is physically attractive? People of different cultures, by and large, seem to agree about which faces are attractive, as do people of different generationsCunningham, 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 learnedLanglois et al., 1987.
38 What is physically attractive? Across ages, generations and cultures, attractive people are almost always those with:Clear skinShiny hairNo visible deformities
39 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 averageGrammer & Thornhill, 1994; Fink & Penton-Voak, 2002; Mealey et al., 1999; Rhodes et al., 1998; Rhodes et al., 1999; Thornhill & Gagestad, 1999.
40 What is physically attractive? However, some departures from average increase attractivenessThese 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 chinA female face will be more attractive if it has slightly larger than average eyes, fuller than average lips, and so on…
45 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 lifetimeThornhill & Gangestad, 1994.
46 What is physically attractive? Body sizeSeems to be an area where preferences vary between cultures and time periods.Even so, there may be consistency in preferred proportions.Waist-to-hip ratioWaist circumference divided by hip circumference.
47 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 preservedFurnham et al., 1997; Henss, 2000; Singh, 1993; Singh & Luis, 1995.
50 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 fatReadiness for pregnancy, signals fertile partnerRelatively low ratio indicates higher oestrogen levels = better overall health and greater fertilitySingh 1993; 1994.Any male with a preference for this shape maximises his chances for reproductive successNatural selection favours individuals with this preference.
51 The biological basis for attractiveness The preference for symmetrical faces may too have evolutionary roots.A number of health problems will lead to asymmetrical facesProximity to the average indicates absence of these problemsAttraction 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
52 The biological basis for attractiveness Scepticism about evolutionary claimsIs facial attractiveness an indicator of health?Kalick, Zebrowitz, Langlois, & Johnson, 1998If not, we must rethink the evolutionary argument just offered.It is possible that our preference for average and symmetrical faces derives from another sourceA general preference for balanceWe prefer average watches and birds over peculiar onesHalberstadt & Rhodes, 2000More data is required…
53 Proximity “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.
54 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 datingClarke, 1952Proximity also predicts who will stay engaged and get marriedThe farther apart the two live, the greater the chance the engagement will be brokenBerscheid & Walster, 1978
55 Proximity 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 thereEbbesen, & Kjos, & Kohecni, 1976.
56 Proximity Proximity allows familiarity to develop People tend to like what is familiarBrickman & D’Amata, 1975; Moreland & Zajonc, 1982; Zajonc, 1968People shown photographs of strangers’ faces judged the strangers to be more likeable the more often they saw themJorgensen & Cervone, 1978
57 Familiarity 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 imageExperimental data confirm this to be the caseMita, Dermer, & Knight, 1977.
59 SimilarityDo “birds of a feather flock together” or do “opposites attract”?People tend to be attracted to others who are like themselves on attributes such asRaceEthnic originSocial and educational levelFamily backgroundIncomeReligionBehavioural patterns, such as drinking habits
60 Burgess & Wallin, 1943Widely cited study showing that engaged US couples tended to be similar along all of these dimensions.These findings provide strong evidence for homogamyA powerful tendency for like to choose like.
61 Homogamy 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, 1976Married couples tend to be similar on nearly all personality dimensionsCaspi & Herbener, 1990
62 What produces homogamy? One possibility is that similarity really does lead to liking.Another is that similarity is a by-product of proximityWe don’t really meet, interact become attracted to, and marry someone hugely dissimilar from ourselvesBerscheid & Walster, 1978
63 HomogamyOnly in Hollywood movies is homogamy violated
64 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 simpleThe female shoulders the major cost of reproduction
65 Who chooses whom? In birds In mammals Either case The female supplies the ovum as well as the food supply for the developing embryo.In mammalsThe female carries the embryo within her body and later provides it with milk.Either caseHer biological burden is vastly greater than the male’s.
