Hector the Tickle Robot, Eyeball Teeth, a Little Bit of ~Spice~ (and Neuroscience)

Author and food historian Priya Mani joins the show to talk about the neuroscience of spice. Plus, Laura explains why whales have teeth on their eyes (SERIOUSLY), and Rachel gets into why a tickle robot exists. The Weirdest Thing I Learned This Week is a podcast by Popular Science. Share your weirdest facts and stories with us in our ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠Facebook group⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ or ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠tweet at us⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠! ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠Click here to learn more about all of our stories! ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Links to Rachel's TikTok, Newsletter, Merch Store and More: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://linktr.ee/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Rachel now has a Patreon, too! Follow her for exclusive bonus content: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://www.patreon.com/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Link to Jess' Twitch: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://www.twitch.tv/jesscapricorn⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Link to all of Jess' content: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://www.jesscapricorn.com/⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ -- Follow our team on Twitter Rachel Feltman: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Produced by Jess Boddy: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/JessicaBoddy⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Popular Science: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/PopSci⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Theme music by Billy Cadden: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://open.spotify.com/artist/6LqT4DCuAXlBzX8XlNy4Wq?si=5VF2r2XiQoGepRsMTBsDAQ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Rachel Feltman?

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• 0:41Rachel Feltman?

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• 0:47Speaker 01

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• 1:50Rachel Feltman?

  At Popular Science, we report and write dozens of science and tech stories every week. And while most of the stuff we stumble across makes it into our articles, we also find plenty of weird facts that we just keep around the office. So we figured, why not share those with you? Welcome to the weirdest thing I learned this week from the editors of Popular Science. I'm Rachel Feltman.

• 2:10Speaker 03

  I'm Laura Visus.

• 2:12Speaker 04

  And I'm Priya Mani.

• 2:13Rachel Feltman?

  Priya, welcome to the show. It's so great to have you.

• 2:16Speaker 03

  Welcome.

• 2:17Speaker 04

  Thank you so much, Rachel and Laura.

• 2:19Rachel Feltman?

  So would you tell our listeners who you are?

• 2:23Speaker 04

  So I'm the author of Spiced: A Recipe Celebrating Spices From Around the World, which is published by Fiden Press. It's open for pre-orders as we speak, but out in bookstores around the world in October this year. And I live in Copenhagen and my studio, which is called Appetite Studio, quite aptly, works on food and flavor projects around the world. And we know, we do a broad arc of projects. F&B industry-focused work with flavor and product development, but also a lot of design and food communication work that is nuanced and culturally rooted storytelling or experimental installations on food and nourishment.

• 3:02Rachel Feltman?

  Very cool. Well, we love food science and we love

• 3:05Speaker 03

  We do.

• 3:06Rachel Feltman?

  food history and we love spices. So we are very excited to have you with us today.

• 3:12Speaker 04

  Thank you.

• 3:13Rachel Feltman?

  So let's jump right into it. On the weirdest thing I learned this week, we start by each offering up a little tease about some kind of fact or story we found in the course of reading, writing, reporting, cooking, et cetera, and decide which one we just absolutely have to hear more about first. Then, once we've all had time to spin our little science yarns, we reconvene and decide what the weirdest thing we learned this week actually was, except there's no winner. We just kind of chat about it. That's fine. Laura, what's your tease today?

• 3:41Speaker 03

  Whale sharks have teeth on their eyeballs.

• 3:45Rachel Feltman?

  Oh.

• 3:46Speaker 03

  Yep. Eyeball teeth.

• 3:48Rachel Feltman?

  Wow.

• 3:49Speaker 03

  Yep.

• 3:50Rachel Feltman?

  Great, great. And Priya, what's your tease?

• 3:53Speaker 04

  Well, chili burns and prickly ash buzzes, but it's your brain that's the one creating both sensations.

• 4:01Rachel Feltman?

  Oh, I can't wait to hear more about this. This is, these are, these are spices I enjoy learning about.

• 4:08Speaker 03

  Burning and buzzing. Interesting. Okay.

• 4:11Rachel Feltman?

  My tease, hard to pick a tease for this one, but I am going to say scientists did engineer a tickle robot.

• 4:21Speaker 04

  That's a cool one.

• 4:22Rachel Feltman?

  Yeah. So I think maybe I might, I might jump in first today with this tickle bot.

• 4:29Speaker 03

  Go, go.

• 4:30Rachel Feltman?

  So yeah, there's sort of, there's a lot to this story, but we're gonna, we're gonna talk about tickling because a, a study came out quite recently, basically looking at the surprising universality of tickling. You might be surprised at how kind of mysterious a phenomenon tickling is. We're not really sure why it exists and it is pretty unique. So just kind of some background, and I promise the tickle robot does come into play. So first of all, tickling is actually divided into two distinct phenomena. One is nismesis,

• 5:14Rachel Feltman?

  spelled with a silent K, which is

• 5:17Speaker 03

  Nismesis?

• 5:18Rachel Feltman?

  Nismesis.

• 5:19Speaker 03

  Nismesis. Okay.

• 5:20Rachel Feltman?

  Yeah. And so that is very common, you know, perhaps even universal among animals. That's the, when like a light brushing sensation occurs because something has stimulated your skin by moving slowly across it. It doesn't make you laugh. It, it gives you an urge to, you know, maybe scratch or pull away. Maybe you feel a little shivery. And we know that this occurs in many, many animals. When a horse twitches their flank because a fly has landed on them. You know, if a dog, a dog have these reflexes when you scratch them in certain places, you know, their legs will kind of like shake. And that's, all

• 6:02Rachel Feltman?

  of this is this nismesis, the, the moving itch, it's sometimes called. And it's pretty clear that that evolved as a sort of defense mechanism. You know, this is about recognizing that something that's not you is touching you and that it's unexpected and that maybe you want to react to that. And it's, so it's not, you know, it's different from feeling pain, which of course elicits a different and perhaps more urgent response, but it is like, oh, what's, what's that? But of course, that's not what most humans think of when they hear the word tickling. And

• 6:41Speaker 03

  Right.

• 6:42Rachel Feltman?

  the laughter provoking tickle is known scientifically as gargalisis.

• 6:47Speaker 03

  I guess because of the throat, maybe?

• 6:49Rachel Feltman?

  Yeah. I really should have looked up, you know what? I'm going to do a quick etymology search because that's one thing I really should have done that I did not.

• 6:56Speaker 03

  Gargalisis?

• 6:57Rachel Feltman?

  Gargalisis and related words come from the Greek gargalos, which is itching.

• 7:06Speaker 03

  Okay.

• 7:07Rachel Feltman?

  So, yeah.

• 7:09Speaker 03

  Not the throat. Interesting.

• 7:10Rachel Feltman?

  Not, not the throat.

• 7:11Speaker 03

  Okay, never mind.

• 7:13Rachel Feltman?

  I would have, I can't tell you where that, what the etymology of that is. So anyway, apparently we've been talking about feeling itchy-tickle feelings for a long time. This is what you're probably thinking of when you think of being tickled. It's like a very deliberate touch on particularly sensitive regions of the body that makes you laugh. You know, it's this involuntary squirming, contractions in your body, laughter, of course. And it's not just humans. Other primates do also get tickled and react in this way.

• 7:52Rachel Feltman?

