Sexual Health Blogs

A Personal Interview with Dr. Justin Lehmiller

An Interview with Dr. Justin Lehmiller

Author of Tell Me What You Want: The Science of Sexual Desire and How It Can Help You Improve Your Sex Life


We would like to start by asking you some questions about your most recent book, Tell Me What You Want. You conducted one of the largest and most comprehensive scientific surveys of Americans’ sexual fantasies as the basis for this book. What was your most unexpected finding?

That’s a really tough question because I found so many things that were fascinating and surprising! That said, one finding that was particularly interesting to me was the way that our sexual fantasies seemed to change with age. For instance, I found that threesomes and group sex were more popular fantasies among older adults, whereas passion and romance were more popular fantasies among younger adults. A lot of people would have expected the reverse pattern. As I discuss in the book, I think what’s going on here is that our psychological needs change as we age and, as they do, our sexual fantasies evolve in ways that are designed to meet those needs. So, for example, when we’re younger and perhaps more insecure, our fantasies focus more on making us feel validated; by contrast, when we’re older and have settled into a long-term relationship, our fantasies focus more on breaking sexual routines and fulfilling unmet needs for novelty. 

How did you get more than 4,000 people to tell you about their deepest sexual fantasies?
Talking openly about our sexual fantasies is something that many of us find to be intimidating. We’re worried that other people will reject us or judge us for our desires, so rather than talking about our fantasies with our partners, we tend to keep them to ourselves. I was able to bypass a lot of this anxiety by collecting data on people’s sexual fantasies anonymously. When people know that their survey responses will stay anonymous, they become far more willing to talk about sex. The fact that so many people took my survey tells me that people really do want to talk about their fantasies—sadly, however, they just find it a lot easier to tell a stranger over the internet than their partner.   

What’s the most common thing that people are fantasizing about? 

When looking at people’s biggest fantasy of all time, the single most common sex act that emerged was having a threesome. And when I looked at whether people had ever had a fantasy about threesomes (or group sex more broadly), I found that almost everyone—male and female alike—had done so. However, I should note that BDSM was another sex fantasy that almost everyone reported having at one time or another, too. 

Did male and female responders have different desires? 

Men and women were surprisingly similar in the types of things they fantasized about. Many of the fantasies that are stereotyped as masculine (like threesomes) or feminine (like emotional fulfillment) were things that a majority of both men and women were fantasizing about. However, there were some important differences that emerged. For instance, women were more likely than men to fantasize about same-sex experiences, whereas men were more likely than women to have gender-bending fantasies (such as crossdressing or having sex with a transgender person). I also found that women were more likely to fantasize about BDSM and to place more emphasis on where they were having sex; by contrast, men reported more taboo sexual fantasies and placed more emphasis on who they were having sex with.

What do a person’s sexual fantasies say about their personality? 

My survey results suggest that people with different personalities tend to fantasize about very different things. For example, people who are more extraverted and outgoing tended to have more fantasies about group sex and non-monogamy (after all, they like meeting new people!). Highly agreeable persons (i.e., those who have more care and concern for the well-being of others) were less likely to fantasize about BDSM, infidelity, and emotionless sex—a pattern that makes a lot of sense because they don’t want to hurt anyone and they want to be sure that their partner is enjoying the sex. Also, those who were more neurotic, meaning they don’t handle stress well, were more likely to include calming emotional content in their fantasies (like romance), while they were less likely to fantasize about trying new things—in other words, neurotics’ fantasies seemed to be designed to avoid stressing them out. I discovered many more connections between our personalities and our fantasies, but it seems that, overall, our fantasies reflect who we are and they appear to be designed to meet our unique psychological needs.  

Were there any sexual fantasies that stood out to you?

One of the most interesting fantasies I learned about through this survey was something that one female participant described as being a “human cow.” Specifically, she wanted to be tied up in the center of town where she would be force fed hormones that would make her lactate constantly while people would come and milk her and have sex with her whenever they wanted. I only received one fantasy like this, but after writing the book, I learned that there’s a whole porn genre devoted to women dressed as cows while they’re tied up and hooked to milking machines. 

What is your advice to someone who has expressed a particular sexual desire to a partner who is unwilling to fulfill it? 

If the results of my survey have taught me anything, it’s that most of us aren’t just fantasizing about one thing and one thing only—we tend to have multiple sex fantasies. So odds are that even if you and your partner aren’t a match on a given fantasy, there will likely be several other areas where you’ll have common ground. Therefore, I would suggest looking for other desires that are mutually shared. The other thing I would advise is to avoid pressuring or coercing your partner into fulfilling a given fantasy because that’s not going to turn out well for anyone. 

What is your advice to someone who may be uncomfortable fulfilling their partner’s desire? 

First and foremost, don’t do anything you don’t want to do. And if you’re uncomfortable with something, consider proposing an alternative activity that could potentially fulfill your partner’s desire while also being of interest to you. For instance, if your partner is turned on by the idea of a threesome but you aren’t, you might compromise by looking for other ways of interjecting novelty into your sex life, such as by role playing or watching porn together. The need for sexual novelty is one that is pervasive, but it’s endlessly flexible and there are so many ways that it can be achieved. 

