What Psychology Says About Women Who Cheat - Macken Murphy

You have caused some drama in the world of evolutionary psychology.

A little bit of drama. I- I try not to get in trouble, but certainly this, uh, last publication, uh, might be a little controversial within the field, sure.

What have you done? What's the current state of the leading infidelity hypothesis?

Well, I- I- I mean, (sighs) I guess we've got time to get into it, but it is a bit of a long story. So I would say that- that the background to know for someone who's just completely entry level here and has not heard about the evo infidelity debate is that there's been a long running debate as to the evolutionary drivers of women's infidelity, female infidelity in humans. And, you know, during the late '90s and the early 2000s and to an extent, uh, the- the 2010s as well, I would say that most evolutionary psychologists would have said that the primary driver of women's infidelity, from an evolutionary perspective, is the powerful benefit of being able to obtain better genes, right, better in a fitness sense, not... (laughs) obviously, not in a moral sense. And we might end up saying, you know, the phrase "good genes" quite a bit, uh, on this show, and- and every time it's always in, it's always good in a fitness sense. But in any case, the mainstream idea was that infidelity is a conditional strategy that women sometimes employ in order to obtain better genes for their offspring, right, so to pair the genetic benefits of one male with the parental investment benefits of another male. So everyone, when we're looking for mates, there are two things that they can give our offspring. They can give our offspring genes, obviously, uh, or they can give our offspring investment. And normally women get genes and investment from the same person, but the idea was is that women's infidelity allows them to get genes from one person and parenting from another. Let's say if they're with a mate who is very high investment, right? They're- they- they love them, they've got lots of resources, but they don't necessarily have, you know, the heretable traits that a woman might want to pass on. So that was the mainstream idea for a very, for a very long time, uh, a- almost 20 years. And then in the late 2010s there was a bit of a reckoning, right, which stemmed from the fact that during the- the 2010s, the original suite of experiments that were used to evidence this idea, which from here on we'll call the dual mating hypothesis... In this case, um, I mean, there's a few ways to use that term. I'm using it to describe that specific strategy. There was a bit of a reckoning because the original support for the dual mating hypothesis was based on these ovulatory shift experiments. So the idea was, and it was a very clever hypothesis, uh, originally put forward by Steve Gangestad and- and Randy Thornell, which is that if it's true that women's infidelity functions to pair, quote-unquote, "good genes with good parenting," well, women can only get pregnant during a brief window in their monthly cycle. And so it would only really make sense for them to have affairs during that time, right? Because the risks of infidelity are evenly distributed, right? Infidelity is a very risky behavior. You could lose your relationship, you could be subject to retaliatory violence or- or social penalties, and- a- and so- it would make sense for women to engage in the, you know, genetic strategy during their peri-ovulatory phase and the parental investment strategy during the rest of their cycle. And so that was their hypothesis. And the first tests which were with, and this isn't their fault, but small samples and relatively primitive methods, those looked quite positive. Then as methods got better, th- th- these effects either shrank or disappeared depending on who you ask, right? It seemed to be-