  There is also some research showing that rats might also be ticklish in this way. They certainly have a very similar response to their bellies getting tickled by folks in the lab. They create 50 kHz ultrasonic vocalization. So we could not hear them, but you can find basically slowed down, pitched down recordings of this that are just rats shrieking with laughter.

• 8:24Rachel Feltman?

  So we don't know for sure that that's actually sort of a, you know, from the same evolutionary root. Because again, it like seems very rare even among mammals, but we know that primates and humans, this is a weird thing that we do. Another, you know, specific thing about tickling that makes it distinct from other kinds of touch, and this is true for both that, you know, that little itch tickle that many animals have and for the, the laugh-out-loud tickles that are more unique to humans. It requires surprise. There's something about it that the reaction is about the intrusion of the sensation. It's, it's not

• 9:02Speaker 03

  Right.

• 9:03Rachel Feltman?

  expected. Yeah.

• 9:04Speaker 03

  Element of surprise is in there.

• 9:06Rachel Feltman?

  Exactly. And that is why you, you can't tickle yourself because, because you know it's coming, it does not elicit the same reaction. So there are parts of your body you might consider ticklish, but you cannot tickle yourself there. One interesting exception is that there is some research showing that people, you know, on various parts of the, the schizotyp spectrum. So, you know, people with schizophrenia or, you know, other type of schizoaffective disorders sometimes seem to be more capable of tickling themselves. And yeah, it's not all or nothing. It's not like everyone who is diagnosed with schizophrenia can tickle themselves. But there, there is some data on this and it's also very strongly

• 9:50Rachel Feltman?

  associated with having more symptoms like auditory hallucinations or what are called passivity experiences. So states of mind where you struggle to strongly associate the thoughts you're having with coming from you. So this is like, not something that there's a ton of research on, but it does sort of make sense when you think about it, that if, if your brain does not register that your thoughts are coming from you, that it might also sometimes not register that your tickles are coming from you. So you may have this strange superpower of being able to tickle yourself.

• 10:25Speaker 03

  Kind of would be a good way to maybe wake yourself up in the morning, like if you're having some trouble. Just trying to think about where that could come in handy.

• 10:33Rachel Feltman?

  Yeah. And so that we know that, you know, typically when, when somebody attempts to tickle themselves, the, in the cerebellum, there are these motor command signals that essentially are like, yeah, I can predict what's coming and suppress it. I'm like canceling it out because that's not an important sensation to register. That's you scratching your, your armpit. You know, it's a, there's no need to have you jump out of your skin and laugh because it's coming from you. So that certainly, you know, feeds into this idea that tickling is part of some evolutionary sort of like situational awareness. It's like an alarm system. But then why do we have this added

• 11:18Rachel Feltman?

  Kind of tickling that makes us burst out laughing and not just the one that makes us go like, huh, what was that? This is much more of a mystery and it's one that people have mused about for a long time. Socrates thought about it.

• 11:33Speaker 03

  Not kidding, long time.

• 11:34Rachel Feltman?

  Yeah, yeah, long time. He talked about it as being, you know, this weird intersection of pain and pleasure. Aristotle thought that it was about areas where the skin was particularly delicate, might be more ticklish. Charles Darwin definitely talked about the element of surprise being important. So he was, you know, of course, on the right track with that. And yeah, so there are still today, like several theories about why we are so uniquely ticklish in this way. One interesting idea is that it may have developed as a tool for play fighting that lots of species,

• 12:15Rachel Feltman?

  including primates, have this sort of, you know, mock fighting play, especially when, when we're young. And so this idea is that these particularly vulnerable spots, like your neck, your armpits, your ribs, might like, maybe there's some benefit to us having a reaction when those are playfully attacked that's different from like fear and pain. Because you want to continue having the play combat so that you continue to learn.

• 12:47Speaker 03

  Learn how to.

• 12:48Rachel Feltman?

  Yeah, learn how to protect them. You know, it's like basically that we have this, this sort of positive, but oh, don't touch me there response. That is, you know, maybe a very specific sort of like learning ground for, for when we're young. You know, another very common theory is that it's all about social bonding, like so many weird things that primates do, especially because babies become ticklish quite early in, you know, their, in their life relative to, you know, having thoughts about things and sharing them with us. They, you know, react to being tickled and they laugh, not immediately, but that starts like pretty early. And so some, some theories hold that this is purely like a pre-verbal bonding activity, that this is about like.

• 13:32Speaker 03

  That makes sense.

• 13:33Rachel Feltman?

  Yeah, a playful, a playful thing that happens when we touch each other.

• 13:37Speaker 03

  Yeah, like you are not a threat. You are part of my group. You are, yeah.

• 13:42Rachel Feltman?

  Yeah, that like, you know, we're sort of developing this, this very, these very specific cases where it's like, oh, that touch does come from someone else, but it's like fun, it's cute. We're, we're friends. And all of this is preamble for this new research that just came out in, in August in Nature Human Behavior. And it is this big cross-cultural study. They looked at 444 participants from China, the Netherlands and Greece. So not the entire world, but like, I think it's fair to say that they picked three cultures that, you know, socially have like pretty distinct vibes. And that was their, their goal, that they, they wanted to like, look at a good swath

• 14:26Rachel Feltman?

  of humankind and be like, these are people who don't necessarily, aren't necessarily socialized in the same way, you know, don't have a lot of the same like learned social bonding behaviors. Um, you know, and so what are the commonalities going to be here? Turns out there were a lot of them. So first of all, tickling itself, 98% of people across of these three cultures had been tickled. More than 95% had tickled others. And, you know, I was thinking, I was like, I guess that's not surprising to me because tickling does feel ubiquitous, but also I don't think there are many random behaviors

• 15:08Rachel Feltman?

  you could ask 448 people about that 98% of them would be like, yeah, that's happened to me, other than like things we need to live.

• 15:16Speaker 03

  Right, eating, breathing, going to the bathroom. Yeah, yeah.

• 15:19Rachel Feltman?

  Yeah. And they also found that the reactions, unsurprisingly, again, were pretty universal, that like you laugh, you like try to escape, you might scream. And this was the same across the board. So then they decided they, they did these like color maps where they had people like basically shade in where they were ticklish. And then they created sort of like heat maps to, to be like, where is everybody ticklish? And one thing that's cool is that they had them do two maps. They had them do one that was like, where would a friend or family member tickle you? And one, where would like an intimate partner tickle you?

• 15:57Rachel Feltman?

  So, you know, this like armpit, neck, rib area, uh, behind the knees, feet was like universal. And then really the only difference for, you know, intimate romantic sexual partners was that it added in and, you know, in some cases focused on more erogenous zones. So, you know, like inner thighs became more, more of a thing, which is unsurprising. But the, the real takeaway is that like, where there are these places that seem to be inherently where people are ticklish. Of course, some people are more ticklish than others and you have your spots where you're particularly ticklish, but like, there are these places that are ticklish places.

• 16:39Rachel Feltman?

  So one thing that's interesting is that where these places are is not a one-to-one match for where we have like the most nerve sensitivity. If that was what dictated where we're ticklish, the palms of our hands would be very ticklish and they're not.

• 16:57Speaker 03

  Finger, do you have fingertips?

• 16:59Rachel Feltman?

