All posts by Amy Alkon

About Amy Alkon

Amy Alkon is the irreverent purveyor of “science news you can use.” Her most recent book is the science-based and bitingly funny "Good Manners for Nice People Who Sometimes Say F*ck” (St. Martin’s Griffin, 2014). Her award-winning, science-based syndicated column runs in about 100 newspapers. She is the 2015 president of the Applied Evolutionary Psychology Society and hosts her own weekly radio show, “ Nerd Your Way to a Better Life,” featuring the luminaries of behavioral science.

The Evolution Of Fun Names For Scientific Theories: The “Sneaky F*ckers” Strategy Has Company

The late British evolutionary biologist John Maynard Smith came up with the “Sneaky F*ckers” strategy — in short, explaining a way that beta males get the girl. DragonflyIssuesInEvolution explains:

The term “sneaky fuckers” was coined by evolutionary biologist John Maynard Smith to describe subordinate males who take advantage of the opportunity to mate with females while dominant males are otherwise occupied, leading to their reproductive success (Smith, 1993). It was originally thought that in some species such as deer and gorillas, only the dominate male mates successfully. But, through direct observation and DNA analysis, it is now known that often other males surreptitiously successfully mate when they can find the opportunity.

Basically, while the alpha male is off, oh, fighting the war, the beta male is sneaking sex with their woman. Maynard Smith has long held the lead for fun names of theories, but there’s a now nice showing from the Los Angeles contingent.

Yes, we’ve got some Americans losing the stuffy on theoretical names, with the “Crazy Bastard Hypothesis.” Evolutionary social psychologist Frank T. McAndrew covers the fun on his blog at Psychology Today:

Recently, a team of anthropologists at UCLA led by Dan Fessler tested what they called the “Crazy Bastard Hypothesis” in a series of studies. They gathered data online from thousands of Americans and in person from dozens of individuals in the Fiji Islands. They had people read short scenarios about individuals who engaged in risky, daredevil behavior or in more cautious, risk-averse behavior. They then asked them to make judgments about the characteristics that they thought the person in the story might possess. Among other things, the daredevil was perceived to be taller, stronger, and generally more physically formidable than the cautious individual.


Their “Crazy Bastard Hypothesis” gives us a fun and more complete way of thinking about risky male behavior.  Now, it is no longer just about advertizing genetic quality, but it is also about advertizing how one might behave as an adversary or an ally. If you see a “crazy bastard” who behaves with apparent disregard for his own personal well-being by doing things that would scare ordinary men away, you definitely end up wanting to have this person as a friend rather than as an enemy. Even though the crazy bastard’s behavior is not overtly aggressive, one can easily imagine the terror of dealing with such a reckless opponent in combat and the comfort that one might have going into battle with that individual as a comrade. Going way back to the dawn of recorded human history one can find rituals (often involving excessive consumption of alcohol) used by warriors to at least temporarily make themselves feel and appear to be formidable crazy bastards as a way of intimidating their enemies and taking the fight out of them before the battle even began.


Perhaps the “Crazy Bastard” is not so crazy after all?

Buy Frank T. McAndrew’s book, Environmental Psychology.

Upcoming Evolutionary Psychology Conferences

HBES, June 29th to July 3rd, 2016, Vancouver, Canada: The 28th annual HBES conference will be held June 29th to July 3rd, 2016 at the Westin Bayshore in Vancouver, Canada. (HBES is the biggie of ev psych conferences, with the most international attendees.)

NEEPS, June 2-5, 2016, in Halifax, Nova Scotia (Canada): The NorthEastern Evolutionary Psychology Society will hold its 10th annual conference, beginning 6/2/16, in Halifax, Nova Scotia. (Our AEPS meetings and sessions will also be held there.)

SEEPS, Feb 12, 2006, Tuscaloosa, Alabama: The SouthEastern Evolutionary Perspectives Society (SEEPS) will hold its inaugural meeting February 12th, 2016 (Darwin Day) through the 14th at the Alabama Museum of Natural History in Tuscaloosa, AL. (SEEPS is the newest ev psych organization.)

