[fostermom]

I would think all of this is conjecture (no REAL way to prove it) but this if from an article on canine body language:
The dogs with the 'clearest' body language are those that most resemble the ancestral wolf. The more a breed has been modified by man, the more difficult these dogs will find being understood. Dogs such as Spaniels, with floppy ears can't prick or flatten their ears back against their heads. If a dogs eyes are obscured by hair, as in Old English Sheep Dogs and Pulis, with their Rastafarian-style deadlocks, other dogs can't read the intention in their eyes. Dogs with long flowing coats, like salukis can't raise their long coats and so can't raise their hackles, while dogs with naturally short or docked tails cant wag them to show they are happy, or tuck them between their legs when afraid. Black dogs may also have a problem making themselves understood, as they may appear as silhouettes to other dogs, obscuring the subtle nuances of their gestures