Steve Levitt

is the ability to inculcate in people a sense of right and wrong. And so the overwhelming majority of people are trained to not do things that are negative to other people.

is the ability to inculcate in people a sense of right and wrong. And so the overwhelming majority of people are trained to not do things that are negative to other people.

I love podcast guests who change the way I think about some important aspect of the world. A great example is my guest today, David Eagleman. He's a Stanford neuroscientist whose work on brain plasticity has completely transformed my understanding of the human brain and its possibilities.

According to Eagleman, the brain is constantly trying to predict the world around it. But of course, the world is unpredictable and surprising, so the brain is constantly updating its model. The capacity of our brains to be ever-changing is usually referred to as plasticity, but Eagleman offers another term, live-wired. That's where our conversation begins.

When I went to school, I feel like they taught me the brain was organized around things like senses and emotions, that there were these different parts of the brain that were good for those things. But you make the case that there's a very different organization of the brain.

So let me pose a question to listeners. Imagine you have a newborn baby and he or she looks absolutely flawless on the outside. But then upon examination, the doctors discover that half of his or her brain is just missing, a complete hemisphere of the brain. It's never developed. It's just empty space.

I would expect that would be a fatal defect, or best the child would be growing up profoundly mentally disabled.

So I first came to your work because I was so blown away by the idea of human echolocation. Yeah. only to discover that echolocation is only the tip of the iceberg. But could you talk just a bit about echolocation, how quickly, with training, it can start to substitute for sight?

And then in these studies, you put a blindfold on a person for two or three days and you try to teach them echolocation. If I understand correctly, even over that timescale, the echolocation starts taking over the visual part of the brain. Is that a fair assessment?

So in your book, you talk about REM sleep. And honestly, if I had sat down and tried to come up with an explanation of REM sleep, I could have listed a thousand ideas. Your pet theory would not be one of them. So explain what REM sleep is and then tell me why you think we do it.

Have you convinced the sleep scientists this is true? Or is this just you believing it right now?

So we talked about echolocation, which uses sound to accomplish tasks that are usually done by vision. And you've started a company called Neosensory, which uses touch to accomplish tasks that are usually done with hearing. Can you explain the science behind that?

Just make sure I understand it. Sounds happen, and this wristband... hears the sounds and then shoots electrical impulses into your wrist that correspond to the high and low frequency?

Do people train? You give them very direct feedback? Or is it more organic?

Okay. So hearing their own voice for the first time through this. Oh God. Yeah. That's interesting.

So then it seems like if I'm deaf and I see the dog's mouth moving, and I now associate that with the sound, do the people say that they hear the sound where the dog is? Or is the sound coming from the wrist?

So you also have a product that helps with tinnitus. Could you explain both what that is and how your product helps?

So what we're talking about is substituting between senses. Are there other forms of this, products that are currently available to consumers or likely to become available soon in this space?

Elon Musk's company Neuralink has gotten a ton of attention lately. Could you explain what they're trying to do and whether you think that's a promising avenue to explore?

So what we've been talking about so far has been sending signals to the brain. But what Neuralink is trying to do is take signals out of the brain. Is that right?