BEHAVIORAL AND BRAIN SCIENCES (1992)15,75-133 Printed in the United States of America Age preferences in mates reflect sex differences in human reproductive strategies Douglas T.Kenrick Department of Psychology,Arizona State University,Tempe,AZ 852871 Electronlc mall:atdtk@asuacad.bitnet Richard C.Keefe Department of Behavioral Science,Scottsdale College,Scottsdale,AZ 85256 Electronlc mall:keefe@scc.bitnet Abstract:The finding that women are attracted to men older than themselves whereas men are attracted to relatively younger women has been explained by social psychologists in terms of economic exchange rooted in traditional sex-role norms.An alternative evolutionary model suggests that males and females follow different reproductive strategies,and predicts a more complex relationship between gender and age preferences.In particular,males'preferences for relatively younger females should be minimal during early mating years,but should become more pronounced as the male gets older.Young females are expected to prefer somewhat older males during their early years and to change less as they age.We briefly review relevant theory and present results of six studies testing this prediction.Study I finds support for this gender-differentiated prediction in age preferences expressed in personal advertisements.Study 2 supports the prediction with marriage statistics from two U.S.cities.Study 3 examines the cross- generational robustness of the phenomenon,and finds the same pattern in marriage statistics from 1923.Study 4 replicates Study 1 using matrimonial advertisements from two European countries,and from India.Study 5 finds a consistent pattern in marriages recorded from 1913 through 1939 on a small island in the Philippines.Study 6 reveals the same pattern in singles advertisements placed by financially successful American women and men.We consider the limitations of previous normative and evolutionary explanations of age preferences and discuss the advantages of expanding previous models to include the life history perspective. Keywords:attraction;ethological theory;evolution;gender differences;life history strategies;mate selection;sexual selection; similarity;social exchange 1.Introduction One reason is that social psychologists have generated a number of empirical findings that could be par- In his 1908 Social psychology,William McDougall ex- simoniously explained within an evolutionary framework. plained human heterosexual attraction in Darwinian Because social psychologists usually fail to consider the terms.In adopting an evolutionary perspective, role that evolutionary pressures might have played in MeDougall followed William James (1890),whom human heterosexual attraction,however,many of these McDougall replaced at Harvard.The evolutionary per- findings have been viewed as anomalies(Kenrick Trost spective adopted by these early functionalists was re- 1989).Another reason is that evolutionary biologists lose jected by psychologists who entered the field after the a valuable source of data when they ignore the social 1920s.Recent research,however,indicates that evolu- psychological literature,which has produced an abun- tionary models might be quite useful for explaining cer- dance of findings with implications for evolutionary mod- tain aspects of human social behavior (e.g.,Buss 1989; els (Kenrick Trost 1987).A combination of the two Daly Wilson 1988a).The ultimate perspective ofevolu- literatures could lead to new hypotheses that would not tionary theory may be particularly pertinent to reproduc- follow from either perspective in isolation. tive behavior,which is arguably the first line of evolution- In this target article,we consider a phenomenon that ary pressure (Barash 1982;Daly Wilson 1983). has been addressed by both social psychologists and Differential reproductive success is,after all,at the heart evolutionary biologists,but which has not been fully of natural selection. explored by either.A number of social psychological Although social psychologists and evolutionary biolo- studies have indicated a sex difference in preferred age of gists have mutual interests in reproductive behavior, mates.We argue here that this sex difference is not well they have,historically,shared little theory and research explained by traditional social psychological models.An with one another.This is unfortunate for several reasons. alternative evolutionary explanation can encompass sev- @1992 Cambridge University Press 0140-525X/92$5.00+.00 75
Kenrick Keefe:Age preferences in mates eral findings and lead to new predictions.Evolutionary attractiveness"overvalued"by males,and economic re- theorists have not generated enough data to distinguish sources "overvalued"by females? between the social psychological and evolutionary expla- Economic models generally explain mate selection in nations of this phenomenon,however,nor have they terms of historically arbitrary normative pressures.As considered how age preferences interact with other fac- one author puts it,"traditionally,in our society,males tors that emerge from social psychological studies of have been valued for their economic success,and females attraction.We present data collected with different for their physical attractiveness"(Brehm,1985,p.76, methods,across different generations,and from several emphasis ours).Similarly,Cameron et al.(1977)explain different cultures suggesting that human mate selection is their finding that females prefer older,taller,high status based,in part,on the partner's reproductive potential males as the result of "traditional sex-role specifica- and,in part,on the partner's similarity to the subject. tions...frequently valued as sex appropriate in Ameri- can society,"which specify that women should "look up to"their male partners(p.29,emphasis ours). 1.1.Social exchange and the preference Along similar lines,Deutsch et al.(1986)speculated for similar mates about Sontag's(1979)suggestion that there is a "double Prevailing social psychological models of mating prefer- standard of aging"in our society: ence adopt a view of relationships as a form of economic .with increasing age women's sexual desirability is exchange (see,for example,Clark Reis 1988;Huston thought to decrease,and women's sexual desire and Levinger 1978;and Walster et al.1978).These economic interest are considered increasingly inappropri- models see potential partners as seeking an equitable ate. ..Even the standards of physical attractiveness bargain in a marketplace of mate competition.For exam- differ for men and women....Those for men are less ple,Cameron et al.