There is no one right smile. A broad one makes you look warmer and happier and costs you competence and dominance; a slight one keeps them. How a smile starts and ends matters as much as its size.
Size
- Rated happiness rises from a straight face to a closed smile to a smile showing teeth (Otta, Abrosio & Hoshino 1996).
- The same person with a broad smile was rated warmer but less competent than with a slight one (Wang et al. 2017).
- Broad smiles cut perceived dominance, and added no further trust over a mild one (Li et al. 2021).
- Against no smile at all, smiling raises rated competence (Reis et al. 1990).
Timing
- Let it build over half a second to a second, and fade over at least a second. In a mock job interview, a smile that built and faded slowly was rated higher than the same smile switched on fast, which did no better than no smile (Krumhuber et al. 2009).
- Spontaneous smiles rise more slowly than posed ones (Guo et al. 2018), and smiles rated genuine drew more trust and more money in trust games (Centorrino et al. 2015).
- Smiles seen as amused lasted about twice as long as polite ones (Ambadar, Cohn & Reed 2009).
Eyes and head
- Cheeks lifted until the eyes narrow make a smile read as more genuine, more so in motion than in photos (Gunnery & Ruben 2016). It is no proof: the cheek lift also shows in many polite smiles (Ambadar, Cohn & Reed 2009).
- Embarrassed smiles come with the head tipped down, amused ones with it tilted up (Ambadar, Cohn & Reed 2009).
- A raised head with a small smile reads as pride (Tracy & Robins 2007).
Which smile for what
- Approachable: a smile that shows; a slight closed one is enough.
- Happy: broad, lips apart, teeth showing.
- Competent and confident: slight, lips closed.
- Trustworthy: mild, and slow to build.
- Mysterious and intimidating: none. A smile at less than half strength already shifted how warmly a face was rated (Hess, Blairy & Kleck 2000).
Where you are
Smiling raised perceived honesty in most of 44 cultures, but in some it made a face look less intelligent (Krys et al. 2016). More: by region.
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