I am an evolutionary psychologist and most of my research is about human attraction. I'm interested in how preferences are shaped by our own characteristics, the influence of the ovulatory cycle on preferences and appearance, mate retention behaviour, and lots of other stuff. Much of my research makes use of the PsychoMorph facial manipulation programme, developed at the St. Andrews’ Perception Lab. Here are some brilliant demos of the software in action.

More about my research

  1. Do women advertise their fertility?
  2. The ‘pill’ and the psychology of attraction
  3. Do opposites attract?
  4. Scarring and facial attractiveness
  5. Voting for the winner
  6. Mate-choice copying
  7. Men’s face perceptions and their partner’s cycle

Do women advertise their fertility?

When chimpanzee females are fertile, their bums go red and swell up like balloons. Humans vary in their fertility too: around ovulation, the chance that sex will lead to conception is quite high, but at other times of the month it is much lower. However, women don't advertise their fertility like chimps.

Or do they? Since 2000, lots of research has shown that when women near ovulation they become more attracted to manly men, more flirtatious, pay more attention to their appearance, and their faces are rated as more attractive. What changes in a woman's face to make her more appealing to men? We're not sure.

One possibility is that her face changes in colour, just like a chimpanzee's bum. This isn't too barmy a notion. Some species of macaque (a type of monkey) get redder faces when they're most fertile. Maybe humans are the same.

Cheek patches
I and my collaborators photographed women multiple times over their cycle and analysed patches of cheek skin for colour changes. Image modified from a photo by Alix Klingenberg.

We photographed a bunch of women every day for a month. We kept track of when they were ovulating using the type of kits women use when they're planning a pregnancy. We also made a note of when their periods started, so we knew how long their cycle was. This way we could match each photograph to a day of the cycle.

Change in skin redness over the cycle
The redness of women's facial skin drops during the first first days of the cycle (her period) and then increase just before ovulation (around day 14). It then falls slightly during the second half of the month. "Adjusted" just means that we fit each woman to a standard 28-day cycle (most women have a cycle that is longer or shorter than 28 days).

We found that women do get redder faces at ovulation, but this redness persists until the end of the month. It drops quite quickly during menses. However, when we used a mathematical model to check if this difference in redness could be perceived by the human visual system, we found that it probably couldn't. The change was just too small. So, it's likely that the changes in attractiveness that women experience over their cycle are not due to changes in facial redness.

The best candidates now are probably face shape, microexpressions, or head posture.

I wrote a piece about the research for my blog, and you can read the paper here.


The ‘pill’ and the psychology of attraction

Some men, like Dwayne “The Rock” Johnson, have very masculine faces. Other men, such as James McAvoy and Tom Hiddleston, have softer, more feminine features. Different women find different types of male face most attractive, but we know that these preferences can change according to circumstance (Little, Jones, & DeBruine, 2011). For example, research has revealed that women who use the hormonal contraceptive pill tend to find feminine men more attractive than they would if they didn’t take the pill (Feinberg, DeBruine, Jones, & Little, 2008).

But it remains a mystery whether the effect of the pill is strong enough to drive differences in real-world choice of partners (Alvergne & Lummaa, 2010). Do women who take the pill not only prefer feminine men, but actually choose to pair up with feminine men?

Average faces of the male partners of women who use the pill (left) or don't use the pill (right)
Average faces of the male partners of women who use the pill (left) or don't use the pill (right). It's difficult to see the differences, but you may just be able to tell that the face on the right has a larger jaw and a more masculine forehead shape.

We invited 336 male-female couples to help us find out. Some couples had been together as little as two weeks, and others as long as 50 years (making their relationships almost as old as the pill itself). The couples were photographed and the women were asked to indicate whether they were using the pill when they first met their partner.

The photographs of the men were measured to see how closely they embodied a typically masculine or feminine shape. They were also rated for masculinity/femininity by a separate panel of volunteers. The results of the experiment showed that men whose partners had been taking the pill when they met were more likely to have a feminine face. The partners of women who hadn’t used the pill tended to be more masculine. So it’s clear that taking the pill doesn’t only influence what women find attractive, but also makes it more likely that they will act upon those changed preferences and choose more feminine men. This is important because we know that facial appearance is related to personality (Berry & Brownlow, 1989), so the impact on relationship quality could be substantial.

Average facial masculinity of the partners of women who use or don't use the pill
Average facial masculinity of the partners of women who use or don't use the pill. As you can see, when we measure the masculinity of men's faces, the typically masculine ones tend to be partnered with non-pill users, and the typically feminine ones with pill users. Redrawn from Little et al. 2013.

Why might the pill have this effect? Well, for over a decade now we’ve known that women tend to prefer more masculine men during the fertile phase of their menstrual cycles (Penton-Voak et al., 1999). This makes sense because it’s at this time when women are most able to conceive, and thereby reap the genetic benefits of having children with masculine men, who may have healthier genes. But because masculine men tend to be less agreeable and might make poorer long-term partners (Perrett et al., 1998), at other times of the cycle women’s preferences for feminine men are stronger. This shift in preference is governed by varying hormone levels.

