I’ve been running at approximately the same time in the morning for several years now. Most mornings I pass many of the same people as they run or walk their dogs. We acknowledge each other with a head nod, or a hand wave or for some a “Good Morning”. I’m not sure how people decide who to nod to, who to wave to and who to speak to. But for some reason it appears that once you put the other person into one of those categories it’s rare that they move to another level. Meaning the guy in the ball cap that runs toward me most mornings has always been a head nod and never a wave. The guy quickly walking his two schnowzers gets a “Good Morning” every time. The walking lady gets a “Good Morning” plus a wave. There are many others and each has a pre-determined acknowledgement. You may think it’s a progression, that people move from nod to wave to greeting. But that does not appear to be the case. Test this theory as you run and let me know what you find.