system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do we nod our head to strangers on the street but raise our chin to acquaintances?
gpt
A lot of this is going to be innate reactions. These days, we don't see people, even every day strangers, as a threat, however our forefathers would have. An upward chin raise can give off a sign of superiority, possibly challenging someone else. All fine and dandy if you know the person, less so if you don't. Perhaps more importantly, for long term survival, is that fact that by lifting your head up, you're exposing your neck to someone you don't know, while a downward nod protects your neck more, while still acknowledging the pressence of the other person.