[If] personality traits have a significant genetic contribution (which seems clear) then we can ask – to what extent do personality traits go along with physical characteristics? This is plausible because sometimes a single gene will code for a protein or enzyme that has multiple functions, and therefore could (for example) affect the development of both the brain and the face.
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The arrow of cause and effect may also go the other way. People who look a certain way may have a particular life experience that contributes to certain personality traits. A baseline aloof expression may, for example, contribute to introversion.
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[One] study was done in a sample of 12 thousand volunteers who completed a self-report questionnaire measuring personality traits based on the “Big Five” model and uploaded a total of 31 thousand ‘selfies’.…
What they found was that the trained neural network AI was able to predict the relative personality trait of two randomly chosen individuals based on photographs with a 58% accuracy, where chance guessing would result in 50%. So in other words, the AI had pictures of two individuals and had to guess which one was more agreeable, or more neurotic. These results are spectacularly unimpressive.