What role does evolution play in sexual fantasy and desire?

As I discuss in the book, there’s a lot of research to suggest that people’s sexual fantasies and desires are shaped, to some extent, by our evolutionary history. The idea here is that the unique reproductive challenges faced by our ancestors may have predisposed us to certain desires that are likely to assist us in meeting those challenges. For example, this would include desiring partners with physical attributes that signify sexual maturity, fertility, and strong genes (think men with chiseled bodies and women with hourglass figures) because this would help to ensure that we focus our attention on prospective partners with whom there would be better odds of successful reproduction. As I discuss in Tell Me What You Want, this line of reasoning helps to explain why the likes of Channing Tatum and Scarlett Johansson top the list of the most fantasized about celebrities.


Thank you for sharing all of this information about your research. Now we have a few questions about you! First, how do other people react to your career as a sex researcher and educator when they find out what you do?

Being a sex researcher is something that’s both a blessing and a curse. I absolutely love my job and the fact that I’m able to learn new things about sex every day, to share this information with the world through my writing, and to contribute to scientific knowledge. At the same time, though, it means that everyone wants to ask me their sex questions—even when I’m at a dinner party or out with my friends. All of us want to be able to escape our work sometimes and even though I find sex to be a really interesting and fascinating subject, I need a break from it sometimes!

You used to work at Harvard University. What did you find the most surprising about working there? 

One of the classes I taught at Harvard was Psychology of Human Sexuality. I was surprised to learn that this course hadn’t been offered in the Psychology Department there for several years before I started teaching it. This meant there was a lot of pent-up demand, so I ended up having some pretty big classes. 

One of the most unique things I discovered about teaching at Harvard, though, was the fact that there aren’t a ton of required courses and students largely get to choose their own curriculum. The first week of every semester is known as “shopping week” and it’s when students go sit in on a bunch of classes and decide what to take. It puts a lot of pressure on you as an instructor to engage your students from the moment they set foot in your classroom because if you don’t capture their attention that first week, they won’t sign up for your course. That experience actually ended up making me a much better instructor because I really had to figure out how to captivate an audience. 

What is the most important thing about sex that you want all therapists and healthcare providers who deal with sexuality issues to know? 

There are so many things! I don’t know that I can recommend just one piece of information, but I think it’s important for them to recognize that our knowledge and understanding of human sexuality is constantly changing and evolving. And the “replication crisis” in science is affecting our field, too. As we go back and revisit older findings in the literature and attempt to repeat them, we’re finding that they don’t necessarily all hold up (such as the finding from the 1980s that men exposed to Playboy centerfolds reported less love for their partners than men exposed to abstract art—that was a highly cited finding for decades, but modern researchers have found that they can’t replicate it). This means that your sex education can’t end with your graduate training and it speaks to the importance of and need for continuing education for therapists and healthcare providers. We all need these opportunities to keep up to date on the literature and to ensure we’re practicing with the best available data and information in mind. The good news is that a lot of these continuing education opportunities are available through the Sexual Health Alliance and elsewhere. All you need to do is seek them out!

What are the most common or influential sex books you reference in your work?

One of the books I reference most frequently is The Social Organization of Sexuality by Laumann and colleagues. This is the book that’s based on the National Health and Social Life Survey from the 1990s. It’s really a treasure trove of information about Americans’ sexuality from that point in time (just like Kinsey’s books were for people in the 1940s and 50s). It’s one of the most comprehensive sex surveys ever conducted, and it’s really useful as a reference point when looking at how sexual behaviors were similar/different a quarter-century ago. 

I reference the book A Billion Wicked Thoughts with some frequency too. This book looks at what our porn searches say about us and it provides some revealing insights about sexuality today.

Who in the field of sex research inspires you?

There are a lot of people who inspire me, but one of the first names that comes to mind is Dr. Lori Brotto. She does it all—she’s has this incredible body of research that is supported by millions of dollars in grants, but she’s also engaged in clinical practice, she disseminates science to the public through the media, she’s an incredibly dynamic public speaker and educator, and she’s written an amazing book called Better Sex Through Mindfulness. She’s also just a wonderful human being who has seemingly managed to find that elusive work-life balance, too. I’m in awe of what she has accomplished.


As a research fellow at the Kinsey Institute, you have made a wonderful career as a sex educator. What would you recommend to young educators wanting to follow in your footsteps?
The most important thing to know is that there isn’t just one path you can pursue. Sex educators come from wonderfully diverse backgrounds. You could get your training in social psychology like I did, but I know sex educators who have backgrounds in public health, biology, anthropology, and several other fields. So start by choosing the discipline that’s the best fit for you and your interests. 

The other big thing to consider is how you want to educate people—do you want to work in a college setting? Do you want to teach adolescents? Do you want to put on workshops or write for the general public? Connect with some educators who are in the area you want to pursue and ask for their advice because each area may require different credentials or experience. 

Thank you Dr. Justin Lehmiller!

-SHA Team