Dear reader, for years I've performed the mysterious head nod when in public around other men. Why do we do it? I scoured the Internet for about ten minutes of grueling research and determined than no one knows. I know I always feel a little uneasy when I lock eyes with a strange dude, give him either the up or down nod, but don't receive a nod in return. I don't know why, but I feel uneasy.
I've noticed the upward nod, as our friend Dave above demonstrates, is typically reserved for guys we know, or our 'bros'. I've been at parties and such and a bro enters. Our eyes meet and we both give the upward nod. It's more the "Hey, what's up?!" nod. As far as strangers on the street, the downward nod seems to be preferred method. I think it's more a respect thing, like, "I see you and acknowledge your presence. Do you see me and acknowledge mine?" Nod is returned and now we can both go about our lives. Again, I don't know why, but I immediately distrust someone who doesn't return my nod of greeting.
I'm sure some women may do this as well, but I haven't observed it nearly as much as with men. I think they smile or raise their eyebrows or something. Thoughts?