"This language could, of course, describe 'swinging' or 'opening up.' But it could also quite plausibly describe casual dating, in which singles knowingly date, and sleep with, multiple people at once," Lehman said.
"Such relationships are perhaps, strictly speaking, a-traditional, but they do not meet most people's intuitive definitions of 'polyamory,' or even 'open relationships' (which connotes a degree of romantic, but not sexual, commitment-a nuance uncaptured by the question)," he added.
Even some CNM relationships would not fit this definition, if they are sexually exclusive relationships between three or more people, but are not open to others outside of the set group, Lehman wrote.
"There's at least one other reason to be suspicious of Haupert et al.'s finding," Lehman added. "Their methodology notes that they deliberately oversampled 'homosexual men and women.' In fact, 15.3% of study 1 and 14.3% of study 2 respondents self-identified as LGB (lesbian, gay, or bisexual). That's substantially higher than the population-wide prevalence of LGB people, which is generally pinned at 3 to 5%."
"Previous research cited by the paper has shown, and Haupert et al. confirm, that identifying as lesbian, gay, or bisexual is associated with a significantly higher likelihood of reporting engaging in consensual non-monogamy," he said.
"In other words, the study substantially oversampled the very subpopulation they then find is far more likely to engage in CNM."
Lehman said it is not explained in the study whether the researchers adjusted for this bias in the results, though he said it seems unlikely. But the frequently-cited statistic that at least 20% of all Americans have dabbled in CNM seems to be a product of sample selection instead of reality, he noted.
"As always, the reality is probably more boring. Some single people engage in non-exclusive relationships; a smaller, unmeasured share probably engage in more formal 'polyamorous' or 'consensually non-monogamous' relationships, and that share has probably risen slightly," he wrote.
In fact, he noted, the 2018 "i-Fidelity" survey by YouGov for The Wheatley Institution at BYU found that roughly 12% of Americans had ever engaged in an "open sexual relationship," defined as "an agreed-upon, sexually non-exclusive relationship with more than one partner."
Millennials were more likely to have engaged in such relationships, but still at a rate of less than 20%, he added.
"Polyamory may sound fun and exotic, but most of us don't live such fun and exotic (and complicated) lives. By their 30s, most Americans (80%) are either married or single, with little evidence that 'alternative' structures are filling the gap for a significant share of adults. As Dr. Alan Hawkins recently put it, 'the norm of marital monogamy is not crumbling' after all."
(Story continues below)
Subscribe to our daily newsletter