Does a forced smile lift your mood? The pen-in-teeth tests

Does smiling make you happier? A little, if at all. The most famous demonstration, a 1988 pen-in-teeth study, did not hold up in a 17-lab replication, while later work that tested more obvious smiles found small gains in reported happiness. Small is the operative word, and it is worth being exact about what each study measured before you decide whether a grimace at the alarm clock is worth 30 seconds.

What did Strack, Martin and Stepper find in 1988?

In their 1988 study, Strack, Martin and Stepper had people rate the funniness of cartoons while holding a pen in their mouth. Participants who held it with their teeth, which forces the face into something like a smile, rated the cartoons as funnier than participants who held it with their lips, which forces something like a pout. The gap was 0.82 units on a 10-point scale, as reported in the 2016 replication paper.

Note what was measured. Participants did not say how happy they felt. They said how funny a cartoon was. That is a judgment about a thing, and it became the textbook case for the facial feedback hypothesis: the idea that the face does not only display emotion but helps produce it. The appeal for a morning routine is obvious. If the face leads, you could smile before you feel like it.

What did the 2016 Registered Replication Report find?

It found almost nothing. Wagenmakers and a large group of co-authors published the report in Perspectives on Psychological Science in 2016. Seventeen laboratories ran Study 1 from the 1988 paper on one pre-agreed protocol, and the abstract says the original paper “has not been replicated directly” until then. A video camera recorded participants so that the labs could check that the pen was held as instructed.

The pooled difference between the teeth and lips conditions was 0.03 units, with a 95% confidence interval from −0.11 to 0.16. The original was 0.82. The paper’s closing section puts the combined analysis at 1,894 participants across the 17 labs.

An interval that runs from slightly negative to slightly positive fits a true effect of zero, and it also fits a true effect of about a sixth of a point. It rules out something the size of the original. That is the strongest sense in which the pen-in-teeth cartoon result failed to replicate. It does not show that no face-to-feeling pathway exists, because the study tested one manipulation and one outcome.

What did the Coles, Larsen and Lench meta-analysis add?

It zoomed out, and the picture was less bleak. Coles, Larsen and Lench published their meta-analysis in Psychological Bulletin in 2019. They pooled 286 effect sizes from 138 studies that manipulated facial feedback and collected emotion self-reports. The abstract reports that the overall effect was “significant but small,” and that the evidence supports the central claim that facial feedback influences emotional experience, though the effects “tend to be small and heterogeneous.”

Two details matter for anyone choosing what to believe:

• Facial feedback influenced emotional experience, such as reported amusement, and “to a greater degree” affective judgments of a stimulus, such as how funny a cartoon is. The pen-in-teeth task sits in the judgment category.
• Three publication bias methods found no evidence of bias in the experience studies, but all three found evidence of bias in the judgment studies.

So the more flattering category is the one with the weaker record, which is a fair description of the pen study’s history. The experience category, which is what you care about at 6:40 a.m., is smaller and cleaner. The abstract also says effects on experience were larger when no emotionally evocative stimulus, such as a cartoon, was present. A bare morning with nothing funny in it is closer to that condition than a lab cartoon booklet is.

One caution from me: the abstract gives the effect as “small” without a number in the text I read, so I am not going to quote a figure I did not confirm.

What did the 2022 Many Smiles Collaboration find?

Positive but modest results, with the pen the weakest of the tasks. Coles and 48 co-authors, forming what they call a global adversarial collaboration, published a preregistered multi-site study in Nature Human Behaviour in October 2022. The abstract reports data from 3,878 participants in 19 countries. A facial mimicry task and a voluntary facial action task “could both amplify and initiate feelings of happiness.” Evidence was “less conclusive when facial feedback was manipulated unobtrusively via a pen-in-mouth task.”

Put the three studies side by side:

Study	What was manipulated	What was measured	Result
Strack et al. 1988, as replicated by Wagenmakers et al. 2016	Pen in teeth vs. lips	Cartoon funniness, 0 to 10	0.82 original; 0.03 (95% CI −0.11 to 0.16) in 17 labs
Coles, Larsen & Lench 2019	Many methods, 138 studies	Emotion self-reports	Significant but small and variable
Many Smiles 2022	Mimicry, voluntary smiling, pen-in-mouth	Happiness	Amplified and initiated happiness for the first two; pen less conclusive

The voluntary smile result is the relevant one for an alarm, because it resembles what you can do in bed. I only read the abstract of this paper, so I cannot tell you the size of the effect in points, and I will not guess.

Does this tell you anything about smiling at your alarm?

Only by extension. None of these studies tested people who had just been woken, nor measured the grogginess that follows, which is covered in the sleep inertia explainer. The Many Smiles tasks asked people to move their faces on instruction and report feelings, which is the closest match, but the participants were awake and seated in a study.

A reasonable expectation is tiny at best, and possibly zero on any given morning. That is the same shape as the evidence on power posing, where the felt effect lingered while the dramatic claims faded. It also means a single smile will not repair a bad night and a 2024 study of 373 Alarmy users found that later alarms and fewer rings went with better mornings, which are things a smile does not touch. And a rough morning is rarely one cause; the Swiss cheese model is a better lens for why.

The cost-benefit is still fine: thirty seconds, no equipment, no known downside. The usual risk with morning rituals is feeling you have done the work. The test below is built to catch that.

How do you test it on yourself?

Use a single 0-to-10 rating of how you feel right now, not a long checklist. The studies above asked for self-reports of happiness or amusement, so a one-item rating fits. Record it before and after, and judge the change, not the level, since your baseline moves with sleep.

Alternate smile and neutral days by coin flip, and compare averages after 14 mornings. A before-and-after gain on smile days means little if neutral days gain the same amount, which is possible because you are getting more awake either way. You will know which condition you are in, so expectation can inflate the smile days. That limit is built in, and it is a reason to read a result of +0.3 as noise and to trust only something clearly larger and consistent.

Log the score before you look at the phone, at the same point in the routine each day. DontSnooze gives you 30 seconds after the alarm to record a video showing you are up, or a random camera-roll photo goes to friends you chose, which gives a fixed daily slot to hang the rating and the smile on. That slot is my inference about convenience, not something these studies tested.

Questions people ask before trying the smile test

Does smiling when you are not happy actually make you happier?

A little, on average, in some tasks. The 2019 meta-analysis by Coles, Larsen and Lench found a significant but small effect on emotional experience across 138 studies, and the 2022 Many Smiles trial found that posed smiling tasks could amplify and initiate happiness. Neither result says the lift is big enough to notice reliably on a given morning.

Did the pen-in-teeth study fail to replicate?

The cartoon-rating result did. The 2016 Registered Replication Report ran 17 labs with 1,894 participants and found a 0.03-point difference on a 10-point scale, against 0.82 in the original. The 2022 Many Smiles trial also found its pen-in-mouth task less conclusive than the more obvious smiling tasks.

What is the difference between rating a cartoon and feeling happy?

Rating a cartoon is a judgment about a stimulus, while feeling happy is a report about yourself. The 2019 meta-analysis found facial feedback moved judgments more than experience, but also found signs of publication bias in the judgment studies and none in the experience studies, so the bigger-looking number is the less trustworthy one.

Is it worth doing a smile test right after the alarm?

It costs about 30 seconds and carries no known downside, so a trial is reasonable. Treat the result as a tiny nudge at best. Nobody has tested a posed smile on waking, and your own ratings will be affected by knowing which condition you are in, which is why the test alternates days and compares averages.

Run it for 14 mornings, write the two averages side by side, and decide then.