Why are you assuming that we can not tell the difference between smiles? There's a huge gradation of social behavior w.r.t smiles and other social cues that we

Why are you assuming that we can not tell the difference between smiles? There's a huge gradation of social behavior w.r.t smiles and other social cues that we use in the west. For us, raised in the culture, it is trivially easy to tell the difference between, say, the smile of a shopkeeper in greeting, the smile of an enemy, the smile of a shopkeeper after asking after your parent (they slightly know you), the smile of the mail man you speak with once a week or so, the smile of the semi-acquaintance that lives one flight up, the smile of a friend you see each day, and the smile of a best friend when reuniting after a long absence. so on. They are all different, and constitute a "meaningful way of interaction". It's just different than your way.