“Stubborn” dogs are often thought to be “less intelligent”. Is it true? Nah.
The breeds considered to be “stubborn”, less intelligent or “hard to train” (hounds, livestock guardians, sight hounds, sled dogs) are actually the complete opposite. They are very intelligent (as are all dogs), and are often reactive to something (actually ALL dogs are reactive to something).
But these breeds do need some special considerations when training them.
Rather than classifying a breed by intelligence or behaviour,
we’re doing something about it (and training them to do a whole bunch of cool stuff).