  Exactly, yeah. Which would be very impractical, so that's how we touch people. So it's definitely not about just like pure sensitivity. It's also not about pure pleasure, because again, those erogenous zones only came up as, as being ticklish when we talked about like being tickled by a romantic partner. So it's very like, that's very context specific. So it's not about just like, we're ticklish in places where it feels good to be touched. It's not that we're ticklish in places that are inherently more sensitive. We're not ticklish in places where the skin is thinner, like I think it was Aristotle or Socrates thought that, but one of those dudes thought that. And that's not the case.

• 17:39Rachel Feltman?

  What, the one sort of like prevailing theory for why certain places are more ticklish, that this study seemed to support was that it's places that we are not touched as often just in the course of our day-to-day.

• 17:56Speaker 03

  Day-to-day.

• 17:56Rachel Feltman?

  Life. And that tracks with a lot of what Charles Darwin thought about tickling. It was about the element of surprise. So yeah, sort of, you know, if you think about like your ribs and your neck and, you know, under your arms.

• 18:10Speaker 03

  Feet, yeah.

• 18:10Rachel Feltman?

  Yeah, like those aren't places that in the course of day-to-day activity, many people are going to reach out and like give a wiggle their fingers on. We still don't know why tickling evolved. You know, like I said, there are these ideas about what it might do for us, you know, socially. And it's also, as is always the case with random behaviors, it's possible it's a holdover from something like that, that it doesn't serve a purpose. It's like just something that sort of happened by accident and that has been preserved because it doesn't hurt us.

• 18:45Speaker 03

  Sensory appendix kind of serves something like that, yeah.

• 18:48Rachel Feltman?

  I feel like there is probably some, you know, social benefit, because we know that it is something we use to social benefit, right? It's something we use to bond and play.

• 18:59Speaker 03

  Yeah, especially with like babies, you know, you think, you know, and I mean, what more like there, I don't, you know, evolutionarily, like there's no more important bond than like keeping your young, happy and close to you. So that, yeah, that, that part of it makes a ton of sense.

• 19:13Rachel Feltman?

  Yeah, and I do, I, I kind of, you know, again, this is just me having vibes, but I, I like the idea of it being, you know, sort of a, a way that we learn to protect our vulnerable spots, but in a way that's fun and playful and that allows us to like learn safe touch from people that we trust, right? That like it can, it can feel nice and be funny to be touched by people who care for you and who you care for, which is, you know, an important lesson to learn. Yeah, and so in, in looking at this research, I then also learned about Hector the tickle

• 19:56Rachel Feltman?

  robot, who as far as I know was not part of this most recent study. In fact, I'm sure he wasn't, because this most recent study was about surveying people about, you know, their experiences being tickled, how they feel about tickling. Hector the tickle robot is all about quantifying, quantifying the tickle. So he is, I believe, in a lab in the Netherlands. Because here's the problem, is that if you want to track exactly what happens in the moment when somebody is tickled, you know, how fast it happens, you need a standardized tickle. And so that's where Hector comes in.

• 20:30Speaker 03

  S T.

• 20:31Rachel Feltman?

  Yes. That's where he comes in. And basically it's like these, these electric motors that slide probes across the soles of the feet. And so they're able to be like, every tickle is exactly the same. We know at the exact moment at which the tickle commenced. I love, I love science, what a, what a life.

• 20:51Speaker 03

  What a life.

• 20:52Rachel Feltman?

  And also, I, I definitely don't recommend trying to find a picture of Hector the tickle robot. You'll find a lot of AI slop of, of people who are interested in the concept of a tickle robot for reasons that are their own business. But anywho, this guy, he's doing his job. There's nothing untoward. Everybody, everybody has consented to the foot tickling and it's being done scientifically. And the studies using Hector found that this response happened so quickly, within 300 milliseconds of a love science tickle onset, we see things. Yeah, T O. We see breathing changes, the circumference of the chest they were measuring, that, that changes within 300 milliseconds.

• 21:37Rachel Feltman?

  We see the facial expression of a genuine smile, you know, you know, the whole face smiling, those happen. And then within 500 milliseconds, people actually start laughing.

• 21:51Speaker 03

  So the wait, the robot was doing the tickling. I apologize if you said that already. The robot is doing, it's not, okay.

• 21:57Rachel Feltman?

  The robot is doing the tickling.

• 21:58Speaker 03

  Got it, got it, excuse me.

• 21:59Rachel Feltman?

  Yes, they are concurrently measuring all of these things.

• 22:02Speaker 03

  Got it, okay.

• 22:03Rachel Feltman?

  People are hooked up to many devices, including a tickle robot. And yeah, they also found that the, the physical parameters of ticklish laughter, so how fast, how loud, how high pitched, were directly and tightly correlated with subjective reports as to how tickled they were. So basically you laugh faster, louder and at a higher pitch when you're like, I'm so being tickled right now.

• 22:32Speaker 03

  Right, right.

• 22:34Rachel Feltman?

  One other really interesting thing I learned that I investigated, I had, I tried this morning for science was that, okay, so we know that you can't tickle yourself, except in very rare cases. So researchers looking at

• 22:53Rachel Feltman?

  how that works, found that if you are tickling yourself while someone else tries to tickle you, you feel less tickled.

• 23:06Rachel Feltman?

  Trying that today for, for science, for science as well. Because basically your brain is then getting the input that they should be cancel, the brain should be canceling out the tickle sense. Now, I am very ticklish and I don't like being tickled, which makes me sad. I, I, you know, not to get into too dark a place, but I had bad experiences with someone who did not respect my boundaries about tickling. And so now I'm, I have a very strong and adverse reaction to being tickled. So this morning I said to my husband, I said, Oliver, I need to try something for science. Thank you, Oliver. I tickled myself and I said, okay, do what you will. And it was genuinely more tolerable for me.

• 23:52Rachel Feltman?

  I then also was curious, I was like, I'm scared. The study definitely looked at whether, if you're already tickling yourself and then someone else starts tickling you, what happens? And I was like, I'm scared to see if you start to clue me and I tickle myself, will that help? But we did it. I was very brave. And I will say, I do think it, it also helped make the tickling less intense for me. So people, if you are also like really, really, really intense about being tickled, this is perhaps, you know, just like wiggle your fingers in your armpit. That might be enough to That might be enough to help. make things be okay. Yeah. So today I learned things I can use and that's cool. And yeah, in general, research does show that, I want to say that, that the study found that

• 24:36Rachel Feltman?

  like a quarter of people say that they like are really not into being tickled, which again, I can really sympathize with. And that seems to like

• 24:45Rachel Feltman?

  often be kind of a learned behavior because we do see that people are more likely to report that they overtly liked tickling when they were children than they do as adults. So people, even people who now say, I don't really like tickling, and this is not necessarily the people who say they hate being tickled, but people who are like, mm, it's not, you know, whatever. It's not for me. Yeah, it doesn't bring me joy. They, some of them will say, but it did when I was a kid. And so again, this maybe gets back to like, is there, you know, a social evolutionary purpose to it that is very specific to like learning and bonding while we're young. But then also I think, you know, there is this learned aversion because tickling was not the

• 25:28Rachel Feltman?

  positive experience that it can be, that it is, it seems physiologically designed to be. So I guess the big, the big takeaway is respect tickling boundaries, or you might be the jerk who ruins somebody's tickling experience forever. But also, you know, if you're, if you really dread being tickled, know that perhaps some, some self-touch to a ticklish zone could, yeah, could, could save you in the moment. And that Hector the tickling robot is out there doing his important work, which I really love. And I, I hope I, I hope I can meet him someday. But yeah, those are my, those are my tickling facts. I, what a journey it's been for me today. I actually broke up with somebody in high school for many reasons, but one of the top