(1977)observed that the singles stringent and less connected to youth,whereas for advertisements they examined in their research sug- women any sign of advancing age is an indication of gested a"heterosexual stock market."They also observed diminished attractiveness....This equation offemale that:The ads in this paper read a little bit like the ask-bid beauty with youthfulness may reflect the more general columns of the New York Stock Exchange.Potential ideal of femininity as a childlike state.(pp.771-72) partners seek to strike bargains which maximize their Although social psychologists do not usually examine rewards in the exchange of assets."(Cameron et al.1977, cross-cultural data,the above quotes reveal a tacit as- p.28) sumption that there are other societies in which gender According to these models,a common mechanism for differences in mate preference are fundamentally differ- achieving equity in the exchange process is to choose a ent from those found in our society.Along these lines, partner who is similar to oneself.Social psychologists who Rosenblatt(1974,p.87)advanced the following reason- study relationships often quote Erving Goffman's state- ing:"I suspect that female beauty is more important ment that:"A proposal of marriage in our society tends to where women have little control over whom they marry be a way in which a man sums up his social attributes and and little power in the family,and that feminine attrac- suggests to a woman that hers are not so much better as to tiveness is not noticeably more important than male preclude a merger or partnership in these matters." attractiveness where women have as much say as men (Goffman 1952,p.456) about whom they marry and about what goes on in their To support these models,social psychological theorists families. frequently point out that mates are matched on a great variety of characteristics(Antill 1983;Byrne 1971;Critelli 1.1.1.Problems for normative social exchange models.A Waid 1980;Hendrick 1981).These include physical number of findings pose difficulties for an explanation of attractiveness,wealth,religion,personality,political at- mate selection that is limited to the norms peculiar to our titudes,degree of psychopathology,and even personal society.We have reviewed several of these problems habits.Social psychological theorists invoke economic elsewhere (Kenrick Trost 1989);two are summarized exchange to explain the similarity findings.Partners pre- below: sumably attempt to match themselves with others who 1.Cross-cultural research indicates that males and have similar social value.Note that "economic exchange' females in other cultures differ in ways that are consistent does not refer solely to the exchange of money;indi- with the gender differences found in our own society.For viduals'economic value is assumed to be based on social, instance,females in different cultures value social status physical,and intellectual assets,as well as their financial in males more than do males,and males in different status.In fact,a woman's social economic value may bear cultures value a potential mate's physical attractiveness only a slight relation to her wealth,as is discussed in more more than do females(e.g.,Buss 1989;Symons 1979;see detail below. also multiple book review BBS 3(2)1980).Given the great The exceptions to the principle that"like prefers like" variability of many human characteristics from culture to are few and worthy of careful examination.One consis- culture,finding invariance across cultures is evidence tent exception to the principle is the finding that females that supports a species-specific,rather than a culture- are attracted to older males,whereas males are attracted specific,explanation(Plutchik 1980). to younger females (Bolig et al.1984;Cameron et al. 2.Comparisons across mammalian species reveal a 1977;Harrison Saeed 1977).Economic models at- number of sex differences that parallel those found in tribute this age preference complementarity to gender humans.For example,dominance is more important for discrepancies in social value.Females presumably ex- male than for female attractiveness in a number of other change youth and physical attractiveness for economic primate species(Sadalla et al.1987;Trivers 1985)and has security (Brehm 1985).But why are youth and physical been linked to the hormone testosterone in humans and 76 BEHAVIORAL AND BRAIN SCIENCES (1992)15:1
Kenrick Keefe:Age preferences in mates other species(Bancroft 1978;Dabbs et al.1987;Mazur (Crawford Anderson 1989).In general,life histories can Lamb1980).2 be divided into somatic effort and reproductive effort We believe that female preference for dominance (Alexander 1987).Somatic effort directs energy to build- across different mammalian species is closely related to ing the body and can be thought of as amassing resources. the preference of human females for wealth and social Reproductive effort is the expenditure of those resources status.Evolutionary theorists assume that a man's eco- in the interest of reproducing the animal's genes.Alex- nomic resources would have been important to our ander(1987)further divides reproductive effort into mat- female ancestors for at least two reasons:(a)They could ing,parental care,and extraparental nepotistic effort(or have been used to make a direct contribution to offspring the provision of resources for siblings). success;(b)they would have suggested the possession of There is a wide variety of life history patterns.For characteristics that,if passed on to the offspring,would example,small birds like chickadees breed in their first make them more competitive in a social hierarchy.In spring and every year thereafter.Pacific salmon develop addition to the theoretical arguments for equating a over a three-year period and "breed in a single suicidal male's status,wealth,and social dominance,empirical burst as three-year-olds"(Partridge Harvey 1988,p. data suggest that these factors have similar effects on 1449).Like salmon,red deer wait several years before contemporary women's preferences(Kenrick et al.1990). beginning to breed,but like chickadees,they continue to This issue is discussed in more detail below. breed for several years (Clutton-Brock et al.1982).A These and other findings of parallel gender differences critical point of life history models is that reproduction across human cultures and across species conflict with entails costs to the animal's individual survival.Some more complicated social psychological theories that ex- costs are direct physiological ones,as animals sacrifice plain gender differences in terms of norms peculiar to a their own bodily resources for their offspring.For exam- particular society.As we try to show below,these gender ple,female elephant seals lose two kilograms for every differences can be parsimoniously explained in terms of kilogram gained by their pups(Trivers 1985).Other costs general biological principles. are indirect,as animals work for and protect their off- spring.For example,male stickleback fish expose them- selves to greater risks of predation when there are rela- 1.2.The evolutionary perspective on tively more eggs in the nests they are guarding(Pressley heterosexual relatlonships 1981).As Partridge and Harvey (1988)note,there is an Evolutionary models agree in several respects with the "implicit trade-off between fecundity and mortality. social psychological economic models.