Now see, in Duolingo, because while you learn you're actually creating value, you're translating stuff which for example, we could charge somebody for translations.

He likened their learning to a living in a mathland, where learning mathematical ideas is as natural as learning French while living in France.

Imagine playing a video game controlled by your mind. Now imagine that game also teaches you about your own patterns of stress, relaxation and focus. At TEDxToronto Ariel Garten shows how looking at our own brain activity gives new meaning to the ancient dictum know thyself.