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Human mate preferences
All human populations known to science practice forms of formal reproductive alliances between men and women (marriages). More than 90% of the individuals in these populations marries a partner (Buss 1985, Epstein & Guttman 1984, Vandenberg 1972). Even though ”it takes two to tango” the reproductive pay-offs associated with such an alliance differ between the sexes since sexual reproduction gives rise to sexual conflicts between the sexes (Arnqvist & Rowe 2013). Men and women’s interests diverge in reproductive contexts ultimately due to anisogamy, where the initial investment differs between the sexes, leading to distinct reproductive roles (e.g. Trivers 1972, Chapman et al. 2003). These differences in basic conditions have driven the sexual selection in two directions, which in turn have generated different adaptive solutions for the two sexes (Thornhill & Thornhill 1983).
Researchers have for decades examined what characteristics humans have preferences for in a potential mate. They have by using different methods and sampled cross cultures produced a somewhat coherent picture. The reproductive successes of men have through human evolutionary history primarily been affected by the sexual access to women of high reproductive capacity (e.g. Williams 1975, Dawkins 1986). Men should therefore have preferences for female attributes that most reliably indicate high fecundity, i.e. youth, associated with a longer time period to produce offspring (Fisher 1930) and beauty, which has been associated with high fertility and good health (Johnston 2000). It has indeed been shown empirically and cross culturally that men have strong preferences for these two traits (Buss 1989, Kenrick & Keefe 1992, Singh 1993). The avenues, in which women have been able to increase their fitness, by mate choice, have been different than for men. Women may to a greater extent than men increase their fitness by tying the reproductive benefits, associated with a particular partner to themselves and their offspring (Trivers 1972). Women are therefore expected to have stronger preferences, relative to men, for attributes that indicate willingness and prospects to invest in partner and offspring. Indeed, the documented differences in mate preferences between men and women are those predicted by evolutionary theory (see Trivers 1972). Women seem to place a great value on cues for high social status (Buss & Barnes 1986, Fletcher et al. 1999, Kenrick et al. 1990, Parmer, 1998, Regan et al. 2000) and pertaining (Townsend & Levy 1990) when choosing a partner. Men place a greater value on physical attractiveness than women, whilst women to a higher degree than men value a potential partner’s financial prospects (Hill 1945, McGinnis 1958, Hudson & Henze 1969, Hoyt & Hudson 1981, Buss 1989, Wiederman & Allgeier 1992, Kenrick et al. 1993, Buss et al. 2001). There are also similarities in mate preferences between the sexes. Buss (1989) showed, in a sample of 37 cultures with a total sample size of nearly 10 000 individuals, that both sexes place strong value on qualities of emotional stability and pleasing dispositions in a potential mate. General mate preferences for traits of kindness/ tenderness have later been documented in other studies (Fletcher et al. 1999, Goodwin & Tang, 1991, Regan et al. 2000).
Women look for any man with an attractive partner
Jones et al. (2007) found that the facial expression of model women may affect focal women’s judgement of target men. Could it be that focal women use other information provided by models when assessing a man’s quality? Since Uller and Johanssons (2003) study “casts doubt on some simplified theories of human mate-choice copying”, they instead, discuss more complex theories of mate choice copying. They propose that women, like some females of other animals e.g. the guppy (Vukomanovic & Rodd 2008) and the sailfin mollies (Hill & Ryan 2006), copy the preferences of attractive but not unattractive females. Furthermore, they propose that the strength of desirability enhancement effects could depend on the target man’s quality, as shown to be the case for male guppies (Dugatkin 1996).
Little et al. (2008) set out to test how the attractiveness of a model depicted next to a target affects focal participant’s preferences for the target. They also tested if this effect was dependent of target attractiveness. This was done by presenting participants, of both sexes, with pairs of facial photographs. The facial photograph-pair was of one man and one woman, who were said to be romantically involved with each other. The photographs had been manipulated to more or less masculinized/feminized versions. The authors assumed that men prefer feminized faces and that women, over all, prefer masculinized faces (see Little et al. 2007). This assumption was later validated by their findings. Even so, the authors did point out that the preference for masculinized facial features is strong in short term but not long term mating contexts (Scheib 2001, Little & Hancock 2002). They also pressed the issue that the relationship between man attractiveness and masculinity is not clear since women have been found to have preferences for both masculinity (e.g. Cunningham 1990, Grammer & Thornhill 1994, DeBruine et al. 2006) and femininity (e.g. Berry & McArthur 1985, Little & Hancock 2002). Each facial photograph of the targets was presented for the focal individuals twice, once as masculinized and once as feminized, paired with a photograph of an opposite sex individual whose face had been either feminized or masculinized. The focal participants were asked to judge their short-term, long-term interest and the attractiveness of the opposite sex individuals presented in each pair.