ISHE, August 1-5, 2016, University of Stirling, Scotland: The 23rd Biennial Congress on Human Ethology will be held at the University of Stirling, in Scotland, from the 1st – 5th of August 2016. What is ethology? More from ISHE’s website.

SPSP (with Evolutionary pre-conference, Jan 28), Jan 28-30, San Diego, California: The annual Society for Personality and Social Psychology conference will be held in will be held in San Diego, Jan 28-30, 2016.

EHBEA, April 5-8, 2016, at the London School of Hygiene and Tropical Medicine: The annual European Human Behavior and Evolution Association’s annual conference will take place in London, April 5-8, 2016.

Evolutionary Tradeoffs: Too Materialistic To Marry And Have Children?

Evolutionary social psychologist Norm Li and his colleagues have posted an interesting open access study at PLOS ONE, exploring materialism’s relationship to attitudes toward marriage and having children. They studied subjects in Singapore, finding that:

Materialistic values led to more negative attitudes toward marriage, which led to more negative attitudes toward children, which in turn led to a decreased number of children desired. Results across two studies highlight, at the individual level, the tradeoff between materialistic values and attitudes toward marriage and procreation and suggest that a consideration of psychological variables such as materialistic values may allow for a better understanding of larger-scale socioeconomic issues including low fertility rates among developed countries.

There’s a drop in fertility in prosperous countries:

In many modern societies, native populations are shrinking as citizens are delaying marriage and having less children. This is especially the case in East Asia, where countries like Singapore, Hong Kong, and South Korea have fertility rates that are far short of what is required to sustain a population. Although this trend seems to be related to economic development, relatively little is known—especially from a psychological perspective—regarding what it is about economic development that may be responsible for inducing aversions to marriage and procreation. In this paper, we considered the possibility that a key factor prevalent in modern societies—materialistic values—may negatively influence the value that individuals place on marriage and children.

They further explain at the end of the paper:

Materialistic values may, from an early age, compete with and displace values relating to cooperation and interpersonal warmth. Such displaced values may directly or indirectly decrease the desire for marriage and family.

There seems to be an evolutionary mismatch here — between our evolved psychology and the modern world:

Modern-day materialism may involve a maladaptive engagement of mental processes evolved to impel individuals to acquire social status and signal their status to others. Although status signaling may be a manageable process in an ancestral village of 100 to 150 individuals, in the modern day, rapid technological advances combined with global competition induce symbols of social status to change at increasingly faster rates and luxury goods to lose their luster exceedingly quickly. Thus, it is not possible for most modern people to acquire what feels like enough status for very long or at all, and materialistic desires may lock individuals into a costly and futile pursuit of status targets perpetually moving upwards. Ironically, then, the pursuit of status may be leading to decreased reproduction in the modern day.

As for possible solutions, Norm Li explained in an email:

As long as evolved mechanisms for social status exist, accompanied by capitalism, technology, globalization, and advertising, there will likely be competitive materialistic processes. However, consistent with our previous findings and those of others, materialistic appetites can be curbed by improving the strength of personal relationships and finding ways to boost overall life satisfaction. At the individual level, though, one can reduce one’s own exposure to mass media, and associate with individuals and communities who aren’t so caught up in the materialistic game. My collaborators and I are looking into new ways to approach the materialism-reproduction tradeoff.  Stay tuned.

Evolutionary Scientists: Collaborate With Local Teachers To Help Them Teach Evolution Better

Dustin Eirdosh, AEPS’s main man in spreading evolutionary education in the schools, writes:

AEPS Members in the US (and all evolutionary scientists): The National Center for Science Education has just started its “Scientists in the Classroom” program, and they are seeking evolution scientists willing to collaborate with local teachers who want help teaching evolution better.


Please consider joining the effort. If you do join, drop me an email [dustin at unitoliara dot info] so we can strengthen our relationship with the important work that NCSE does!

