Modern WisdomWhat Psychology Says About Women Who Cheat - Macken Murphy
CHAPTERS
- 0:00 – 2:21
The infidelity debate in evolutionary psychology: dual mating vs. mate switching
Chris opens by asking about the controversy Macken sparked and the current state of hypotheses about women’s infidelity. Macken lays out the long-running debate between the dual mating ("good genes" + investment) account and the mate-switching (trading up) alternative.
- •Dual mating: pairing genetic benefits from an affair partner with investment from a primary partner
- •Mate switching: affairs function to move to a better overall mate
- •Why the debate became central in late 1990s–2010s evo psych
- •Clarification that “good genes” is fitness-related, not moral
- 2:21 – 8:25
Why ovulatory-shift evidence faltered—and why that doesn’t kill dual mating
Macken explains how early ovulatory-shift studies were used as key support for dual mating, then weakened as methods improved. He argues ovulatory shifts were only a sub-hypothesis and that dual mating could still be true even if cycle effects are small or absent.
- •Original ovulatory-shift logic: affairs should cluster around fertile window if function is conception
- •Early studies used small samples and low-reliability cycle estimation (self-report counting)
- •Later preregistered/better-method studies found smaller or disappearing effects
- •Dual mating doesn’t require strong ovulatory shifts; human sexuality is relatively stable across cycle
- 8:25 – 16:07
Designing a direct test: recruiting actual cheaters and pitting predictions head-to-head
To avoid prior literature’s reliance on people who hadn’t cheated, Macken describes recruiting participants who reported real sexual affairs. He lays out the clean competing predictions for mate switching versus dual mating and how the study measured them.
- •Recruitment via broad survey screening; final sample ~254 people with affair experience
- •Mate switching predicts affair partner rated higher overall and as a co-parent
- •Dual mating predicts crossover: affair partner higher physical attractiveness, primary partner higher parental/investment attractiveness
- •Measured physical, parental, mate value/desirability, and personality with validated scales
- 16:07 – 25:36
Results: crossover interaction supports dual mating (and a surprising pattern for men too)
The study finds affair partners rated notably more physically attractive while primary partners rated more attractive for parenting/investment—exactly the dual-mating crossover. Macken notes the result is unlikely to be a halo-effect artifact and highlights the unexpected finding that men show a similar pattern.
- •Affair partners ~2 points higher in physical attractiveness; primary partners ~3 points higher in parental attractiveness
- •No significant differences in overall mate value/desirability or personality between affair vs primary partners
- •Crossover pattern is hard to explain by generalized positivity/halo effects
- •Men also tended to “cheat up” in looks and “cheat down” in parental attractiveness
- 25:36 – 28:44
Is it just novelty? Limits of self-report and what qualitative data can (and can’t) tell us
Chris challenges whether the attractiveness gap might be novelty/biased perception rather than objective differences. Macken acknowledges limitations, explains why novelty alone doesn’t fit the full pattern, and emphasizes discrepancies between stated motivations and quantitative preferences.
- •Novelty could inflate perceived attractiveness, but should also inflate other ratings if it’s just positive illusion
- •If novelty drove effects, mate value/personality should rise too—yet they don’t
- •Self-report motivations are distorted by limited insight and self-serving narratives
- •Example: few women cite “he was hot,” yet quantitative ratings strongly favor affair partner looks
- 28:44 – 35:23
Top motivations for women’s affairs: dissatisfaction, low partner investment, and revenge
Macken reports the most common coded themes in women’s stated reasons for cheating. He stresses strategic diversity: dual mating may be a bias, but many affairs appear driven by relationship conditions such as low investment or retaliation.
- •Women’s #1 stated motive: relationship dissatisfaction (~65%)
- •#2: primary partner perceived as uninvested (~20–22%)
- •#3: revenge, especially in response to partner’s affair (~15.5%)
- •Not all women’s affairs fit dual mating; multiple motivations can co-occur
- 35:23 – 1:02:50
Do women fall in love with affair partners? Emotions vs sex and the “mate switching” inference
Chris asks about the idea that women can’t separate sex from emotion and whether love-for-affair-partner supports mate switching. Macken says love rarely appeared as a stated motive in their sample, cautioning against inferring motives from outcomes like emotional attachment.
- •Mate-switching advocates cite women falling in love more often as evidence
- •In this dataset, love as a stated motive was rare (sub-5%)
- •Emotional entanglement doesn’t necessarily imply the affair’s function is switching
- •Women’s higher risk in cheating complicates simple “they must want to leave” interpretations
- 1:02:50 – 1:04:58
Men’s motivations and sex differences in stated reasons (with strong reporting-bias caveats)
They review men’s top stated motivations and compare them to women’s. Macken notes men more often cite an attractive affair partner and sexual desire, but argues self-reports likely understate sexual motives due to impression management.
