No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Consistency of mate choice in eye and hair colour: Testing possible mechanisms
Abstract
Partner preferences are formed by several mechanisms, including an imprinting-like effect (parent-similarity) and homogamy (self-similarity). It is still unknown, however, whether these preferences remain stable throughout an individual's lifetime. We have therefore tested the consistency of mate choice in eye and hair colour both in a shortand long-term context. In other words, we tested whether people systematically choose partners with a particular eye and hair colour. We asked 1,048 respondents to indicate the eye and hair colour of themselves, their opposite-sex and same-sex parent, and all the romantic partners they had in their lives. Our results show that people consistently choose partners of a particular eye and hair colour in both short- and long-term contexts, which suggests that people do have their ‘types’. Nevertheless, the consistency was significantly higher in a long-term context than in a short-term context. Furthermore, the eye colour of one's partner was predicted by the eye colour of one's opposite-sex as well as same-sex parent, but the strongest parental effect was found when both parents had same eye colour. There were no significant results for hair colour. Our results thus suggest that preferences for eye colour are determined by the imprinting-like effect rather than by homogamy, and that they remain stable over time. These findings also indirectly support an assumption of stability of this imprinting-like effect in humans, since people consistently choose partners with their opposite-sex parent's eye-colour.
... In short, it has been established that over time, mate preferences are to some degree plastic, but research of intraindividual stability in real mate choice in humans is sparse. To the best of our knowledge, only three studies so far tested individual consistency of mate choice (Eastwick et al., 2017;Newman et al., 2018;Štěrbová et al., 2018). They found consistency in preferences for eye color (Štěrbová et al., 2018;but cf. ...
... To the best of our knowledge, only three studies so far tested individual consistency of mate choice (Eastwick et al., 2017;Newman et al., 2018;Štěrbová et al., 2018). They found consistency in preferences for eye color (Štěrbová et al., 2018;but cf. Newman et al., 2018), hair color (Štěrbová et al., 2018), attractiveness, masculinity, vitality, depression, delinquency, religiosity, educational aspirations, self-esteem, and intelligence (Eastwick et al., 2017). ...
... Results revealed that fathers in general fit the women's 'type, ' although differences between them and other (ex-)partners are not large. Our findings are in line with earlier research (Eastwick et al., 2017;Štěrbová et al., 2018Štěrbová et al., but cf. Newman et al., 2018, which found that people consistently choose partners with certain traits, although reported effect sizes were rather small. ...
In mate choice, individuals consider a wide pool of potential partners. It has been found that people have certain preferences, but intraindividual stability of mate choice over time remains little explored. We tested individual consistency of mate choice with respect to a number of demographic, physical, and personality characteristics. Only mothers were recruited for this study, because we wanted to find out not only whether women choose long-term partners with certain characteristics but also whether the father of their child(ren) differs from their other long-term (ex-)partners. Women (N = 537) of 19–45 years of age indicated the demographic, physical (by using image stimuli), and personality characteristics of all of their long-term partners (partners per respondent: mean = 2.98, SD = 1.32). Then we compared the average difference between an individual’s long-term partners with the expected average difference using a permutation test. We also evaluated differences between partners who had children with the participants (fathers) and other long-term partners (non-fathers) using permutation tests and mixed-effect models. Our results revealed that women choose long-term partners consistently with respect to all types of characteristics. Although effect sizes for the individual characteristics were rather weak, maximal cumulative effect size for all characteristics together was high, which suggests that relatively low effect sizes were caused by high variability with low correlations between characteristics, and not by inconsistent mate choice. Furthermore, we found that despite some differences between partners, fathers of participants’ child(ren) do fit their ‘type’. These results suggest that mate choice may be guided by relatively stable but to some degree flexible preferences, which makes mate choice cognitively less demanding and less time-consuming. Further longitudinal studies are needed to confirm this conclusion.
... Popular culture leads us to believe that individuals have a "type," a predilection for certain physical characteristics that is apparent across sequential partner choice. Indeed, as set out in the Introduction, there is a good theoretical justification for anticipating some degree of consistency in eye coloration (and also in general physical appearance) across partners, given that people prefer or select partners who resemble themselves and their parents in relation to physical characteristics such as eye color (Bressan, 2020;Bressan & Damien, 2018;Little et al., 2003;Saxton, 2016;Štěrbová et al., 2018Wilson & Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
Studies have indicated that people are attracted to partners who resemble themselves or their parents, in terms of physical traits including eye color. We might anticipate this inclination to be relatively stable, giving rise to a sequential selection of similar partners who then represent an individual’s “type”. We tested this idea by examining whether people’s sequential partners resembled each other at the level of eye color. We gathered details of the eye colors of the partners of participants (N = 579) across their adult romantic history (N = 3250 relationships), in three samples, comprising two samples which made use of self-reports from predominantly UK-based participants, and one which made use of publicly available information about celebrity relationship histories. Recorded partner eye colors comprised black (N = 39 partners), dark brown (N = 884), light brown (N = 393), hazel (N = 224), blue (N = 936), blue green (N = 245), grey (N = 34), and green (N = 229). We calculated the proportion of identical eye colors within each participant’s relationship history, and compared that to 100,000 random permutations of our dataset, using t-tests to investigate if the eye color of partners across an individual’s relationship history was biased relative to chance (i.e., if there was greater consistency, represented by higher calculated proportions of identical eye colors, in the original dataset than in the permutations). To account for possible eye color reporting errors and ethnic group matching, we ran the analyses restricted to White participants and to high-confidence eye color data; we then ran the analyses again in relation to the complete dataset. We found some limited evidence for some consistency of eye color across people’s relationship histories in some of the samples only when using the complete dataset. We discuss the issues of small effect sizes, partner-report bias, and ethnic group matching in investigating partner consistency across time.
... That imprinted preferences apply to all sexual mates squares with the discovery that people's long-and short-term partners and ex-partners tend to have the same eye colour 50 . That this still shows up as a very feeble effect is rendered unsurprising by the findings discussed in the next section. ...
Early exposure to parental features shapes later sexual preferences in fish, birds, and mammals. Here I report that human males’ preferences for a conspicuous trait, colourful eyes, are affected by the eye colour of mothers. Female faces with light (blue or green) eyes were liked better by men whose mother had light eyes; the effect broke down in those who had felt rejected by her as children. These results, garnered on over one thousand men, complete those of a symmetrical study on one thousand women, painting a fuller picture of human sexual imprinting. Both men and women appear to have imprinted on their opposite-sex parents unless these were perceived as cold and unjustly punitive. Birds require strong attachment to sexually imprint—a constraint in place to reduce the perils of acquiring the wrong sort of information. Parents who form no bond with their offspring may fail to be recognised as appropriate parental imprinting objects. Consistent with human females being, as in most of the animal kingdom, the choosier sex, imprinted preferences were displayed by both sexes but translated into real-life partner choices solely in women—attractive women. Apparently, not all of us can afford to follow our own inclinations.
