Daryl Hall

I've always been a spontaneous singer. And all the stuff that you hear on the end of the songs, what they call the ad libs - that just comes out of my head. That's not thought out at all. I have the verses and the choruses, and then after that it's total improvisation.

The idea of critical windows extends beyond just vision, of course: almost every system in the brain has a critical window when it needs to experience certain stimuli, or it won't get wired up properly. The most obvious example is language: if you don't learn a language early on, it's nigh impossible to become truly fluent.