# What is the sense of smell?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 6 Sep 2026, 13 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19723360-what-is-the-sense-of-smell.mp3

Did you know you actually have up to thirty-three different senses feeding your brain right now?! In this mind-blowing episode of Science is Not Boring, Mira and Finn uncover the wild secrets of the human body and how our incredible senses work together as the ultimate superhero team. Have you ever wondered why your favorite cheesy pizza tastes like boring, mushy cardboard when you have a stuffy nose? It turns out, eighty percent of flavor actually comes directly from your sense of smell! Your nose is doing all the heavy lifting at dinner time! Join us as we explore the squishy fluid in your inner ear that gives you balance, and uncover the invisible body GPS that knows exactly where your fingers are in the dark! Plus, find out how a crazy potato chip experiment proved that the crunchy sounds you hear can actually change the way your food tastes. Your brain acts like a master DJ mixing sight, sound, smell, and touch into one giant movie. Get ready to put your four hundred smell receptors to work—science has never been this delicious!

## Transcript

[0:00] SPEAKER_00: Welcome to Science Is Not Boring by Kidopoly.com.
[0:04] SPEAKER_00: I'm Mira! And I'm Finn! Finn, did you know that when you eat your absolute favourite slice of warm cheesy pizza, you are actually tasting it with your nose.
[0:17] SPEAKER_00: And hearing it with your ears.
[0:19] SPEAKER_01: Ew, wait, what?
[0:22] SPEAKER_01: I definitely do not stick pizza inside my ears, Mira.
[0:25] SPEAKER_01: That is totally gross and a waste of good cheese.
[0:29] SPEAKER_00: You do not have to shove food in your ears.
[0:32] SPEAKER_00: Today, we are exploring how our incredible senses work together as a team.
[0:37] SPEAKER_00: And, spoiler alert, you do not just have the five senses you learn about in school.
[0:43] SPEAKER_00: Scientists actually recognise up to 33 different senses, all feeding information to your brain at the exact same time.
[0:53] SPEAKER_00: 33?
[0:54] SPEAKER_01: That is like having a superhero body.
[0:57] SPEAKER_00: What are they all doing inside me?
[0:59] SPEAKER_00: That is exactly what we are going to find out.
[1:02] SPEAKER_00: We will discover why food tastes super boring when you have a winter cold, why your nose is the real hero of dinner time, and how your brain acts like a master computer, blending everything you see, hear, smell, touch, and taste into one giant, amazing movie.
[1:21] SPEAKER_00: So, let's start with a science mystery right in your own body.
[1:25] SPEAKER_00: Finn, remember last month when you caught that terrible cold?
[1:30] SPEAKER_01: Oh man, it was the absolute worst.
[1:33] SPEAKER_01: My nose was totally stuffed up with thick, gooey yellow snot.
[1:37] SPEAKER_01: I was going through a whole box of tissues every single day.
[1:41] SPEAKER_00: Gross, but perfect for our science investigation.
[1:45] SPEAKER_00: When you were super sick, did you notice anything weird about eating your meals?
[1:50] SPEAKER_01: Yeah, actually.
[1:52] SPEAKER_01: Mum made my favourite homemade macaroni and cheese, but it tasted like warm mushy cardboard.
[1:58] SPEAKER_01: It had zero flavour.
[2:00] SPEAKER_01: I was so sad.
[2:02] SPEAKER_01: Why does that happen?
[2:04] SPEAKER_00: It happens because 80% of what we think of as flavour actually comes directly from our sense of smell.
[2:11] SPEAKER_00: Wait, 80%?
[2:13] SPEAKER_01: But the food goes straight into my mouth.
[2:15] SPEAKER_01: My tongue is doing the tasting, right?
[2:18] SPEAKER_00: Your tongue does taste the basics, like salty, sweet, sour, and bitter.
[2:24] SPEAKER_00: But as you chew, tiny invisible scent molecules from the food drift up a secret backdoor passage behind your throat and right into your nasal cavity.
