you look up and notice a man looking at you, at your face. Not leering, not ogling, just looking. And you look directly back at him for three or four seconds. What should he do, if anything. And does the location make a difference in what happens next.
Everything is relative in this case. Being an adult male I am sure you can decide on your own when it is appropriate to stare, or even approach a woman. If a man has my attention like that- a 4 second blinking contest is a long time, then I would hope he would at least smile and greet me. This would be appropriate say in line at a store, or while reading at a coffee shop. It wouldn't be appropiate under or over a bathroom stall, or when I am searching the bra and panties rack.
i think it depends. obviously 4 seconds is a long time to be looking at someone you don't know, at least it feels like it. i usually don't stare at anyone that long so if somehow i was compelled to hold eye contact with a guy for that long then yea i think he should at least try to approach me
