When a dog encounters a stranger, are they less hostile to a stranger who is a dog owner, going on the basis of scent?
I keep a cat in my pocket & that usually keeps them being nice to me.
Dog owners usually know how to act around dogs.
In particular, they are not generally scared by the approach of a dog. Non-dog-owners often are, and that fear reaction, with the body posture and fear sweat accompanying it, is alarming to a dog, leading to hostile reactions. Most dog owners have a calm attitude, assuming the dog will be friendly – so they usually are!
I doubt scent of the dog-owners dog has much to do with the initial reaction.
Once they get close enough to the dog owner to smell the scent of their own dog on their clothing, the dog has already evaluated the person as ‘non-threatening’ (otherwise they wouldn’t have come that close), and dogs are smart enough to recognize that this is a human, not another (possibly enemy) dog. So they identify the scent as just remains from a previously-present dog. Like all the places they sniff at when out for a walk.
One somewhat amusing* reaction: male dogs sometimes recognize the scent on a dog owners pants as that of another male dog and try to cover it uo – by lifting their leg and peeing on the pantleg! Male cats will sometimes do the same by ‘spraying’ on the pantleg of the owner of another male cat.
*Well, amusing to those watching, at least.
Probably not so amusing to the occupant of the pantleg at the time.
I believe dogs know dog owners, even if the scent of the other dog isn’t clear. I went with Mr. Vigilante to Vegas and his sister’s dog (big German Shepherd) took to me immediately, although we’d been far from our own dogs.
Here where I live, we visited friends who had just rescued a greyhound. The dog jumped up to lick my face immediately (I caught her front legs with my forearm like I do with my own dogs); her owners remarked that she had never ever done that before.
They later returned her due to “allergies” but it was really due to “destroying the couch”.
Never had this happen - though all but one of our dogs have been females.
I think t-bonham has it right though - people who’ve been around dogs a lot have a generally friendly and relaxed demeanor that reassures another canine. Once they get close enough, they may be distracted by the need to evaluate the residual dog scent on the person’s clothes to the point where it diverts the animal from potentially hostile action. 
My Mother owns a kennel.
One day I was at her kennel, I saw this giant rottweiler in his cage. I went to his cage and stuck my hand out so he could smell it. Once the dog didn’t object to my being there, I started to pet it.
At that point my Mom walks by and says: “Hey, look at that! He’s letting you pet him! He usually tries to bite people’s head off!” (Gee, thanks for the warning Mom.)
I think the reason this dog gave me a free pass was because of the hand sniffing thing. (Something I do for all strange dogs.) And the fact that I had zero fear.
Less fear than I normally would have approaching a giant strange dog because my Mother never warned me to stay away from that one. Something she would normally do.
Absolutely agree. I came to dog ownership late in life due to allergies, and it was amazing how strange dogs got friendlier all of a sudden. You can tell that a little dog barking is doing so out of friendship, not hate, and that a dog rushing up to you may want a treat, not a bite out of your leg.
I think it’s a “dog people” vs “non-dog-people” thing. I haven’t owned a dog in 20 years, but I grew up with them and work with them as a vet tech. I own cats, and I think I smell very interesting to dogs in general. They will break from their owners while walking outside, to change direction and sniff me if I walk past them. I expect it and don’t mind at all making new doggie friends, the owners are always confused their dog did that and are apologetic. I think the dogs doing that are comfortable doing so because they are good at reading people’s body language and they get nothing but approachability from me, plus I smell neato.
Another thing I’ve noticed is when taking dogs from their owners in the exam room, especially nervous dogs, the dog does much better with their nervousness if I continue to make sure I’m the one handling them. I think this is because the dog recognizes being handed off by their owner to me as sort of safer, the dog has seen me and the owner interact with no hostility, and now know that I’m “OK.” They can get more nervous and snappy if an assistant or another tech have to take over the case. Though all bets are off if the dog is unsocialized and totally untrained in the first place, they’re unpredictable no matter what.
It’s definitely a dog people vs not thing. I haven’t owned a dog in almost thirty years and yet I still have no problem with strange dogs. I hold my hand out and let them approach me if they want to, and check with their owners first! I hate people who just pet other people’s dogs. You have no idea if the owner is training the dog or maybe it’s a little jumpy. WAIT and see.
Not sure there’s a scientific answer, but for another data point…
I am a “dog person” and have a decent track record with dogs I’ve met, even gentling down a few growling ones and luring some strays close enough to rescue them.
One time I was walking past a woman letting her dog run off-leash in a strictly-leashes-only area where we’d had trouble before. I was pissed off that she was flouting the rules and giving other dog people a bad reputation, as well as risking her dog. I was mad at her as I strolled past – from about a hundred feet away.
Despite the positive way dog encounters usually go for me, this one changed immediately – her dog ran over and began barking and growling at me. I stopped immediately and stood stock still. As she screamed ineffectually at her dog from a distance, he took a few lunges at me, although not really coming close.
I’m in that area a lot and I’d seen that dog (albeit from a distance) before. The only difference this time was emotional, and the dog picked up on it immediately, from a distance, and behaved accordingly.
I think that supports the idea that people who feel fear, hate, or anger toward a dog will get a poor reaction from the dog, whereas dog lovers will generally get much better responses.