[See Caporael et Animals(like the salmon)that end their lives in the act of al.:"Selfishness Examined,"BBS 12(4)1989.]For exam- reproduction demonstrate the trade-off most dramat- ple,both models assume the use of social strategies that ically.This pattern is called semelparity,colorfully de- balance potential costs and benefits in the interest of fined by Stearns(1976,p.4)as:"The big bang reproduc- motivations that are,at some level,selfish(Cooper 1987; tive pattern;giving birth only once and committing Frank 1988:Kenrick Trost 1989).They differ in several suicide in the process...."The pattern of giving birth important ways,however.Social psychological models several times in a lifetime is called iteroparity.Evidence assume a more or less conscious weighting of rewards and suggests that there is a trade-off between mating and costs,,emphasizing"“perceptions,.”“expectations,”and longevity even in iteroparous species(Daly Wilson "attributions"in the assessment of equity(Brehm 1985; 1983).For example,lizards with high fecundity are less Walster et al.1978).The value placed on any particular likely to survive from one mating season to the next reward or cost is presumably influenced by cultural (Tinkle 1969);a similar relationship has been found in norms(e.g.,Deutsch et al.1986).An evolutionary model, studies of red deer(Clutton-Brock 1984).Drosophila that on the other hand,bases the exchange process not on are experimentally denied the opportunity to mate live arbitrary norms,but on the hard currency of biological longer than those given access to mates,and this effect fitness and reproductive value.These processes are not obtains for males as well as for females(Maynard Smith necessarily accessible to conscious calculation but reflect 1958;Partridge Farquhar 1981). evolved adaptations that may operate below the level of Just as reproductive strategies differ across species,so consciousness do they differ within species(Darwin 1859;Trivers 1985). An evolutionary model can incorporate the social psy- For example,males in some species of fish may develop chological findings and can parsimoniously explain cross- into more than one adult form,depending on both genet- cultural similarities,cross-species similarities,and hor- ic differences between males and ecological conditions monal effects on gender-linked mating behaviors.In the confronted during development.Male bluegill sunfish,to following sections,we briefly review several general take one example,may develop into either large parental principles of the evolutionary approach that we use to males,or smaller males who attempt to cuckold the larger develop specific predictions about age and attractiveness. males.The parental males mature at a later age,court females,and guard the eggs in their nest.The smaller 1.2.1.Life history,reproductive effort,and differential males attempt sneak copulations,darting in to release parental investment.Evolutionary biologists assume that sperm after a female has laid her eggs,but before the each species has evolved a characteristic life history larger male has fertilized them (Gross 1984) adapted to the particular ecological problems encoun- The most important division of reproductive strategy tered by its ancestors (e.g.,Alexander 1987;Partridge within a species is often related to gender.One species of Harvey 1988;Stearns 1976).A life history is a genetically fly (Johannseniella nitida)provides a vivid example(Par- organized set of general strategies and specific tactics for ker 1970).After copulating with a female,the male allocating energy to survival,growth,and reproduction deposits his genitalia as a plug to prevent other males BEHAVIORAL AND BRAIN SCIENCES (1992)15:1 77
Kenrick Keefe:Age preferences in mates from mating with the same female.The female then consumes the remainder of the male's body.Although of dates,sexual partners,and long-term mates.On the this fly is an unusual example,evolutionary models as- other hand,both Buss and Barnes(1986)and Kenrick et sume that males and females will generally use somewhat al.(1990)found that males valued a potential partner's different reproductive strategies.In one marsupial(Ante- physical attractiveness more highly than did females. chinus stuartii),the male is semelparous (expending all Several authors have suggested that physical attrac- his bodily resources during mating competition and copu- tiveness might be important to males as an indirect means lation,and then dying),whereas the female may be to assess age and physical condition(e.g.,Buss Barnes iteroparous (surviving to mate in more than one season). 1986;Symons 1979).There is some indirect evidence supporting this reasoning;cues for youthful appearance 1.2.2.Differential parental investment.The concept of are related to ratings of a woman's physical attractiveness (Cunningham 1986).Mathes et al.(1985)asked subjects differential parental investment is important in under- standing sex differences in reproductive strategy(Trivers of different ages to judge the physical attractiveness of 1972).The sex investing more in the offspring will gener- photographs of males and females of different ages.Com- pared with younger women,older women were judged ally be more selective in choosing a mate.In most animal species(but not all),females have a higher initial invest- less physically attractive by judges of both sexes and all ment in each potential offspring than males do.Consider, ages.Photographs of older men were not judged as less attractive than those of younger men. in particular,the mammalian reproductive pattern. Female mammals,compared to males,heavily invest their own bodily resources in each offspring (through 1.2.3.Sex differences in human life history strategies. Human males and females differ in the way they divide pregnancy and lactation).These costs limit any given female to mothering