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The world doesn’t appear the same to every animal — or every human

By Dr. Sanjay Gupta, CNN Chief Medical Correspondent

Sight, smell, hearing, taste and touch — you know them as the five traditional senses.

They are meant to protect us from danger. They help us find food and potentially even a mate. They create order in the happenings of the world around us, and if we are properly tuned in, they reveal some of the natural beauty and wonder that surround us.

The thing that all the senses have in common is that they are processed through the brain. In fact, everything we see, hear, feel, smell and taste is perceived by — and many would even argue created by — our brains.

That’s right: It is our brains that can translate tiny, invisible airborne molecules into the smell of baking bread or a stinky sock. Our brains can turn pressure waves or vibrations into the sound of a loved one’s whisper or a distant thunderclap. Our brains can also weave the visible light portion of electromagnetic radiation into a beautiful mountain or the glow on our mother’s face. And our brains can recognize the infrared portion of that same electromagnetic radiation as the warmth we feel when we sit by a lit fireplace. It is pretty amazing.

In the newest season of the podcast “Chasing Life,” which kicked off this week, we’ll explore many of the mysteries of the senses.

I’m a practicing neurosurgeon, and my first love has always been the brain, but reporting on this season’s stories was a chance to combine that with another love: journalistic storytelling. And what I’ve heard, seen, smelled, tasted and felt has been quite remarkable.

Our five traditional senses might seem straightforward, but they’re actually not. Each is multifaceted and nuanced, with many variations among humans.

Take touch, for example. Some people need to be touched and others much less so. And far from being only one sense, touch can be broken down further into pressure, temperature, tactile sensations and pain. And we are still in the process of learning how it all works.

It was only last year, in 2021, that two scientists, working separately, shared the Nobel Prize in Medicine for their work in identifying a sensor in the nerve endings of our skin that responds to heat and other sensors that respond to pressure. And just this year, researchers published a paper describing some of the possible neuronal underpinnings of pleasant sensations like cuddling and caressing.

What’s more, the traditional five are not the only senses we have. It might surprise you to learn that we have at least seven, maybe eight. You’ll learn more about the other secret senses most humans possess in this season of “Chasing Life.”

In addition, we’ll examine what happens when people don’t have a sense or a component of a sense. We have an episode on prosopagnosia, commonly called face-blindness, a condition in which people can see faces but can’t recognize them — sometimes not even their own family members. And we’ll learn how people in the deafblind community have created a language to help them better communicate.

We will also dig into synesthesia, when two senses blend together to create a unique “combination sense,” such as colored hearing, where certain sounds elicit colors. You will learn why synesthesia occurs and how the experience is so inherent to the individual that many who have it don’t realize (for a long time) that others don’t perceive the world in the same way.

We will additionally take a deep dive into the promise of psychedelics, which distort the senses and dissociate us from our familiar way of being and can be used to treat mental health conditions, like post-traumatic stress disorder and depression.

Animals and their umwelten

We kick off the season with an interview with award-winning science journalist Ed Yong. He’s the author of a new book, “An Immense World: How Animal Senses Reveal the Hidden Realms Around Us.”

Ed explains how all creatures, not just humans, live in their own “sensory bubble” through which they experience a sliver of reality — the very specific sliver of reality that happens to be crucial to their survival and well-being. The phenomenon is called the umwelt, a concept pioneered in 1934 by Baltic German biologist Jakob von Uexküll.

Ed takes us on a fascinating journey through the animal kingdom’s many mysterious senses that exist outside of our own umwelt, beyond the reach of what we humans can know for certain. If you’ve ever wondered what it might be like to socialize by scent like a dog, use echolocation to navigate like a bat, feel the earth’s magnetic pull to migrate in the right direction like a bird or discern the environment via electricity like an eel, you won’t want to miss this conversation.

Ed told me, “I start the book with this thought experiment, to imagine that you’re sharing a room with an elephant and a bee and rattlesnake, a spider, a bat. … You could all be in the same physical space, but you would have radically different experiences of that space. The rattlesnake will be able to sense the body heat of the animals around it; the elephant could make low infrasonic rumbles that the other creatures couldn’t hear. A dog in that space would be able to get so much scent … that its fellow animals couldn’t get. So, each of us is trapped in our own sensory bubble and perceiving just this thin sliver of the fullness of reality.”

What is truly incredible, Ed said, is that each of those living creatures, including us, thinks we are getting the full picture of what reality is.

“I’m sitting here in this room, and I don’t feel as if my perception of the world is incomplete. I’m not sitting here marveling at the gaps in what I’m perceiving. But this feeling of getting everything is such an illusion, and it’s an illusion that every animal shares,” he said. “It tells us that even the most familiar parts of our world are full of unknowns and extraordinary things.”

Ed delves into these mysteries — into the different umwelten of animals — and brings them to life for us. You can listen to my full conversation with Ed Yong here.

Join us this and every Tuesday on “Chasing Life” as we set off on an exploration of the senses and how they bring the world to life for us, so we can live our best lives in the world.

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CNN Health’s Andrea Kane contributed to this report.

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