[2:34] SPEAKER_00: Scientists call this retronasal olfaction.
[2:37] SPEAKER_01: Whoa, so my mouth is just feeling the texture and the salt, but my nose is doing all the heavy lifting to figure out it is cheddar cheese.
[2:45] SPEAKER_00: Exactly! Humans have about 400 different types of olfactory receptors, hidden way up high in the nose.
[2:53] SPEAKER_00: They are like tiny chemical detectives waiting to decode your food.
[2:58] SPEAKER_00: Oh, I get it.
[2:59] SPEAKER_01: So when my nose was completely stuffed up with gooey snot, it acted like a giant wall.
[3:05] SPEAKER_00: Yes.
[3:06] SPEAKER_00: The mucus blocked those scent molecules from ever reaching your 400 receptors.
[3:11] SPEAKER_00: Your brain couldn't smell the cheese, so it just tasted like bland, boring mush.
[3:16] SPEAKER_00: Your nose is the real chef of the body.
[3:19] SPEAKER_00: So we know about taste and smell.
[3:21] SPEAKER_00: But Aristotle, a famous Greek philosopher from over 2,000 years ago, came up with the idea that humans only have five senses: sight, hearing, touch, smell, and taste.
[3:34] SPEAKER_01: But you told me we have up to 33.
[3:37] SPEAKER_01: Where are the other 28 hiding?
[3:39] SPEAKER_00: Are they invisible?
[3:41] SPEAKER_00: They are working constantly inside your body.
[3:44] SPEAKER_00: Let's talk about a huge one called the vestibular system.
[3:48] SPEAKER_00: It is your built-in sense of balance.
[3:50] SPEAKER_00: Balance is a sense.
[3:52] SPEAKER_01: Where is the balance organ located?
[3:55] SPEAKER_01: Is it somewhere down in my feet?
[3:57] SPEAKER_00: Nope, you won't find it in your shoes.
[3:59] SPEAKER_00: It is actually located deep inside your head, inside your inner ear.
[4:05] SPEAKER_00: You have three tiny loop-shaped tubes in there, called semicircular canals, and they are completely filled with a special fluid called endolymph.
[4:15] SPEAKER_01: Fluid?
[4:16] SPEAKER_01: Sloshing around inside my head right now.
[4:19] SPEAKER_01: Ew, that sounds so weird and squishy.
[4:23] SPEAKER_00: It might sound squishy, but it is brilliant engineering.
[4:27] SPEAKER_00: As you move your head, that fluid swooshes around and bends tiny microscopic hairs called stereocilia.
[4:36] SPEAKER_00: When those hairs bend, they send lightning fast electrical signals to your brain, telling it exactly which way is up, down, left or right.
[4:46] SPEAKER_01: So when I spin around really fast on the playground merry-go-round and get dizzy, that is because the fluid is still spinning inside my ears even after I stop.
[4:55] SPEAKER_00: Spot on! Your eyes say you stopped, but your ears say you are still spinning.
[5:01] SPEAKER_00: Now, let's try another secret sense.
[5:04] SPEAKER_00: Close your eyes and without looking at all, touch your right index finger exactly to the tip of your nose.
[5:12] SPEAKER_01: Okay, eyes closed tight.
[5:14] SPEAKER_01: Boop! Got it on the first try.
[5:17] SPEAKER_01: Wait, how did my finger know exactly where my nose was in the dark?
[5:22] SPEAKER_00: That is a sense called proprioception.
[5:25] SPEAKER_00: It is your body's ability to know exactly where its parts are in space without having to look at them.
[5:31] SPEAKER_00: Your muscles and joints are constantly whispering their exact coordinates to your brain.
[5:37] SPEAKER_01: Proprioception?
[5:39] SPEAKER_01: That is a massive word.
[5:41] SPEAKER_01: But it is basically like having an invisible GPS tracker for my arms and legs.
