Jealousy. More like jea-LOUSY, am I right? Jealousy is a terrible feeling, especially when it comes to romance. The thought of someone you like or love becoming romantically (or physically) entwined with someone else feels like someone put a soda infuser directly into the chambers of your heart responsible for pumping blood, then turned that infuser all the way up while simultaneously emptying your stomach and replacing its contents with one big, solid rock. I’m pretty sure that’s the dictionary definition of jealousy, actually. Who says verbal imagery is dead? No one, I guess.


Anyways, jealousy is awful. What causes the strongest jealousy reaction though? Does it happen when your romantic interest falls in love with someone else? Or when that person sleeps with someone else? David Frederick and Melissa Fales from UCLA decided to test that very question, presumably because their childhoods were devoid of love. They set up a simple test whereby people would imagine their love interest either falling in love with or having sex with another person, and asked which thought made the person feel worse. They conducted this study with 63, 894 people, I guess because 63, 900 people would have been ridiculous. Seriously, why not just ask the entire world while you’re at it? We’re all for comprehensive testing, but everyone would have been impressed if you had stopped at 1000 or so, you didn’t need the extra 63 000. We at Science Ninjas like to imagine this study was done by one lone undergrad research assistant who went out on the streets of LA and just started asking people to imagine their romantic partner getting involved with someone else. Like, the lab just sent out an undergrad and forgot about him, and he was too afraid to ask when he could come back. This study could have been the first to have ever been stopped due to police detainment.



Anyways, the results! Turns out heterosexual men were the only group who thought the idea of their interest sleeping with someone else was worse than their interest falling in love with someone else (54% of answered this way). Heterosexual women, bisexual men and women, and gay men and lesbian women all felt worse about the love option. To be clear, both options are painful here, I’m sure no one answered “oh, sex is worse than love. I would die if my partner had sex with someone else. I would have no emotional response whatsoever if they fell in love with someone else.” Also, we’re talking about trends here, where 50% of a group answering a certain way represented chance, these results aren’t true of every single person. On average, though, heterosexual men feel a little worse about the thought of their partner having sex than getting emotionally invested with someone else.



Why is this the case? Despite the urge to just categorize straight men as sex-driven maniacs whose sole purpose for romance is to mark their territory for sleeping rights, there is a more nuanced explanation. Think about it from an evolutionary perspective, where reproductive fitness and passing on genes is the entire goal of life (by the way, this is a simplified version of how the theory of evolution works, but I’m 500 words into this and have probably lost half my audience already, so let’s keep it simple). A man can produce millions of sperm cells a day and could, in theory, have an unlimited number of kids until he stops being fertile or dies. He doesn’t need to waste time raising the kids to adulthood, he’s better off just making babies everywhere and hoping for a few to survive somehow, just like the sea turtle videos everyone loves where the mom turtle lays a bunch of eggs and let their newly-hatched offspring make a mad dash for the ocean. Most human cultures and customs require a man to put in at least some effort raising kids, though. So if a man’s partner has sex with someone else and gets pregnant, and contra Billy Jean, he doesn’t know the kid is not his son, then he gets tricked into 18 years of raising a another guy’s offspring and loses out on raising his own.



Human women, on the other hand, have a very finite capacity for having kids, despite what shows on TLC may have you believe. A woman has to spend 9 months carrying a fetus in her womb, and can’t make any more kids during this time, and it takes a toll on her body, and from what I’ve seen from birth videos, the whole process is just awful. So she is much more invested in raising her few kids to adulthood, where they can pass on genes themselves. Child rearing is generally easier with two parents, though, and so it’s best for the woman if the man sticks around, which is less likely to happen if he falls for another person.



This is all extremely simplified, of course, and there are many layers of culture and higher cognitive functioning that play into feelings of love and jealousy, and I know a lot of people have non-traditional relationship set-ups, so you don’t have to tell me that in the comments. The underlying evolutionary psychology does explain the general trends for jealousy in this study, though, and why it differs for heterosexual men and women.



Anyway, time for real talk: Frederick and Fales may have collected data from 64 000 people, but they’re up there in their Ivory Tower (grammar nuts: appreciate). They’re not from the STREETS. So we replicated the experiment with unsuspecting couples, who were minding their own business, having romantic walks around town, because I too had a childhood devoid of love.



Anyways, for the most part, our results replicated those of Frederick and Fales: men didn’t like the thought of their partner having sex with someone else, and women didn’t like the thought of their partner falling in love with someone else, and no one liked me interrupting their day to ask them this question.  I really did make people uncomfortable. Science does not stop for social norms. Of course, we didn’t ask 64 000 people like Frederick and Fales, but our science was done on the STREETS, where the real folks are. Also Frederick and Fales didn’t get escorted out of public areas by security. Watch the video here.



In conclusion, remember: if your partner is a heterosexual male, go ahead and fall in love with someone else, if not, go and sleep with someone else. [Editor’s note: You’re an idiot, change this].



In conclusion, evolved psychological adaptations make the heterosexual men slightly more sensitive to the idea of their partner having sex with someone else than getting emotionally invested with someone else, while all other groups are the other way around. Also, it’s probably best not to actually ask people to visualize this, it gets awkward.



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Dan Re