Modern WisdomWhat Psychology Says About Women Who Cheat - Macken Murphy
At a glance
WHAT IT’S REALLY ABOUT
New Study Revives Controversial Theory On Why Women Cheat
- The conversation explores competing evolutionary psychology theories about female infidelity: the traditional Dual Mating hypothesis versus the newer Mate Switching hypothesis. Macken Murphy describes a preregistered study of 254 men and women who actually cheated, directly pitting the two theories’ predictions against each other. Results show affair partners are rated as more physically attractive but worse as parents than primary partners, strongly supporting Dual Mating and undermining Mate Switching in this dataset. The discussion also covers motives for cheating, sex differences in jealousy, predictors of infidelity, and broader implications for how ‘natural’ monogamy and cheating are in humans.
IDEAS WORTH REMEMBERING
5 ideasNew empirical data strongly supports the Dual Mating hypothesis over Mate Switching.
In Murphy’s preregistered study, affair partners were rated about two points higher in physical attractiveness, while primary partners were about three points higher in parental attractiveness—exactly the crossover pattern Dual Mating predicts (good genes from the affair partner, good parenting from the primary partner), and not what Mate Switching (trading up overall) would expect.
Women’s infidelity is multi-motivated, not explained by a single strategy.
Women most often cited relationship dissatisfaction, followed by an uninvested primary partner and revenge (often for a partner’s affair), and only a small fraction explicitly mentioned physical attractiveness—even though quantitative ratings show they clearly did ‘cheat up’ in looks.
Men show a similar cheating pattern: up in looks, down in parenting.
Contrary to the idea that men simply ‘cheat down’ for easy access and variety, male cheaters also tended to rate affair partners as more physically attractive but worse in parental qualities, suggesting a broader human pattern of seeking conceptive benefits in affairs and parental benefits in primary relationships.
Stated reasons for cheating often diverge from actual patterns of behavior.
Only about 5% of women said they cheated because the affair partner was attractive, yet 77% were more likely to prefer the affair partner’s looks in forced-choice ratings—highlighting limited self-insight and social desirability bias in people’s narratives about their own behavior.
Attachment, jealousy, and investment concerns map onto evolved risks for each sex.
Men are relatively more distressed by sexual infidelity (risk of cuckoldry) and women by emotional infidelity (risk of losing partner investment), aligning with paternity uncertainty for men and investment uncertainty for women, and fitting better with Dual Mating than pure Mate Switching.
WORDS WORTH SAVING
5 quotesOur study ended up being the best case scenario for dual mating, and the worst case scenario for mate switching.
— Macken Murphy
Women were 77% more likely to prefer their affair partner’s physical attractiveness than their primary partner’s. What a coincidence if that’s not a motivating factor.
— Macken Murphy
It’s incredibly patronizing how everyone’s happy when you talk about men’s evolved psychology, but as soon as you talk about women’s, it’s almost as if the whole story is about men.
— Macken Murphy
If you label everything as ‘the patriarchy’, then you’re basically saying that men are the only ones with their hands on the wheel.
— Macken Murphy
The consistent themes that you find throughout your life—if they continue to come up—have to have something to do with you.
— Chris Williamson
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