[5:46] SPEAKER_01: Exactly!
[5:47] SPEAKER_00: Now, here is where it gets totally mind-blowing.
[5:51] SPEAKER_00: All of these senses, your 400 smell receptors, your inner ear fluid, your muscle GPS, your eyes, your ears, they all send millions of messages to your brain at the exact same millisecond.
[6:07] SPEAKER_01: That sounds like total chaos.
[6:09] SPEAKER_01: How does my brain not just short circuit and explode from all that loud sensory noise?
[6:15] SPEAKER_00: Your brain does something incredible called multisensory integration.
[6:20] SPEAKER_00: It acts like a master music DJ, taking all those different sensory tracks and mixing them together so perfectly you do not even notice.
[6:29] SPEAKER_00: But sometimes scientists love to trick the DJ.
[6:33] SPEAKER_01: Ha! Ooh, I love a good trick.
[6:36] SPEAKER_01: What kind of trick did they play on the brain?
[6:38] SPEAKER_00: In 2004, a brilliant scientist at Oxford University named Professor Charles Spence did a famous experiment.
[6:47] SPEAKER_00: He wanted to see if what we hear can actually change what we taste.
[6:52] SPEAKER_00: So he brought people into a lab and gave them potato chips to eat.
[6:56] SPEAKER_01: That sounds like the best science experiment ever.
[6:59] SPEAKER_01: I volunteered to eat potato chips for science.
[7:03] SPEAKER_00: Well, there was a catch.
[7:05] SPEAKER_00: The people had to wear special noise-cancelling headphones while they ate the chips.
[7:10] SPEAKER_00: The headphones played the exact sound of their own mouth crunching.
[7:14] SPEAKER_00: But Professor Spence secretly changed the volume and the high-pitched frequencies using the computer.
[7:21] SPEAKER_00: What happened?
[7:22] SPEAKER_00: Did the potato chips taste weird?
[7:24] SPEAKER_00: When he made the crunching sound louder and sharper in the headphones, people actually reported that the chips tasted 15% fresher and crispier.
[7:34] SPEAKER_00: Even though they were eating the exact same batch of potato chips.
[7:39] SPEAKER_01: No way! Just hearing a crunchier sound made their brain literally think the chip was fresher in their mouth.
[7:46] SPEAKER_01: That is completely wild!
[7:48] SPEAKER_00: It really is! Professor Spence's experiment proved that flavour is not just happening on your tongue.
[7:54] SPEAKER_00: It is a full-body experience, created by your brain, combining sight, sound, smell, and touch.
[8:02] SPEAKER_00: That is why food companies spend millions of dollars making sure potato chip bags are super noisy when you open them.
[8:09] SPEAKER_01: Ha! I knew it.
[8:11] SPEAKER_01: They want my brain to think the snack is extra crunchy and fresh before I even take a single bite.
[8:16] SPEAKER_00: You got it! Understanding our hidden senses completely changes how we experience the world.
[8:23] SPEAKER_00: And we have even more weird senses protecting us every day.
[8:27] SPEAKER_00: Have you ever heard of no susception?
[8:29] SPEAKER_01: No see what?
[8:30] SPEAKER_01: Is that the sense of not being able to see things in the dark?
[8:34] SPEAKER_00: Nope.
[8:35] SPEAKER_00: No susception is your highly advanced sense of pain.
[8:38] SPEAKER_00: When you stop your toe on the couch, the touch signals zoom up your leg at over 250 miles per hour.
[8:45] SPEAKER_00: And then the no susception pain signals follow right behind to make you say, ouch!
[8:52] SPEAKER_01: Yikes! I definitely use my no susception way too much when I walk around barefoot.
[8:58] SPEAKER_01: Are there any other hidden ones?
[9:00] SPEAKER_00: Oh, there is a very important one called interoception.
[9:04] SPEAKER_00: It is your ability to feel what is going on deep inside your internal organs.