fewer offspring than a male is poten- their lifetime energy resources between somatic effort tially capable of fathering.For this reason,mammalian and the various components of reproductive effort.Males females tend to be more selective about mates,and mature more slowly,grow to a larger size,and invest mammalian males tend to compete amongst themselves more energy in attracting mates (Alexander 1987;Daly for mating opportunities (Hinde 1983;Symons 1979: Wilson 1983).As just noted,females invest more of their Trivers 1972;Williams 1975). somatic resources in parental care.After approximately This general mammalian model must be qualified in its age 50,human females go through menopause,and cease application to humans.Because human males invest the direct production of young(Menken Larsen 1986). heavily in their offspring,they will also be selective about Note that menopause is not necessarily the end of re- choosing a mating partner(Buss 1989;Daly Wilson productive effort,however.Reproductive effort includes 1983;Kenrick et al.1990:Symons 1979).Humans are not only mating and the production of offspring,but also the care of those offspring.Alexander(1987)speculates among a minority of species in which males invest very heavily in their offspring.It is a general rule that as males that female menopause might have evolved because a invest more heavily in potential offspring,they become woman's reproductive success depends on tending the offspring she has produced.Naturalistic studies of other more selective about the characteristics of acceptable female mates (Trivers 1985). animal species have demonstrated that,beyond a certain Because human males and females both invest heavily age,females and their offspring suffer increasingly high in their offspring,they are both expected to be selective mortality (e.g.,Clutton-Brock 1984).Maternal age in about their partner's characteristics.Nevertheless,males humans has been connected to increasing health prob- and females invest different resources and should be lems for the pregnant and nursing mother,as well as expected to value different characteristics in a mate. offspring genetic defects and perinatal mortality(Resnik Males invest relatively more indirect resources (food, 1986).During most of human evolutionary history,a woman who reached age 50 was likely to have had several money,protection,and security),and females invest relatively more direct physiological resources(contribut- offspring,some of whom might still be directly depen- ing their own bodily nutrients to the fetus and nursing dent on her for survival,and some of whom might have child).For this reason,females who are choosing mates offspring of their own that could profit from grandparental care.Under those circumstances,the costs involved in are assumed to pay particular attention to a male's ability to provide indirect resources,and males are assumed to further production of infants were likely to have out- pay special attention to signs of a female's apparent health weighed the benefits of caring for existing offspring and grandchildren. and reproductive potential. A number of researchers have found support for the Males do not undergo the physiological changes of assumption that women value men who show charac- menopause.Although males do physically decline with teristics related to resource acquisition.For example, age,and in fact die earlier than females,they do not in Sadalla et al.(1987)manipulated a target individual's general lose the ability to reproduce.A recent report concluded: social dominance several ways across several experi- ments.In each case,dominance enhanced a man's attrac- A review of the available studies on testicular function tiveness to women,but had no influence on a woman's in old age provides neither biochemical nor mor- attractiveness to men.Similarly,Buss(1989)found that a phological evidence for a physiological process in men potential mate's social status was more important to that could be compared to the female climacteric.. women than to men across 37 different cultures(see also All investigators agree that the alterations in testicular Hill 1984;Mealey 1985).Likewise,Kenrick et al.(1990) and pituitary function observed in senescence occur found that characteristics related to dominance were over long periods of time and remain subtle compared more central criteria in a woman's than in a man's choice to the sudden and profound changes in gonadal func- tion during female menopause....While women lose 78 BEHAVIORAL AND BRAIN SCIENCES (1992)15:1
Kenrick Keefe:Age preferences in mates their reproductive capacities during the menopause, experienced as more rewarding than interactions with sustained androgen and sperm production indicate that dissimilar individuals.A history of positive interactions impotence and infertility are not a corollary of advanc- will generalize to similar individuals in new situations. ing age in men.(Nieschlag Michel 1986,p.69) When we are looking for new partners,past positive Because our male ancestors did not contribute their associations with family members,playmates,and others own bodily resourees to offspring,the costs of reproduc- who have been positive toward us in the past,including tion for older males did not outweigh the benefits.In fact, age mates,will have conditioned us to favor similar the indirect resources that a male contributed,such as individuals (Byrne 1971). skills in hunting or toolmaking,might well have con- Our prediction for a preference for similarity was tinued to accrue with his age.Because the majority of generated from the strong empirical support for such a human societies have been somewhat polygynous(Daly phenomenon in social psychology.The notion of attrac- Wilson 1983),older males with resources sometimes tion for genetic similarity (Rushton 1989)has difficulty had the opportunity to acquire additional younger wives accounting for a preference for similar age,because (Mealey 1985).Thus,the benefits of reproduction during similar age is no indication of genetic similarity.The a male's later years might well have continued to out- preference for similar age in a male,however,is not weigh the costs. incompatible with a more general evolutionary perspec- tive.It is important to consider that"reproductive effort" means more than simply effort involved in mating;it also 2.A prediction:Age preferences change includes parental effort.The evidence suggests that the over the lifespan most common pattern of parental effort throughout human history has been one in which men and women A consideration of lifespan changes in residual reproduc- bond