The authors found that women find men on photographs more desirable as long-term partners when depicted with photographs of feminized rather than masculinized women. The corresponding relationship, increased preference for women depicted with masculinized man models, was found for focal men. Interestingly this social transmission effect was not affected by the masculinization/feminization of the targets themselves, indicating that the social transmission effect is independent of the attractiveness of the target. Furthermore, the fact that desirability enchantment was found only for long-term-interest suggests that copying is a way for women to increase direct benefits with mate choice.
Speed dating and real mate choice decisions
Studies investigating non-independent mate choice in humans, i.e. studies of the wedding ring effect (Uller & Johansson 2003, Eva & Wood 2006, Bressan & Stranieri 2008, Parker & Burkley 2009) and social transmission of preferences (Jones et al. 2007, Waynforth 2007, Little et al. 2008, Hill & Buss 2008) have all relied on simulated mate choice situations. In three of these studies the authors have assumed that the focal participants interpreted the targets as being chosen by models. One of these three has later tested this assumption (Uller & Johansson 2003) while two have not (Jones et al. 2007, Hill & Buss 2008). Other studies have had focal participants receive the information that a target has been chosen through social communication (Eva & Wood 2006, Waynforth 2007, Little et al. 2008, Bressan & Stranieri 2008, Parker & Burkley 2009). Finally, neither of the studies above have had focal individuals witness interaction between models and targets. By contrast, researchers of other animals have created settings where focal individuals witness models and targets interact semi naturally (e.g. Witte & Ryan 2002). Would the desirability enhancement effect, found in previous studies, persist after focal women observing real mate choice?
Place et al. (2010) set out to surmount the limitations from previous studies on humans. They did so by having focal participants witness target and models interact in a real mate choice interaction. Place et al. (2010) had focal participants evaluate their short term and long term interest of opposite sex individuals depicted on photographs. They were asked to do this pre and post looking at film clips of real speed dates between the targets and models. The photographs were of the individuals acting as targets on the speed-date films. There were two different film clips per target. One of the film clips showed an interaction where the target and the model had reported mutual sexual interest and the other was of a situation where there had been mutual disinterest. The focal participants each viewed eight film clips of target-model interactions. To test whether the participants were able to correctly assess the situation, the participants answered if they thought that there been interest between the model and the target.
The focal participants self-reported short term and long-term interest in the opposite sex targets increased both for focal women and men after seeing the target in a successful dating interaction. The focal participants were shown to accurately assess interest shown by models and targets. Also, the focal women’s interest declined after seeing the target in a dating interaction where target and model showed mutual disinterest. Furthermore, the focal men’s interest increased with the attractiveness of the model man. This pattern was not found for the focal women’s judgement. When discussing their findings Place et al. (2010) argues that their “results suggest that both men and women are influenced by social information when making both short-term and long-term relationship attractiveness judgments”. This could very well be true as suggested by Hill and Buss (2008). Place et al. (2010) continue, arguing that their results support the idea that men and women alike are positively affected by a desirability enhancement effect due to being chosen. This, on the other hand, directly contradicts the findings of Hill and Buss (2008) who argue that men and women might use the same contextual information but with the opposite outcome when assessing a potential mate’s quality. Place et al. (2010) have with their study progressed the work on independent mate choice by letting participants themselves gather the contextual information that might affect mate choice. By doing this they have successfully subverted the limitation of previous studies who had participants learn about the targets civil status through social communication. The results of Place et al. (2010) may be considered a novel contribution to the knowledge of the variability of human mate preferences. Unfortunately there is however no way of telling if the desirability enhancement effect documented in their study is actually due to the targets being chosen. I find it as likely that the effect is due to the focal participants signalling sexual interest i.e. increased courting behaviour or male display rate, a stimulus enhancement effect (see Westneat et al. 2000). Female Japanese medaka (Oryzias latipes) has a preference for actively courting males. This preference increases with increased male display rate due to males courting model females (Grant & Green1996). Such a preference for courting males could very well explain the results by Place et al. (2010). This alternative explanation could easily be controlled for by minor changes in their experimental design. One could have participants watch film clips where the model but not the targets showed sexual interest. If one were to perform such a study, one has to keep in mind that the disinterest shown by a target may constitute negative information regarding model quality and therefore affect the desirability ratings (see Jones et al. 2007).