[9:08] SPEAKER_00: It tells you when your stomach is totally empty, or when your heart is racing fast.
[9:14] SPEAKER_01: Or when my bladder is totally full of water, and I need to run to the bathroom immediately.
[9:20] SPEAKER_00: Exactly! Without interoception, you wouldn't even know when you needed to pee.
[9:25] SPEAKER_00: And here is one last crazy fun fact.
[9:29] SPEAKER_00: Remember those 400 smell receptors in your nose?
[9:32] SPEAKER_00: By mixing and matching those signals, scientists estimate human beings can distinguish up to one trillion different odours.
[9:41] SPEAKER_00: One trillion?
[9:42] SPEAKER_01: If you counted one smell every second, it would take over 30,000 years.
[9:47] SPEAKER_01: Our bodies are basically superheroes.
[9:50] SPEAKER_00: Alright, Finn, time for the quiz.
[9:52] SPEAKER_00: Are you ready?
[9:53] SPEAKER_01: Okay, I am ready.
[9:55] SPEAKER_01: I hope my brain's DJ can remember all this information.
[9:59] SPEAKER_00: First question.
[10:00] SPEAKER_00: What percentage of what we think of as flavour actually comes from our sense of smell?
[10:10] SPEAKER_00: Next one.
[10:11] SPEAKER_00: How many different types of olfactory receptors do humans have inside their noses?
[10:20] SPEAKER_00: Question three.
[10:22] SPEAKER_00: What is the scientific name of the hidden sense that tells us where our body parts are without looking?
[10:32] SPEAKER_00: Alright, here's number four.
[10:34] SPEAKER_00: Where exactly is your vestibular system, or your sense of balance, located?
[10:43] SPEAKER_00: Last question.
[10:45] SPEAKER_00: What snack food did Professor Charles Spence use in his famous sound experiment in 2004?
[10:52] SPEAKER_00: Great job! Let's go through the answers.
[10:55] SPEAKER_00: The answer to question one is 80% of flavour comes from smell.
[11:01] SPEAKER_00: For question two, humans have about 400 different types of olfactory receptors.
[11:08] SPEAKER_00: Number three, the answer is proprioception, that is your internal body GPS.
[11:17] SPEAKER_00: Question 4.
[11:18] SPEAKER_00: Your vestibular system is located deep inside your inner ear.
[11:23] SPEAKER_00: And the final answer is, Professor Spence used potato chips.
[11:28] SPEAKER_01: I am definitely never eating potato chips the exact same way again.
[11:33] SPEAKER_01: I'm going to put on headphones and listen to every single crunch just to see if they taste fresher.
[11:40] SPEAKER_00: And I am definitely going to appreciate my 400 smell receptors.
[11:45] SPEAKER_00: It is so amazing how our brains take all these trillions of tiny signals and turn them into the beautiful world we experience every single day.
[11:55] SPEAKER_00: Science is seriously the best.
[11:58] SPEAKER_01: Our bodies are basically running on extreme high-tech supercomputers.
[12:02] SPEAKER_00: If you loved learning about all 33 of your amazing senses today, please leave us a five-star review.
[12:10] SPEAKER_01: Yeah.
[12:11] SPEAKER_01: Just scroll down on your podcast app and tap the five stars.
[12:15] SPEAKER_01: Do it for the 400 hard-working smell receptors in your nose.
[12:19] SPEAKER_00: Oh, and don't forget to check out our site, kidopoly.com.
[12:23] SPEAKER_00: We've got tons of fun learning games and awesome activities waiting for you right there.
[12:29] SPEAKER_01: And if you want a shout out on the show or just want to say hi, send us an email at hello at kidopoly.com.
[12:36] SPEAKER_01: We would really love to hear from you.
[12:38] SPEAKER_00: Thanks for exploring with us today.
[12:40] SPEAKER_00: See you next time on Science is Not Boring.
[12:43] SPEAKER_00: Bye everyone! Keep crunching those chips.

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