Journalist Pamela Druckerman didn't think it would be hard to discuss sex issues with Alain Giami of the French National Institute of Health and Medical Research.

After all, he was one of the top sex researchers in a nation known for its freewheeling, laissez faire attitudes about matters of the heart. However, Giami silenced her when she used a dangerous word.

"What do you call 'infidelity'? I don't know what 'infidelity' is," he said, in what the former Wall Street Journal correspondent later described as a "rant."

"I don't share this view of things, so I would not use this word," he added, and then delivered the coup de grace. "It implies religious values."

Thank goodness Druckerman didn't say "adultery." For most researchers, this term has become a judgmental curse that cannot be used without implying the existence of the words "Thou shalt not commit." This issue came up over and over as she traveled the world doing interviews for her book "Lust in Translation: The Rules of Infidelity from Tokyo to Tennessee."

"If I asked someone, 'Have you ever committed adultery?', it was like God entered the room at that moment," said Druckerman, reached at her home in Paris. "That really is the religious word, 'adultery.' I had to start saying 'infidelity' or use a more careful combination of words."

While she didn't set out to write a book about sex and religion, Druckerman found that in large parts of the world -- from Bible Belt cities to Orthodox Jewish enclaves, from Islamic nations to post-Soviet Russia -- it's hard to talk about infidelity without talking about sin, guilt, confession, healing and a flock of other religious topics.

However, she also reached a conclusion that many clergy will find disturbing. When push comes to shove, cheaters are going to do what they're going to do -- whether God is watching or not.

What does faith have to do with it? Not much. That's the bad news. The good news is that there is evidence that adultery is nowhere near as common as most religious people think it is.

Take, for example, the numbers that many consider "gospel" on this issue -- the claims by sex researcher Alfred Kinsey in the mid-20th Century that half of American men and a quarter of women have cheated on their spouses. While some writers keep using these statistics, Druckerman said they are "extremely problematic."

Recent studies offer a vivid contrast. In the early 1990s, she noted, 21 percent of American men and 10 percent of women said they had cheated while married. In 2004, 21 percent of men and 12 percent of women said they had strayed at least once.

Meanwhile, 3.8 percent of married French men and 2 percent of married French women say they've had an affair during the past year -- in one of the world's most secular nations. And in highly religious America? The parallel figures are 3.9 percent of the married men and 3.1 percent of the women.

While Americans remain obsessed with adultery, this now seems to be rooted in this culture's commitment to an "ubermonogamy" built on the all-powerful doctrines of modern romance, argued Druckerman. Lacking shared religious convictions -- while living in the era of no-fault divorce -- millions of Americans have decided that having a happy, fulfilling, faithful marriage is an entitlement, a kind of sacrament in and of itself.

If a marriage crashes, both religious and non-religious Americans usually place their faith in another substitute for the old structures of faith and family. They turn to professional counselors linked to what Druckerman calls the "marriage industrial complex," where, for a price, repentance and restoration can take place in public or in private. Ask Bill Clinton about that.

All of this represents the reality of America's "sexual culture," which, while it may have Puritanism in its DNA, has also been shaped by the modern sexual revolution.

"Even when I talked to religious people about adultery, they weren't really worried about God, about God striking them down for their sins," concluded Druckerman. "Americans just don't think that way now. Even the religious people were more worried about what their families, or perhaps the people in their religious communities, would think of them. ...

"When it comes to matters of infidelity, Christian Americans act more like Americans than they do like Christians."