• 26:13Rachel Feltman?

  one that I cited was he tickled me too much. And because I am also very ticklish and like, it's fun to a point, right? Like they're like that, those first couple of seconds. And then when it's like, okay, I'm having some trouble breathing, like it, you know, yeah. So we should, we, we share that a little bit. Yeah. I honestly, I would say that multiple times is like tickled me too much, tickled me too much. Yeah. Well, because it's, you know, it's like any other, any other boundary. If you're, Right. if you're enjoying that I'm not enjoying this, that's not That's a problem. That's not good. Yeah. It's funny. I, because I'm so ticklish and do not like being tickled, like to the extent that I sometimes will like react as if I'm being tickled when definitely that's not what's happening. Did you have any of that like response when you were researching this at all, like

• 26:57Rachel Feltman?

  psychosomatically? Like, because I've been itching a little bit during this whole segment. Like I've noticed like, oh, my feet are a little itchy or Well, I definitely, I, I read this book when I was getting ready to become a parent called Baby Ecology, which I do really recommend. It's, it's a great book in terms of like sort of getting you to just sort of stop and be like, what is going on in this little brain? And how might that be? How can I contribute to that experience in a positive way? And I remember at one point it was like, yeah, that's why it's not really recommended to like, to tickle kids extensively because they can't tell you when they're really not into it. And me feeling the way I do about tickling, I was like, ah, wow, confirmation that I should

• 27:39Rachel Feltman?

  never tickle a child. And now that I actually have a nine and a half month old, he loves being tickled in, you know, in reasonable, reasonable doses. Reasonable amounts. And I really, I was so, so cautious about it. And I really needed to like have several moments of being like, oh, no, this baby's having a really good time and I should probably facilitate that. So reading these studies also made me be like, mm, yes, what that book was talking about was tickling for like a long time while your kid's screaming. That's not good. But I, it, humans are so funny. We do weird stuff.

• 28:13Speaker 04

  We have a little rhyme in Tamil. It goes like

• 28:20Speaker 04

  You do that to little babies and it literally means, well, it sounds a bit scary if I translate it because it would mean opium is coming and, or something like, what's this thing? It's like, you know, it's tropical stuff that you would What I noticed when my babies were little, I know they're not that little anymore, but they don't react the first few weeks of there's simply no reaction. They don't smile. They don't feel ticklish. Then as they grow older, a few weeks old and a few months old, and then it gets really you know, by the time they're nine months old, they absolutely love it.

• 28:58Rachel Feltman?

  Yeah.

• 28:59Speaker 04

  It's a daily massage bath and a little bit of tickle time, you know, it sets your day.

• 29:05Rachel Feltman?

  Yeah. Absolutely. Yeah. And I love, again, like how universal it is. That's so cool. Yeah. Especially given that it seems to not be universal for most animals. It's a weird thing primates decided to start doing it at some point.

• 29:22Speaker 04

  There was a rhyme for it, you know, even

• 29:24Rachel Feltman?

  Yeah.

• 29:24Speaker 04

  That rhyme would make my son smile.

• 29:27Rachel Feltman?

  Yeah. Oh my gosh. Well, because I think, because so much of it is about the anticipation of it. And then the, you know, I think the, the anticipation coupled with like, you have no control over exactly when it's going to happen.

• 29:40Speaker 04

  That's a surprise.

• 29:41Rachel Feltman?

  Yeah. Yeah, exactly. Yeah. So yeah, I think then all of this, the sort of expectation of maybe being tickled becomes its own whole thing, which is so interesting. All right, we're going to take a quick break and then we'll be back with some more facts.

• 29:58Rachel Feltman?

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• 30:41Rachel Feltman?

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• 31:18Speaker 01

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• 32:21Rachel Feltman?

  Okay, we're back. And Laura, let's talk about some eye teeth.

• 32:27Speaker 03

  Eye teeth. So this was one of those fun facts that kind of rendered me completely speechless when I first heard it. And it's an example of like, why I really do love what I get to do here in talking to scientists every day and hearing all of the really cool things that they're working on. I was interviewing marine biologist Jada Elcock about her work tagging whale sharks. She is so cool. She will literally just swim right up to these giants. You know, we're talking 50 to 60 foot long fish and put this little tag on them. So I had to do, I had to do a story, just kind of learning more about how they do this, why they do this. And luckily, towards the end of the interview, she drops this bomb on me

• 33:10Speaker 03

  that whale sharks have teeth on their eyeballs. And like, I was having trouble forming words, which is not great when you work with words for a living. So it was really good that she didn't start the interview with that. Otherwise, like, I don't think we would have gotten to the tagging. It just would have been like, tell me everything you've ever read about these eyeball teeth. Um, you know, we were talking about like, what does that even feel like? Like, does it, does it feel like you're closing your eyelid over like a shard of glass all the time? Like, what's, what's going on here? We don't know, obviously, because the whale sharks can't talk to us, but they really do have teeth on their eyeballs. Um, which is just, again, completely fascinating. And I don't know, maybe that won't stop everybody

• 33:52Speaker 03

  in their tracks. Maybe I'm just weird, but it's, it completely derailed in the end of an interview for me a couple of weeks ago. Um, yeah, before we get in too much, just some background on these animals, they're honestly one of my favorites. They are sharks, not whales. So fish, not mammals. And they are the biggest known fish in the world. Their maximum, their complete maximum isn't well known, but they can grow again as large as 60 feet and weigh about 11 tons. They're mostly found across the Atlantic, Pacific, and Indian oceans in the tropics, but they can be come as far north as like the waters off of New York and New England. That's actually where she was tagging the whale shark in the video that I saw. But yeah, the tropics are kind of mostly, you know, around Florida,

• 34:36Speaker 03

  the Philippines, that's really where they're spotted the most. They are filter feeders, so they don't have like the giant jagged teeth, like a great, like a, like a white shark or a tiger shark. And they mostly feed on plankton with those filters. So that, and that way they're kind of like a baleen whale. And they can live upwards of 50 years. So they got, they have a nice little decent lifespan. And their teeth, their eyeball teeth, actually, these are called dermal denticles. And they're basically tiny teeth that cover the, the eyes themselves. A team in Japan first detailed them in a study that was published in 2020 in the journal Plus One. Um, and dermal denticles themselves aren't just exclusive to the eyes. Obviously, you see the word derm in there, which indicates skin. And

• 35:21Speaker 03

  they are found on several shark species, shark species and cover their bodies kind of along with the scales. They're small, V shaped, and they sort of, they help decrease drag and turbulence as they swim, helping them move faster, and also giving a little bit of, a little bit of defense against other sharks and critters that might want to, you know, take a, take a little bite out of them. When it, now, when it comes to the whale sharks eyeballs, they're, as of now, I believe, the only known shark species that has the, that have these, I'm sure they're probably, it probably could be on some others, but we're not sure yet. They help shield their eyes from the elements. So sun, maybe bits of debris that can get in the water, because they don't have eyelids. So that thought that

