Married men are more likely to overestimate their value in the dating market — because they’re not on it anymore.

Confident men often misread social cues from single women, economist Marina Adshade, author of the book Dollars and Sex: How Economics Influences Sex and Love told Fatherly, and this can result in cheating, divorce, and men opening up their relationships only to find themselves utterly alone, their stock not nearly as high as they had thought.

“This is really common, and I think a lot of it is being driven by men overstating their value,” Adshade says. “They think ‘I’m married to this woman, but if we’re nonmonogamous or polyamorous I’m going to have a new woman every week,’ and it doesn’t work that way.”

There’s at least some anecdotal evidence that women in polyamorous communities have more power in their relationships. One notable example involved a man who posted on Reddit about how he convinced his girlfriend of two years to open their relationship, only to discover that she was highly desirable, and he was not. Predictably, the internet was less than sympathetic.

This isn’t that surprising to Adshade — she suspects it is part of a scientific phenomenon known as self-assessment bias. Drivers tend to evaluate themselves as much better drivers than they actually are. Employees generally assess their performance higher than it actually is. And men generally consider themselves desirable, studies show.

Part of the reason married men are especially prone to these biases of self-assessment is that they have the endorsement of the woman who married them, something they didn’t have the last time they were on the market.

Their partner’s paranoia only reinforces this. “Women think other women are going to steal their husbands when they’re some middle-aged overweight man that no other woman is trying to take off their hands,” Adshade says. “So it’s not only men who overestimate their value.”

There are also cultural norms at play. Boys are taught to be over-confident, from a young age. At the same time, women learn to focus their energy on fending off unwanted attention from mainly single men.

However, they frequently feel more comfortable letting their guards down with married men — not because they’re trying to steal them, but because they don’t consider it an issue, so they can relax. It’s not that the attention married men receive from women is all in their heads. They’re just misinterpreting where it’s coming from, Adshade says.

“I think this is generational, but it’s all coming from this inability to properly interpret what it means when a woman is nice to them,” Adshade says. “Just because a woman at work is nice to you doesn’t mean she wants to date you. This overconfidence creates very real problems.”