Dustin Eirdosh (on Research Gate) is a curriculum designer at the Berlin-based NGO Big Red Earth (, an organization that supports a university-led development approach in southwestern Madagascar. This region is characterized by high food insecurity, poverty, low quality of education and unsustainable use of natural resources, while it is at the same time an important biodiversity hot spot. Utilizing perspectives in Evolutionary Educational Psychology (Evo-Edu) and the tools of cultural evolution studies, Dustin has developed a governance education program focused on connecting university classrooms with sustainable development initiatives in the region.

Meet The Greats Of Evolutionary Psychology: The HBES Founders Videos

BELOW ARE THREE TERRIFIC VIDEOS — 15-minute interviews with three major evolutionary scientists: Steven Pinker, David Buss, and Leda Cosmides. There is also a link to many more from the series.

About the videos: In 2013, evolutionary psychology professors Catherine Salmon and Barry X. Kuhle videotaped oral histories of the researchers who founded the major international organization for evolutionary psychology, the Human Behavior and Evolution Society, and who were substantial in fostering the emergence of evolutionary psychology as a science of public import. (The taping of these videos coincided with the 25th anniversary of HBES.)

Thus far, with funding from HBES, and the participation of filmmaker Dave Lundberg Kenrick, Salmon and Kuhle have taped interviews with David Buss, Steven Pinker, Leda Cosmides, John Tooby, Douglas Kenrick, Martin Daly, Randy Thornhill, Mark Flinn, William Irons, Napoleon Chagnon, Sarah Hrdy, Don Symons, Raymond Hames, Bobbi Low, Peter Richerson, David Sloan Wilson, Dick Alexander, Randy Nesse, and E. O. Wilson. (The entire series of interviews can be found here.)

(Sadly missing from this series are pioneers and pillars of sociobiology and evolutionary psychology who’ve passed on, including Bill Hamilton, Dave Rowe, Dev Singh, John Maynard Smith, George C. Williams, and Margo Wilson.)


And now…those videos: 

Steven Pinker (introduction below by David Sloan Wilson)

Looking back, Pinker recalls how he first adopted an evolutionary perspective, based on thinkers such as Noam Chomsky and Jerry Fodor, who stressed the need to posit a nativistic dimension to human cognition and language. Looking forward, Pinker advises new students to think of themselves as psychologists first and evolution as an essential perspective for the study of all aspects of psychology, rather than a sub-discipline of the field. He describes the self-described field of evolutionary psychology as a stepping stone toward this end. He calls for more integration with evolutionary genetics and more generally the fully rounded approach associated with Nobel Laureate Niko Tinbergen, who stressed that all evolved traits should be studied from functional, mechanistic, developmental and phylogenetic perspectives. He also shares his own best idea that has not yet received the attention that it deserves.

Buy books by Steven Pinker (for which AEPS gets a wee kickback, at no cost to you).



David Buss (introduction below by Diana Fleischman)

This interview in the series “On the Origin of the Human Behavior and Evolution Society” is with David Buss, Professor of Psychology at the University of Texas at Austin. David is one of the founders of evolutionary psychology but initially made significant contributions to personality psychology. He is perhaps best known for groundbreaking work in human sex differences and mating including jealousy, cross-cultural mate preferences, and the strategies people use to retain a mate. Oftentimes his discoveries come with their own snappy nomenclature like “mate poaching” and “exploitability.” David professes he is especially interested in the “dark side” of human nature. Many of the initial forays David made into new territory have spawned whole new lines of research.

Some highlights of this interview include David’s rebellious roots and how an early hypothesis about dominance was purely designed to upset one of his teachers, how he began to acclimatize to John Tooby and Leda Cosmides’ night owl schedule when they became fast friends at Harvard, the advice he would give to graduate students and the way he demonstrates how to derogate a rival male on his interviewer and former graduate student Barry X. Kuhle, maybe a little too effectively.

Buy books by David Buss (for which AEPS gets a wee kickback, at no cost to you).



