[jcrites]

> Only recently have researchers developed learning procedures that can learn these deep architectures efficiently, using some clever unsupervised learning techniques.

Would you mind naming some of these techniques, if you're familiar with them? I'd like to take a deeper look.

[visarga]

Restricted Boltzmann Machines. https://www.youtube.com/watch?v=AyzOUbkUf3M

This video drives the point home, and is made by the author of this technique.