together in the care of the offspring(Daly Wilson tive value(Fisher 1930)leads to a prediction that would 1983).To the extent that common habits and common not follow from the social exchange models.Several cohort history facilitates cooperative and friendly rela- evolutionary theorists have discussed male age prefer- tions between parents the same way that they do between ence in mates and emphasized the reproductive advan- friends and dating partners(Byrne 1971),age similarity tages in male's preference for youth.Williams (1975) carries some reproductive advantage.We return to the recognized the importance for males of the fact of female issue of similarity preference later.The critical point we age-dependence in fertility.He suggested that,"the make now is that despite the advantages of similarity value of copulation for the male would be described by between parents a strong countervailing pressure oper- the age-distribution of female fertility."While recogniz- ates to prevent relying on a strict similarity criterion. ing the lack of data on the point,he predicted a universal Because a female's reproductive potential declines male attraction to sexually mature but youthful women as more rapidly,the preferred age ofa male's partner should the most important standard of beauty(p.128).Symons change as he ages.For a teenage male,the differences in (1979)in turn speculated on the age at which females remaining reproductive years between women his age should be most attractive to males,predicting 23-28+2, and those a few years older are not great,and slightly ..if males have been designed by selection to 'evalu- older females have the advantage ofhigher fertility.Thus, ate females primarily as sex partners,"and 17-22+2 if a teenage male would be expected to show little or no ..designed by selection to 'evaluate'females pri- discrimination against women a few years older than he. marily as wives."(p.189) For a male in his 40s,however,a woman's remaining Although evolutionary theorists have touched on the reproductive years should become a more important relationship of female age to attractiveness,they have not consideration that acts against using similarity as a sole fully articulated the differences between men and women criterion.Whereas aging males should prefer progres- over the lifespan,nor have they considered how age sively older women (because of similarity),they should preferences would interact with other factors known to also prefer women progressively younger than them- influence mate choice (e.g.,similarity).In addition,evo- selves (to maximize reproductive opportunities). lutionary theorists have not generated data that would distinguish evolutionary from sociocultural explanations. We consider below how the different reproductive life 2.2.Female choice histories of males and females lead to predictions of The evolutionary model does not offer as clear a predic- gender differences in age preferences that change across tion for females.Males mature later than females,which the lifespan. may reflect the past pressures of intrasexual selection mediated by male competition for females (Chiselin 1989).During our ancestral past,a young teenage male 2.1.Male choice was therefore less physically ready to compete with larger We hypothesize that males will weigh at least two consid- males a few years older.As a corollary,very young males erations in the choice of a female partner-similarity and may have been unable to provide physical protection or reproductive potential.Our expectation that similarity resources for females their own age.Whatever the ulti- will be important was derived from the overwhelming mate genesis,earlier maturation in females suggests a empirical evidence for the similarity/attraction phe- history in which females mated with older males,and we nomenon in the social psychological literature (e.g., would expect young females to prefer relatively older Byrne 1971),including findings ofage similarity in friends males.Once a male reaches full maturity,he continues to (Rushton 1989).Byrne has shown that interactions be- accrue economic resources for several decades (e.g., tween people who are relatively similar to each other are Jencks 1979),and he also accumulates such indirect BEHAVIORAL AND BRAIN SCIENCES (1992)15:1 79
Kenrick Keefe:Age preferences in mates resources as social status that females value in a mate (Buss 1989;Kenrick et al.1990;Sadalla et al.1987).He Oldes1 prelerred loses physical resources in the form of health and virility, ●Youngest preferred however,and his economic position may also begin to 20- drop as he ages (e.g.,Jencks 1979).Older males decrease their rate of copulation,and a lowered rate ofcopulation is in turn related to lessened probability of insemination (James 1974).As we noted above,however,testosterone and sperm counts in older males remain adequate for fertilization. Leonard(1989)discusses a factor that would incline females against choosing males who are much older than they are: Females...should show a preference for males who have achieved full maturity and high rank,which will 3040 0 60 typically mean older males,but perhaps males still MALE'SAGE FEMALE'S AGE young enough to retain effectiveness as providers until Figure 1. Age differences preferred in mate advertisements, the females'last reproductive efforts have reached plotted as minimum and maximum differences from advertiser's adulthood.If one assumes (conservatively)that a age female marries at age 20 and can expect to bear her last child no later than age 40,and that that child will require some degree of parental care until age 20,then maximum desired age for a partner.When these data were broken down by the advertiser's gender and decade if pair bonds are long-lasting,she should prefer a male of age,they yielded the pattern shown in Figure 1. who is currently a good provider and likely to remain so for 40 years.This would mean a male older than she is, As can be seen in the figure,female specifications but not much more than 10 years older (p.26). remained fairly constant throughout the age range. Leonard's reasoning could be extended to older Females were interested in partners who,on average, females choosing a mate.Compared with a 20-year-old,a ranged from 0 to 5 years younger,and from 8 to 11 years 30-year-old female would have 10 fewer years of expected older than themselves.Males,on the other hand, remaining parental care,and could "afford"to marry a changed their preferences in a systematic fashion as their slightly older man,with fewer remaining productive own age increased.Males in their 20s were equally