According to The Intelligence of Dogs, the Afghan Hound is the dumbest canine breed.
Other sighthounds with independence and aloofness include the Basenji.
Bulldogs are lethargic, but some like more active pastimes than lounging on the couch.
Chows are serious, independent, and detached. They are one of the dumbest dog breeds because they are stubborn and hard to train.
Borzois perform better with frequent, short training sessions than hour-long classes.
Pekingese are stubborn and hard to housebreak. This doesn't make them dumb, but it makes training difficult.
The Beagle's gentle, friendly personality and happy-go-lucky perspective may make him seem empty-headed.
Basset Hounds are lazy. Their long, low physique or laid-back demeanor may explain this.
They are headstrong and harder to teach than some breeds.