... Such preferences may likely arise through imprinting-like effects on parental traits [23]. Consistent with https://doi.org/10.1016/j.physbeh.2019.05.002 the latter, several studies suggest that preferences for facial shape and eye colour in potential partners is strongly influenced by the traits of the opposite-sex parent [24,25]. ...
There is substantial evidence for assortative partner preferences in humans based on physical characteristics. In contrast, evidence suggests that olfactory preferences tend to be disassortative, with people preferring body odour of potential partners who are dissimilar at key genetic loci, perhaps to gain fitness advantage through offspring heterozygosity. We compared ratings of perceived body odour similarity of real couples with those of randomly paired 'fake' couples. Contrary to prediction, we find that odours of real partners are perceived more, rather than less, similar to each other than fake couples. However, this applied only to natural odour samples: there were no differences in similarity levels of real and fake couples' samples which were collected while wearing artificial fragrances. Furthermore, in light of suggestions that hormonal contraception (HC) disrupts disassortative odour preferences in women, we compared odour similarity among real couples in which the female partner was using or not using HC at the time when the relationship began. We find that odours of HC-using couples are of intermediate similarity between non-using and fake couples, suggesting that HC use during partner choice could affect odour-influenced assortment. We also examined the association between relationship satisfaction and perceived similarity of unfragranced odours of real couples. We found that these are positively correlated in male partners but negatively correlated in the female partners, indicative of a sex difference in the relative favourability of odour similarity in partner preference. Finally, by comparing odour similarity ratings with those given by perfumers using a novel olfactory lexicon we found evidence that similarity judgements were based on the Spicy/Animalic aspects of individual odour profiles. Taken together, our results challenge the conventional view that odour-mediated partner preferences in humans are typically disassortative.
... Despite the success of evolutionary psychological approaches in understanding human mating, it is perhaps time to significantly broaden the scope of understanding beyond honest signalling approaches to different viewpoints, such as imprinting [124] or Fisherian runaway [125]. Recent evidence has indicated that mate choice decisions are consistent, that people seem to have a "type" of partner they prefer [126,127], and that optimising their preferred traits are what drives attractiveness perceptions. Focusing more closely on these approaches allows for a systematic exploration of the theoretical space of psychological and morphological traits of possible partners. ...
The factors influencing human female facial attractiveness—symmetry, averageness, and sexual dimorphism—have been extensively studied. However, recent studies, using improved methodologies, have called into question their evolutionary utility and links with life history. The current studies use a range of approaches to quantify how important these factors actually are in perceiving attractiveness, through the use of novel statistical analyses and by addressing methodological weaknesses in the literature. Study One examines how manipulations of symmetry, averageness, femininity, and masculinity affect attractiveness using a two-alternative forced choice task, finding that increased masculinity and also femininity decrease attractiveness, compared to unmanipulated faces. Symmetry and averageness yielded a small and large effect, respectively. Study Two utilises a naturalistic ratings paradigm, finding similar effects of averageness and masculinity as Study One but no effects of symmetry and femininity on attractiveness. Study Three applies geometric face measurements of the factors and a random forest machine learning algorithm to predict perceived attractiveness, finding that shape averageness, dimorphism, and skin texture symmetry are useful features capable of relatively accurate predictions, while shape symmetry is uninformative. However, the factors do not explain as much variance in attractiveness as the literature suggests. The implications for future research on attractiveness are discussed.
... Despite the success of evolutionary psychological approaches in understanding human mating, it is perhaps time to significantly broaden the scope of understanding beyond honest signalling approaches to different viewpoints, such as imprinting [124] or Fisherian runaway [125]. Recent evidence has indicated that mate choice decisions are consistent, that people seem to have a "type" of partner they prefer [126,127], and that optimising their preferred traits are what drives attractiveness perceptions. Focusing more closely on these approaches allows for a systematic exploration of the theoretical space of psychological and morphological traits of possible partners. ...
The theoretical factors influencing human female facial attractiveness – symmetry, averageness,and sexual dimorphism – have been extensively studied. However, through improved methodologies, recent studies have called into question their links with life history and evolutionary utility. The current study uses a range of statistical and methodological approaches to quantify how important these factors actually are in perceiving attractiveness, through the use of novel analyses and by addressing methodological weaknesses inherent in the literature. Study One examines how manipulations of symmetry, averageness, femininity, and masculinity affect attractiveness using a two-alternative forced choice task, revealing that increased masculinity is unattractive, but increased femininity is not, and large effects observed for averageness. Study Two utilises a naturalistic ratings paradigm, finding similar effects of averageness and masculinity, but no effects of femininity and symmetry on attractiveness. Study Three applies a random forest machine learning algorithm and geometric measurements of the factors from faces to predict perceived attractiveness, finding that averageness and dimorphism are useful features capable of relatively accurate predictions. However, the factors do not explain as much variance in attractiveness as the wider literature suggests. Implications for future research on attractiveness are discussed.
Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. The cooperative eye hypothesis suggests the white sclera of humans to be a derived adaptive trait that enhances eye-mediated communication. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) that show marked differences in social cognition and quantify scleral exposure at the genus level. Our data reveals a continuum of eye pigmentation traits in hominoids which does not align with the complexity of gaze-mediated communication in the studied taxa. Gibbons display darker eyes than great apes and expose less sclera. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other apes. We reevaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot explain the patterns observed. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.
Previous research (Laeng et al., 2007) conducted on Norwegian samples showed that blue-eyed men rate blue-eyed women as more attractive, while brown-eyed men and all the women show no differences in attractiveness assessments with respect to eye colour. Correspondingly, positive assortative mating was found for blue, but not brown eyes, and it most often occurred in blue-eyed men. We aimed to replicate this blue-like-blue effect in the Croatian population, which differs in the ratio of eye colour phenotypes (blue eye colour is the most prevalent in Norway while brown is the most prevalent in Croatia). Additionally, we examined whether this effect is moderated by life history strategies and sociosexuality. Our hypothesis was that the effect would be larger in those blue-eyed men who exert a slower life history strategy and who are sociosexually restrictive. One hundred and twenty-eight participants assessed the attractiveness of blue-eyed and brown-eyed models, whose eye colours were experimentally manipulated in such a way that participants were shown models with natural or artificially changed eye colours. The blue-like-blue effect was replicated in the context of preferences, although it was smaller than in the original study. However, unlike the original study, in a sample of 138 participants no assortative pairing by eye colour was found between participants and their romantic partners. Finally, the hypothesis about the moderation was supported for life history strategies, but not for sociosexuality. In addition to the rationale for the blue-like-blue effect based on the paternity uncertainty account, which was offered by the authors of the original study, we discussed other accounts of this phenomenon.
Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. In the context of the cooperative eye hypothesis, the white sclera of humans has been viewed as a derived adaptive trait, enhancing communication via glance cueing. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) representing all extant ape genera, based on photographs and literature data. Additionally, we quantify hominoid scleral exposure on the genus level during different glancing situations. Our data reveals a continuum of eye pigmentation traits among the studied taxa. Gibbons display darker, more uniformly colored eyes than great apes and expose less sclera, particularly during averted glancing. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other great apes and that does not enhance glance cueing or gaze following. We critically evaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot convincingly explain the patterns observed. Although the human eye exhibits unique traits that are likely linked to social communication, high iridoscleral contrast is not one of them. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.