years,but more present resources. attracted to women above and below their own age, In summary,males are hypothesized to begin with a specifying partners ranging,on average,from 5 years preference for females around their own age,but,as they younger to 5 years older.As males got older,however, grow older,to develop a preference for women who, their preferences increasingly diverged from those of although not absolutely younger,are progressively females in the same age group.Among males in their 50s younger than themselves.We hypothesize that females and 60s,the maximum acceptable age was several years will begin with a preference for older males,and com- below their own age,and the minimum specified was pared to males,show less variation in that preference almost a generation discrepant from their own age.Analy- over their lifespan.This gender and age-differentiated ses of variance indicated a significant sex x decade interac- prediction was tested in six studies. tion for both minimum (F,4,190 =3.81,p.39). the nonreactive naturalistic examination of mating prefer- When age preferences from mating advertisements are ences,and social psychologists have regarded them as examined more carefully,they yield results that were not particularly well suited for examining what are usually predicted by social economic models.If there is a"norm" tacit economic exchange considerations.Because earlier for men to prefer younger women it should show up most researchers considered only the general "norm"that markedly in younger men,who tend to be more con- females mate with older males and found support for that cerned with behaving in a stereotypically sex-typed man- expectation,they did not further partition the preference ner.A number of studies have found that men become data.A test of the present hypothesis calls not only for less concerned with gender-specific norms as they age separating male and female advertisers,but also for (e.g.,Deutsch et al.1986).The interesting feature of dividing them by the advertiser's age. younger men's preferences,however,is that they ex- We analyzed a sample of 218 personal advertisements tended equally above and below their own ages.Thus, from three issues of a "singles"newspaper(the Arizona these data provide no evidence that a preference for Solo).We used only advertisements that specified the age younger women is a consistent feature of the normatively of the advertiser,and that indicated a minimum and/or defined role for males. The results do fit well with an evolutionary model.The 80 BEHAVIORAL AND BRAIN SCIENCES(1992)15:1
Kenrick Keefe:Age preferences in mates data from Study I are inherently limited,however.For MARRIAGES PHOENIX 1986 one thing,preferences expressed in singles advertise- ments may not reflect preferences in the larger popula- 20 tion.For another,such preferences may not transfer into actual reproductive behaviors because they may be lim- ited by a number of constraints.Although older males might be interested in females 15 or more years younger than themselves,for example,they must still deal with female preferences.The choice of a marriage partner is, after all,mutual,rather than unilateral;people may not get what they want.In addition,other factors,including physical attractiveness,personality,and preferences for similarity on other dimensions could all act to weaken the importance of initial age preferences in actual mate selection. 10120139440s50601 04030404 MALE'S AGE FEMALES AGE Figure 3. Actual age differences in marriages in Phoenix,AZ 4.Study 2:Marriage age statistics (aggregated for January and May 1986),plotted according to husband's and wife's ages. Because of the inherent limitations on advertised prefer- ences,we examined age differences in actual mate choice,as reflected in marriage statistics.Our first sample Once again,the same sex difference obtains.As pre- included all the marriages (n =753)for the month of dicted by our evolutionary model,the age of a man's wife January 1986 in a large city in the western United States significantly decreased in relation to his own age as he got (Seattle,WA).We first analyzed the data using the male's older (F,5,435 30.81,p <.001).An analysis using age as the predictor,and his partner's age as the depen- female's age as predictor again produced a statistically dent variable.We next analyzed the same data using significant,but much smaller F value (F,5,435=2.25,p female's age as predictor.The results are depicted in <.05).As examination of the figure indicates,women Figure 2. usually married men who were just a little older than they Those results are consistent with the evolutionary were.As men grew older,they tended to marry women model,and they fall cleanly within the preference ranges who were younger and younger relative to their own age. found in Study 1.Using age of male as predictor variable, In summary,data from two distinct geographical regions the change over the decades yields an F(5,752)=41.90,p of the United States suggest that the age preferences <.001.A comparable analysis using female age also expressed in singles advertisements reflect general popu- yields a significant F,but it is much smaller in magnitude lation preferences that translate into reproductive behav- (3.42). ior.Marriage patterns from the two cities fall squarely To guard against the possibility that spurious factors within the preference limits specified in Study 1. might have influenced the data for the month of January 1986 in Seattle,WA,we also collected data for the same 5.Study 3:Cross-generational analysis month,and from May 1986 from another large western U.S.city (Phoenix,AZ).The overall Phoenix population From an evolutionary perspective,human mate prefer- of cases was larger,and we randomly sampled 436 mar- ences reflect selection pressures that have occurred over riages from the two months.Because preliminary analysis several million years.If the sex differences described in revealed that the two months did not differ from one the above studies reflect past evolutionary constraints, another,they are collapsed for presentation in Figure 3. they should be relatively impervious to changing norms such as those that have affected sex roles in the United States during the latter half of this century.This is a MARRIAGES SEATTLE 1986 relatively conservative prediction because evolutionary theorists assume that behaviors influenced by human 20 genetic predispositions are modifiable by features of the physical and cultural environment(Lumsden Wilson 1981).In fact,natural selection can result in variable behavior patterns for several reasons.If an animal's an- cestors encountered a variable environment,that could select for a facultative strategy in which certain environ- ments lead to certain behavioral strategies,and other environments lead to different such strategies (see Crawford Anderson,1989,for a more extensive discus- sion).Environmental factors that might lead to facultative 20 20 variations in the magnitude of age discrepancies are 20304制6 1070430445060 discussed below.We would expect the general sex dif- MALE'S AGE FEMALES AGE ference in age preference to be a robust effect,however, Figure 2. Actual age differences in marriages for Seattle,WA, because the selection pressure on males to prefer in- January 1986,plotted according to husband's and wife's ages. creasingly younger females is likely to have been consis- BEHAVIORAL AND BRAIN SCIENCES(1992)15:1 81
