Created 21 Jun 2012 • Last modified 21 Jun 2016

I introduce the goal of this book—to determine what sexual attitudes we should endorse if we want our attitudes to be as faithful as possible to the available empirical evidence—and provide some background.

As long as sex is dealt with in the current confusion of ignorance and sophistication, denial and indulgence, suppression and stimulation, punishment and exploitation, secrecy and display, it will be associated with a duplicity and indecency that lead neither to intellectual honesty nor human dignity. [Gregg, 1948, p. v]

Historically and to this day, people have had strong opinions about sex. Religions have praised some sexual behaviors as spiritually productive while condemning others as contrary to divine plans. Physicians, since the Victorian era, have offered a similar range of commandments, from branding masturbation as self-abuse to warning against the perils of sexual repression. And laypeople of all kinds have opined, sometimes in yet more emphatic terms, as to what kinds of sexual expression or abstinence are virtuous, disgusting, immoral, unnatural, innocent, beautiful, heroic, unthinkable, satisfying, worthwhile, dangerous, or stupid.

The only thing that such opinions can defensibly be founded on is the one thing they're least likely to be founded on: empirical evidence. Think about it: in the twenty-first century, it's no secret that human intuition about the way the universe works is wrong. We aren't born knowing that the earth orbits the sun, bananas gravitationally attract other objects, microorganisms live under our skin, and the best choice in the Monty Hall problem is to switch.1 Our own behavior is no different. As much as we observe and reason about each other in everyday life, experimental psychology has shown time and again that human behavior and cognition can be nothing like what we expect. The ultimate demonstration is Nisbett and Wilson (1977), which shows through converging evidence that despite a persistent intuition to the contrary, people do not have special introspective access to the causes of their own behavior. The paper is thus a defense of the necessity of experimental psychology by means of experimental psychology itself.

Unfortunately, experimental psychology hasn't filtered down to the lay public. This problem isn't confined to psychology: a typical person doesn't even understand the falsificatory scientific method to begin with, any more than they realize that pure mathematics concerns proof rather than computation. But it seems all the more galling in the case of psychology. Whereas research-level mathematics is rarely directly relevant to everyday life, we rely on our own ideas of how people think and behave all the time: our decisions are (or at least, should be) based on what we expect the consequences of our actions will be for others' and our own behavior. Incorrect expectations will thus lead to incorrect decisions.

In the case of sexuality, things only get worse. We tend to have strong opinions, not mere intuitions, and sexual attitudes can be surprisingly high-stakes considering how sexual matters are sometimes dismissed as trivial. Think of STDs, unwanted pregnancies, rape, and violence against gay men and lesbians. Or, just notice how people's decisions about whom to marry and how much to reproduce play a major role in determining the course of their lives. Perhaps most importantly of all, sexual motivation can have consequences for behavior that seemingly has nothing to do with sex, as discussed in this book's chapter on cognition. You may not agree that these are all issues of sexuality per se. Fair enough. For the purposes of this book, let's just take "sexuality" to refer to the set of emotions and motivations that seem closely tied to sex and masturbation, where "sex" includes (now and hereinafter) coitus, oral sex, anal sex, and so on. How sexuality thus defined relates to rape etc. is an empirical matter, one of the several empirical matters that I hope to shed light on in the course of this book.

As disparate as the topics I'll discuss may seem to be, I have a single overarching goal: to provide a foundation for empirical sexual attitudes. I've just complained about how sexual attitudes tend not to have much to do with empirical truth, and how sexual attitudes can ultimately matter a lot. What I want to do, then, is try to junk all our accumulated, entangled ideas about what sexuality is or ought to be and replace them with notions that are as faithful as possible to the available evidence.

That evidence isn't nearly as good as it could be. Sexuality isn't the most popular of research topics. And studies that do concern sexuality are rarely true experiments—that is, studies in which subjects are randomly assigned to experimental conditions, which are the only sort of study that provides direct evidence of causation. Non-experimental research, in which subjects are only observed without being manipulated by the researcher, or are manipulated but without true random assignment, predominates. Why is this so? Partly because of theoretical and practical difficulties inherent in manipulating relevant variables (such as sexual experience) and partly because of antagonism that some clinical psychologists, psychiatrists, sociologists, and anthropologists have towards the artificiality of the lab.