In recent years there have been many modalities to change and enhance the color of the eye. Many studies have been reported on anthropological and evolutionary significance of the eye color. There is a significant market in cosmetic industry for eye color change as exist with skin whitening, Hair color products and nail polishes. At present, the eye color change options have become available by introduction of colored contact lenses, laser intervention and surgical implants, also other small molecules and topical applications are in the process of investigation by research and commercial institutions. Here, each option has been discussed and their benefits and disadvantages were reviewed. The benefits and side effects as are summarized in relevant tables.
Red hair is associated in women with pain sensitivity. This medical condition, and perhaps others, seems facilitated by the combination of being red-haired and female. We tested this hypothesis by questioning a large sample of Czech and Slovak respondents about the natural redness and darkness of their hair, their natural eye color, their physical and mental health (24 categories), and other personal attributes (height, weight, number of children, lifelong number of sexual partners, frequency of smoking). Red-haired women did worse than other women in ten health categories and better in only three, being particularly prone to colorectal, cervical, uterine, and ovarian cancer. Red-haired men showed a balanced pattern, doing better than other men in three health categories and worse in three. Number of children was the only category where both male and female redheads did better than other respondents. We also confirmed earlier findings that red hair is naturally more frequent in women than in men. Of the ‘new’ hair and eye colors, red hair diverges the most from the ancestral state of black hair and brown eyes, being the most sexually dimorphic variant not only in population frequency but also in health status. This divergent health status may have one or more causes: direct effects of red hair pigments (pheomelanins) or their by-products; effects of other genes that show linkage with genes involved in pheomelanin production; excessive prenatal exposure to estrogen (which facilitates expression of red hair during fetal development and which, at high levels, may cause health problems later in life); evolutionary recentness of red hair and corresponding lack of time to correct negative side effects; or genetic incompatibilities associated with the allele Val92Met, which seems to be of Neanderthal origin and is one of the alleles that can cause red hair.
Assortative mating refers to the tendency of two partners' characteristics to be matched in a systematic manner, usually in the form of similarity. Mating with a similar partner has profound implications at the species, societal, and individual levels. This article provides a comprehensive review of research on couple similarity since 1980s. The review begins with the general patterns and trends observed in couple similarity on a range of domains including demographic variables, physical/physiological characteristics, abilities, mental well-being, habitual behaviors, attitudes, values, and personality. Next the bulk of the review focuses on analyses of 4 mechanisms leading to similarity: initial active choice, mating market operation, social homogamy, and convergence. Specific future research avenues are outlined to improve understanding of these mechanisms. Finally, the review discusses genetic, social, and psychological consequences of couple similarity.
Past research on married couples has documented positive assortment on cognitive abilities, attractiveness and physical features, attitudes and values, and, to a lesser degree, personality. in the current study, we proposed that if partners mate assortatively rather than converge over time, then assortative mating coefficients for dating couples should be similar in magnitude to those found for married couples. Second, as per filter models of relationship development, we hypothesized that similarity in dating partners' political and religious attitudes (as opposed to personality) would be associated with staying together over time. With a sample of 51 heterosexual dating couples, we found a pattern of assortative mating coefficients that mirrored the pattern found among married couples. As expected, couples still together at the 11-month follow-up had more similar attitudes at studyonset compared to those who had broken up.
Previous reports suggest that average faces are attractive, and that humans innately recognize and appreciate the attractiveness in the average face. The exception report model of face recognition employs the koinophilic fittest (modal) face for efficient and rapid recognition of conspecifics. The closeness of a face to the modal face is a measure of its attractiveness, whereas the departures from it are a measure of its ugliness and individuality. The 'fusiform face area' on the inferior surface of the temporal lobes of the brain might evaluate both the beauty and individuality of a face in a single, efficient and an evolutionarily well-honed operation. ABILITY to judge the potential fitness of a mate and the highly specialized cognitive skills that help us identify individuals in the community appear to have little in common. While both are critical for survival, there is no recorded literature on any explicit connection between the two. This article aims to highlight an evolutionary link connecting mate selection and face recognition. Before trying to explain how the cognitive skills that guided mate selection improved the recognition between conspecifics (members of the same species), it is impor-tant to set the stage for understanding the context that invokes the connection between two seemingly independ-ent cognitive domains. In the following pages, I propose to outline the body of research that suggests a strong evo-lutionary connection between the two phenomena.
Europeans, particularly northern and eastern Europeans, are unusually colored. Their hair can be not only black but also brown, flaxen, golden, or red, and their eyes not only brown but also blue, gray, hazel, or green. Their skin is pale, almost like an albino’s. This color scheme is more developed in women than in men and seems to have been selected for its visual properties, particularly brightness and novelty. Sexual selection is a likely cause. It favors eye-catching colors and, if strong enough, can produce a color polymorphism, i.e., whenever a visible feature becomes differently colored through mutation, the new color will spread through the population until it loses its novelty value and becomes as frequent as the original one. Such selection is consistent with 1) the many alleles for European hair and eye color; 2) the high ratio of nonsynonymous to synonymous variants; and 3) the relatively short time over which this color diversity developed. Sexual selection will target women if they outnumber men on the mate market. Among early modern humans, such imbalances resulted from 1) a low polygyny rate (because few men could provide for a second wife and her children) and 2) a high risk of early male death (because long hunting distances increased exposure to environmental hazards). Sexual selection of women was stronger at latitudes farther from the equator, where men were less polygynous and more at risk of death while hunting. It was strongest on continental steppe-tundra, where men provided for almost all family food needs by pursuing herds of reindeer and other herbivores over long distances. Although this type of environment is now fragmentary, it covered until 10,000 years ago a much larger territory—the same area where, today, hair and eyes are diversely colored and skin almost milk white.
There are two basic theories explaining possible principles on which people are attracted to each other
and how individuals create sexual and romantic relationships. The theory of homogamy states that in their potential or
actual partners individuals prefer characteristics that are similar to themselves ("birds of a feather flock together").
One of the mechanisms that can cause homogamy in partners might be sexual imprinting. According to this theory, individuals prefer in potential partners traits that are similar to those of the opposite sex parent. In contrast, the theory of complementarity suggests that individuals are attracted to partners with traits that are opposite to their own ("opposites attract"). From an evolutionary perspective, homogamous preferences can be explained by the theory of kin selection and outbreeding depression avoidance, while pairing on the principle of complementarity is advantageous in terms of inbreeding avoidance. We will critically review these two theories – including their implications and empirical support – from the perspective of evolutionary psychology and human ethology. We will argue that principles of homogamy and complementarity are not necessarily mutually exclusive but, rather, are complementary.
We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.