Kenrick Keefe:Age preferences in mates MARRIAGES PHOENIX 1923 103044s4 0n39:你5040 MALE'S AGE FEMALE'S AGE MALE'S AGE FEMALE'S AGE Figure 4.Actual age differences in marriages in Phoenix,AZ. 1923,plotted according to husband's and wife's ages. Figure 5.Age preferences stated in German singles advertise- ments,plotted as minimum and maximum differences from target's age. tent over our evolutionary history.The persisting dif- ferences in the reproductive life histories of males and newspapers provide a somewhat more distinct source. females would serve to anchor the age discrepancies in Although Indian culture also has connections to Euro- pean culture,Indian marital advertisements indicate mate preferences against short-term variations in the cultural milieu. very different cultural criteria from those seen in Ameri- Assuming a historically unidirectional selection pres- can advertisements.Most advertisements include strict sure on males to prefer females of reproductive age,we limitations by caste and religion,and they commonly request horoscope information.For instance: would predict a similar age-discrepant pattern in mating ages during our grandparents'generation.To test this Wanted:a non-Bharadwaj smart good-looking preferably em- prediction,we analyzed a sample of 100 marriages re- ployed Kerala lyer girl below 25 for a Kerala lyer boy 29. corded in Phoenix,AZ,for 1923(the earliest year for Chemical engineer.Contact with horoscope. which well-organized records were available).The results (Times of India,Bombay,Sunday,Jan.29,1989) are depicted in Figure 4. As earlier,we selected advertisements that included These data conform reasonably well to the pattern of the advertiser's age,and that stipulated a minimum the data from the 1980s.Once again,the age of a man's and/or a maximum age for preferred partners.Unfortu- partner decreases directly with his age(F,5,99=8.07,p nately,we found no advertisements for women above age <.001).The changes in women's age preferences were 40 in our sample.As an Indian informant explained to us, not significantly different across decades(F<1). Indian women who do not marry by their 40s are not Thus,the sex differences in age choices have shown considered marriageable.Nevertheless,the gender dif- consistency across generations despite changes in sex- ferences in the pattern of the data are similar to those role norms during the intervening historical period. found in the American sample (Figure 7). These advertisements indicate that,as they age,males prefer increasingly younger females,whereas females 6.Study 4:Mating advertisements in continue to prefer males slightly older than themselves. different cultures The analysis for a gender x decade interaction yields an F An evolutionary model would also lead us to predict that these sex differences in the preferred age of a partner HOLLAND (Tibur 1989 would be consistent across cultures.As we noted earlier, facultative mechanisms could have evolved to vary the size of the sex discrepancy to fit varying ecological condi- tions.Several of these factors are discussed in a later section,but again note that the consistent evolutionary pressures for age-related changes in male preference should lead to some consistency in the pattern of sex discrepancies across cultures. We analyzed personal advertisements from Germany and Holland and found that the pattern in both countries is essentially the same as the pattern in American adver- tisements(see Figures 5 and 6).3 It could be argued that European countries are not the 23345 best test of the cross-cultural robustness of this phe- MALES AGE FEMALE'S AGE nomenon,because American society is deeply rooted in European culture.Matrimonial advertisements in Indian Figure 6. Age preferences stated in Dutch singles advertisements. 82 BEHAVIORAL AND BRAIN SCIENCES(1992)15:1
Kenrick Keefe:Age preferences in mates ●Youngest preferred 20 10 0 10 MALES AGE FEMALE'SAGE Figure 8.Actual age differences in 1,511 marriages on the 1 island of Poro(1913-1939),plotted according to husband's and 20 2s30s4050 2043040n503 wife's ages,respectively. MALE'S AGE FEMALE'S AGE Figure 7.Age preferences stated in Indian matrimonial advertisements. We also separately analyzed the 278 marriages re- corded between 1913 and 1920,to provide the most (4,106)=8.03,p.20).These data either minimum (F,2,46 =2.36,p>.10)or maximum argue strongly against the sociological explanation of age age preferences (F,2,83 =0.24,p >.78). discrepancies that attributes them to norms based in modern“cultural images”of“an advertising culture' (Neal,cited in Winegar 1989). 7.Study 5:Marriage ages on a small Philippine island,.1913-1939 8.Gender differences in economic resources As an additional test of the cross-cultural and cross- historical robustness of the age discrepancies in mate As we noted earlier,social psychological models some- choice,we examined marriage ages on the island of Poro times attribute the gender difference in emphasis on between the years 1913 (the earliest year for which youth and attractiveness to culturally bound differences records were available)and 1939.Poro is a small isolated in economic resources.As Margolin and White (1987) island in the Visayas region(approximately 500 kilo- note: meters southeast of Manila),with its own distinct dialect. One social norm clearly related to this asymmetry is the The natives of Poro had little contact with Europeans or long-standing tradition for beautiful women to trade Americans during the years studied.The economy was their looks for economic status in cross-gender rela- based on fishing and agriculture.Because ofthe relatively tionships....For centuries women have relied on the small size of the community,we were able to examine the commodity value of physical appearance to achieve total sample