>>13338088well one idea is that if a face has imperfections then the mind has a greater difficulty reconciling the face with the more abstract ideas of how a face should look, especially if one idea of beauty is very fixed (which largely comes from learning). This attempt at reconciliation causes stress to the mind, therefore a face should be easy to process (1)
Now a face that is easy to process is relaxing. Second, a face has to be recognized as a face, for if it's not then it feels less personal, it might be beautiful but it's only a "coldly beautiful" rather than the "warm beauty" that is characteristic of living beings. (2) But still a beautiful face in spite of being warm, feels relaxing because of point 1
When you can observe more than a face, like say parts of a body, then it makes one feel like if one is caressing such body, and this leads to similar reactions as imagined if one would caress one's own body (3)
Now point 3 might for example suggest to the imagination that there's more so that it imagines more specifically sexual features like what's down there, and specifically about the other sex one might feel greater curiosity, or curiosity about people that one is intimate with (4)
Features like softness (which is related to cuteness) or dominance (which might give a feeling of coolness), suggest certain kinds of personality, so that one feels say a woman to be more communal and a man to be more agentic, which can be valuable in themselves (5) or in relation to how one stands towards another, if one prefers a more submissive or dominant position, this would in turn affect one's preferences (6)
