There was a time when I just loved TED talks. That has changed. I am not so sure why. But I think I got the feeling the insights I’m getting are not worth the time spent.
This is bad advice for people wanting to learn a musical instrument. It takes way more than 20 hours because much of what you do when you play say the mandolin has to become automatic in order for you to do it well. There are no shortcuts.
I learned to recognize hiragana and katakana like this. But learning the language itself took me a lot more time and effort. Had to practically immerse myself in Japanese 24/7.
I enjoyed his book "The First 20 Hours". Most of the content is how he specifically applied it to learn certain skills: Switching from Qwerty to Colemak keyboards, and learning to play Go were interesting. He also had a chapter of learning to program in 20 hours.
I find it takes 45 minutes to really get into some dense subjects. Without putting in the second, third, or fourth 45 min chunk that same evening, I'd personally have a hard time unless it was an easy task/subject.