of marriages during these years(n =1511).4 upward mobility because,in comparison to men,they As in Studies 2 and 3,we analyzed the data using male age have had little else to bargain with(p.22). as the independent variable and the discrepancy between As we noted earlier,Rosenblatt(1974)speculated that his age and his wife's age as the dependent variable.We such gender differences would be less pronounced in then analyzed the data using the wife's age as the inde- societies in which women had more wealth and power.It pendent variable.Results are depicted in Figure 8. is also consistent with an evolutionary perspective that When analyzed using male age as the dependent vari- wealth might influence age preferences in a mate.As we able,the pattern was consistent with that found in the noted above,wealth can affect an individual's ability to studies discussed above-a consistent increase in age make indirect contributions to offspring survival.As dis- discrepancy as the male aged(F,5,1510 124.76,p< cussed below,it might also have an indirect influence on .001).Once again,the youngest males married women the aging process itself.Nevertheless,other research has close to their own age(0.69 years discrepancy for teens), indicated that traditional sex differences in mate prefer- whereas the oldest males married women much younger ence persist even with increases in social status and than them(20.75 years discrepancy for men in their 60s). wealth (Townsend 1989).That is,high status men con- Women's preferences also showed changes over the life- tinue to weight physical attractiveness more highly than span (F,5,1510=13.94,p<.001),but women at all ages do high status women,and high status women continue to married men slightly older,and the changes across de- weight status and wealth relatively more highly than do cades did not manifest the consistent downward trend high status men.Thus,high status American women and shown in the male data. men continue to demonstrate the same differences that BEHAVIORAL AND BRAIN SCIENCES (1992)15:1 83
Kenrick Keefe:Age preferences in mates Buss(1989)found across numerous cultures.We would therefore not expect social status to erase the pattern of WASHINGTONIAN,1989 sex differences found in the other data sets reported above. Actually,some segments of modern American society may provide a reasonable test of these speculations. Compared to women in hunter-gatherer and agrarian societies,contemporary urban professional women are much more equivalent to men in wealth and status. Although this increase in power has not occurred for all women in our society,it is possible to examine women whose personal socioeconomic status exceeds not only the status of most males in other cultures and historical epochs,but also that of the average American man Certain newspapers and magazines,like the New York 450 Review of Books and Washingtonian regularly include MALES AGE FEMALES AGE personal advertisements from women of higher socioeco- Figure 9.Age preferences stated in Washingtonian magazine. nomic status.Consider the following advertisement: with separate plotting for those specifying high SES. Wealthy attractive DWF 49,brown-eyed brunette,5'4"120 Ibs.,wants tall handsome blue-eyed monogamous unmarried ing no differences between the social class groups for the gentleman,no dependents,50-65 for long term relationship. highest age preferred.5 (Washingtonian,June 1989) In summary,the interaction between gender and age We analyzed advertisements in Washingtonian maga- persists even among those at the highest levels of income. zine that indicated a minimum and/or a maximum age Wealth does have a weak effect on preferences for youth. preferred in a partner and that specified the age of the That effect is independent of gender,so that the differen- advertiser.In addition,we coded the ads in terms of tial gender pattern remains among wealthy individuals information related to the advertiser's wealth and social Unlike older men,wealthy older women are still in- status(hereafter SES).The analysis divided advertisers terested in men their own age and older,but as they grow into those who specified that:(1)they were wealthy or had older,wealthy people of both sexes show a relatively a professional occupation(physician,lawyer,etc.),or(2) lower "floor"in the ages in which they are interested. no information or specific mention that they were not wealthy or in a relatively low-paying occupation (e.g., 9.Discussion clerical or secretary).Relatively more males than females listed themselves as wealthy or professional.Out of 182 men,129 reported themselves as high SES,versus 84 out The data we have presented indicate that age preferences are more complex than earlier social psychological mod- of 184 women.Results including this variable are de- els led us to expect.Earlier studies suggested a simple picted in Figure 9. relationship:Males seek younger females and females As indicated in this figure,the basic sex difference seek older males.Our results are consistent with half of found in the earlier studies also obtained in this study. that generalization;females tend to seek males who are Specifically,there was the predicted gender x decade interaction for both maximum (F,3,365 18.42,p slightly older than they are.For males,however,the preference for younger females is weak or nonexistent .001)and minimum age differences (F.4,369 12.07,p during early years,but becomes increasingly pronounced profiles in this magazine were not looking for the women 25).For exploratory purposes,we nevertheless exam- who placed profiles (nor were the women looking for ined the data separately by gender and social class. these men)."The preferences ofolder females indicate an Neither women nor men showed a significant interaction interest in males who are themselves interested in much of wealth and decade for either the high or low preferred younger women.Given the general tendency for males to difference.Consistent with the two-way interaction re- prefer younger females,however,the older females may ported above,however,there was a similar marginal tendency toward a decade by wealth interaction for both be following a somewhat"rational"strategy.On the other hand,if the goal of these advertisements is simply to men(F,4,170=2.10,p<,09)and women(F,3,191= maximize the probability of acquiring a partner,males 2.39,p<.08)on the lowest age preferred.The analogous F's for the high differences were both less than 1,suggest- would fare better by expressing an interest in females in their own age range,as well as in younger females.Given BEHAVIORAL AND BRAIN SCIENCES (1992)15:1
