how can they tell you apart??

like how can a dog tell if a human is male or female? you always here people saying their dog doesn't like men/women...or only likes men/women..how can a dog tell what you are??? My dog is like that..our poodle doesn't like strange guys but she's fine w/ a girl she doesn't know..

My RB Cody preferred women. He wasn't abused or unsocialized to men, so I have no clue. I think, maybe it's odor or voice or size. Mz Logan likes everyone basically. She'll menacingly bark if a guy (repairman, my uncles) walk in, but after a few minutes, she's fine. I never understood the stories of racial differential in dogs. Cody and Logan never cared if people were purple.

Dogs can smell things we humans can't even begin to imagine smelling. Dogs can smell a tiny bit of a drug, even if it's hidden inside a container of coffee, amonia, etc. Dogs can smell cancer cells deep inside the human body. I would imagine dogs can smell the male of female hormones as well.

I find the theory that dogs can smell emotions very fascinating, incidently. We always say that our pets "have ESP" or "just know" when we are feeling happy or sad, even if we aren't showing it in our behaviors. One theory states the every emotion has a scent, we just are incapable of smelling it.

I'm sure it is scent-based with many dogs, and voice-based or vision-based with others. I've known a dog that was afraid of men wearing baseball caps, for example. Baseball cap on a woman - no problem. On a guy - major fear. If the same guy approached another time without the cap, no reaction ... so we figured he must have been abused by a man in a baseball cap when he was a pup.