But taking the pill knocks out the natural hormone variation and eliminates the fertile phase. Not only does this stop a woman from being able to conceive, it also influences her psychology. What this experiment shows is that pill-related changes in psychology can translate into real-world differences in mate choice, and influence long lasting relationships. » DOI PDF


Do opposites attract?

Opposites attract. Or so the saying goes. In fact, there is overwhelming evidence that people are attracted to similarity in age, personality, beliefs and appearance. The most basic observation we can make about attraction is that people tend to pair with others whom they match in attractiveness. This is an example of what we call “assortative mating”.

Brangelina. So similar they share a name.

Much laboratory-based attractiveness research has focussed on two facial traits: symmetry and masculinity. Symmetric people are attractive, and so are masculine men and feminine women, probably because these traits are related to health. I and my collaborators sought to determine whether these preferences translate into real behaviour: do couples match in facial symmetry and masculinity?

We found that men and women who were partnered tended to have similarly symmetric faces: symmetric men were paired up with symmetric women, and asymmetric men were paired up with asymmetric women. We didn’t find any such relationship for facial masculinity. Another finding from this study was that relationship duration tends to be shorter the more attractive the female partner is (unless the male partner is the more attractive of the pair). Perhaps understandably, this secondary finding was the one that received more media attention. » DOI PDF


Scarring and facial attractiveness

Chicks dig scars. It’s a common belief, but several researchers have shown that scars reduce attractiveness, rather than increase it. I and my collaborators decided to test whether subtle facial scars influence attractiveness positively or negatively.

Example stimuli with artificial scars
Example stimuli with artificial scars

We found that these subtle scars didn’t affect women’s attractiveness at all. Men with scars, however, were more attractive, but only for short-term relationships. This makes sense if we think of scars as advertisements of bravery, dominance or masculinity. Previous research has shown that women prefer men with these masculine traits for flings but not for marriage, perhaps because masculine men produce healthy offspring but are less committed to their long-term relationships. » View paper on publisher's website | Download a PDF of the paper


Voting for the winner

Come election-time, we often like to think that we cast our votes for the candidates with the best policies. Is it possible, though, that we’re swayed by other factors, such as the politicians’ appearance? My collaborators and I made composite images of the winning and losing candidates in a number of recent national elections in the UK, USA, Australia, Canada and New Zealand. We concealed the identities of the faces using computer trickery, and then had members of the British public “vote” for their preferred face.

Click the image to see their true identities.
Which of these two candidates would you vote for to run your country?
Click here to see their true identities.
McCain and Obama

We found that our participants’ votes very closely matched those which were cast in the genuine elections. Blair beat Howard (and Major and Hague) in our poll, just like he did in real life. We also found that differences in the hypothetical environment affected voting preferences: when asked to imagine that they were voting in a time of war, our participants came out in force for George Bush Jr. over John Kerry; when imagining themselves voting in a time of peace, they instead plumped for Kerry. » DOI


Mate-choice copying

Ever found yourself attracted to someone who was already taken? Perhaps they were attractive because they were already taken. We know that in other species, such as grouse and guppies, females are more attracted to males that are surrounded by other females. The rule of thumb appears to be “these other females think he’s a catch, so I might as well agree”. This is a kind of behavioural shortcut: it allows females to spend less time and effort on mate-choice than if they assessed males individually.

My collaborators and I conducted a series of experiments to test whether humans also copy mate-choice. We presented women with male faces that were paired with smiling or neutral faced women. Men paired with smiling women were rated as more attractive than men paired with the neutral faced women. The men’s actual attractiveness was held constant, so this was purely an effect of how positively each man’s female companion seemed to view him. In another experiment we showed that men and women were rated as more attractive if they were paired with an attractive rather than an unattractive partner. » DOI (paper 1) DOI (paper 2)


Men’s face perceptions and their partner’s cycle

Women’s mate-preferences vary predictably over the course of their menstrual cycle. Around ovulation, women prefer masculine men, but later in their cycle they find feminine men more attractive. This so-called “preference shift” has been interpreted as evidence that women have an evolved propensity to pair-up with feminine men for the long-term, whilst seeking illicit affairs with bad boys when their chances of becoming pregnant are at their peak.

If this is true, we might expect men whose partners are ovulating to be more sensitive to facially masculine rivals. If men’s ability to spot rivals is flexible, they will be better prepared to prevent their partner being poached mid-cycle by a square-jawed caveman. This is precisely what we found: men whose partners were ovulating perceived other men’s faces to be more dominant than did men whose partners were not ovulating. As a bonus, we also found that this effect was absent in men whose partners were on the pill. This is what we’d expect to see, because women who are on the pill don't experience preference shifts. » DOI PDF


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