Human hair and eye color is unusually diverse in northern and eastern Europe. The many alleles involved (at least seven for hair color) and their independent origin over a short span of evolutionary time indicate some kind of selection. Sexual selection is particularly indicated because it is known to favor color traits and color polymorphisms. In addition, hair and eye color is most diverse in what used to be, when first peopled by hunter-gatherers, a unique ecozone of low-latitude continental tundra. This type of environment skews the operational sex ratio (OSR) of hunter-gatherers toward a male shortage in two ways: (1) men have to hunt highly mobile and spatially concentrated herbivores over longer distances, with no alternate food sources in case of failure, the result being more deaths among young men; (2) women have fewer opportunities for food gathering and thus require more male provisioning, the result being less polygyny. These two factors combine to leave more women than men unmated at any one time. Such an OSR imbalance would have increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of color traits: hair-and eye-color diversity and, possibly, extreme skin depigmentation.
Positive sexual imprinting is a process by which individuals use the phenotype of their opposite-sex parent as a template
for choosing mates and is suggested to play an important role in human mate choice. In contrast, negative imprinting, or “The
Westermarck Effect”, is characterized by individuals developing a strong sexual aversion to others with whom they lived closely
in infancy and early childhood. In this review, we evaluate the literature on their effects on mate choice in humans. We find
little evidence to support positive imprinting in humans because the studies either have serious design flaws, do not exclude
effects of heritable mating preferences, or do not account for several possible alternative explanations. Instead, it seems
that the opposite phenomenon, negative sexual imprinting, has some support from natural experiments which have found that
individuals avoid mating with those with whom they lived closely in infancy and early childhood. However, it seems that early
association does not produce a strong-enough aversion to completely annihilate sexual desire, probably because the mind uses
multiple kinship cues to regulate inbreeding avoidance. Thus, it appears that the evidence for both types of imprinting is
fairly weak in humans. Thus, more studies are needed to test the role of sexual imprinting on mate choice in humans, especially
those measuring interactions between positive and negative imprinting.
KeywordsAssortative mating–Evolved mating preferences–Freud–
Homo sapiens
–Homogamy–Incest avoidance–Imprinting–Partner similarity–Phenotype matching–Sexual selection–Westermarck
The human eye color blue reflects a simple, predictable, and reliable genetic mechanism of inheritance. Blue-eyed individuals
represent a unique condition, as in their case there is always direct concordance between the genotype and phenotype. On the
other hand, heterozygous brown-eyed individuals carry an allele that is not concordant with the observed eye color. Hence,
eye color can provide a highly visible and salient cue to the child’s heredity. If men choose women with characteristics that
promote the assurance of paternity, then blue-eyed men should prefer and feel more attracted towards women with blue eyes.
To test these predictions, close-up photos of young women and adult men with either blue or brown eyes were rated for their
attractiveness by young women and men observers with either blue or brown eyes (N=88). The eye color in the photographs of each model was manipulated so that a same face would be shown with either the natural
eye color (e.g., blue) or with the other color (e.g., brown). Both blue-eyed and brown-eyed female participants showed no
difference in their attractiveness ratings for male models of either eye color. Similarly, brown-eyed men showed no preference
for either blue-eyed or brown-eyed female models. However, blue-eyed men rated as more attractive the blue-eyed women than
the brown-eyed ones. We interpret the latter preference in terms of specific mate selective choice of blue-eyed men, reflecting
strategies for reducing paternity uncertainty. In a second study, a group of young adults (N=443) of both sexes and different eye colors (blue, brown, and green) were asked to report the eye and hair color of their
romantic partners. Their responses indicated the presence of assortative mating by eye color as well as, to a less degree,
for hair color. Most importantly, blue-eyed male respondents were the group with the largest proportion of partners of same
eye color. These findings 1) indicate that blue-eyed men do prefer women with the same eye color and 2) specifically suggest
the presence of a male adaptation for the detection of extra-pair paternity based on eye color, as a phenotypically based
assurance of paternity (i.e., when the father’s and offspring’s phenotypes match) as well as a defense against cuckoldry (i.e.,
when the phenotypes do not match).
Models of inter-sexual selection generally assume heritable variation in mating preferences among females within populations. However, little is known about the nature of such variation. The aim of this study was to characterize quantitatively the phenotypic variation in female preference for a sexually selected male trait, body colour pattern, within a population of the Trinidadian guppy, Poecilia reticulata. Significantly more female guppies preferred the more brightly coloured of two similar-sized males presented simultaneously as potential mates. Mating preference scores for individual females were significantly and positively correlated between two repeated trials on successive days. Females were thus individually consistent in their particular choice of mates, and the calculated repeatability of their mating preference was relatively high. Notwithstanding the aforementioned, significant variation existed among females in the degree of their preference for brightly coloured males. Individual mating preference scores were not normally distributed, but were rather skewed to the right (i.e. towards greater values). These results suggest that additive genetic variation for mating preferences based on male colour pattern is maintained, and the opportunity for the further evolution of both bright male colour patterns and female preference for this trait appears to exist in the study population from the Quaré River, Trinidad.
This study focuses on the relationship between eye color, gender, and psychological characteristics perceived from the human face. Photographs of 40 male and 40 female students were rated for perceived dominance and attractiveness. Attractiveness showed no relation with eye color. In contrast, eye color had a significant effect on perceived dominance in males: brown-eyed men were rated as more dominant than men with blue eyes. To control for the effect of eye color, we studied perceived dominance on the same photographs of models after changing the iris color. The eye color had no effect on perceived dominance. This suggests that some other facial features associated with eye color affect the perception of dominance in males. Geometric morphometrics have been applied to reveal features responsible for the differences in facial morphospace of blue-eyed and brown-eyed males.
Although eye color is usually modeled as a simple, Mendelian trait, further research and observation has indicated that eye color does not follow the classical paths of inheritance. Eye color phenotypes demonstrate both epistasis and incomplete dominance. Although there are about 16 different genes responsible for eye color, it is mostly attributed to two adjacent genes on chromosome 15, hect domain and RCC1-like domain-containing protein 2 (HERC2) and ocular albinism (that is, oculocutaneous albinism II (OCA2)). An intron in HERC2 contains the promoter region for OCA2, affecting its expression. Therefore, single-nucleotide polymorphisms in either of these two genes have a large role in the eye color of an individual. Furthermore, with all genetic expression, aberration also occurs. Some individuals may express two phenotypes--one in each eye--or a complete lack of pigmentation, ocular albinism. In addition, the evolutionary and population roles of the different expressions are significant.
People often prefer familiar stimuli, presumably because familiarity signals safety. This preference can occur with merely repeated old stimuli, but it is most robust with new but highly familiar prototypes of a known category (beauty-in-averageness effect). However, is familiarity always warm? Tuning accounts of mood hold that positive mood signals a safe environment, whereas negative mood signals an unsafe environment. Thus, the value of familiarity should depend on mood. We show that compared with a sad mood, a happy mood eliminates the preference for familiar stimuli, as shown in measures of self-reported liking and physiological measures of affect (electromyographic indicator of spontaneous smiling). The basic effect of exposure on preference and its modulation by mood were most robust for prototypes (category averages). All this occurs even though prototypes might be more familiar in a happy mood. We conclude that mood changes the hedonic implications of familiarity cues.