When a focal individual perceives a target as increasingly desirable after watching the target being chosen by a model, has the focal individual then learned something only of the target (individual based copying) or has the focal individual also learned something about potential mates with traits similar to the target (trait based copying)? When investigating trait based copying, scientists have found it wherever individual based copying has been found e.g. female Japanese quail (White & Galef 2000), sailfin mollies and guppies (Witte & Noltemeier 2002), zebra finch (Swaddle et al. 2005) and female fruit flies (Mery et al. 2009). Since these five species constitute a group which is quite different from each other in terms of ecology, mating system and phylogeny, trait based copying seems to be a reliable predictor of individual based copying (Bowers et al. 2012). Humans have been shown to generalize in attractiveness ratings on arbitrary traits such eye spacing (Little et al. 2011) and shirt colour (see Bowers et al. 2012). Could perhaps generalization be a feature in human mate copying?
Bowers et al. (2012) set out to test whether human mate choice copying, i.e. the desirability enhancement effect found by Place et al. (2010), is merely individually based or also trait based. They did so by using more or less the same experimental design as Place et al. (2010), presented above. Just like the study by Place et al. (2010), Bowers et al. (2012) had focal participant rate the attractiveness of target individuals before and after watching a film clip of a successful or an unsuccessful mate choice situation. They replicated the study made by Place et al. (2010) by having the participants rate the same target before and after watching a film clip where the same target interact with a model. They also developed the study by having the participants’ rate photographs of targets other than the target on the film clips. These, for the participants, novel targets had either been manipulated or remained unaltered. The altered photographs were manipulated to look like the target men shown on the film clips. This was done by manipulation so that the targets on the photographs wore the same clothes, the same hair or the same face, i.e. lips, eyes and mouth as the targets on the film clips. The unaltered photographs were of targets that did not look like the targets on the film clips.
Focal/Model-women attractiveness dependence and mate value
Men have mate preferences for physical attractiveness (e.g. Buss 1989, Kenrick & Keefe 1992, Singh 1993). The avenue to monopolize on partners of high mate value, i.e. discriminate amongst potential mates is therefore greater for attractive women than for unattractive women. The attractiveness of a woman choosing a man should for this reason provide other women with information of the chosen man’s mate value. Women should therefore be psychologically primed to incorporate cues of same sex rivals attractiveness when making mate choice evaluations. This adaptation should work in different ways depending on the difference in mate value between the model and the focal woman. Since an attractive woman’s choice of a man is not only based high mate value of the chosen man but also smaller chance to monopolise on the man due to increased competition. Women of low mate value should therefore focus their mating effort where the competition for mates is less prominent, i.e. on potential mates who is not chosen by same sex rivals of high mate value. In contrast, women of high mate value should focus their mating effort on the pursuit of chosen men since that strategy carries a greater chance of success.
Model attractiveness evaluation
The desirability of the model women was determined by having female students rate the attractiveness of the model women during a lecture in developmental psychology at NTNU. The female students were informed that two women were going to enter the lecture hall. They were asked to rate the attractiveness of these two women using a ten-point scale provided to them on a questionnaire (see appendix), which also contained some general information. The students were asked to perform the evaluation independently and to avoid interacting with each other while filling in the questionnaire. Participation was voluntary and no student that knew any of the two women partook in the evaluation. The model women entered the lecture hall together and made their way, along the side of one wall, to the front of the hall where they were visible to everyone. They then proceeded to give each other positive attention, much like the attention given to the target men during the field experiment. This interaction lasted for 40 sec in total. They switched sides after half the interaction time (20 s) to minimize effects of lateralization biases. They then left the room together, this time along the other wall of the room, making sure that everyone got a close look at them. The data collector/questioner then gathered the questionnaires and left the room. This procedure was performed without the presence of the targets since the targets may affect how the ratings of the models. This was done so that the quality of the stimuli would be comparable to that of other, future, studies.
Table of contents :
Introduction
Theoretical background
Mate choice
Non-Independent mate choice
Study system
Mating system
Human mate preferences
Theory development
The wedding ring effect
Social transmission of mate preferences
Speed dating and real mate choice decisions
What have we learned from previous work?
Hypotheses and predictions
Women should copy
Focal/Model-women attractiveness dependence and mate value!
Long-term/short-term desirability
Sexual experience and ag
Material status
Progression to the field
Short description of the procedure
Rational!
Methods!
Initial preparation
Field experiment
Model quality determination
Results
Target desirability
Civil status
MVI
SOI
Age
Sexual experience
Seen the procedure
Model and focal women attractiveness
Discussion
Considerations if assuming that the results of present study are reliable
Considerations if assuming that the results from present study are unreliable
General discussion
Thank you
References