- •Men’s #1 stated motive: relationship dissatisfaction (~30%)
- •Men more often cite attractive affair partner (~16%) and sexual desire (~14%)
- •Some men and women both report mate switching; it’s not sex-exclusive
- •Self-report likely downplays “unseemly” motives; qualitative counts aren’t literal causal weights
- 1:04:58 – 1:12:20
Other “ghost hypotheses”: multiple investors, skill-building, and mate-value calibration
Chris asks what explanations lie outside the dual mating vs mate switching frame. Macken discusses additional theories, especially resource acquisition via multiple partners and a lesser-discussed idea that affairs can provide information/skills and calibrate mate value.
- •Multiple-investors hypothesis: affairs to gain additional resources (notably in resource-scarce contexts)
- •Himba evidence suggests resource supplementation can be central in some ecologies
- •Jeff Miller-style idea: affairs to learn seduction skills / calibrate desirability
- •Anecdotal modern analogs: “sugar” arrangements or pragmatic resource support
- 1:12:20 – 1:15:17
Jealousy, paternity uncertainty, and why dual mating aligns with classic sex-difference findings
They connect infidelity theories to jealousy research, where men tend to be more distressed by sexual infidelity and women by emotional infidelity. Macken argues dual mating naturally explains this pattern as paternity uncertainty vs. investment uncertainty.
- •Cross-cultural pattern: men relatively more upset by sexual infidelity; women by emotional infidelity
- •Men’s jealousy maps onto paternity uncertainty (risk of cuckoldry)
- •Women’s jealousy maps onto investment uncertainty (risk of losing resources/parental effort)
- •Both sexes care about both types; differences are relative within cultures
- 1:15:17 – 1:20:28
How common is cuckoldry really? Modern low rates vs ancestral conditions
Chris probes whether dual mating implies more cuckoldry ancestrally. Macken explains modern misattributed paternity estimates are low in WEIRD contexts but can be much higher without contraception and with different norms, including striking cross-cultural variation.
- •Modern estimates of misattributed paternity often ~1–3% in many industrial contexts
- •Rates can rise in low-contraception contexts; some populations report far higher figures
- •Distinguishing “attempt rate” of affairs from “hit rate” of conception
- •Contraception and social suppression change modern observed outcomes vs ancestral dynamics
- 1:20:28 – 1:33:21
Predictors and telltales: who is more likely to cheat, and signs someone may be cheating
They shift into practical correlates: what predicts future infidelity and what signals might indicate ongoing cheating. Macken emphasizes prior cheating, extra-pair interest, narcissism, and promiscuity/sociosexuality, while noting limits in detecting active affairs scientifically.
- •Best predictor: prior infidelity; longitudinal work suggests ~3x risk in next relationship
- •Extra-pair interest/flirtation and attention patterns can predict infidelity
- •Narcissism and promiscuity/sociosexuality correlate with cheating risk
- •Potential active-cheating sign: increased digital secrecy (with many alternative explanations)
- 1:33:21 – 1:38:07
What counts as cheating, emotional affairs, and why operational definitions shape findings
Macken notes huge variation in what people label “cheating,” from porn/fantasy to sex, depending on relationship rules. He clarifies his study focused on sexual affairs and entertains the idea that emotional affairs may be more tied to mate switching, which could alter results under different definitions.
- •Cheating definitions vary widely across monogamous/open and restrictive relationships
- •This study operationalized cheating as sexual affairs only
- •Women may engage more in emotional affairs; those could be more mate-switching oriented
- •Emotional affairs provide deniability and lower immediate costs than sexual affairs
- 1:38:07 – 1:53:33
Is infidelity heritable, are some people repeat victims, and are humans ‘naturally’ monogamous?
They cover behavioral genetics (twin studies suggest heritability), repeat victimization (being cheated on predicts future cheating experiences), and the monogamy question. Macken argues extra-pair mating is compatible with social monogamy and that biology distinguishes social vs sexual monogamy.
- •Twin research suggests a heritable component to cheating (polygenic, not a single “cheating gene”)
- •People cheated on previously may be ~2x more likely to be cheated on again (plus detection/selection biases)
- •Repeat victimization may reflect mate-choice patterns (e.g., attraction to traits linked to infidelity)
- •Humans can be socially monogamous while still showing extra-pair mating; many ‘monogamous’ species cheat
- 1:53:33 – 1:57:45
Wrap-up: ovulatory shifts revisited, sexual stability, and where to find Macken’s work
Chris returns to the intuition that ovulatory shifts seem evolutionarily plausible, while Macken reiterates dual mating doesn’t depend on them and humans show notable stability across the cycle. They close with thanks and pointers to Macken’s podcast, app, and course.
- •Ovulatory shifts might require more nuanced designs, but dual mating can stand without them
- •Humans aren’t “werewolf-like” across the cycle; weekend/weekday effects may dwarf cycle effects
- •Monogamy terms: social vs sexual monogamy clarifies public misunderstandings
- •Macken plugs Species, Couply, and his human evolution course
