If you ever feel cynical about human beings, a good antidote is to talk to artificial-intelligence researchers. You might expect them to be triumphalist now that AI systems match or beat humans at recognizing faces, translating languages, playing board and arcade games, and remembering to use the turn signal. To the contrary, they’re always talking about how marvelous the human brain is, how adaptable, how efficient, how infinite in faculty. Machines still lack these qualities. They’re inflexible, they’re opaque and they’re slow learners, requiring extensive training. Even their well-publicized successes are very narrow.