• 36:05Speaker 03

  I had of like, oh, man, does it feel like they're, you know, closing their eye on a nail? Probably not the case. That was more, that would be, that's more a Laura thing. Because they don't have eyelids. And their eyes are also positioned on either sides of their head, either sides of their heads. And so they're kind of vulnerable if they can't see something coming, or if it's like, not quite in their field of view. And it protects, again, also from other animals. And their eyes are actually kind of small compared to the size of their body. You know, you'd think like, a giant squid that has, you know, eyes that are the size of like, a giant plate. These giant fish surprisingly have pretty small eyes. So for this study, they looked at the eyes of both living whale sharks and

• 36:48Speaker 03

  some dead whale sharks that had washed up on shore, died of natural causes. And they found that a single whale shark could have over 3,000 dermal denticles around their eyes alone. Yeah. And all of them are kind of clustered around the shark's iris. They said that they kind of looked like oak leaves. So not, not so much triangular, like the ones that are on skin. And some actually kind of resembled human molars, which makes it even more interesting as far as like this teeth and eyeball connection. And it, yeah, it just kind of made sense that there would be some sort of like a tooth shape in there somewhere. And so while they don't have eyelids, they can partially retract their eyes into their skulls. And again, that's where this eye teeth and that retraction

• 37:33Speaker 03

  might be helpful in shielding their eyes from, you know, just from elements. And it could also indicate something interesting about the whale sharks' evolution and survival. Um, as we kind of know, sharks in general are not known for their eyesight. They're not like eagles, they're not like other animals that can really see things. Well, they rely more on their sense of smell. You know, a lot of bites on humans are kind of chopped up to mistaken identity with a shark thinking that they're going after a seal because of the way like, a bodyboard or a surfboard might be shaped. They are really mostly using smell to kind of navigate. And the same likely goes for whale sharks. Scientists assumed that whale sharks were kind of in that same camp, where they mostly

• 38:18Speaker 03

  used smell and other senses, because they have such relatively small eyes compared to the rest of their bodies. But here's the thing. Why have all of that protection, these eye teeth and this ability to sort of partially retract your eye into your body, if eyesight isn't as important as it is to say, a white shark? So it's possible that they evolved the, these denticles because vision is more important to their survival than it is with other sharks. So it's just kind of like this, it's this weird, like, evolutionary math problem, sort of. It's like, okay, if this one, if this is important, I have to evolve this, but it might not be here. Like, it's just kind of one of those,

• 39:03Speaker 03

  you know, odd little quirks of evolution that these giant fish have, might, just might stand out, just because their eyesight might be better than so many of the other shark species that are swimming in the ocean, which is very cool. Yeah. And then, yeah, like, they also, the fact that they're filter feeders, they're just, they're really just a very interesting fish, even when you, even when you take the eyeballs out of the equation, they're like, they're absolutely fascinating. Like the, the spots, the patterns that they have, like, I love them. Now, I like to end my segments with a question, because it's, you know, the other very fun part of my job is I get to ask questions all day. Um, if you could be any shark species for a day, which one would you be and why? I'll give you a minute.

• 39:47Rachel Feltman?

  Um, that's a great question. I definitely have done, I have, I have made some content in the past about deep sea sharks and how weird looking they are. So many of them look like they belong in, like, a stop motion Timber movie.

• 40:04Speaker 03

  Yes, yeah.

• 40:05Rachel Feltman?

  So those are cool. But I think if I was gonna be one, I don't, which shark is the one that's just like, ah, like the mouth is just open?

• 40:16Speaker 03

  The basking sharks?

• 40:17Rachel Feltman?

  Uh, maybe. Let me think.

• 40:18Speaker 03

  Look it up. Yeah, yeah.

• 40:19Rachel Feltman?

  Oh, that one also has a big wide open mouth. It is not the one I was thinking of. That one's scary looking.

• 40:26Speaker 03

  The hammerhead sharks, because that's my answer to you. Well, that's, oh, oh, I, I interviewed Anthony Mackie from the most well known from the Marvel movies. He did a great shark documentary a few years ago, and I asked him this question, and that was his answer, too.

• 40:39Speaker 04

  I love him. I just love him.

• 40:41Speaker 03

  They're so cool. They're so cool looking. And the way that they move, yeah.

• 40:45Speaker 04

  I have planned so many of them for my kids, because I just have to look at them.

• 40:48Speaker 03

  Yeah, yeah. Yeah, we had, um, a researcher on talking about hammerhead sharks. I'll have to link to that episode in our, in our article for this one. Just incredible. I think, okay, I think the one I'm thinking of is the megamouth shark, which is perhaps actually is as freaky looking as the basking shark. And I just had never seen a picture of it head on. But anyway, I just really like the idea of a filter feeding shark that just kind of is going around always kind of like, always looking like it's about to eat a Scooby Doo sandwich, you know? There you go. Yeah.

• 41:30Rachel Feltman?

  It just seems very, they seem really calm.

• 41:33Speaker 03

  Yeah.

• 41:34Rachel Feltman?

  Um, but if I wanted to really scare someone, it would be the frilled shark, because those look frightening, freaky little guys.

• 41:42Speaker 03

  It's, it's, I mean, I would say whale shark even beyond doing this story, but and it also is cliche, but being a white shark would be cool, just because you have your own theme music. I mean, you've got like a great theme written for you as you're swimming to like, to the point where one of my nieces now, whenever she sees something with a shark on it, will say, ba-dum, because I do that all the time when I see a shark around her. Like, I don't know, I think that, I think that that would be fun. But yeah, my answer would definitely be whale shark. And that's, that was even before I knew about the eyeball teeth.

• 42:12Rachel Feltman?

  Also, I just looked up a picture of a whale shark and realized that's the shark I was thinking of. I was thinking of, I had, I had nurse sharks in my head as we were talking about whale sharks. But no, a whale shark, because yeah, they have, I, I love their little mouths. They're funny looking.

• 42:28Speaker 03

  Their mouth. They are. They are. They're so cool.

• 42:30Rachel Feltman?

  Great. Now I have the right name for the shark I want to be in my head. So thank you for that. All right, we're gonna take one more break, and then we will back with some more facts.

• 42:46Speaker 01

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• 44:20Rachel Feltman?

  Okay, we're back and let's talk about some spices and how they work in the brain. Why do they make our brains buzz? Please tell me more.

• 44:28Speaker 03

  Let's spice up our lives, shall we?

• 44:30Speaker 04

  Let's do that. And chilies and prickly ash are fascinating precisely for these reasons because they produce very, very different neurological sensations. So chili primarily activates our heat and pain sensing systems while prickly ash produces a very different sensory experience. There is, there is tingling, there is buzzing, there is vibration, and then eventually numbness too for many people. And one of the interesting things about my book Spiced is that I look at several prickly ash varieties, all the way from West Africa via Goa, then Nepal, China, Japan and Korea.

• 45:13Speaker 04

  And you know, Sichuan pepper is one culinary expression of a much larger botanical and cultural diversity. So I would just prefer to call them prickly ash and not just Sichuan peppers. And I hope that's okay.

• 45:27Rachel Feltman?

  Oh, it's definitely okay by us and I'm excited to learn more. I love Sichuan pepper and I want to hear about everything else related.

• 45:36Speaker 04

  So let's go through prickly ash first and then I'll jump onto chilies. And then let's consider what happens when we put them together in our mouth, say in a plate of maputofu, yeah? So most people know prickly ash as Sichuan pepper, as we just talked, and they probably tasted it in a Chinese restaurant serving Sichuanese fare. A plate of maputofu has probably become the most iconic dish using this spice. And the place itself lending its name to the spice now, right? It's Sichuan peppers. But well, it's made from, you know, the dried outer covering or botanically speaking, the berry carp of the fruits of several Xanthus island species. And this biodiversity of prickly ash, it's, it's truly spectacular.

