age is in the eye of the beholder

So I get a haircut today and the woman cutting asks if I have any plans for the night. You know, just usual small talk exchanged at monthly trimmings. I tell her I have a paper to work on for school. Her next comment was "so you must be in the graduate program then?" I say no, undergrad. Her facial expression was one that indicated surprise. Which lead me to believe she thought either I was older than I really am or that 24 year olds should be in grad school. I have been predicted to be older than I really am by numorous people before. I always thought I appeared fairly young, but I guess not. One man told me I looked older because I never cry. Implying those who cry look much younger. Not sure where he gets his evidence for that theory.