Leda Cosmides (Introduction below by Robert Kurzban)

Leda is one of the pioneers of the field of evolutionary psychology. She is a professor at the University of California Santa Barbara, where she co-founded the Center for Evolutionary Psychology (CEP) with husband and collaborator John Tooby. Leda’s impact on evolutionary approaches cannot be overstated. Her awards and honors are numerous, and include the prestigious National Institutes of Health Director’s Pioneer Award. Even if you are very familiar with Cosmides’ work, you’ll learn a lot from this video, including how being 5 minutes late to a meeting with E. O. Wilson (when she was an undergrad at Harvard) was “key to her future,” how her seminal and award winning 1989 paper on cheater detection took four years and several rejections before getting published in Cognition, why she called the field she and John helped start “evolutionary psychology” as opposed to “human sociobiology,” and much more.

Buy books by Leda Cosmides and her colleagues.


Also check out the fantastic interviewers and their research and thinking: 

Barry X. Kuhle’s Psychology Today page can be found here.

Catherine Salmon’s Psychology Today page can be found here. Buy books by Catherine Salmon (for which HBES gets a wee kickback, which we very much appreciate).

The Personal is Universal: How To Put Your Science Out for the General Public

A big part of putting out applied science is communicating to the general population in a language they can understand. A post by editor Katie L. Burke at American Scientist on how to do this (and much more) has some helpful tips.

This is one of the most important:

8. If you want people to understand that a problem addressed by your research affects real people, you need to illustrate the problem by telling a story about real people.

Scientists often want to connect with the public by talking about how their research affects issues of widespread concern. But they are used to talking about these effects in abstract ways, such as giving statistics about groups of people. The stats are important, but they’ll hold more weight and be more memorable for the reader if real people are also written as characters in the narrative. When scientists rattle off statistics but do not talk about how they connect to people’s lives, they risk coming off as cold and distant. Anecdotes may not have a place in science writing, but they are absolutely essential to journalistic and literary nonfiction.

Personal stories are stories that connect with people. We care about people. We don’t connect over big social issues we can do nothing about.

David Carr, the late media columnist at The New York Times, spoke about this at an alternative weekly newspaper conference in around 2008, saying (best I can recall), “Don’t talk about poverty; talk about how little Tasha doesn’t get lunch.”

Garry Shandling puts this another way: “The more personal it is, the more universal it is.”


Three Things We Now Know About Being Human, Thanks To Ev Psych

Evolutionary psychologist Glenn Geher posts at Psychology Today on three big findings about humans that wouldn’t have been possible without the “mountain of research” done by evolutionary psychologists.

Here are two of the three findings:

1. Men are more than twice as likely to experience early mortality (death) during young adulthood compared with women (Kruger & Nesse, 2006).

Men are more likely to die than are women at any and all phases of the life cycle. Applying an evolutionary lens, Kruger and Nesse (2006) hypothesized that this phenomenon should be exacerbated during young adulthood when males are more likely to be courting mates and, as a result, engaging in male/male (intrasexual) competition. And that’s exactly what they found.


2. Step-parents are, by a large order of magnitude, more likely to engage in filicide (killing of offspring) compared with genetic/biological parents (see Daly & Wilson, 2005).

Filicide is universally seen as horrific. So it would benefit humanity writ large to understand its antecedents. Applying evolutionary-based reasoning, Daly and Wilson (2005) reasoned that as step-parents do not share the same genetic investment with offspring as biological parents do, then step-parents might be more likely to engage in filicide. And this is, by a large order of magnitude, exactly what they found.

For the third, check out Glenn Geher’s blog post on More about Glenn.

“Yes, But…”: Answers To Ten Common Criticisms of Evolutionary Psychology

Excellent myth-busting post by evolutionary psychologist David Schmitt. It came out of an invited talk he gave on evolution and human reproductive strategies to an audience of mostly sociologists and family studies professors. Schmitt writes at

I mentioned that some social scientists hold false beliefs about “evolutionary psychology,” such as the mistaken assumption that evolutionary psychologists think all men are interested in bedding as many women as possible (often called short-term mating), whereas all women are only interested in marrying a single man and staying faithful to him for a lifetime (i.e., long-term mating).