This study attempted to determine whether people who live with each other for a long period of time grow physically similar in their facial features. Photographs of couples when they were first married and 25 years later were judged for physical similarity and for the likelihood that they were married. The results showed that there is indeed an increase in apparent similarity after 25 years of cohabitation. Moreover, increase in resemblance was associated with greater reported marital happiness. Among the explanations of this phenomenon that were examined, one based on a theory of emotional efference emerged as promising. This theory proposes that emotional processes produce vascular changes that are, in part, regulated by facial musculature. The facial muscles are said to act as ligatures on veins and arteries, and they thereby are able to divert blood from, or direct blood to, the brain. An implication of the vascular theory of emotional efference is that habitual use of facial musculature may permanently affect the physical features of the face. The implication holds further that two people who live with each other for a longer period of time, by virtue of repeated empathic mimicry, would grow physically similar in their facial features. Kin resemblance, therefore, may not be simply a matter of common genes but also a matter of prolonged social contact.
A. L.
Dear A. L.: As far as physical appearance is concerned, likes seem to attract. Some experts feel that this resemblance may partly be explained by the fact that couples who've lived together for some time usually eat the same diet and share the same habits.
The Joyce Brothers Column
April 1985
Human romantic partners tend to have similar physical traits ¹ , but the mechanisms causing this homogamy are controversial. One potential explanation is direct matching to own characteristics 2,3 . Alternatively, studies showing similarity between parent and partner 4,5 support positive sexual imprinting 6,7 , where individuals are more likely to choose mates with the physical characteristics of their other-sex parent. This interpretation has been strongly criticized because the same pattern could also be caused by sex-linked heritable preferences ³ , where similarity in appearance between an individual’s partner and their other-sex parent is caused by similarity in preferences between the individual and their same-sex parent. The relationships among own, parents’ and same-sex partner’s eye color provide an elegant test of these hypotheses, which each postulate a different best predictor of partner’s eye color. While the matching hypothesis predicts this will be own eye color, the sex-linked heritable preference hypothesis predicts this will be the other-sex parent’s eye color and the positive sexual imprinting hypothesis predicts this will be the partner-sex parent’s eye color. Here we show that partner eye color was best predicted by the partner-sex parent’s eye color. Our results provide clear evidence against matching and sex-linked heritable preference hypotheses, and support the positive sexual imprinting hypothesis of the relationship between own and partner’s eye color.
Body constitution plays an important role in human mate choice. Cross-cultural research reports that women on average prefer men with muscular physique. It is still unclear, however, what mechanisms influence the inter-individual variation in mate preferences and choices of partner's physique. In this study, we tested the mechanisms of an imprinting-like effect (similarity between father and an ideal and actual partner) and of homogamy (similarity between self and an ideal and actual partner) for male physique in heterosexual women and homosexual men. To assess the variation in male physique, we employed somatotype paradigm which characterizes body constitution using three components: endomorphic (heavy-set), mesomorphic (muscular), and ectomorphic (lean). In total, 149. homosexual men and 769. heterosexual women from the Czech Republic indicated the somatotype of their father, ideal and actual partner, and in homosexual men also their own somatotype. In line with previous research, the somatotype most preferred by both men and women was the mesomorphic, followed by the ectomorphic and the endomorphic one. Women's preferences for an ideal partner somatotype weakly correlated with their fathers' somatotype, especially in women who reported a positive relationship with their fathers during childhood. Among homosexual men, we found imprinting-like preferences only for the ectomorphic somatotype component and no significant association with the quality of their relationships with their fathers. We also found no significant relationship between the fathers' and actual partners' somatotype in either heterosexual women or homosexual men. Our research indicates that fathers have a rather weak influence on mate preference for somatotypes and no influence on actual mate choice.
Theoretical perspectives on mating differentially emphasize whether (and why) romantic partner selection and maintenance processes derive from stable features of individuals (e.g., mate value, mate preferences, relationship aptitude) and their environments (e.g., social homogamy) rather than adventitious, dyad-specific, or unpredictable factors. The current article advances our understanding of this issue by assessing how people’s actual romantic partners vary on constructs commonly assessed in evolutionary psychology (Study 1), sociology (Study 2), and close relationships (Study 3). Specifically, we calculated the extent to which the past and present partners of a focal person (i.e., the person who dated all of the partners) cluster on various measures. Study 1 investigated consistency in the observable qualities of the romantic partners, revealing substantial evidence for clustering on coder-rated attributes like attractiveness and masculinity. Study 2 examined qualities self-reported by romantic partners themselves in a demographically diverse sample and found modest evidence for clustering on attributes such as IQ and educational aspirations; however, clustering in this study was largely due to demographic stratification. Study 3 explored target-specific ratings by partners about the focal person and found little evidence for clustering: The ability to elicit high romantic desirability/sexual satisfaction ratings from partners was not a stable individual difference. The variables that affect mating may differ considerably in the extent to which they serve as stable versus unpredictable factors; thus, the fields of evolutionary psychology, sociology, and close relationships may reveal distinct depictions of mating because the constructs and assessment strategies in each differ along this underappreciated dimension.
Objective:
To determine whether eye color changes after 6 years of age.
Design:
Longitudinal data on eye color were obtained from the Louisville Twin Study, Louisville, Ky. Twins (n=1513 [individuals]) were assessed at least once and most twins (n=1386) were examined on 2 or more occasions. Parents of twins were also examined at the study inception, 128 of whom were assessed again from February 1989 to October 1993.
Main Outcome Measure:
Eye color was assessed at each examination by matching the iridial coloration of the subject to 1 of 15 painted glass eye anterior segments, similar to those in artificial eyes, mounted on a circular disk. The spectrum ranged from light blue (1) to dark brown (15).
Results:
Among whites (n= 1359), the eye color of 3.8% to 8.6% of the sample twins became 2 U or more darker or 2 U or more lighter during 3- to 9-year intervals between 6 years of age and adulthood (>18 years, <24 years). Among identical (monozygotic) twin pairs, there was a high degree of concordance in eye color (r=0.98 [P<.001]), while in fraternal (dizygotic) twin pairs, the concordance was less pronounced (r=0.49) and decreased with age (r=0.07). Among the sample of the mothers of twins, 9% had irides that lightened by 2 U or more during the follow-up period.
Conclusion:
Most individuals achieve stable eye color by 6 years of age. However, a subpopulation of 10% to 15% of white subjects have changes in eye color through-out adolescence and adulthood in the eye color range that can be expected to reflect changes in iridial melanin content or distribution. These data also suggest that such changes in eye color, or the propensity to such changes, may be genetically determined.
Using the five-factor model of personality, this study investigates the contribution of personality traits to marital adjustment. The sample is composed of 446 couples who completed the NEO Five-Factor Inventory, which measures the personality traits of neuroticism, extraversion, openness, agreeableness, and conscientiousness, as well as the Dyadic Adjustment Scale. Results of hierarchical regression analyses indicated that self-reported and partner-reported personality traits were significant predictors of self-reported marital adjustment for both men and women. Personality traits were found to contribute to the prediction of marital adjustment over and above the effect of neuroticism.
