Mate Copying In Females: A Functional Magnetic Resonance Imaging Test
In some species – including guppies, quail, and zebra finches – there is an interesting phenomenon called mate copying in which an individual’s choice of a mate is influenced by other individuals’ choices. That is, an individual is more likely to prefer and attempt to mate with a particular individual if that other individual is already mating with or is preferred by others. Moreover, this phenomenon is more often found in females choosing male mates than vice versa. Evidence from several studies on humans shows that women are no exception.
Why are females copycats when it comes to mating, and why only women? A likely cause is that mate copying is a shortcut that adaptively saves mental resources required for the careful mate choices that females evolved to make.
Take humans, for instance. A male’s minimum physiological investment for reproduction is about a teaspoon of seminal fluid and the mere minutes it takes for him to deposit that into a female (many men invest heavily in their children and family but we’re talking about absolute minimums here). A female, on the other hand, contributes a much more nutrient-dense egg and incurs the hardships and risks from nine months of pregnancy and, in natural settings, several years of nursing. Thus, making a poor mating choice is a much costlier mistake for females than for males. As such, females may have evolved to be more selective when choosing mates (and consenting to sex) than males. Mate copying takes advantage of someone else’s carefully-made choice – if a male has already passed the rigorous inspection of other females, it can be quickly inferred that he is of good quality.
We tested these ideas with an important design feature: we had female participants judge the quality of men from inside the chamber of a functional magnetic resonance imaging (fMRI) machine. That way, we could examine brainwave patterns to discern what specific cognitive processes are involved in mate copying. Specifically, we positioned women inside an fMRI scanner and asked them to judge the attractiveness of pictures of average-looking men before and after the men were paired with females who were described as either the males’ romantic partners or their ordinary friends. Furthermore, the pairings were with females who were either physically attractive or unattractive.
Here’s what we found. After male targets were paired with attractive females described as romantic partners, women’s ratings of the male targets’ physical attractiveness increased. This boost in perceived attractiveness tended not to occur, however, if the male targets were paired with unattractive female partners. Furthermore, when male targets were paired with attractive females described as platonic friends, the opposite occurred: women rated the males as less attractive.
Taken together with previous findings that women rate men paired with attractive same-sex friends as being less attractive, this pattern of results suggests that when women see a man with an attractive romantic partner, they engage in mate copying, which positively biases their judgments of that man’s attractiveness (and hence, the likelihood that she will want him as a mate). However, when there is not a compelling motivation to copy someone’s mate choice, judgments of a man’s attractiveness require higher levels of cognition and are subject to comparing and contrasting him with the company that he keeps.
Our fMRI results support this distinction. Evaluation of males with female friends (versus romantic partners) utilized significantly more brain regions previously shown to be involved in beauty comparisons and in calculating and comparing non-social stimuli (e.g., middle frontal gyrus, inferior frontal gyrus, superior parietal lobule, and visual areas), as well as value (e.g., beauty, height) comparison (e.g., cerebellum and precentral gyrus) and associative learning (e.g., hippocampus, amygdala, OFC, and ACC).
In contrast, brain regions where most of the mirror neurons are located (e.g., inferior parietal lobule, superamarginal gyrus, and insula) as well as empathy-related brain regions (including the putamen, inferior frontal gyrus, middle cingulate, SMA, insula, and thalamus) were more active when women were observing men with romantic partners than with female friends. Neuronal mirroring mechanisms allow individuals to directly understand the meaning of the actions and emotions of others by internally replicating (simulating) them without explicit contemplation. Additionally, when attractive females were paired with target males as romantic partners, women’s brains showed increased activation in regions associated with the bilateral fusiform gyrus (FFA), a specialized module involved in rapidly processing information related to faces.
Thus, these fMRI results suggest that when women copy an attractive female’s mate choice, it is accomplished by having increased empathy and mentally simulating the choice that the attractive female has made. Women, however, tend not to copy the mate choices of unattractive females. Furthermore, if an attractive female is only a platonic friend of a guy, then women may downgrade the guy and see him as less attractive. Advice to men who are looking for mates: don’t show off your attractive female (and male) friends.
These findings are described in the article entitled The neural basis of human female mate copying: An empathy-based social learning process, recently published in the journal Evolution and Human Behavior. This work was conducted by Jin-Ying Zhuang, Xiaoqing Ji, Zhiyong Zhao, and Mingxia Fan from East China Normal University, and Norman P. Li from Singapore Management University.