When I tried to dispel this common misperception by noting, for instance, that evolutionary psychologists have hypothesized women are just as designed for short-term mating as men are—in some ways even more so such as women’s heightened desires for cues to genetic quality in short-term mates—an audible gasp swept through the conference hall. I kid you not, I could see rows of people who looked genuinely horrified.


I was a little taken aback, so I asked an audience member near the front row who had her hand over her mouth if something was unclear, to which she proclaimed, “that’s not the evolutionary psychology I know.”


When I tried to explain that women’s evolved short-term mating desires have been studied by evolutionary psychologists since the early 1990s and the topic remains a very active area of inquiry today, heads swiveled in disbelief.


…It seems to me many critics of evolutionary psychology cling steadfastly to false stereotypes of the field, both theoretical and empirical.


…Beyond simply not knowing about the empirical breadth and methodological richness of modern evolutionary science, many critics exhibit a certain kind of “empirical nihilism” toward any psychological findings even remotely portrayed as supporting evolutionary hypotheses.


For instance, when one points to a set of studies that respond to a specific criticism, some critics reply with a “yes, but” attitude and set forth new criticisms requiring more evidence (sort of a serial “moving the goalposts” maneuver). Now, in science extreme skepticism is generally a good thing. For scientists, there are no capital “T” Truths, and every claim about reality is tentatively true with a small “t” and is always adjustable as more evidence is accumulated over time.


Sometimes, though, this attitude is more than healthy skepticism about a particular empirical finding and is, instead, clearly an attitude of irrefutable empirical nihilism toward evolutionary psychology studies in particular.


As an example of this type of unshakeable attitude of disbelief, I list below 10 of the more common “yes, but” criticisms of evolutionary findings on women’s long-term mate preferences.

Here’s one of those 10 — starting with the “Yes, but…” criticism of ev psych:

5) Yes, but…this [women’s long-term mate preferences for cues to a man’s ability and willingness to devote resources] is only because women are denied access to resources themselves. If women have higher status themselves, they would not prefer men with high status. It’s just basic rationality, not evolved psychology, causing these sex differences in mate preferences for status.


Actually, it is a compelling test of women’s long-term mate preferences for men’s status-related traits (including their ability and willingness to provide resources) to evaluate whether their expressed preferences disappear when women have ample resources of their own. It could be women only prefer cues to men’s ability and willingness to provide resources because women are structurally denied access to resources[39].


Addressing this alternative explanation, Townsend and his colleagues have found women in medical school[40] and law school[41] are more selective of a future mate’s financial status, not less. Similarly, Wiederman and Allgeier[42] found college women’s expected income was positively associated with their ratings of the importance of a potential long-term mate’s earning capacity.


Regan[43] found as women’s mate value goes up, so does their insistence on men’s high status and resources (i.e., they “want it all”; see also[44]). Having higher personal status and resource-related traits appears not to attenuate women’s preferences for cues to men’s ability and willingness to provide resources. Instead, at least in the USA, women achieving high status themselves appears to make their long-term mate preferences for men’s high status even more intense!

For the rest of the 10, go to the link.

Twins Researcher Nancy Segal, Studying The Bogata Twins, Separated At Birth

In New York Times Magazine, Susan Dominus tells the riveting story of two pairs of Colombian identical twins raised as fraternal twins — how they found each other and what happened after they met.

However, there’s a science story here, and it involves twins researcher Dr. Nancy Segal, who is studying the four brothers.

But first, a little preface from Dominus’s piece about why the study of twins is important for the rest of us:

Identical twins don’t make obvious evolutionary sense; fraternal twins at least have the benefit of genetic diversity, improving the odds that at least one might survive whatever misfortune comes their way. And yet, in their utter inexplicability, identical twins have helped elucidate our most basic understanding of why, and how, we become who we are. By studying the overlap of traits in fraternal twins (who share, on average, 50 percent of their genes) and the overlap of those traits in identical twins (who share 100 percent of their genes), scientists have, for more than a century, been trying to tease out how much variation within a population can be attributed to heredity and how much to environment.