• 46:20Speaker 04

  It, it belongs to the citrus family, like

• 46:23Speaker 03

  Wow.

• 46:24Speaker 04

  and lemons and oranges and mandarins, which probably explains its very citrusy aroma.

• 46:30Rachel Feltman?

  Yeah.

• 46:31Speaker 04

  Right?

• 46:31Rachel Feltman?

  Yeah.

• 46:32Speaker 04

  So, okay, let me tell you the first time I tasted it, right? I tasted prickly ash in Goa in India, where fresh cuttings of these small clustered green fruits were being sold by tribal women on the roadside. And so we stopped by the car and, and I bought a few bundles and the lady's called it tepal, which I had certainly heard of, but I had not tasted at that time. And so curious, I plucked one berry and I popped it in my mouth and the experience was mind blowing. Literally, I could feel the citrus in my head, my nose, my mouth and thronging as

• 47:12Speaker 04

  if there was a fine spray of very potent citrus extract and it had exploded inside my head. There was like this warm, numbing sensation. I remember that so vividly because it crept up so slowly and it spread along my tongue. And this is freshly plucked berries, mind you. So they're still green, they're tender, and it's a whole other experience to the dried berries that you may have used for cooking, which is what we get to buy in supermarkets and spice purveyors, because these spices don't grow everywhere really, right? And that's just a fraction of this insane potency. So you can just imagine, go imagine that.

• 47:52Speaker 04

  Actually, Rachel, when you were talking about 50 hertz, I, I remembered a study I had read a couple of years ago, and it was by researchers led by Nobuhiro Hagura and Patrick Haggard at the Institute of Cognitive Neuroscience at the University College in London. And they measured the tingling sensation caused by Sichuan peppers to be perceived at approximately 50 hertz in a study that they did in 2013.

• 48:22Speaker 03

  Wow.

• 48:22Rachel Feltman?

  Wow.

• 48:23Speaker 04

  It's so interesting. And, and that distinctive sensation actually comes from a large group of compounds called sanshuls, particularly one called hydroxy alpha sanshul. So instead of producing this straightforward burning sensation of chilies, what sanshul does is it, it goes in a series. It starts with this tingle, which moves on to become a buzz. And then it, you start feeling things vibrating and then there's a numbing sensation. So there's a curious trick to this.

• 48:58Speaker 03

  Yeah.

• 48:58Speaker 04

  And I think it's because our, our sensory neurons are constantly regulating their electrical activity at a cellular level, right? And there is potassium channels that are part of this large control system. And by allowing this potassium to move out of the cell, they help keep this neuron from becoming electrically stimulated and excited very easily. So sanshul does is it comes in and it interferes with some of these potassium channels. And particularly one that scientists have called as Tresk or T R E S K.

• 49:39Speaker 04

  What Tresk does is it changes a neuron's electrical balance, making it easier for the sensory neuron to become active. And so the neuron becomes very excited. So, but here's the extraordinary part. Sanshul can activate some sensory neurons, a bit like the tickling that normally help us and they tell us that something is touching or moving across our skin. And then these neurons start firing in small bursts when you eat a, a small pepper berry, yeah? And your brain receives this very strange pattern of activity. And then it begins to interpret this as, oh, it's tingling, oh, it's buzzing, and then there's a vibration.

• 50:23Speaker 04

  And this happens not if you just place it in your tongue, you have to chew it.

• 50:28Speaker 03

  To like activate to kind of

• 50:29Speaker 04

  Activate it, exactly. And that releases this, this whole thing because what you, yeah, you know, it's the, it's the oil glands that rupture. So when you, when you eat Sichuan peppers, your tongue isn't actually or literally vibrating. It's that sensation. Your neurons are sending your brain a pattern of electrical signals that your brain experiences as vibration really. And I think what happens is when you contribute, you know, when you keep digging into your maputofu, for example, that is, let me put it scientifically, this continued stimulation. That pain sensing machinery in those neurons, they become less responsive temporarily.

• 51:12Speaker 04

  Essentially, they start turning down their signaling after being so excited for a while. So that's also another interesting thing that happens on your tongue. There are so many studies that show that when the sensory neurons on the tongue are activated, it triggers this rush of saliva.

• 51:33Speaker 04

  And that begins to shift how we register taste that follow.

• 51:38Rachel Feltman?

  Oh.

• 51:40Speaker 04

  Heightening them even.

• 51:41Rachel Feltman?

  Yeah.

• 51:42Speaker 04

  So, you know, food begins to taste delicious because

• 51:45Rachel Feltman?

  Yeah.

• 51:46Speaker 04

  suddenly all those taste buds are more open, more receptive. And so go ahead, spice your food with some prickly ash and will taste delicious. This probably explains, you know, the use of Chinese spice salts like jiao yan. Cantonese seasoning blend, which literally means pepper, salt. Xiao meaning three peppers in the blend, there's Sichuan pepper, there's white pepper and classic black pepper. But then there is yan, that means salt, and the peppers are mixed with salt and blended. And they're used in a lot of Cantonese style wok, wok fried dishes. Pork chops, they could be squid, tofu, shrimp. But it's a classic seasoning and it's really, really quick and delicious. There's nothing much to it, really.

• 52:32Rachel Feltman?

  Yeah, I have a jar of that that I use all the time. It, it is a great, easy hack to just make most food taste even better.

• 52:41Speaker 04

  Exactly, there you go. It's such a classic and simple thing that you can easily make at home, actually. So there is a recipe for that in the book as well, just as spice also showcases so many flavors of prickly ash, so you know this wide arc that I just talked about. And explains how you can cook with it so that you can enjoy these berries at peak flavor. So, you know, there was, when I had to test for the book and I sourced so many different varieties of prickly ash. Traveled and therefore bought many, also heard of it from friends and then they got me many samples from different parts of the world. There was something extraordinary that I experienced when I cooked with these different types of, of prickly ash berries. Let me tell you what happened.

• 53:26Speaker 04

  So when you crush them between your fingers, they're raised oil glands rupture. You know, and they, and this is, you know, you can try them in your kitchen with dried store bought Sichuan peppers, fresh, good quality. You know, prickly ash berries. The, the, the fruits release a very heady citrusy scent. And they're all different depending on which ones you're trying. So Sichuan pepper, which is sparkles like, I think like calamansi.

• 53:58Speaker 04

  Timor and tingay, which grow in the, uh, the sub Himalayan ranges and that region. They have a more, um, honeyed bergamo kind of smell. And tepal, the one that I first tasted from Goa, remember that's by the coast, so there's not much of an altitude there. It's bitter and brisk, more like grapefruit, actually. Very heavy and, you know, strong. While Japanese Sancho, um, can smell, um, sun warmed, orange peel, bit of resin and maybe even a bit of spice like yuzu. So very, very different citrus smells from different varieties of prickly ash.

• 54:42Speaker 04

  And all of this also then depending on whether they are fresh or dried, right?

• 54:47Rachel Feltman?

  Yeah, right.

• 54:47Speaker 04

  Not just the smell, it's also on the tongue. There is an initial bitterness that I could experience when I tasted them just on their own. But then as you begin to chew on them, there is that numbness, there is that tenderness.

