How much do you really trust people?

That's what scientists in Spain wanted to find out. So they staked out a festival in Barcelona and recruited about 500 volunteers to play a little carnival game for fun, prizes, and, you know, advancing our knowledge of human psychology.

Step right up! Step right up and learn whether you can trust your friends! Photo from iStock.


The games were all variations of the prisoner's dilemma.

What's the prisoner's dilemma? I'll explain. (You can read this section in a gangster-y detective voice if you want).

Image from iStock.

It's a famous thought experiment that helps us figure out how people manage trust, risk, and temptation while making decisions, see? If you're being traditional, what you do is get two wise guys, separate the lugs, and tell 'em that they're both under arrest. But you're a nice guy, and you've really got their best interests at heart, so you'll cut 'em a deal: If they rat on their buddy, they go free.

But here's the twist, if they both rat, both go to the slammer. Of course, they could both clam up, in which case you can't do much. Maybe give 'em a little time in the clink, but that's about it.

Imagine that you were the prisoner: Do you trust your friend and clam up so you're both safe from prison?

Or do you think you can play 'em by turning them in and getting yourself a better deal? (You can stop the gangster voice now. Or don't. It's a free country.)

This kind of game also happens on reality TV all the time when partners have to decide whether they want to split the money or take it all. And you can tweak the game by changing how big the rewards and punishments are, too.

In the case of the Spanish study, the scientists made the volunteers play a few different games with different setups.

Instead of trying to place people's reactions in pre-existing categories, the scientists in this study gathered everyone's results, then let a computer group the people together as best it could.

This is what it found:

First, there were the optimists. These people will work together whenever the everyone-works-together option is most rewarding. They seem to believe that when the payoff's obvious, everyone will work for it.

Then, there were the pessimists. These people always expect to get screwed over and will only try to cooperate when they'll benefit anyway.

Thirdly, there were the trusting people. They'll always cooperate, whether it makes sense or not. Bless their (naive) little hearts.

Finally, we get the envious people. Envious players don't really seem to care what the outcome is, as long as they're getting more.

There were roughly the same number of optimists, pessimists, and trusting people — about 20% of the group each. Envious was a bit more, at about 30%. There was also a mysterious fifth category, which the computer couldn't classify.

Living in a world of envious people might seem like a downer, but we can actually do a little scientific jujitsu on this and turn it into something awesome.

That's because this experiment is part of game theory, a branch of mathematics that studies how people make decisions, which carries important consequences in designing things like laws, political systems, or jobs.

While we like to assume people will always act rationally, this study suggests that people think with their gut as much as their brains. And knowing more about people's motivations means we can add new little incentives to big projects that affect lots of people. Maybe that new anti-poverty law needs a little bonus for the rich to appease envious players, for example — or maybe it needs a fail-safe to keep the pessimists happy.

By understanding what motivates people, we can motivate people to do good in the world.

As for what the mysterious fifth category is, maybe it's this guy:

Leah Menzies/TikTok

Leah Menzies had no idea her deceased mother was her boyfriend's kindergarten teacher.

When you start dating the love of your life, you want to share it with the people closest to you. Sadly, 18-year-old Leah Menzies couldn't do that. Her mother died when she was 7, so she would never have the chance to meet the young woman's boyfriend, Thomas McLeodd. But by a twist of fate, it turns out Thomas had already met Leah's mom when he was just 3 years old. Leah's mom was Thomas' kindergarten teacher.

The couple, who have been dating for seven months, made this realization during a visit to McCleodd's house. When Menzies went to meet his family for the first time, his mom (in true mom fashion) insisted on showing her a picture of him making a goofy face. When they brought out the picture, McLeodd recognized the face of his teacher as that of his girlfriend's mother.

Menzies posted about the realization moment on TikTok. "Me thinking my mum (who died when I was 7) will never meet my future boyfriend," she wrote on the video. The video shows her and McLeodd together, then flashes to the kindergarten class picture.

“He opens this album and then suddenly, he’s like, ‘Oh my God. Oh my God — over and over again,” Menzies told TODAY. “I couldn’t figure out why he was being so dramatic.”

Obviously, Menzies is taking great comfort in knowing that even though her mother is no longer here, they can still maintain a connection. I know how important it was for me to have my mom accept my partner, and there would definitely be something missing if she wasn't here to share in my joy. It's also really incredible to know that Menzies' mother had a hand in making McLeodd the person he is today, even if it was only a small part.

@speccylee

Found out through this photo in his photo album. A moment straight out of a movie 🥲

♬ iris - 🫶

“It’s incredible that that she knew him," Menzies said. "What gets me is that she was standing with my future boyfriend and she had no idea.”

Since he was only 3, McLeodd has no actual memory of Menzies' mother. But his own mother remembers her as “kind and really gentle.”

The TikTok has understandably gone viral and the comments are so sweet and positive.

"No the chills I got omggg."

"This is the cutest thing I have watched."

"It’s as if she remembered some significance about him and sent him to you. Love fate 😍✨"

In the caption of the video, she said that discovering the connection between her boyfriend and her mom was "straight out of a movie." And if you're into romantic comedies, you're definitely nodding along right now.

Menzies and McLeodd made a follow-up TikTok to address everyone's positive response to their initial video and it's just as sweet. The young couple sits together and addresses some of the questions they noticed pop up. People were confused that they kept saying McLeodd was in kindergarten but only 3 years old when he was in Menzies' mother's class. The couple is Australian and Menzies explained that it's the equivalent of American preschool.

They also clarified that although they went to high school together and kind of knew of the other's existence, they didn't really get to know each other until they started dating seven months ago. So no, they truly had no idea that her mother was his teacher. Menzies revealed that she "didn't actually know that my mum taught at kindergarten."

"I just knew she was a teacher," she explained.

She made him act out his reaction to seeing the photo, saying he was "speechless," and when she looked at the photo she started crying. McLeodd recognized her mother because of the pictures Menzies keeps in her room. Cue the "awws," because this is so cute, I'm kvelling.

A simple solution for all ages, really.

School should feel like a safe space. But after the tragic news of yet another mass shooting, many children are scared to death. As a parent or a teacher, it can be an arduous task helping young minds to unpack such unthinkable monstrosities. Especially when, in all honesty, the adults are also terrified.

Katelyn Campbell, a clinical psychologist in South Carolina, worked with elementary school children in the aftermath of the Sandy Hook shooting. She recently shared a simple idea that helped then, in hopes that it might help now.

The psychologist tweeted, “We had our kids draw pictures of scenery that made them feel calm—we then hung them up around the school—to make the ‘other kids who were scared’ have something calm to look at.”



“Kids, like adults, want to feel helpful when they feel helpless,” she continued, saying that drawing gave them something useful to do.

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