This entry was written by Martha Gledhill-Tuite as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2.
Introduction
Non-independent mate choice refers to mate choice in which the chooser’s decision is influenced by other individuals (Pruett-Jones, 1992). "Mate Choice Copying" (MCC) is a type of non-independent mate choice, when an individual is more likely to select a mate after observing them mating with another individual (Pruett-Jones, 1992). It usually occurs in females, however has been observed in males in some non-human species. Many studies of MCC have been performed on non-human animals but it is likely that human MCC is significantly more complicated than that of other animals. Behind MCC are two main explanations: cost-avoidance and facilitation of discrimination. Below are four studies focusing on different aspects of MCC, including explanations, relationship of the model female to the target male, generalisation of traits and the effect of facial expressions.
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Occurrence of MCC (Rodeheffer, Profitt Leyva & Hill, 2016)
A number of studies have revealed detailed information about MCC in humans. Two experiments by Rodeheffer et al. (2016) tested MCC. Firstly, they showed females photos of a target male with a model female, both of average attractiveness, and told the participants that the model female was either the cousin, adopted sibling, girlfriend or ex-girlfriend of the male. The participants were asked to rate the target males on how desirable they appeared as a partner. The target male was judged to be significantly more desirable when participants thought the model female was a girlfriend, compared to the other conditions.
In their second experiment they showed the target male alone or with the model female, told the participants that the female was his girlfriend, and asked them to rate the male on numerous positive traits that are physically unobservable. The participants who saw both the male and female rated the male higher on all traits. These results indicate that MCC occurs only when the model female actively chooses the target male, as in the girlfriend condition. Furthermore, it suggests that MCC might have evolved as a mechanism to infer unobservable positive traits, as this seems to be correlated with the positive judgements of the target male when accompanied by a girlfriend.
Theories Behind MCC (Vakirtzis, 2011)
There are two main evolutionary theories as to why MCC occurs, which are discussed by Vakirtzis (2011). The cost-avoidant theory states that MCC is advantageous because it allows females the benefits of specifically selecting mates, without experiencing the costs of searching for and choosing them. Choosing a mate can present risks such as predators, injury, parasites, sexually transmitted diseases, and the risk of choosing a male of low fitness. These can be avoided if the female copies the mating practices of those around her.
The second theory is that MCC is practiced to facilitate discrimination. Because errors in mate choice can have significant negative consequences, making the correct decision is vital. MCC occurs when a female is uncertain between two similar males. In this case, copying has a better chance of leading to the correct decision than random choice. According to this theory, MCC appears more frequently in females who are younger and less experienced, as they are less confident in their ability to discriminate between males. These two theories are different but it is entirely possible that they were both involved in the evolution of MCC.
Generalisation in Mate Choice Copying (Little, Jones, DeBruine & Caldwell, 2011)
An experiment by Little et al. (2011) further illuminates the mechanisms of MCC. They suggest the technique of generalisation, in which females observe the mating choices of model females and proceed to choose different males with similar traits to the target male. This is beneficial because in monogamous species, it is useless to simply choose a male who has already been chosen by another female. Generalisation is not contradictory to directly copying mate choice, as both can occur.
This study tested both male and female participants, giving them targets of whichever gender each individual was attracted to. The experimenters showed composite face pairs to 53 participants and asked them to select the most attractive from each pair. Each pair consisted of two different versions of a composite face: one with wide-spaced eyes and one with narrow-spaced eyes. The participants then viewed different faces grouped into male-female pairs, and were told that the pairs were in relationships. Some participants viewed attractive models matched with targets with narrow-spaced eyes, and some viewed attractive models matched with targets with wide-spaced eyes. There is evidence to suggest that MCC is strongest or only occurs when the model is attractive (Waynforth, 2007). The participants were then asked to repeat the first test in which they selected the most attractive composite face from pairs, with the same faces as they initially viewed.
The results showed a significant effect of condition on the preference for eye spacing: that is, participants preferred wide eye spacing when this trait had been paired with attractive models, and narrow eye spacing when it had been paired with attractive models. This occurred despite the fact that the faces being rated were not the same faces that were shown in pairs. This supports the concept that generalisation of traits is used as a mechanism of MCC.
MCC and Facial Expressions (Jones, DeBruine, Little, Burris & Feinberg, 2007)
Finally, an experiment by Jones et al. (2007) focused on the social transmission of mate preferences through facial expressions. Humans are adept at gathering information from gaze and expression, so it is foreseeable that information on mating could be transmitted in this way. Female participants were shown male faces and were asked to rate them, before viewing a slideshow. The slideshow consisted of the male faces in pairs, with the profile of a female face between them, viewing one of the males. The female face was either smiling or had a neutral expression. The women were then asked to rate the male faces again.
Men at whom the female had been smiling showed a significant increase in attractiveness ratings, compared to those who had received the neutral expression. This study shows that MCC can occur simply from information gleaned from positive facial expressions. Humans have evolved to utilise social cues such as facial expressions when copying mates. It also shows that human mate choice and MCC is considerably more complicated than that of other animals.
Conclusion
The two theories behind MCC are complimentary and it is possible that both played a part in the evolution of MCC. Numerous experiments have provided more information about MCC and its use by humans. The Rodeheffer et al. (2016) study showed that it is necessary for the model female to have chosen the target male. The experiment by Little et al. (2007) explored generalisation of chosen traits. Lastly, The Jones et al. (2007) experiment viewed how humans have evolved to consider facial expressions in MCC.
Literature Cited
Jones, B. C., DeBruine, L. M., Little, A. C., Burriss, R. P., & Feinberg, D. R. (2007). Social transmission of face preferences among humans. Proceedings of the Royal Society B: Biological Sciences, 274(1611), 899-903.
Little, A. C., Jones, B. C., DeBruine, L. M., & Caldwell, C. A. (2011). Social learning and human mate preferences: a potential mechanism for generating and maintaining between-population diversity in attraction. Philosophical Transactions of the Royal Society B: Biological Sciences, 366(1563), 366-375.
Pruett-Jones, S. (1992). Independent versus nonindependent mate choice: do females copy each other? The American Naturalist, 140(6), 1000-1009.
Rodeheffer, C. D., Proffitt Leyva, R. P., & Hill, S. E. (2016). Attractive female romantic partners provide a proxy for unobservable male qualities: The when and why behind human female mate choice copying. Evolutionary Psychology, 14(2), 1474704916652144.
Vakirtzis, A. (2011). Mate choice copying and nonindependent mate choice: a critical review. Paper presented at the Annales Zoologici Fennici.
Waynforth, D. (2007). Mate choice copying in humans. Human nature, 18(3), 264-271