• 55:01Speaker 03

  That just comes in.

• 55:03Speaker 04

  It comes in, but the buzz varies. And this is my experience and I would love to hear if at all any of you tasted, what, what your sensations were. Indonesian and Dali man is quick and very prickling. The tepal from Nepal was more woodsy and the buzz creeps in slowly, maybe because there's more to chew, you know?

• 55:27Rachel Feltman?

  Yeah.

• 55:27Speaker 04

  But wajao, which is Sichuan pepper cones, they linger, but they linger on the lip.

• 55:33Rachel Feltman?

  Right, yeah.

• 55:35Speaker 04

  So there are these different zones they were activating, which I thought was very fascinating.

• 55:40Speaker 03

  I find the ones that, when it lasts on the lips, that's the har- I personally, that's always the one that's the, the, the most difficult. I guess that's maybe more sensitive, maybe there are more nerve endings. But that's the one that always like, you know, if I don't like a spice, it's usually because of like that, that little lip linger.

• 55:59Speaker 04

  Yeah, and then I learned that altitude, soil and climate affects what is known as the alchymite levels in these fruits. So why I believe these taste so different? And, and I think from all these experiments in my home kitchen and in my studio kitchen, I think what we've learned is that high quality prickly ash should have a balance of low bitterness. But a very high citrus nose, which means the oil glands are really fresh and rich in oils. And then there is the tingling numbness. So that's something that you can, you can look for, a very sensory experience when you buy,

• 56:40Speaker 04

  you know, these prickly ash spices in your, in your grocery. You can look, look, you can look at these for quality. And now let's move on to chilies, which was the other spice we were considering. And with chilies, capsaicin is the molecule that makes chili feel hot.

• 56:57Rachel Feltman?

  Right.

• 56:58Speaker 04

  But it doesn't actually make your mouth hotter. What it does is it activates a heat sensing protein called trip V one, which you were to spell it, it would be T R P V one. We just call it trip V one on your sensory nerves. Your nerves normally use trip V to detect dangerous heat.

• 57:20Rachel Feltman?

  Right.

• 57:21Speaker 04

  And so when capsaicin switches it on, your brain receives this message, that's hot. Even though there isn't actually a rise in temperature. Whereas capsaicin finds trip V one on our pain sensing nerve endings. And it's, it's, you know, trip V one is basically an ion channel. Think of it as a, as a doorway, a tiny, tiny molecular doorway in the cell membrane of a nerve. So when capsaicin opens this door, all the positively charged sodium and calcium ions can rush into the cell. And that makes the neuron's electrical charge less negative because we're positively charged.

• 58:02Speaker 04

  And this process is what neuroscientists call as depolarization, sort of like a canceling of charges in a way. And if it reaches the right threshold in this exchange, the neuron fires an electrical impulse, which then travels towards the brain. And then the brain interprets that activity as burning heat.

• 58:24Speaker 03

  Got it.

• 58:25Speaker 04

  Except that there isn't any fire. Um, and, and chili has simply hijacked one of our body's detection systems in a way. So your nervous system is being persuaded to believe that it's getting hotter. And scientifically speaking, it has sort of changed the electrical state of your new sensory neuron. Or something like that. Crazy to think about it, that it's

• 58:50Speaker 03

  I know.

• 58:51Speaker 04

  So discreet and it happens and you experience it all the time.

• 58:55Rachel Feltman?

  Yeah, yeah.

• 58:56Speaker 04

  I see food, there's so much that your body is coping with and, and talking to itself in its own way. But I think there's one more curious question, which is not about the buzz or the heat, which is more about why does eating more chili eventually make the burning more bearable? You know, it's, it's intriguing, isn't it? This is, I think to me, this is actually the more interesting part of the chili story because you might expect that the more capsaicin you eat, the more your nervous system would scream, stop it.

• 59:27Speaker 03

  Right, right.

• 59:28Speaker 04

  Happening, chili has this built in paradox in a way that the molecules that initially make this pain sensing neurons fire. And with continued exposure, eat more and more, basically, make that same neuron less responsive. So you keep activating those trip V one neuron channels. And you're pouring all this calcium into this nerve cell. And it sets off a whole series of, you know, chemical messages that's saying enough already.

• 59:58Rachel Feltman?

  I'm done, I'm done.

• 59:59Speaker 04

  Yeah, and there's, that's one reason that the first bite of a very hot chili can feel absolutely ferocious if I may put that there. But while several bites later, you may find yourself thinking, yeah, you know what, actually I can handle this.

• 1:00:14Speaker 03

  Yeah.

• 1:00:15Speaker 04

  And that makes me think, you know, when you watch all these shows, if people come to eat super spicy chilies.

• 1:00:20Rachel Feltman?

  I was like, hot, that's how people get to hot ones.

• 1:00:23Speaker 04

  There's a sport around that and then there's a sport around watching all of that stuff. I wonder if they actually eat some super hot chilies, kind of just condition their mouth.

• 1:00:33Speaker 03

  Yeah.

• 1:00:34Speaker 04

  You know, because there is something about how convenient and how easy they make it look. I'm sure there's a lot of pain, the pain bearing going on, but there could be something behind that. There's a green room chili eating spirit.

• 1:00:49Speaker 03

  Or like, is there, is there like a doping scandal, like you, you use the wrong types of chilies to prepare for this? They were super, super intense and you weren't allowed or something like that.

• 1:01:00Speaker 04

  Exactly, yeah, so well, this is just my hypothesis, I could be.

• 1:01:07Speaker 04

  I have been invited, I have not been invited to eat any chilies in any contest and I don't think I'm, I'm a contender for that at all. No, but your nerves haven't necessarily become tougher just because you're eating that. And so I think there is a distinction, right? There is like, when you say that the nerve gets used to chili, it sounds more like a sort of psychological tolerance that you're building up. But versus putting it this way, as the sensory machinery becomes temporarily less responsive, which is, which is actually the neurophysiology that's going on in your brain.

• 1:01:44Rachel Feltman?

  Okay.

• 1:01:44Speaker 04

  Yeah. The, here's the thing about chilies, they come in a very wide range of capsaicin content. So you have very mild chilies, or you even have bell peppers which have zero capsaicin, moving all the way up the scale to ghost peppers and, you know, things that have way more heat than that. And, you know, midpoint maybe can, which is super common in, in most people's kids. It's the standard stuff, moderate heat. And, you know, you also have the more popular hot varieties, like there's the habanero and the scotch bonnets that you may encounter in a hot sauce. But then the extreme heat ones were the ones that we just talked about, being the sport almost, right?

• 1:02:24Rachel Feltman?

  Right.

• 1:02:24Speaker 04

  So in spiced, there is a chapter on chili, so every spice is a chapter. The chapter on chilies is arranged in the increasing order of their heat. So you start with traditional recipes with, say, Hungarian paprika, which by the way was a chili developed to have no heat at all, all the way to, the chapter goes on to touching about Naga ghost peppers and traditional dishes cooked with that. So this wonderful spectrum of recipes to cook with there. If I can just plumb in back into the paprika, maybe you want to use it later on. Paprika is so uniquely Hungarian.

