David Eagleman

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

what's called hyperphantasia, or at the other end of the spectrum, aphantasia, which is how you visually image something.

So if I ask you to imagine an ant crawling on a tablecloth towards a jar of purple jelly, for some people, that's like a movie in their head.

They can see the whole thing.

Other people, it's just conceptual.

There's no picture there at all.

So the first group is called hyperphantasic.

The second group is called aphantasic.

And it turns out that across the population, everybody is smeared way out here.

And so although we would assume that everyone has mental imagery that's like ours, in fact, everybody's totally different with this stuff.

So this is what I've been spending my time writing about lately is the differences between humans.

Extremely fascinating to me.

Well, okay, so almost all animals have a sense of smell that's so much better than ours.

I don't know if you saw my TED Talk, but I did this example of, you know, really imagine that you are a dog.