Worst of all, a large part of academic research on sexuality is not empirical. It eschews the scientific method in favor of the critical method, replacing repeatable procedures and numerical measurement with anything-goes interpretation. Society has somehow chosen writers like Sigmund Freud, Michel Foucault, bell hooks, and Judith Butler to represent academia's opinions on sexual matters. All this noise masks the important gaps in empirical sex research. So, I have a limited supply of raw material—empirical truth—with which to construct this book, but I'll do the best I can.

On the subject of this book's limitations, let me say a bit about where I'm coming from and what my biases are. Unlike virtually every other academic who writes about sex these days, I'm more sex-negative than sex-positive. Although raised by atheist parents with reasonably liberal attitudes about sex, I developed a very dim view of human sexuality during puberty. My views have mellowed since then, but I remain celibate, and my scientific interest in sexuality has its roots in my fear and distrust of these strange and powerful motivational forces.

As for my qualifications, my formal education is exclusively in psychology and mathematics. I've learned some other things on my own, but for some of the disciplines touched on this book, including psychiatry, ethology, anthropology, criminology, and history, what I've read hardly extends beyond what I've cited here. Please let me know of any errors or omissions.

Finally, a few words on feminism. I am sympathetic to feminism, but more to the second-wave, radical feminism of the early 1970s than the third-wave, sex-positive feminism that is popular today. Insofar as sex-positivity is the assumption that human sexuality is intrinsically good and thus any way in which sexuality seems to have bad consequences (such as rape) doesn't count as sexuality (along the lines of "no true Scotsman"), sex-positivity is dogmatic. And I see it as less important to assert women's femininity and unity than their personhood and individuality, as Haack (2001) describes, and as opposed to what Echols (1989) calls "cultural feminism". I would like not to equalize gender roles but to abolish them. To borrow some rhetoric from the Brown v. Board of Education decision, there is no "separate but equal": separate is inherently unequal. In any case, various points of feminist thinking, second-wave and otherwise, will be among the things we examine from an empirical point of view in this book.


Thanks to (in alphabetical order) Jeffrey H. Arfer, Nicholas R. Eaton, Gambit Garrison, Edvard Karlsen, prude, Leianne Stafford, and Elizabeth M. Trimber for their thoughtful comments on various drafts of this book and the productive discussions I had with them.


Echols, A. (1989). Daring to be bad: Radical feminism in America, 1967-1975. Minneapolis, MN: University of Minnesota Press. ISBN 978-0-8166-1786-9.

Gregg, A. (1948). Preface. In A. C. Kinsey, W. B. Pomeroy, & C. E. Martin (Eds.), Sexual behavior in the human male. Philadelphia, PA: Saunders.

Haack, S. (2001). After my own heart: Dorothy L. Sayers's feminism. New Criterion, 19(9), 10–14. Retrieved from

Nisbett, R. E., & Wilson, T. D. (1977). Telling more than we can know: Verbal reports on mental processes. Psychological Review, 84, 231–259. doi:10.1037/0033-295X.84.3.231



The Monty Hall problem is a math problem with a famously counterintuitive answer. Suppose you're a contestant on a game show and there are three doors, one of which has a car behind it, whereas each of other two doors has only a goat behind it. The car and the goats are assigned to the doors at random, with each possibility being equally likely. You may choose any door without opening it, and then the host will open a door that you didn't choose to reveal a goat. (If your initially chosen door had the car, the host has two goat doors to select, and will select one at random. If your initially chosen door had a goat, there is only one other door with a goat, so the host will open that door.) Now the host lets you either open the door you first picked, or open the remaining unopened door. Are you more likely to get the car if you stay or switch? It turns out that your chance of getting the car is 1/3 if you stay but 2/3 if you switch. See the Wikipedia article "Monty Hall problem" for a full discussion.