• 1:03:05Speaker 04

  It arrived in Hungary in the mid 16th century with the Ottoman occupation. For a very long time, it was little more than a, you know, botanical curiosity. The sweet peppers we know today grow across Hungary, but paprika, the spice, right? Becomes particularly associated with two places in southern Hungary, Szeget and Kaloxa, which are on the flat fertile plains between the Danube and the Caesar rivers. And we know that from, from, you know, historical records, we know that there's been intensive breeding work in this region. Together with what I find very fascinating is the first research institute for chili peppers.

• 1:03:50Rachel Feltman?

  Wow.

• 1:03:51Speaker 04

  Yeah, the Pepper Research Institute of Kaloxa was already founded in 1917, over a hundred years ago. So it's this ecosystem of having a scientific approach, but also farmers really invested in the idea, um, trying to understand the breeding of chili plants and, and how to create hybrid chili varieties for different heat needs or fruit needs. I think it's this ecosystem that they had that really helped develop very sweet varieties of Hungarian paprika that became so characteristic of this region. The urban legend, or the legend goes that there was a farmer who found one pepper that was not hot at all and then used to then, you know, develop the variety. But I believe-

• 1:04:36Rachel Feltman?

  Europe is gonna love this.

• 1:04:39Speaker 04

  But, you know, by the late 19th century, we do have a lot of writing where we can see that farmers around this region had begun using mechanized tools in the production of paprika. So they had small machines. It was not no more a hand done activity, by shredding the peppers, removing the seeds and grinding them, and then, you know, adding the seeds back and then grinding them again to create this really vivid red powder. So there was already machines to do this and today it's a proper industry, right? But here's the fun fact, a very big international debut moment came only when Auguste Scopia, the legendary French chef, put paprika from Szeget into his goulash at Monte Carlo.

• 1:05:23Rachel Feltman?

  Wow, that's what did it.

• 1:05:25Speaker 04

  That's what did it. And suddenly this intensely colored spice, very mellow, had a new international audience. I think that's, paprika is just such a marvel, right? You can use it in-

• 1:05:38Rachel Feltman?

  Everything.

• 1:05:38Speaker 04

  -and it just brings the dish alive. There is a cooking trick though. When you add paprika, and this is what Hungarian grandmas have told me, when the oil is hot and everything is ready, you have to pull the pan, the braising pan away from the heat and then add all that paprika you need to add. Let's say you're making a paprikage, then put in the paprika. So the paprika is sizzling in the warm oil, but it's not burning. It kind of just lets go of all that color into the oil. So you've colored the oil and the oil then colors everything else that you add to it. You know, it could be your peppers, there's, just everything about that dish is so red, but it's that oil and careful handling of paprika that is so important there.

• 1:06:23Speaker 04

  But anyway, you know, when someone says paprika, there isn't just one flavor behind that word. There's just a variety there, right? There is, there is the, the very mild ones, which are called edis, literally meaning sweet. And then they progressively go, I think, seven or 11 varieties, including eros, which is the hottest variety. So remember the trip we won, the molecular doorway that capsaicin opens, making a pain sensing of fire? You remember Tresk, you know, we talked about it with prickly ash, this potassium channel that sanshu inhibits. What happens when you eat these two things together? You eat chilies and prickly ash together? What happens? Have you ever thought about it?

• 1:07:07Speaker 04

  I mean, to me, I think that's neurologically extraordinary as a situation.

• 1:07:12Rachel Feltman?

  Yeah. On paper, that's what it, yeah, that, it would be kind of just like a, kind of- Yeah. Explosive, maybe. That's what mala is, right?

• 1:07:21Speaker 04

  Yeah, exactly.

• 1:07:22Rachel Feltman?

  But, but I don't, but what's going on in the brain? Right. Very complicated.

• 1:07:28Speaker 04

  Because these two sensations, they arrive simultaneously and through very different sensory pathways to your brain. The important thing is that chili and prickly ash are not simply adding two kinds of spiciness. They stimulate different sensory mechanisms at the same time. The chili is burning you and the prickly ash is making your sensory system buzz and your brain experiences these two together. So it's not just hotter, it's neurologically busier.

• 1:07:59Rachel Feltman?

  Hmm. So it's like, hot, right, hot and there's a lot going on. It's, it's like, you know, if you're tasting wine, it's like, it's a more complex bouquet or something like that.

• 1:08:09Speaker 04

  So what I find fascinating, and I highlight this through numerous recipes in the book, is this gorgeous interplay of chilies and prickly ash, which is celebrated by so many cultures across the world. You know, the most famous is the Chinese word for this sensory flush, if I may, the mala experience that you just said, ma meaning numbing and tingling and la meaning hot and spicy. But you see it repeat over and over again. It's a motif, it's a spice motif that comes again and again in a go and gassi stew or sprinkled on top of a Bhutanese cucumber and salty cheese salad. It's called go and ho gay.

• 1:08:52Speaker 04

  Or you should try this superbly spiced Nepali condiment called timurko chop. And several Sichuanese classics, of course, including some recipes for crispy chili oil that include both. Then you have the Indonesian sambal tuk tuk, which is a batak classic. And even all the way in Japan, a classic shichimi togarashi would have that, both of them powdered into this seven spice blend. So, you know, it's, it's really fascinating how so many different cultures have clicked upon the same combination.

• 1:09:27Rachel Feltman?

  Yeah, like tickling.

• 1:09:28Speaker 04

  Yeah, the tickling and the heat. And the heat is, the, I think it's, it, this is the beauty of traveling the world and looking at people and learning from traditions. You see that there's not one kind of chili.

• 1:09:41Rachel Feltman?

  Right.

• 1:09:41Speaker 04

  Right?

• 1:09:42Rachel Feltman?

  Right, there you go.

• 1:09:43Speaker 04

  They use the facing heaven chilies, which is chautian jau, which is mild. While in Indonesia, it's chaberabit, it's pretty sharp.

• 1:09:51Rachel Feltman?

  Yeah.

• 1:09:52Speaker 04

  Right? So there's different kinds of heat that you can pair with this buzz sensation. So I think everything is game, you can experiment, there is no rules here, combine whatever you want, but I think experience this, this thrill, which is very, very fascinating.

• 1:10:08Rachel Feltman?

  Yeah, it's so fascinating. And also like, you know, as, as someone who loves, you know, this combo and this sensation in Sichuan food, I really, like, now that you're saying it, I've definitely experienced it in other cuisines, but didn't really register that, you know, this was prickly ash and spice. And now I'm very excited to like, you know, dive into more versions of this and explore. And also buy too many kinds of prickly ash peppercorns and berries.

• 1:10:43Speaker 04

  That's the funny thing, I love doing that, you know, just having varieties and then playing with it. I think that's the best part of working with ingredients.

• 1:10:52Rachel Feltman?

  Yeah, absolutely. Well, thank you so much for, for coming on. This has been so fun and I'm really excited to, to check out your book and to start cooking some, some recipes from it. Thank you so much for joining us.

• 1:11:07Speaker 04

  Thank you so much, Rachel and Laura, for having me.

• 1:11:10Rachel Feltman?

  The weirdest thing I learned this week is produced by all of our hosts, including me, Rachel Feltman, along with Jess Bodie, who also serves as our audio engineer and editor extraordinaire. Our theme music is by Billy Cadden. Our logo is by Katie Belloff. If you have questions, suggestions, or weird stories to share, tweet us at weirdest underscore thing. Thanks for listening, weirdos.

• 1:11:43Speaker 06

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