Empirical Sexual Attitudes is a short book on the psychology of sexuality. I've aimed to make the book scientifically rigorous but also accessible to a general audience. Technical details that are present only for completeness are confined to footnotes and appendices. It should mostly be possible to read chapters out of order, although it is a good idea to read the preface before anything else.
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.
There is currently no empirical basis for condemning most sexual practices, as strange or disgusting as people may find them. Nor is there any empirical basis for condemning sexual abstinence: in particular, there is at best weak support for the idea of a hunger-like sex drive. The one randomized controlled study of sexual frequency found that increasing couples' frequency of sex worsened their mood. Clinical trials of sexual behavior would be necessary to begin shedding light on the issue of what sexual habits are most beneficial.
Why have animals evolved to have sex? The obvious answer, "for reproduction", is at odds with the diversity of non-reproductive sexual behavior. Some non-reproductive sexual behavior may exist merely by accident, but there's a variety of ways non-reproductive sexual behavior may otherwise benefit animals. There's no ready answer to the general question of why animals have sex.
We tend to classify people's sexual preferences into sexual orientations, such as "straight", "gay", and "bisexual". I argue that, on the contrary, we should expect sexual preferences to be just as idiosyncratic as ice-cream preferences. Indeed, there are many ways in which familiar sexual orientations do not seem to adequately describe people's sexual preferences and sexual behavior. While it is legitimate to want to categorize sexual preferences, laypeople and scientists alike have been too eager to do so with scant regard for empirical reality. A misleading taxonomy is worse than no taxonomy at all.
Why do strange, apparently useless sexual taboos appear in all human societies? Experiments show that people associate sexuality with animals and the body, and thus with mortality. It appears that social norms ranging from disapproval of prostitution to the ideal of romantic love exist, in part, to provide us a kind of symbolic immortality and buffer us from existential threat. There exist other potential explanations for sexual taboos, but the overall picture is not favorable to anyone who would seek to free human sexuality from artificial restrictions.
Experiments have demonstrated a wide variety of ways sexual emotion can influence how we think and decide. Importantly, such findings have been obtained even for non-sexual domains of behavior, and with very weak manipulations of sexual affect, such as the gender of a name. Sexuality then appears to have pervasive, albeit subtle, consequences for human thought. There is no clear overall theme to the findings, except, perhaps, that sexuality often influences us in ways we'd rather not be influenced.
Sexual activity to which one partner does not consent is seen in all human cultures and many non-human species. Its frequency can differ dramatically between cultures, but it is very common in the United States, especially between acquaintances and romantic partners and in its milder forms. Rape is associated with even more psychological damage to the victim than non-sexual traumas, and even sexual abuse short of rape is damaging. The evidence of damage from child sexual abuse, however, is less clear than the evidence of damage from abuse of adults. Precisely what makes sexual abuse aversive during the event and traumatizing afterwards is unclear.
The idea that sexual abuse is an act of desperation by sexually deprived men is not supported. However, sexual abuse does seem to be motivated by sexual interest in the victim and by less selective sexual preferences (specifically, a tendency not to be sexually inhibited by expressions of non-consent). In terms of non-sexual causes, abuse seems to share the causes of non-sexual crimes and antisocial behavior, and it is enabled by cultural environments in which women are less powerful and by sexist attitudes. What all this means for prevention and treatment is unclear.
[I may someday write additional chapters about sexism and behavioral endocrinology.]