In dating as in marriage, infidelity gets low marks from the public. But when you ask a group of daters how often they think it happens, they perceive it's common in other relationships.

But those same couples haven't defined or talked about infidelity together.

Those are among the findings of a study just published in the Journal of Social and Personal Relationships.

In a survey of 200 individuals ages 17-32 who had been dating an average of 22 months and generally considered their relationships to be "exclusive," the Canadian research team found that while 90 percent said they'd want to know if a partner cheated, 70 percent had never had "an explicit conversation with their partner about what counts as cheating or what they expect from their partners in the fidelity department."

When asked to guess what percentage of the opposite sex who were dating in a relationship similar to their own had ever cheated, the average answer of those surveyed was 40 percent. At the same time, 9 percent admitted to having cheated in their own relationship at some point, but only 5 percent thought their partner had or ever would cheat.

"In other words," the researchers said in a Science of Relationships article, "daters in this study were unlikely to talk about infidelity with their partners but at the same time presumed that the likelihood of cheating in the general population was fairly high. And they reported cheating at twice the rate than they thought their partners would cheat.

"Add this pattern of results to the lowest published rate of infidelity in dating relationships — 14 percent — and it becomes pretty clear that folks are engaging in some fairly risky wishful thinking," they wrote.

Cheating is a hot topic on online dating sites, which discuss fidelity and offer tips for clarifying what is and isn't expected in a relationship. For example, Neal Litherland writes on Match.com, "Fidelity is one of the most stressed aspects of a relationship. Fidelity or loyalty boils down to the same thing; you both have agreed that your partner has your love, affection and commitment over other potential partners. Fidelity can be a complicated thing though, especially if one partner considers a certain act to be cheating, while the other partner doesn't see the big deal."

An article on infidelity in the Deseret News noted that men and women in a romantic partnership cheat on each other for different reasons: "Research says men are more likely to pursue illicit relationships for sex, while women are more often drawn to an emotional appeal. They want to be desired."

"There are differences in individuals' definitions of 'cheating,'" said Kristin Hodson, therapist/founder of Salt Lake-based The Healing Group, who wrote the book "Real Intimacy: A Couples' Guide to Healthy, Genuine Sexuality." "While virtually everyone recognizes sexual intercourse as cheating, many don't consider an emotional relationship or even one involving passionate kisses to be infidelity. … I think they still damage. They are disrupting the baseline of trust."

People may also have different standards regarding what's cheating depending on whether or not a couple is married. But an article in The Atlantic in 2013 noted that cheating on someone you married meets a great deal of public disapproval. The article said marital infidelity is a "sexual taboo."

Email: lois@deseretnews.com, Twitter: Loisco