Marc Andreessen, venture capitalist and one of the pioneers of the world wide web, once declared:

"The spread of computers and the internet will put jobs in two categories. People who tell computers what to do, and people who are told by computers what to do."

Andreessen has since repudiated this declaration, and taken a more optimistic stance. But economists, a more pessimistic bunch, are taking the possibility of this sort of bifurcated future more seriously. As machine-learning technology enjoys rapid progress, more top researchers are investigating the question of what work will look like in a world filled with computers that can replicate or surpass many of humanity's own mental abilities.