The Quest to Measure Machine Intelligence

We have self-driving cars, knowledgeable digital assistants, and software capable of putting names to faces as well as any expert. Google recently announced that it had developed software capable of learning--entirely without human help--how to play several classic Atari computer games with skill far beyond that of even the most callus-thumbed human player. But do these displays of machine aptitude represent genuine intelligence? For decades artificial-intelligence experts have struggled to find a practical way to answer the question. AI is an idea so commonplace that few of us bother to interrogate its meaning.