Border collies are widely called the smartest dogs on the planet. Bred for herding sheep in the UK borderlands, they can learn hundreds of words, anticipate what their owner wants, and figure out problems on their own. In sports like agility and obedience, they’re always the ones to beat. It’s no wonder this breed has been called the “canine Einstein” of the dog world. Dr. Cahn warns, though, that border collies require lots of attention. “They require a huge amount of mental and physical stimulation to stay happy, engaged, and out of trouble, and often do best with experienced owners,” she says.