The various milestones and transitions of emerging adulthood have led previous researchers to investigate continuity and change in personality traits during this life period. In the current study, we build on that research by investigating continuity and change during emerging adulthood in mate preferences and mating orientations. Following past research, we hypothesized that mate preferences and mating orientations would demonstrate weak-to-moderate rank-order stability over 3 years of emerging adulthood. We also hypothesized that emerging adults would display mean-level changes that reflect increasing maturity, such as an increased emphasis on long-term committed relationships and partners’ internal attributes and a decreased emphasis on short-term sexual relationships and partners’ physical attractiveness. We followed 200 young adults from their first year to their fourth year in college. Analyses revealed weak-to-moderate rank-order stability but very little mean-level change in mate preferences and mating orientations. We discuss limitations of this study and directions for future research.
Human hair and eye color is unusually diverse in northern and eastern Europe. The many alleles involved (at least seven for hair color) and their independent origin over a short span of evolutionary time indicate some kind of selection. Sexual selection is particularly indicated because it is known to favor color traits and color polymorphisms. In addition, hair and eye color is most diverse in what used to be, when first peopled by hunter-gatherers, a unique ecozone of low-latitude continental tundra. This type of environment skews the operational sex ratio (OSR) of hunter-gatherers toward a male shortage in two ways: (1) men have to hunt highly mobile and spatially concentrated herbivores over longer distances, with no alternate food sources in case of failure, the result being more deaths among young men; (2) women have fewer opportunities for food gathering and thus require more male provisioning, the result being less polygyny. These two factors combine to leave more women than men unmated at any one time. Such an OSR imbalance would have increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of color traits: hair- and eye-color diversity and, possibly, extreme skin depigmentation.
Assortative mating in human and other animal species is reviewed. Assortive mating is most often positive (between individuals sharing phenotypic similarity), occurs on a variety of normal and abnormal traits, strengthens the mating bond, and increases fertility. These results can best be understood if it is assumed that natural selection operates to increase genetic homology between mates and between parents and off-spring. The outcome of selection for positive assortment is to increase the genetic relatedness among family members, thus facilitating communication and altruism and increasing inclusive fitness without an additional reproductive effort. The opposing evolutionary vector is to restrict excessive homozygosity and consequent inbreeding deppression by minimizing matings between individuals of greatest similarity (e.g., members of nuclear families). The result of these opposing evolutionary vectors is a negative relationship between the degree of positive assortative mating and heritability (h2): individuals gravitate toward those of similar but not identical phenotypic (and genetic) similarity. Individuals may assess their own and their potential mates' homozygosity and mate so as to maximize genetic homogamy and still avoid excessive inbreeding. Early imprinting and learning within the family unit act as the proximate mechanisms to establish the criteria for optimal mate selection. Predictions that follow from this model are advanced, and several problems are discussed. Laboratory and field work with animals will be especially valuable in advancing our understanding of assortative mating.
The present study investigated the validity of stereotyped beliefs about sex differences in preferences for opposite sex coloration. The likes and dislikes of 482 female and 549 male Caucasian college students for eye color, hair color, and complexion color of the opposite sex were investigated by means of a sexual selection questionnaire. Results indicated sex differences in both likes and dislikes for all three features. Males indicated somewhat greater preference for lighter female coloration, while females indicated somewhat greater preference for darker male coloration. These results were discussed in terms of the “kernel of truth” hypothesis of stereotyping, and the possible relationship to earlier research on semantic meanings of color and gender words. Special attention was paid to the tremendous aversion of both sexes to redheads, and to the possible implications of the study for understanding the predominance of black male/white female couplings in black-white interracial marriage in contemporary America.
We staged female mate choice trials between pairs of males and repeated the process for each female to determine the repeatability
of female preference for males in red jungle fowl (Gallus gallus) in the first and second half of the breeding season. We measured male morphological traits (the size and color of the comb
and the brightness of the hackle feathers) that females are known to use in choosing a mate. In the first half of the breeding
season, females showed repeatability in their choices of mate with respect to the male's comb characters. Females did not
show a repeatable preference with respect to male hackle feathers, and we found no repeatability of mate choice in the second
half of the season. Females seem to primarily look at the male's comb when choosing a mate, and other ornaments seem only
of secondary importance.[Behav Ecol 7: 243-246 (1996)]
In recent years, several studies have greatly increased our understanding of the genetic basis underlying human eye colour variation. A large percentage of the eye colour diversity present in humans can already be genetically explained, so much so that different DNA-based eye colour prediction models, such as IrisPlex, have been recently developed for forensic purposes. Though these models are already highly accurate, they are by no means perfect, with many genotype-phenotype discrepancies still remaining unresolved. In this work we have genotyped six SNPs associated with eye colour (IrisPlex) in 535 individuals from Spain, a Mediterranean population. Aside from different SNP frequencies in Spain compared to Northern Europe, the results for eye colour prediction are quite similar to other studies. However, we have found an association between gender and eye colour prediction. When comparing similar eye colour genetic profiles, females tend, as a whole, to have darker eyes than males (and, conversely, males lighter than females). These results are also corroborated by the revision and meta-analysis of data from previously published eye colour genetic studies in several Caucasian populations, which significantly support the fact that males are more likely to have blue eyes than females, while females tend to show higher frequencies of green and brown eyes than males. This significant gender difference would suggest that there is an as yet unidentified gender-related factor contributing to human eye colour variation.
Research has shown that human partners are more similar than expected by chance on a variety of traits. Studies examining hair and eye colour show some evidence of positive assortment. Positive assortment may reflect attraction to self-similar characteristics but is also consistent with attraction to parental traits. Here, we examine self-reported partner hair and eye colour and the influence that own and parental colour characteristics have on these variables. Parental characteristics were found to correlate positively with actual partner characteristics for both men and women. Regression analysis predicting partner characteristics from maternal and paternal traits (which controls for own traits) revealed the greater importance of the opposite-sex parent over the same-sex parent in predicting both hair and eye colour of actual partners. The findings may reflect an influence of parental colour characteristics on human partner choice. Attraction to opposite-sex parental characteristics is seen in a wide variety of animals where it is usually attributed to imprinting processes in infancy. Although the mechanism is unclear and not necessarily confined to infancy, the data reported here are consistent with a somewhat analogous process to imprinting occurring in humans.
The limbal ring of the eye appears as a dark annulus where the iris meets the sclera. Both width and opacity of the limbal ring are influenced by iris pigmentation and optical properties of the region. With age the limbal ring becomes less prominent, making it a probabilistic indicator of youth and health. This raises the question: Are judgments of facial attractiveness sensitive to this signal in a potentially adaptive way? Here we show that the answer is yes. For male and female observers, both male and female faces with a dark and distinct limbal ring are rated as more attractive than otherwise identical faces with no limbal ring. This result is observed not just for upright faces but also for inverted faces, suggesting that the limbal ring is processed primarily as a local feature rather than as a configural feature in the analysis of facial beauty. We also discuss directions for future research that can clarify the role of the limbal ring in the visual perception of facial attractiveness.
