Americans love dogs. The American Veterinary Medical Association reports that over 48 million American households have one, and many have more than one.

Having a dog can be expensive. The cost of dog ownership runs between $1,500 and $9,500 a year, according to one estimate. This generally includes the cost of food, toys, and trips to the vet. Puppies also can be expensive. Depending on the breed, a puppy can cost over $1,000, and some cost considerably more. An Afghan Hound of show dog quality, for instance, might run as much as $2,500 – and Afghan Hounds are considered the most difficult dog breed in America.

Dogs are often picked by breed characteristics. Some dogs are good with families and children. Some are good guard dogs. Some are good hunters. Some can spend most, if not all, of the time indoors. The American Kennel Club has gone so far as to have a section of its website where people can compare breeds based on size, life expectancy, and even how hard or easy they are to train. (These are the hardest dog breeds to train.)

Another measure of breeds is intelligence, which dog experts do not agree upon. 

Canine psychologist Stanley Coren rates dog breeds according to three kinds of intelligence: instinctive (natural skills or abilities), adaptive (ability to think independently and solve problems), and obedient and work (how obedient a dog is and how quickly it can learn commands).

The dog information website the Smart Canine considers the last of these to be the most objective and easily measured, though it notes that a breed that might not score well for obedience and learning commands might excel in instinctive and adaptive intelligence.

An article on the site called 35 Least Intelligent Dog Breeds & Why They’re Actually Not Dumb Dogs points out that some breeds not considered to be intelligent may simply be “aloof” and not interested in obeying commands. Its list of dumbest dogs relies on how many times a command has to be repeated before the dog understands. Another criterion is whether a dog can understand a known command the first time it is given. 

When tested by Dr. Coren, the dogs on Smart Canine’s list required between 40 and 80 repetitions to learn a new command. (On the other hand, these are the smartest dog breeds in America.)

Click here to see the 35 of the most difficult dog breeds in America

Based on these metrics, the most difficult dog breed is the Afghan Hound. This breed does have some attractive characteristics. The American Kennel Club describes them as royal, magnificent, and independent. That independence may be what hurts their score – and in the listing of positive and negative qualities for dogs that follows, note that “independence” may appear under both headings.