66 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
67 Interesting exceptions Seahorsesmales exhibit greatersexual discriminationPhalaropesgreater sexual choosiness
68 Human mate choiceIn humans, both males and females are selective in choosing their sexual partnersMating only happens when both partners consentHowever, the two sexes differ in the criteria they use in making their choices…
69 Human mate choice According to studies: Physical attractiveness of partner seems more attractive to men than to womenMen generally prefer younger womenWomen prefer older menSocial and financial status of partner matters more to women than to men
71 Human mate choiceMale-female differences are not unique to our societyChina, India, France, Nigeria and IranBuss, 1989, 1992; Buss & Barnes, 1986Interestingly, both sexes agree on one pointBoth men and women value intelligence and kindness in their prospective matesBuss, 1992
72 Practical ExerciseRead through these selections of adverts from the Financial Times (15/07/06) magazineLook for differences between “Men seeking women” and “Women seeking men” on whether theyState their age / State the age (or range of ages) of their preferred partnerAdvertise their physical featuresHeight, signs of youthfulness, facial featuresAdvertise their height / desired height of partnerAdvertise their social / professional status / desired status of partner
73 Human Mate Choice According to Buss The best explanation for these preferences is evolutionaryIf 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
74 Human Mate Choice Likewise for a woman’s age The younger she is, the more reproductive years she is likely to have ahead of herTherefore, 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
75 Human Mate ChoiceFemale’s preferences easy to understand from this perspectiveHigh investment in each child means it is better to have just a few and do all she can to ensure survival of eachA wealthy, high-status male would help her achieve this goalAble to provide food and other resources neededReproductive advantage associated with such a preferencegradual evolution toward all females in the species having this preference
76 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 mateIn many cultures, women’s professional and educational opportunities are limited, and so “marrying wealth” is their best resource-gathering strategy
77 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 womenA potential husband’s resources become less important in mate selection(Kasser & Sharma, 1999; Eagly & Wood, 1999)
78 Mating Systems Polygamy Monogamy Several members of one sex mating with one individual of another.PolygynySeveral females mating with one malePolyandrySeveral males mating with one femaleMonogamyReproductive partnership based on a more or less permanent tie between one male and one female
79 Mating Systems Mammals vs. Birds Evolutionary economics 90% of all birds are monogamousThrough a breeding seasonIn contrast, more than 90% of all mammals are polygynousEvolutionary economicsWhat can an organism do to maximise its reproductive success?
80 Mating SystemsIn many bird species, successful incubation requires both parentsOne to sit on the eggs, one to forage for food.After hatching, finding food may still require the efforts of both birdsMonogamy makes reproductive sense for both the male and femaleEach needs its partner’s help, otherwise no chicks, and therefore no genes, survive
81 Mating Systems Situation is different for mammals No issue of tending the nestAfter birth, only the mother can secrete milk to the youngMother can still forage for food during gestationThe young can often survive under the mother’s care alone, and the male’s genes will be carried into the next generation nonetheless
82 Mating Systems How should a male behave? In evolutionary terms, a successful organism is one that perpetuates its genes through successive generationsThe most successful organism therefore is the one that has the greatest number of thriving and fertile offspring
83 Mating Systems If the young can survive without his care End result The male maximises his reproductive success by mating with as many females as possible.End resultPolygyny, with each male looking to mate with a number of females.
84 Mating Systems Anatomical consequences Polygynous males must be physically distinctiveTo attract a femaleTo win in competition with other malesPolygyny is almost always accompanied by sexual dimorphismPronounced differences is the size or bodily structures of the two sexes
85 Mating SystemsThe more polygynous the species, the more dimorphic it tends to be.
86 Mating systemsIn polyandrous species, females are larger, more aggressive etc…
87 Mating SystemsIn monogamous species, there is no such dimorphism
88 Human Mating SystemsAre humans biologically inclined towards monogamous relationships?Humans are moderately dimorphicOn average the human male is about 10% larger and 5 inches taller than the female.Suggests a tendency towards polygyny.
89 Human Mating Systems Most traditional cultures do allow polygyny Only 16% of those studied require monogamous marital arrangementsFord & Beach (1951).Most modern societies frown on polygamyNonetheless, some evidence suggests that men desire a greater number of sexual partners than women doSymons, 1979
90 Human Mating SystemsEvolutionary theorists believe that these differences between the sexes are ultimately rooted in our biological natureMen wanted greater sexual variety because for them it is reproductively adaptive.Their investment in each child (in terms of time or resources) is smallThey can afford to have many childrenMore children = more genes in next generationMore women they mate with = more children likely to be fathered
91 Human Mating SystemsWomen need to evaluate sexual partners more cautiouslyMore interested in stable familial relationshipWomen cannot afford (biologically) to have child after child after childHuge stake in finding the best possible father for their youngOne who’ll provide resources and support
92 Human Mating Systems Again, controversy over evolutionary account Sexual attitudes reflect cultural values rather than biological preprogrammingMale’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
93 Human Mating SystemsThe data surrounding the evolutionary explanation are also controversialPedersen et al, 2002Men 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.
94 Human Mating Systems Overall However, We can find a difference between men and women in the direction predicted by an evolutionary accountHowever,Other results run contrary to evolutionary predictionsCultural values and expectations play at least as strong a role as biology
95 Essay QuestionDiscuss evidence for evolutionary causes of attractiveness judgements.Sources of informationGleitman, 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 ScienceScienceDirect -