Well, we'll never know unless we are dogs! But one thing we know - it's that dogs use their bark and body language (hair on nape of neck, eye contact, ear, body and tail positions) to communicate their intent. If you are interested, I can send you my set of slides on dog language to you.
As to whether one dog will understand each other, it depends on whether the dogs have been socialized with other dogs before.
Many dog aggression incidents among pet dogs is because the puppies have been raised by humans and thus they understand human body language more than that of other dogs.
Also, some dogs have their tails cropped, thus hampering their ability to communicate with their tails.
The worst thing that can happen is when the dog is on a leash and the owner pulls his/her dog to socialize with the other dog that is displaying aggression. The poor dog does not want to approach the fierce dog that is giving out warning signals, but the owner keeps pulling the pet dog closer.. until...
doggy language?
Actually, the sequence was - Dogs, rabbits, then birds. Oh, the Pet Shop closed already. We have moved on into Real Estate.
Cheers!
Cheers!
[80% Steve, 20% Alfred] ------- Probability of Clear Skies = (Age of newest equipment in days) / [(Number of observers) * (Total Aperture of all telescopes present in mm)]