Nancy Segal, by the way, is not one to do her studying from afar:

William had only one condition for his participation: He insisted that Segal and Montoya visit the home in which he grew up in Santander. Without that, he thought, they could never really understand who he was. He did worry, however, that if he told Segal and Montoya how long it would take to get to Santander, they would never agree to go. So he dodged and evaded whenever the subject of travel time came up. It’s a four- or five-hour drive, William would say, and then add, almost as an afterthought, that when the road could get them no closer to their destination, they would get out and walk. For how long? A little while, William would say; it might be a little muddy. How muddy? Maybe, he would suggest, it would be easier if at that point Segal traveled by horse. Would she, by any chance, rather ride a horse? Segal, a woman in her early 60s who grew up in the Bronx, said no.

And a few words about the science, quoting from Dominus:

The casual observer is fascinated by how similar identical twins are, but some geneticists are more interested in identifying all the reasons they might differ, sometimes in significant ways. Why might one identical twin be gay or transgender and not the other? Why do identical twins, born with the same DNA, sometimes die of different diseases at different times in their lives? Their environments must be different, but which aspect of their environment is the one that took their biology in a different direction? Smoking, stress, obesity — those are some of the factors that researchers have been able to link to specific changes in the expression of specific genes. They expect, in time, to find hundreds, possibly thousands, of others.


…Before she left for Bogotá, Segal contacted Jeffrey Craig, who studies epigenetics at Murdoch Childrens Research Institute in Australia, to ask if he would analyze the epigenetics of Carlos, Jorge, Wilber and William, using saliva swabs she would obtain while she was there.


Craig has analyzed the epigenetic profiles of 34 identical and fraternal twins at birth, collecting swabs from their inner cheeks. To Craig, it was noteworthy that in some cases — not many, but some — the epigenetic profile of one newborn twin was more similar to an unrelated baby than to the identical twin with whom that baby shared a womb. Structural differences in the womb could possibly account for it, Craig says — a thicker umbilical cord for one than the other (there are, in fact, two cords) or an awkward site of connection for the umbilical cord on the placenta. But he recognizes that there could be additional factors still in the realm of guesswork. Perhaps one twin is farther from the sound of the mother’s heart, its reassuring steady beat, sending that child on a slightly different life course.

Segal and Craig were eager to see the epigenetic results for the Colombian twins. Whose epigenetic profile, they wondered, would look more alike? The biologically unrelated twins who shared an environment — Segal calls them virtual twins — or the ones whose DNA was the same?

A sample of four subjects could only raise questions, not answer them. But epigenetic testing on larger samples of twins reared apart could one day provide a valuable resource for epigenetic science, says Kelly Klump, who is the co-­director of the Michigan State University Twin Registry. ‘‘You can’t look at how the environment will change the function of the genome without holding constant the genome,’’ she says. ‘‘Identical twins allow you to do that.’’ Given how hard it is to find identical twins raised apart, twins researchers working in epigenetics have mostly been focusing on the identical twins who show difference. Tim Spector, a professor of genetic epidemiology at King’s College London, is generating a huge global registry for identical twins in which only one twin has, for example, diabetes or autism.

And Segal’s findings, also quoted from Dominus’s piece:

Before starting her research, Segal would not have been surprised if each young man tested similarly to his identical twin, despite their different environments. But her preliminary results, she said, show that on a number of traits, the identical twins were less alike than she initially anticipated. ‘‘I came away with a real respect for the effect of an extremely different environment,’’ Segal said.

Perhaps the results merely indicate that people raised in deeply rural environments, with little education, take tests in a wholly different manner from those who attended a university. William, who managed a small business with competence, at times seemed overwhelmed by the test. But Segal considered the young men’s story a case history that might provoke further research, inspiring others to seek out more examples of twins reared apart with significantly different upbringings, whatever they were.

