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You know that smiling can cheer you up, right? That while being happy makes you smile, things go in the other direction, too? If you force yourself to smile, that is, good feelings will follow. That’s the idea you’ll get from a lot of psychology blogs and websites, at least. Heck, even from textbooks: Many of them discuss a famous 1988 Journal of Personality and Social Psychology study led by Fritz Stack in which students who were asked to hold a pen between their teeth, forcing them into a smile without them even knowing it, reported that a Far Side cartoon was more amusing than students whose faces were forced into a frown. It’s been held up again and again as solid evidence for various strains of the “fake it till you make it” idea, and a bunch of other research has appeared to confirm it.

There’s a but, though — and it’ll be grimly familiar to anyone who has been reading about psychology’s ongoing troubles successfully replicating broadly accepted past findings: A team just tried to replicate this classic finding in a rather ambitious fashion, and failed.

In Slate, Daniel Engber offers a characteristically interesting and nuanced explanation of what happened. The study was a big effort, consisting of 2,000 subjects in 17 labs in eight countries, and as Engber reports, the results, recently posted online, “weren’t good”:

In one-half of the participating labs (nine of 17, to be exact), the subjects who were smiling gave slightly higher average ratings to the cartoons—they reported feeling one- or two-tenths of a point more amused, on the 10-point rating scale. (In Strack’s original study, the difference between the smilers and frowners had been much bigger, 0.82 points.) In the data from the other labs, the effect seemed to go the other way: The smiling subjects rated the cartoons as one- or two-tenths of a point less amusing. When Wagenmakers put all the findings in a giant pile, the effect averaged out and disappeared. The difference between the smilers and frowners had been reduced to three-hundredths of a rating point, a random blip, a distant echo in the noise.

Now, this is just one failed replication, and it comes at the end of a long line of research which seem to support the general theory being tested. But still: For a study like this, 2,000 subjects is a very large sample size. It’s hard not to be a little discouraged. Plus, Engber makes a strong case that when you dig into the initial, epochal study, it was a bit weaker than meets the eye: For one set of students in the study, for example, the “frowners gave the higher ratings, by 0.17 points,” on a question assessing the cartoon’s funniness. But the experimenters were able to report an interesting finding by also asking a second question which did seem to garner a positive result. “If the facial feedback worked,” Engber writes, “it was only on the second question, ‘how amused do you feel?’”

While the new study is a big challenge to the smiling research, it’s certainly not enough to declare this line of research “debunked” or “dead.” But one thing that’s worth asking as these null results seem to pop up: Maybe psychological ideas that tell inspiring stories about human nature get graded on a more forgiving curve?

Think about two of the other lines of research that have recently hit rocky replication waters: ego depletion and grit. Both have been presented to the public as evidence that people might have more control over their circumstances than one might think. If you accept the grit research, it suggests that even kids from troubled, low-income backgrounds can be taught skills to help them achieve and close the gap with their more privileged peers. If you accept the ego-depletion research, at first it sounds depressing — but dig a bit deeper and it suggests that there could be fairly simple, conscious ways to overcome the self-control issues that many people grapple with for their entire life. Then there’s the smiling research: Sure, some people are unhappy, but if you make a conscious and diligent enough effort to fake it, you will feel better.

I’m sanding the rough edges off this research and making stronger claims that many researchers themselves would, of course, but that’s the point: By the time these ideas filter down to the public, they sit closer to the “Self-Help” aisle than the “Psychology” aisle. They tell simple, satisfying stories. Perhaps most important, they sweep aside other, more depressing accounts that have been posited by psychologists: that for a given person, it’s unlikely their happiness level will change much over the course of their life span; that seriously underprivileged kids arrive at kindergarten so profoundly disadvantaged relative to their wealthier peers that it’s almost impossible for them to catch up.

It would be wrong to say it’s been proven that happiness is stable for most people, or that there’s no realistic way to help kids who are really underprivileged attain the same opportunities as rich kids. As is the case almost everywhere, there’s controversy and debate. But there’s definitely some support for these ideas, and these aren’t fun of sexy concepts to think about. It is fun to think that we can teach impoverished kids from broken homes “grit” and turn them into future CEOs, or that if you smile enough you’ll get happier. And researchers and universities pay attention to which findings catch on and get circulated on social media and lead to books published outside of academia and so on — they’re not immune to the effects of a given idea’s level of popular appeal, or lack thereof. And once psychology is locked onto a given idea, history has shown, there are a zillion ways for it to rack up seemingly impressive lab results that may not hold up in the long run.

I’m not trying to posit some Grand Unified Theory of Replication Problems Here. Rather, I’ll make a modest prediction: As things continue to unfold, there will be at least some correlation between which areas of research get hit the hardest by replication issues and which areas of research offer the most optimistic accounts of human nature, potential, and malleability.