A new theory of attraction and liking based on kin selection suggests that people detect genetic similarity in others in order to give preferential treatment to those who are most similar to themselves. There are many sources of empirical and theoretical support for this view, including (1) the inclusive fitness theory of altruism, (2) kin recognition studies of animals raised apart, (3) assortative mating studies, (4) favoritism in families, (5) selective similarity among friends, and (6) ethnocentrism. Specific tests of the theory show that (1) sexually interacting couples who produce a child are genetically more similar to each other in blood antigens than they are either to sexually interacting couples who fail to produce a child or to randomly paired couples from the same sample; (2) similarity between marriage partners is most marked in the more genetically influenced of sets of anthropometric, cognitive, and personality characteristics; (3) after the death of a child, parental grief intensity is correlated with the child's similarity to the parent; (4) long-term male friendship pairs are more similar to each other in blood antigens than they are to random dyads from the same sample; and (5) similarity among best friends is most marked in the more genetically influenced of sets of attitudinal, personality, and anthropometric characteristics. The mechanisms underlying these findings may constitute a biological substrate of ethnocentrism, enabling group selection to occur.
Human homogamy may be caused in part by individuals' preference for phenotypic similarities. Two types of preference can result in homogamy: individuals may prefer someone who is similar to themselves (self-referent phenotype matching) or to their parents (a sexual-imprinting-like mechanism). In order to examine these possibilities, we compare faces of couples and their family members in two ways. First, "perceived" similarity between a pair of faces is quantified as similarity ratings given to the pair. Second, "physical" similarity between two groups of faces is evaluated on the basis of correlations in principal component scores generated from facial measurements. Our results demonstrate a tendency to homogamy in facial characteristics and suggest that the tendency is due primarily to self-referent phenotype matching. Nevertheless, the presence of a sexual-imprinting-like effect is also partially indicated: whether individuals are involved in facial homogamy may be affected by their relationship with their parents during childhood.
Models of sexual selection by female choice require heritable variation in female mating preferences in order for sexual
selection to operate. However, recent theoretical work shows that female preferences which are transmitted non-genetically
can result in exaggeration of male ornamentation. Guppies exhibit both mate copying and considerable heritable variation in
female preferences. I studied the importance of these phenomena by measuring repeatability of female mate choice, which acts
as an estimate of the upper limit to which a feature may be heritable, and the incidence of mate choice reversal in paired-trial
binary mate choice experiments. Mate choice was significantly repeatable except in the treatment where females were given
the opportunity to copy a female that contradicted their original choice. Apart from this, I found no evidence that females
copy the mate choice of others. The differences between males in ornamentation had no effect on the consistency of female
mate choice or the probability that they would reverse their original choice decision (in both controls and the copying experiment).
The interval between choice trials did not influence repeatability significantly, indicating that the independence of choice
decisions is not related to the time interval between them.
HYPOTHESIZES THAT MERE REPEATED EXPOSURE OF THE INDIVIDUAL TO A STIMULUS OBJECT ENHANCES HIS ATTITUDE TOWARD IT. BY "MERE" EXPOSURE IS MEANT A CONDITION MAKING THE STIMULUS ACCESSIBLE TO PERCEPTION. SUPPORT FOR THE HYPOTHESIS CONSISTS OF 4 TYPES OF EVIDENCE, PRESENTED AND REVIEWED: (1) THE CORRELATION BETWEEN AFFECTIVE CONNOTATION OF WORDS AND WORD FREQUENCY, (2) THE EFFECT OF EXPERIMENTALLY MANIPULATED FREQUENCY OF EXPOSURE UPON THE AFFECTIVE CONNOTATION OF NONSENSE WORDS AND SYMBOLS, (3) THE CORRELATION BETWEEN WORD FREQUENCY AND THE ATTITUDE TO THEIR REFERENTS, AND (4) THE EFFECTS OF EXPERIMENTALLY MANIPULATED FREQUENCY OF EXPOSURE ON ATTITUDE. THE RELEVANCE FOR THE EXPOSURE-ATTITUDE HYPOTHESIS OF THE EXPLORATION THEORY AND OF THE SEMANTIC SATIATION FINDINGS WERE EXAMINED. (PsycINFO Database Record (c) 2006 APA, all rights reserved).
Spousal similarity in terms of personality is advanced as a theoretically important factor to consider in subjective well-being (SWB). This is logically derived from four findings: (1) the consistent relationship between marital status and SWB, with married Ss having the highest SWB scores, which is attributed to good marriage quality; (2) good marriage quality is significantly correlated with high SWB; (3) marriage stability and marriage quality are predicted by similarity between partners in terms of personality; and (4) homogamy in psychological distress and SWB is the rule in (non-clinical) general population couples. The hypothesis that high similarity in personality scores of intimate partners from the general population would correlate significantly with SWB (as assessed with the Satisfaction With Life Scale or SWLS) was confirmed in both sexes. Other things (e.g., individual personality factors, marriage quality and marital intimacy) being equal, high partner/spouse personality-similarity predicted high SWB in males, but not in females. Potential explanations for this sex difference are briefly discussed, as are its clinical implications.
Numerous studies have measured the mating preferences of female zebra finches, Taeniopygia guttata, using choice-chamber experiments, but no study has focused on how consistent individual females are in their choices and the extent to which females agree on their preferences, although these questions are of great conceptual importance. We conducted a large number of mate choice trials involving unmanipulated stimulus males, and found low but significant consistency (repeatability of time allocation by a female tested twice with the same set of males R = 0.29), and very low but significant between-female agreement (different females tested with the same set of males: R = 0.11). Although low individual consistency indicates that preferences were relatively weak or hard to measure, we found significant repeatability of individual preference functions with regard to beak colour, song rate and male aggressiveness when individual females were tested twice with different sets of males. This means that some females consistently preferred red-beaked males whereas others preferred orange-beaked males, some preferred high and others low song rates, and some preferred aggressive and others less aggressive males. Of these male traits, only song rate was positively related to average male attractiveness. Low between-female agreement did not seem to result from assortative mating for quality, because there was no repeatability of an individual female's preference for attractive or unattractive males. It is possible that disagreement follows from choice for genetic compatibility, but much of it could also result from weak preferences and little variation in male quality.
Increasing evidence suggests that both mating patterns and fecundity correlate with the genetic similarity of the interactants in plants, animals and humans. Direct evidence is reported here for this phenomenon in humans. Based on blood antigen analyses of nearly 1,000 cases of disputed paternity, it was found that the degree of genetic similarity within pairs predicts (1) whether the pair is sexually interacting or randomly generated, and (2) whether the pair produced a child together or not. Seven polymorphic marker systems (ABO, Rhesus (Rh), P, MNSs, Duffy (Fy), Kidd (Jk), and HLA) at ten loci across six chromosomes were examined. Sexually interacting couples were found to share about 50% of measured genetic markers, part way between mothers and their offspring who share 73% and randomly paired individuals from the same sample who share 43%. Moreover, in the cases of disputed paternity, degree of genetic similarity in the sexually interacting couple predicted male inclusion: males not excluded from paternity were 52% similar to their partners whereas those excluded were only 44% similar.
