For the paparazzi of the polling profession, lying about sex is an area surrounded by as much controversy as the President's lies about sex.

Even when social scientists have "results" from survey questions about sexual behavior, problems of interpretation abound. Men, for example, report having more frequent sex than women. University of Maryland sociologist John Robinson says the explanation isn't that "men are more driven or boastful," it's simply demographics. One in five adults in a major sex survey by the National Opinion Research Center at the University of Chicago say they have not engaged in sex in the previous year. Widows and older women without husbands or partners dominate this group.

If we can't be confident of what individuals are willing to say about their own behavior, can we rely on what they say about other people's behavior? Here, too, the surveys raise as many questions as they try to answer. It's hard to tell from survey questions, for example, whether sexual behavior has really changed, or whether people are more willing to talk about it to survey researchers.

There is a long-standing belief in the surveys that men are more prone to temptation than women. In 1943, pollster Elmo Roper didn't even think it necessary to ask men about women's extramarital involvements. Instead, in a question that seems quaint and charming in comparison to its modern-day equivalents, women were asked (by women interviewers) whether many, only a few, or practically no men were "untrue" to their wives: some 48 percent of women said many men were, 43 percent said only a few were, and five percent said that practically none were. In 1946, when Gallup asked married women to volunteer the chief faults of their husbands, thoughtlessness topped the list, followed by bossiness and "other women." "Other men" wasn't even mentioned by men who were asked about their wives' faults. In 1950, when Gallup asked who was more easily "led astray," 40 percent said men were, 29 percent said women, and 24 percent said there was no difference. A September 1997 CBS News/48 Hours poll found that two-thirds of men and women said a man was more likely to "cheat" on a spouse than a woman.

In 1964, in the first question I have been able to find that asked people whether they knew anyone "who has an unfaithful wife or husband," 24 percent said they did. Louis Harris and Associates repeated the question three times in the 1960s, and the number edged up gradually to 41 percent in 1969. When CBS News repeated the Harris question word-for-word in 1995, 58 percent said they knew of someone, and 39 percent said they did not. Are there more unfaithful people, or are we just willing to talk more openly about infidelity? The surveys can't answer the question.

Whatever we're saying (or willing to say), there has been no change in the past quarter century in the belief that extramarital sex is always wrong. In polls, around 80 percent choose the response that it is "always wrong," the most severe of the categories. The belief that premarital sexual activity and same-sex relations, however, are "always wrong" has declined over the span.