Many people would doubt the sincerity of this moment and thus also Miss Kazantsev's facial expression - Yet they both are very sincere.
Notice her vertically oval-shaped mouth as well as the fact that no teeth are visible. People who make a faked surprise expression will have a mouth opened with a significantly wider horizontal component. In addition the feigned surprise will always have teeth showing. Even all but the best character actors will still make this mistake.
Her eyelids are also opened very widely along with extremely elevated eyebrows - mirroring the configuration of her mouth. Intriguingly, as all women who wear eye make-up know - it is much easier to open eyes widely if their mouth also adopts a similar morphology.
What are some other nonverbal components of sincere surprise? We should see her forehead contract - it is, however it is very minimally. The reason for this is because she has had Botox injections. The lack of normal and expected contraction of the forehead muscles (and thus dynamic furrows) diminishes the appearance of sincerity.
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