Two experiments explored the relationship between familiarity, similarity, and attraction. In the first experiment, subjects viewed photographs of faces at various exposure frequencies and then rated them for likeableness and similarity. Familiar people were regarded by the subjects as both more likeable and more similar to themselves. The effects of familiarity on perceived similarity were primarily mediated by changes in attraction, although some evidence of a direct link between familiarity and perceived similarity was also found. In the second experiment, subjects viewed the same stimuli at a single exposure frequency, and received bogus information regarding the similarity of the people shown therein. Subsequent ratings of likeableness and perceived familiarity revealed that people who seemed similar to the subjects were regarded as both more likeable and more familiar. The effects of similarity on perceived familiarity were almost entirely mediated by changes in attraction. Some of the theoretical implications of these findings are discussed.
Whereas the hypothesis of genetically mediated homogamy has been supported by several studies, certain theoretical and methodological criticisms have been raised against genetic similarity theory. As an alternative approach to assortative mating, we suppose that imprinting-like mechanisms, rather than “direct” genetic detection, are responsible for choosing similar spouses. In a study aimed at comparing more than 300 facial photographs of family members and controls, the judges correctly matched wives to their mother-in-law at a significantly higher rate than expected by chance. Furthermore, a higher degree of similarity was ascribed between the husbands’ mother and the husbands’ wife than between the husbands and their wives. A regression analysis has revealed that men who had been more frequently rejected by their mother during childhood were less likely to choose mates who resemble their mothers in physical appearance. These results suggest that under the influence of childhood experiences, sons internalize their mother’s phenotype as a template for acquiring similar mates.
In a population whose members' genomes are subject to degradation by random mutations, the heritable vigour of the most common phenotypes is unquestionable (though not necessarily optimal), and that of fringe individuals is always suspect. Natural selection will therefore support the evolution of an affinity for modal mates (i.e. koinophilia). The population's genetic make-up can then not readily be invaded by non-cryptic mutations. This imposes considerable phenotypic conservatism on sexually reproducing creatures, and inexorably canalizes them into sexually isolated, phenotypically distinct species. The model predicts, and the empiric data confirms, that the phenotypic gaps between largely monomorphic sexual species do not characterize the taxonomy of longstanding apomicts, where variation below the genus level is often continuous. The bias against the propagation of all forms of phenotypic novelty and non-conformity stabilizes social animals against selfish mutants, thus removing the barriers to the evolution of "group adaptations".
Do girls fall in love with an image of their father? This study tested the hypothesis that, in choosing a partner, people tend to replicate the physical and mental attributes of their opposite-sex parent more than of the same-sex parent. A sample of 314 women, mostly in their late teens and describing themselves as ‘in love’, supplied details of their boyfriends and parents. A tendency for the boyfriend's eye colour to match that of the father more than of the mother was found, as well as a tendency for girls to replicate the age and dominance relationships of the parental partnership in their own relationship. These effects were very small and of marginal significance.
This paper is concerned with the evolution of the species phenotype (morphology and behaviour) when sexual organisms identify mutant traits by their unusual (or rare) appearance. Mate-seeking individuals are assumed, however, to have no means of distinguishing the occasional beneficial mutation from the others. We show that the resulting preference for mates with predominantly common traits (koinophilia) transforms the prevailing phenotype (as perceived by conspecifics) into an evolutionary stable strategy (ESS), as defined by Maynard-Smith (1974). This has far reaching evolutionary implications, permitting, in particular, the evolution of true "group adaptations". A subsidiary finding shows that koinophilia always has a substantial, immediate, selective advantage over panmixis, rendering koinophilia, itself, an ESS with respect to panmixis. This is particularly pronounced when the mutation rate is high, but beneficial mutations with high fitnesses are rare. The mean fitness of mutations has only a minor effect on the relative advantage of koinophilia.
The present research examined the possibility that repeated exposure may simultaneously produce specific and diffuse effects. In Study 1, participants were presented with 5-ms exposures of 25 stimuli each shown once (single-exposure condition) or with five repetitions of 5 stimuli (repeated-exposure condition). Participants in the repeated-exposure condition subsequently rated their own mood more positively than those in the single-exposure condition. Study 2 examined whether affect generated by subliminal repeated exposures transfers to unrelated stimuli. After a subliminal exposure phase, affective reactions to previously exposed stimuli, to new but similar stimuli, and to stimuli from a different category were obtained. Previously exposed stimuli were rated most positively and novel different stimuli least positively. All stimuli were rated more positively in the repeated-exposure condition than in the single-exposure condition. These findings suggest that affect generated by subliminal repeated exposure is sufficiently diffuse to influence ratings of unrelated stimuli and mood.
The past two decades have seen extensive growth of sexual selection research. Theoretical and empirical work has clarified many components of pre- and postcopulatory sexual selection, such as aggressive competition, mate choice, sperm utilization and sexual conflict. Genetic mechanisms of mate choice evolution have been less amenable to empirical testing, but molecular genetic analyses can now be used for incisive experimentation. Here, we highlight some of the currently debated areas in pre- and postcopulatory sexual selection. We identify where new techniques can help estimate the relative roles of the various selection mechanisms that might work together in the evolution of mating preferences and attractive traits, and in sperm-egg interactions.
Eumelanin (brown/black melanin) and pheomelanin (red/yellow melanin) in human hair can be quantified using chemical methods or approximated using spectrophotometric methods. Chemical methods consume greater resources, making them less attractive for epidemiological studies. This investigation sought to identify the spectrophotometric measures that best explain the light-dark continuum of hair color and the measure that is best able to distinguish red hair from nonred hair. Genetic analysis was performed on these two measures to determine the proportion of genetic and environmental influences on variation in these traits. Reflectance curves along the visible spectrum and subjective ratings of hair color were collected from 1730 adolescent twin individuals. Discriminant class analyses were performed to determine the spectrophotometric measure that could best proxy for eumelanin and pheomelanin quantities. The ratio of light reflected in the green portion of the spectrum to that reflected in the red portion of the spectrum was best able to distinguish red hair from nonred hair. Melanocortin 1 receptor (MC1R) genotype explained some, but not all, variation in this measure. Light absorbed in the red portion of the spectrum was best able to explain the light-dark continuum of hair color. Variance components analysis showed that there were qualitatively different genetic influences between males and females for the light-dark continuum of hair. Our results show that spectrophotometric measures approximating variation in eumelanin and pheomelanin may be considered as an alternative to chemical methods in larger epidemiological studies.
Mate preferences of married persons in the newlywed year and three years later
- Shackelford
Shackelford, T. K., Schmitt, D. P., & Buss, D. M. (2005). Mate preferences of married
persons in the newlywed year and three years later. Cognition & Emotion, 19,
1262-1270. https://doi.org/10.1080/02699930500215249.
Happiness cools the warm glow of familiarity: Psychophysiological evidence that mood modulates the familiarity-affect link
- De Vries
Positive sexual imprinting for human eye color
- Debruine