On this episode Connor Leslie tells us about her work on agression detection from both an evolutionary and forensic psychology perspective. Connor discusses the importance of detecting agression for preventing violence. Look out for those aggressive behaviors and try to avoid them on the International Day of Non-violence! #internationaldayofnonviolence
To follow Connor’s research check her out on Twitter @ConnorLeslie91.
Want to know more about motion capture and psychology research of a more non-violent nature? Check out these studies from members of our department:
Have you ever thought there was an uncanny family resemblance between your friend and her partner? Or wondered for a fleeting moment whether the pair walking down the road were husband and wife, or brother and sister? You might not be imagining things. Animals of many species “learn” what a suitable mate looks like based on the appearance of their parents, and so, it seems, do humans.
This isn’t Freud’s Oedipus complex revisited. Freud believed that children have a suppressed desire for their parents. But this branch of research doesn’t in any way show that we secretly desire our parents, just that we simply tend to be attracted to people who resemble them to some extent.
If anything, we seem to find our immediate family members unattractive. For instance, people find the very idea of sexual relationships with their siblings deeply unappealing. This aversion seems to develop automatically through two distinct processes. One process turns off attraction to those that we spend a lot of time with during childhood. The other turns off attraction to any infants that our mother looks after a lot. Sexual aversion to siblings might be nature’s way of ensuring we don’t try to reproduce with someone who is too closely related to us and reproduction with close relatives is linked to an increased likelihood of genetic disorders in any resulting offspring. This aversion to close relatives is known as negative sexual imprinting. However, genetic sexual attraction can occur between siblings that have been separated and meet first as adults.
But when do we develop these preferences? Perhaps we learn that our parents looks are attractive early in life, and then tuck that learning away – only to let it reemerge when we’re ready for adult relationships. Or perhaps more recent experiences override earlier learning? To test this, I asked heterosexual adult women about their relationships with their parents at different ages during their development, and I assessed how much their current preferences matched up with the appearance of their parents.
I found that the women who reported a better relationship with their parents after puberty were more likely to be attracted to partners with similar eye colour to them. In contrast, if a woman was close to her parents earlier in life, she was actually less likely to prefer the eye colour of her parents in a partner. In science, we always like to see replications with different samples, methodologies and research groups before we generalise findings too much. So far though, the intriguing pattern of this early study suggests that there may be complex developmental patterns underlying how we construct our idea of an ideal partner. Perhaps we are seeing the actions of both positive and negative sexual imprinting at work.
But one question remains. If we’re finding preferences for parental resemblance across different populations, then what is the biological explanation for this behaviour? It turns out that coupling up with a distant family member seems to be the best bet, biologically, to produce a large number of healthy children. One possibility is that if you are attracted to people who look like your parents, then chances are you may get a crush on distant relatives. This might give you better chances of more healthy children, and so this behaviour persists.
What is the point of a beard, evolutionarily speaking? Children, women, and a whole bunch of men manage just fine without one. But take a walk down some streets these days and you’ll be confronted with all sizes and shapes of groomed (and less groomed) facial hair – from designer stubble to waxed moustaches and hipster beards.
When we see men paying attention to their appearance, it’s easy to assume that they’re just angling for partners. But our research on beards and voices shows that beards probably evolved at least partly to help men boost their standing among other men.
Compared to males and females of many other primates, men and women on average look very different from each other – partly thanks to men’s facial hair. And when we see differences between males and females, the explanation often boils down to evolution through sexual selection – the process that favours traits that boost mating opportunities.
But interestingly, women don’t seem that interested in beards. While some studies have found that women like a bit or even a lot of facial hair on men, other studies have reported that they prefer the clean-shaven look. The lack of consistent evidence means we can’t conclude that beards evolved because women were attracted to them.
Researchers have therefore suggested that a second type of sexual selection may hold the answer. To reproduce, it’s often not enough to simply be attractive. You also have to compete with the same sex for mating opportunities. The funny, shy guy at the back of the bar isn’t going to stand a chance when competing with his bolshier brothers otherwise. And there’s evidence that beards evolved to help men do just that.
A man’s ability to grow a fulsome beard isn’t actually neatly linked to his testosterone levels. Despite this, a number of studies have suggested that both men and women perceive men with beards as older, stronger and more aggressive than others. And dominant men can get more mating opportunities by intimidating rivals to stand aside.
This is something that holds true both in modern times and throughout human history. Dominance can provide a staggering short-cut to mating opportunities: genetic evidence indicates that about 8% of the male population of Asia today is a descendent of Genghis Khan and his family.
A study by the appropriately-named Nigel Barber linked British facial hair fashions between 1842 and 1971 to the ratio of men to women in the marriage market. It found that in times with a greater proportion of single men competing for fewer women, beards and moustaches became more fashionable.
Beards aren’t the only feature that can convey dominance – voices do too. People tend to vote for leaders with lower-pitched voices, and during competitive tasks men lower the pitch of their voice if they think they are more dominant than their opponent. Like facial hair, voice pitch also easily distinguishes men and women.
To help trace the evolutionary origin of beards and voices, we tested whether they were seen as attractive, dominant or both. We asked 20 men and 20 women to rate the dominance and attractiveness of six men who were video-taped on four occasions as they let their facial hair grow. We then used computer software to create four versions of each video where the men’s voices had been changed to sound higher and lower-pitched.
We found that male voices that sounded deeper than average were rated as the most attractive. Really deep or high pitches weren’t as popular. In contrast, men’s voices were perceived as increasingly dominant the lower they were. Beards didn’t affect a man’s attractiveness rating consistently, but those who let their facial hair grow were perceived as more dominant than others – in line with previous research.
The tension between attracting a mate and competing with others doesn’t just apply to beards and voices. Men on average also think their body should be more muscular than women report that they want, while women on average believe they need to be thinner and wear more make-up than men report that they want. We’re not always that great at judging what the other sex finds appealing, but maybe that’s in part because our instincts are to out-compete our peers as well as attract a partner.
Of course, most of this research has been carried out within western populations. Make-up use, average body composition, and even the very ability to grow facial hair all differ enormously across the world – meaning we could get different results elsewhere.
But the point is that, whether it’s facial hair or something else, we often see this pattern of competing requirements leading to differences in appearances. Think you can please everyone all of the time? You can’t.