Do read the whole compelling story in New York Times Magazine.

Learn more about Dr. Nancy Segal here. You can also buy her books through this link at Amazon — and, by going through this link, you’ll be supporting AEPS at no cost to you!

Sometimes We Have Sex Because We Don’t Want To Do The Dishes

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Evolutionary social psychologist Carin Perilloux was one of the co-authors on a new study“Sex and Mating Strategy Impact the 13 Basic Reasons for Having Sex.” (It’s the Kennair et al paper referenced below.)

And most helpfully — this being the Applied Evolutionary Psychology Society blog — Perilloux put the findings in context for us in this piece below.

Have you ever wondered why people have sex?

If you’re like most people, the answer might have seemed so obvious to you that you never stopped to wonder about it. Just a decade ago, psychologists probably would have had the same reaction, citing a few reasons such as reproduction and physical pleasure.

But a recent study led by Leif Kennair has confirmed that humans have sex for a large suite of reasons. Replicating the original findings of Cindy Meston and David Buss (2007), Kennair and colleagues show that the reasons men and women give for having sex fall into 13 categories:

•Stress reduction – “I thought it would relax me” “I’m a sex addict”

•Pleasure – “I was horny” “It feels good”

•Physical desirability – “S/he was naked and I couldn’t resist” “His/her appearance turned me on”

•Experience seeking – “I was curious” “I wanted to see what s/he was like in bed”

•Resources – “I wanted a child” “I wanted to make money”

•Social status – “I wanted to be popular” “I wanted to brag to my friends about it”

•Revenge – “I wanted to make someone jealous” “I wanted to get back at my cheating ex”

•Utilitarian – “I wanted to keep warm” “I wanted to get out of doing something else”

•Love and commitment – “I wanted to show my feelings for him/her” “I wanted to take the next step in our relationship”

•Expression/consolidation – “I wanted to celebrate his/her birthday” “I wanted to say I was sorry”

•Self-esteem – “I wanted attention” “I wanted to boost my self-esteem”

•Duty/pressure – “I wanted to stop my partner from nagging about it” “I felt it was my duty”

•Mate guarding – “I wanted to prevent a breakup” “I wanted to decrease my partner’s desire to cheat”

Now that you’ve read the list, your perspective might have shifted since the beginning of the post: perhaps now it seems obvious to you that people have loads and loads of different reasons for having sex! And these reasons are not simply idiosyncratic: there’s a pattern to them.

First, the reasons replicate cross-culturally: Meston and Buss (2007) originally documented these 13 categories in a US sample while Kennair (2015) found the same 13 categories in a Norwegian sample.

Second, Kennair and colleagues (2015) showed that gender and mating strategy are good predictors of who endorses which reasons for having sex. For example, men are more likely to cite Stress Reduction reasons for sex than women. And men and women who are more interested in short-term mating (e.g., hooking up, one night stands) are more likely to cite reasons for sex in the Pleasure, Experience-Seeking, and Revenge categories.

Learning that people have sex for a multitude of reasons can help us understand ourselves better – and our sex partners. It can perhaps give us pause in our assumptions about why someone might want to have sex with us – and addressing our own assumptions is generally a good exercise.

These findings also help many of us to feel more normal about why we have sex. Sure, a lot of times we have sex for the big reasons – it feels good, we want to have kids – but sometimes we have sex because it will make our ex jealous, or we don’t want to do the dishes, or it’s simply a little more interesting than the novel on the nightstand.

Our reasons for having sex might not always be grand or fun or even healthy, but they are part of the suite of motivations for sex that makes us human. Researching these underlying motivations is a step toward understanding our mating psychology even better. And as mating researchers (and all of you who have ever engaged in mating) know: it’s complicated!

See more about Perilloux’s research here.

Read Meston and Buss’s (popular science) book on this subject, Why Women Have Sex: Women Reveal the Truth About Their Sex Lives, from Adventure to Revenge