Facial feedback: does smiling make you feel happier?

Facial feedback is the idea that moving your face can influence how you feel. Research supports some small, immediate effects, but the famous pen-in-mouth experiment has not proved reliable. Those conclusions can both be true.

The reason is that the experiment and the theory are not the same thing, even though people often treat them as interchangeable. The theory is often called the facial feedback hypothesis. A failed attempt to reproduce one way of making people “smile” does not test every possible connection between facial movement and emotion. Nor does an effect found with another method rescue the original experiment.

The practical claim needs two further distinctions. First, a brief change in a happiness rating is not evidence that smiling will fix an unhappy situation or produce lasting wellbeing. Second, one smile is not the same as smiling on demand. In a 2026 experiment, a single posed smile lifted mood in a negative context. But the lift weakened when people repeated the smile, and all but vanished when they also faced a penalty for not complying.

Why researchers put a pen in people's mouths

In a 1988 experiment, Fritz Strack, Leonard Martin, and Sabine Stepper asked participants to hold a pen in their mouths in ways intended to help or hinder the muscles involved in smiling. Holding it between the teeth produced a different facial position from holding it with the lips. Participants then rated cartoons, and those holding the pen in their teeth rated the cartoons as funnier. Original paper.

The odd procedure had a purpose. Simply telling someone to smile can give away the hypothesis: they may guess that the researcher expects a happier response. The pen task tried to change facial activity without explicitly asking anyone to adopt an emotion.

But the outcome was a judgment of how funny the cartoons were. That is narrower than a general improvement in happiness. The experiment did not show that smiling improves someone's relationships, work, or life satisfaction. Each of those claims would need evidence of its own.

Seventeen replications found almost no difference

In 2016, a Registered Replication Report brought 17 laboratories together to repeat the experiment with a shared protocol. In this format, the journal reviews and accepts the plan before any of the new data are collected. The analysis included 1,894 participants. In the original study, the difference in cartoon ratings was .82 points on a ten-point scale. Across the replications, the estimated difference was .03 points, with a 95% confidence interval from −.11 to .16. Replication report.

That interval matters. This was not a smaller experiment that happened to miss statistical significance. The combined evidence placed the likely size of the difference much closer to zero than the original estimate.

The replication also differed in some details. It used updated cartoons, video instructions, and video cameras to check that people held the pen correctly. Pointing to a difference does not show that it caused the disagreement, so Tom Noah, Yaacov Schul and Ruth Mayo tested one of them. In a preregistered 2018 experiment with 166 analyzed participants, they ran the pen task with and without a camera. Without a camera, people holding the pen in their teeth rated the cartoons as funnier than people holding it with their lips (average ratings of 5.75 versus 4.92). With a camera, the difference almost disappeared (5.21 versus 5.15). Noah, Schul and Mayo, 2018.

That pattern fits the camera explanation, but the decisive test fell short. The preregistered test of whether the camera changed the effect was only marginal (p = .051, one-tailed), and the authors described it as greatly underpowered. The camera is a plausible explanation that deserves a larger test, not a settled one.

The replication report's own conclusion was narrower than “facial feedback is false.” It found that this procedure did not reproduce the original result, and it left open whether other procedures might provide better evidence.

The broader literature did not disappear

Facial feedback research includes more than pens and cartoons. A 2019 meta-analysis by Nicholas Coles and colleagues brought together studies that used different ways of changing facial activity and measuring emotion. It concluded that effects on emotional experience were small and variable.

“Small and variable” is not a satisfying slogan, but the variation raises useful research questions. Does the method produce something resembling a natural smile? Does the person know what the researcher expects? Is there something amusing to respond to, or is the setting emotionally neutral? Each of these can change what an experiment is actually testing.

The second question has been tested directly. In six experiments with 995 participants across 29 countries, Coles and colleagues told some participants that posed expressions would affect their mood, told others that they would not, and told others nothing. What people were told changed the size of the effect, but it did not explain the effect away. Participants still reported more happiness after posing a smile even when the researchers had said that facial poses do not influence emotions. Coles and colleagues, 2023.

A later exploratory reanalysis, published online in 2023 and in a 2024 journal issue, proposed that social context helps explain the differences. It regrouped earlier studies by features such as whether another person was present. That can suggest a hypothesis. But the studies were not randomly assigned to those contexts, so the regrouping cannot settle the explanation by itself.

What the Many Smiles project found

The Many Smiles Collaboration, published in 2022, tested several procedures across 19 countries. Participants copied smiling faces, deliberately moved facial muscles into a smile, or completed a pen-in-mouth task. The project collected data from 3,878 people; its primary analysis used 1,504 after preregistered exclusions, including exclusions related to awareness of the hypothesis.

The study found evidence that copying a smile (facial mimicry) and deliberately moving the face into one (voluntary facial action) could increase reported happiness. The pen task gave less clear evidence. So the project supports a narrower version of facial feedback, but it gives no new reason to trust the familiar pen demonstration.

The two sample sizes matter too. “Nearly 4,000 participants” describes the data collected, not the number included in every analysis. Preregistering exclusions makes the analysis plan clearer, but you should still know which participants the main result describes.

And the measured change was still an immediate report of feeling. The study did not test how long a benefit lasts, or what happens when people smile again and again.

What happens when smiling is repeated or required?

Much popular advice is not about one smile in a laboratory. It is about smiling through a shift, a sales call or a bad week. Research on emotional labor, the work of displaying the feelings a job requires, has often linked that kind of smiling to worse work-related mood, lower wellbeing and more burnout. In 2026, Coles, Annabel Dang and Joao Takayanagi tested three features that separate workplace smiling from the laboratory: smiling in a negative emotional context, smiling repeatedly, and smiling to avoid a financial penalty. Coles, Dang and Takayanagi, 2026.

The study was a Registered Report: the journal reviewed and accepted the design before the results were known, which limits the room for choosing an analysis after seeing the data. It extended the Many Smiles procedure and collected data from 1,201 people.

No single prediction fit all the results. In negative contexts, one posed smile still raised reported happiness compared with expressing feelings naturally. That benefit weakened when people posed the smile repeatedly, and it was virtually nil when they also faced the threat of a penalty for not complying. In positive contexts, repeated or enforced smiling lowered reported happiness. The authors conclude that a posed smile can lift mood in some situations and dampen it in others.

A feeling is an outcome, but it is not every outcome

Do not dismiss a change in reported emotion just because it is subjective. Feelings are part of what emotion researchers want to understand. The mistake comes when that outcome is quietly swapped for something else.

Imagine an employer asking staff who are upset about an unpredictable schedule to smile more. The 2026 experiment did not study a real job, but it tested the ingredients of this request: an unpleasant situation, repetition and pressure to comply. A single smile before a difficult phone call is closer to the condition that raised happiness. A smile demanded all shift is closer to the conditions under which the lift weakened or vanished. And even a real lift in mood would say nothing about whether the schedule becomes manageable. The study and the workplace problem operate at different levels.

For the same reason, these experiments do not test smiling as a treatment for depression. They study a more limited question about facial movement and short-term emotional experience.

When you hear “smiling makes you happy,” ask which smile, compared with what, and measured how. A change on a rating scale during an experiment can be real without carrying the much larger promise attached to it. The power posing research makes the same point about body posture: keep feelings separate from hormones and performance.