A dog isn’t inherently dumb just because he can’t pick up a specific trick, or he doesn’t seem to realize that when the sliding door to the backyard is clean, there is still glass in it.
A “dumb” dog, according to these rules, are dogs that lack a willingness to learn and perform new tasks. Dogs that are unable to fulfill the role they were intended to have, be it herding, helping, or more.
If a dog lacks working and obedience intelligence, it may mean that that breed struggles to interpret clues from humans and learn new skills. If it lacks adaptive intelligence, it may not want to perform tasks or work with others. And if it lacks instinctive intelligence, it may not be able to do the basic tasks it was bred for.
As you’ll soon learn, many of these dogs weren’t bred for a specific task or goal, which does shape their “ranking” on the intelligence meter.