The face you walked into the room with this morning was being read, by every person who looked at you, in the first moments of being seen. None of the studies cited in this article measured how quickly that judgement forms, so the frequently repeated one-tenth-of-a-second figure should not be attributed to them. The reading was not primarily about the features that took your DNA twenty years to assemble. The bones of your face, the colour of your eyes, the shape of your jaw, the symmetry of your features — these all contributed to the judgement, but they were not, on the available evidence, the only ingredients of it. A substantial part of how attractive any individual stranger perceived you to be, in the brief moment before they had any other information about you, was almost certainly whether you appeared to be having a good time. Some experiments find that smiling faces receive higher attractiveness ratings than neutral expressions of the same faces. Those studies do not establish that smiling rivals clothing, makeup, or grooming.
According to a 2014 paper by Jessika Golle, Fred Mast, and Janek Lobmaier published in Cognition and Emotion titled “Something to smile about: The interrelationship between attractiveness and emotional expression”, smiling can raise how attractive a face is judged to be. That paper reports two forced-choice experiments using morphed faces varying in attractiveness and happiness; its participant numbers sit behind a paywall and could not be verified for this correction, and it does not demonstrate replication across cultures. Smiling faces have been rated more attractive than neutral faces of the same person in a number of studies, but the sources cited here do not establish that the finding holds across essentially every population that has been examined. The neuroimaging result usually invoked at this point is O’Doherty and colleagues’ 2003 event-related fMRI study in Neuropsychologia, which scanned 25 adults (13 men and 12 women, 24 of them Caucasian) viewing 48 faces selected from a pool of 138. Medial orbitofrontal cortex responded to facial attractiveness, and that response was modulated by how happy observers judged a face to be. The main effect of happiness on its own produced no significant orbitofrontal effect, and the attractiveness-by-happiness interaction was reported only at an uncorrected threshold, so it is not accurate to say that a smiling face by itself produces a substantially stronger orbitofrontal response than a neutral one.
What kind of smile actually works
The specific type of smile matters substantially. The most extensively studied distinction in the smile literature is between what researchers call Duchenne smiles and non-Duchenne smiles. The paper previously cited at this point, a three-dimensional imaging study of 613 volunteers (214 men and 399 women, aged 21 to 35) rating their own smiles, measures self-perceived smile attractiveness and does not examine the Duchenne distinction or observer ratings. The Duchenne smile, named after the 19th-century French neurologist Guillaume Duchenne who first characterised it, activates two distinct sets of facial muscles: the zygomatic major, which pulls up the corners of the mouth, and the orbicularis oculi, which creates the small crinkles around the outer corners of the eyes. The combined activation is often associated with spontaneous enjoyment, but it is not an infallible test of whether an emotion is genuine. The non-Duchenne smile activates only the mouth corners and is the kind of polite, social smile produced on demand for photographs or to acknowledge a casual greeting.
Observers may rate smile types differently, but facial muscle activation alone does not reliably reveal a person’s internal emotional state.
What the effect-size evidence supports
The effect-size claims previously made here rested on Carrito and colleagues’ 2023 paper in Evolutionary Human Sciences, When he smiles: Attractiveness preferences for male faces expressing emotions. It reports three experiments: 36 men and 39 women in the first, 35 women in the second, and 84 women recruited in the third of whom 78 were retained after exclusions. Participants throughout were Caucasian, heterosexual and aged 18 to 35, the second and third experiments used women only, and the stimuli were digitally masculinised and feminised male faces from the Karolinska Directed Emotional Faces set. Its finding was that women preferred feminised male faces in every condition but preferred femininity less when the face was happy than when it was neutral or angry, which the authors describe as smiling attenuating the avoidance response toward masculinity. The paper does not measure how far smiling shifts attractiveness ratings of female faces, and samples of this size and composition cannot establish the general magnitude of the effect.
The evolutionary and social explanation for this effect is, in the relevant literature, fairly direct. A smile is one of the few human expressions that is broadly cross-cultural — recognised across nearly every population that has been tested — and that consistently signals friendliness, low threat, willingness to engage, and positive emotional state. For an observer making rapid social judgements about whether to approach a stranger, the smile is a substantial piece of information: it indicates that the encounter is likely to go well, that the person on the other side is in a positive frame of mind, and that initial overtures will probably be reciprocated. The attractiveness boost is, in this account, the observer’s brain doing what brains do — bundling the information about the smile into a single quick-summary judgement about whether this stranger is worth engaging with. The summary judgement, in shorthand, comes back as “attractive.”
What the framework does not claim
Intellectual honesty requires noting the limits of the smiling-as-attractiveness effect. The research does not show that smiling can substitute for every other physical or social factor in attractiveness ratings. As covered by a 2025 review at All About Psychology on the broader smile-attractiveness literature, static physical features — facial structure, body shape, height, age, grooming — still contribute substantially to first-impression attractiveness ratings, and the smile effect is best understood as a substantial modifier of these underlying factors rather than as a replacement for them. A smiling face is more attractive than the same face not smiling. A smiling person is generally more approachable than a neutral one. Whether the smiling person is, in absolute terms, more attractive than a non-smiling person with substantially different underlying physical features is a question the research does not consistently answer.
What the research does support is a more specific and more practically useful claim. For any given person, in any given moment, the version of that person who appears to be genuinely enjoying themselves is going to be perceived as more attractive than the same person looking flat, distracted, or unhappy. The variable that each individual has the most direct control over, in the seconds before a first impression forms, is not their face or their body — those are mostly fixed at the moment of the encounter. The variable that is actually within their control is their expression, their visible emotional state, the degree to which they appear genuinely engaged with what is happening around them. The studies cited here support the narrower point that expression can shift the attractiveness ratings given to the same face. They do not rank expression against the other factors an observer weighs, and they do not establish it as one of the larger of them.