I have many thoughts on how thinking like a child can lead to easier learning, less stress, and overall a simpler life. However, this short extract made me think that I've been using the wrong word. Maybe the quality I've been thinking of is foolishness, or more precisely, to be willing to have yourself portrayed as a fool, albeit temporarily.
It's a bit extreme, but here is a snippet from the epilogue that presents an example of being a fool:
Or you might take the case of an eighteen-month-old infant learning to talk. Imagine the father leaning over the crib in which his baby son is engaging in what the behaviorist B. F. Skinner calls the free operant; that is, he's simply babbling various nonsense sounds. Out of this babble comes the syllable da. What happens? Father smiles broadly, jumps up and down with joy, and shouts, "Did you hear that? My son said 'daddy.'" Of course, he didn't say "daddy." Still, nothing is much more rewarding to an eighteen-month-old infant than to see an adult smiling broadly and jumping up and down. So, the behaviorists confirm our common sense by telling us that the probability of the infant uttering the syllable da has now increased slightly.
The father continues to be delighted by da, but after a while his enthusiasm begins to wane. Finally, the infant happens to say, not da, but dada. Once again, father goes slightly crazy with joy, thus increasing the probability that his son will repeat the sound dada. Through such reinforcements and approximations, the toddler finally learns to say daddy quite well. To do so, remember, he not only has been allowed but has been encouraged to babble, to make "mistakes," to engage in approximations—in short, to be a fool.
The idea is that this "foolish" behaviour and the freedom to make mistakes were the reason behind the learning.
I may be stretching the snippet that I've quoted here, but I think the concept of being able to make mistakes goes further than just learning new skills. It's a fundamental part of any form of evolution.
I would recommend reading the full epilogue that Tim Ferris shared on his blog, and if it interests you, checking out the book.