My new book, Tell Me What You Want: The Science of Sexual Desire and How It Can Help You Improve Your Sex Life, will land in bookstores next week (July 10 in the US, to be exact). I couldn't be more thrilled, especially after all the years I spent writing it!

This book is built around a massive survey of sexual fantasies that I spent almost two years working on. I learned a lot in the process of conducting this survey and writing the book, so let me take a moment to share some of the key insights and takeaways. To that end, here's an excerpt from a recent Q&A I did about Tell Me What You Want, which will give you a better sense of what the book is all about and some of the most interesting things I discovered along the way:

How did you get more than 4,000 people to tell you about their deepest, sometimes darkest, 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 largely able to bypass 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—and pretty much everything else for that matter! 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 them to a stranger over the internet than their partner.

You conducted one of the largest and most comprehensive surveys of Americans’ sexual fantasies. 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 seem 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.

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. Indeed, many of the fantasies that are stereotyped as masculine (like threesomes) and 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 (like crossdressing or having sex with a transgender or transsexual 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 does 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.

What’s the most unusual or interesting sexual fantasy you’ve ever heard?

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. It seems that whenever I think I’ve seen or heard it all, I learn about a new fetish.

When does a fantasy become a problem that requires professional help?

If you find yourself frequently fantasizing about nonconsensual sex acts or activities that pose a great risk of harm to you or to others and you’re worried that you might act on these desires, it’s time to seek help. Also, when a fantasy—no matter what it is—starts to take over your life to the point where it’s highly distressing or starts to interfere with your work or relationship, that’s another good sign that professional counseling is in order.

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 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.

Exclusive offer for readers of the blog: If you preorder Tell Me What You Want, you will receive a bonus package that includes an extra chapter (which focuses on the psychology behind some of the less common sex fantasies), some fun fantasy-related infographics, and more. Click here for complete details on this offer.