David Eagleman

Let's out a chirp and it gets an echo back.

And that's how it figures out the three-dimensional structure of the cave it's flying through.

Or for the black ghost knife fish, it has electrical fields around it, and it's detecting when that gets perturbed by, let's say, a rock or some predator there.

And those are the only signals that it has that it can pick up on from the world.

And so that's this concept of the umwelt, which is, you know, that's how it constructs its reality.

And what I've always found interesting is that presumably...

We all, you know, every animal species accepts its reality as the entire reality out there, because why would you stop to ever question or think that maybe there's something beyond what you can detect?

But what you said is also correct.

And this is actually the topic of my next book, which is the difference from human to human has been fascinating to me, just as one example.

Well, an easy example is colorblindness, right?

So let's say...

This person's colorblind, this person's not.

They're actually seeing the scene differently.

And we now know that a small fraction of women have not just three types of color photoreceptors in their eye, but four types, which means they're seeing colors the rest of us aren't seeing.

Or it takes something like synesthesia, which is,

where someone, let's say, looks at letters or numbers and it triggers a color experience, or they taste something and it puts a feeling on their fingertips, or they hear something and it causes a visual for them.

There are many forms of synesthesia, but the point is it's not a disease or a disorder.

It's just an alternative perceptual reality.

And different people, like 3% of the population has synesthesia and others don't.

Or something that I've been studying a lot lately is