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

0:00For yourself from big wireless and all their gimmicks and gotchas, and switch to Mint for high-speed data and coverage on the T-Mobile 5G network. To get your new wireless plan for just $15 a month, go to MintMobile.com slash weirdest. That's MintMobile.com slash weirdest. Cut your wireless bill to $15 a month at MintMobile.com slash weirdest. That's it, there's no catch. Up front payment of $45 for three months, $90 for six months, or $180 for 12 months plan required, $15 per month equivalent, taxes and fees extra, initial plan term only. Greater than 50 gigabytes may slow when network is busy. Includes up to 20 gigabyte hotspot capable device required, availability speed and coverage varies. See MintMobile.com. What if doctors could detect Alzheimer's before symptoms appear or treat cancer with unprecedented precision? On the new season of tomorrow's cure, the chart topping and 2025 AmbioWord finalist podcast from Mayo Clinic,

1:01we explore how breakthroughs like these are already reshaping the future of healthcare. I'm Lindsay Seever, the new host of Tomorrow's Cure, and this season I'm joined by leading physicians, researchers, and Mayo Clinic experts exploring everything from AI-powered diagnostics to precision cancer treatments. Follow Tomorrow's Cure wherever you get your podcasts. 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. I'm Laura Bysis, and I'm Priya Money. Priya, welcome to the show. It's so great to have you. Welcome. Thank you so much, Rachel and Laura. So would you tell our listeners who you are? So I'm the author of Spice, Recipes Celebrating Spices from Around the World,

2:04which is published by Fight and 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 Apatite's studio, quite aptly, works on food and flavor projects around the world. And we do a broad arc of projects, FNB 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. Very cool. Well, we love food science and we love food history and we love spices. So we are very excited to have you with us today. Thank you. So let's jump right into it. On the weirdest thing I learned this week, we started by each offering up a little tease about some kind of factor story we found in the course of reading, writing, reporting, cooking, etc. And aside from which one we just absolutely have to hear more about first. Then once we've all had time to spin our little

3:06science yarns, we reconvene and decide what the weirdest thing we learned this week actually was, except there's no winner. We just kind of had about it. That's fine. Laura, what's your tease today? Well sharks have teeth on their eyeballs. Oh, yeah, eyeball teeth. Wow. Yep. Great, great. And Priya, what's your tease? Well, chili buns and prickly ash buzzes, but it's your brain. That's the one creating both sensations. Oh, I can't wait to hear more about this. These are these are spices I enjoy learning about. Everything and trusting. My tease, hard to pick a tease for this one, but I am going to say, scientists did engineer a tickle robot. So I think maybe I might I might jump in first today with this tickle bot. So yeah,

4:08there's a lot to this story, but we're going to we're going to talk about tickling because 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. 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 misces, spelled with a silent K, which is misces. Nisces. Nisces. Nisces. Okay. Yeah. And so that is very common, you know, perhaps even universal among animals. That's when like a light brushing sensation occurs because something has stimulated your skin by moving slowly across it.

5:14It doesn't make you laugh. 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 of this is this misces, the moving it should 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 that? But of course, that's not what most humans think of when they hear the word tickling. And the laughter provoking tickle is known scientifically

6:22as gargolysis. I just because of the throat. Maybe gargolysis. I really should have looked up, you know I mean, quick get a ball just because that's one thing I really should have done that I did not gargolysis. Gargolysis unrelated words come from the Greek gargolose, which is itching. Okay, so yeah, not the throat. Not the throat. 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 itch-etiquely 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. There is also

7:30some research showing that rats might also be ticklish in this way. They certainly have a very similar response to their bellies getting tickled, so by folks in the lab, they create 50 kilohertz 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 the laughter. So we don't know for sure that that's actually sort of a, you know, from the same evolutionary route. Because again, it seems very rare even among mammals, but we know that primates and humans, this is a weird thing that we do. Another specific thing about tickling that makes it distinct from other kinds of touch. And this is true for both 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 not expected. Yeah.

8:41The surprise is there. Exactly. And that is why you can't tickle yourself 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 schizo type spectrum. So, you know, people with schizophrenia or, you know, other type of schizo effect 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 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

9:45ton of research on, but it does sort of make sense when you think about it that 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. 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. Yeah. And so, that we know that, you know, typically when somebody attempts to tickle themselves, 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 armpit. You know, 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.

10:47It's like an alarm system. But then why do we have this added kind of tickling that makes us burst out laughing and not just the one that makes us go like, what was that? This is much more of a mystery. And it's one that people who muse about for a long time, Socrates thought about it. Not kidding. 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, including primates,

11:53have 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 and learn how to learn how to protect them. You know, it's like basically that we have this sort of positive but oh, don't touch me. Their response that is, you know, maybe a very specific sort of like learning ground 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. It's relative to, you know, having thoughts about things and sharing them with us. They, you know,

12:56react to being tickled and they laugh, not immediately, but that starts like pretty early. And so some theories hold that this is purely like a preverbal bonding activity that this is about like. That makes sense. Yeah. A playful, a playful thing that happens when we touch each other. Yeah, like you are not a threat. You are part of my group. You are. Yeah. 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 friends. And all of this is preamble for this new research that just came out 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 goal that they,

13:59they wanted to like look at a good swath 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. And so what are the commonalities going to be here? Trinot 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 it 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 you could ask 448 people about that 98% of them would be like, yeah, that's happened to me other than right things to live. So eating, breathing, food, bathroom. Yeah. Yeah. And they also found that the reactions unsurprisingly, again, were pretty universal that like, you laugh, you like trying to escape, you might scream. And this

15:05was the same across the board. So then they decided 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? So, you know, this like armpit neck rib area behind the knees feet 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 ironscent zones. So, you know, like it's energized became more more of a thing, which is unsurprising. But the real takeaway is that like, where there are these places that seem to be inherently where

16:06people 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 articlish places. 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 were ticklish, the palms of our hands would be very ticklish and they're not. Finger tips. Exactly. Yeah, which would be very impractical. That's how we take you know. So it's definitely not about just like pure sensitivity. It's also not about pure pleasure because again, those irrogenous zones only came up as being ticklish when we talked about like being tickled by a romantic partner. So it's really like that's very context specific. So it's not about just like where ticklish in places where it feels good to be touched. It's not that where ticklish in places that are inherently more sensitive. We're not ticklish in places where the skin is thinner like, I think it

17:09was Aristotle or I don't remember who was Aristotle or Socrates. He's thought that. But one of those do. He's thought that. And that's not the case. 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. Day to day life. And that tracks with a lot of what Charles Darwin thought about ticklish. It was about the other one to surprise. So yeah, sort of you know, if you think about like your ribs and your neck and you know, under your arms. Yeah. 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.

18:11It'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. Sensory appendix. Yeah. Yeah. I feel like there is probably some, you know, social benefit. Because we know that it is something we use to social benefit, right? And especially. And especially with like babies, you know, you think, you know, and I mean, what more like there, I don't think, you know, evolutionarily, like there's no more important bond than like keeping your young happy and close to you. Yeah. That part of it makes a ton of sense. Yeah. And I do. I kind of, you know, again, this is just me having vibes. But I like the idea of it being, you know, sort of 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?

19:13That 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 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 at. ST. Yes. That's where he comes in. And basically it's like these these electric motors that slide probes across the souls of the feet.

20:18And 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 so I just what a life. What a life. I also I definitely don't recommend trying to find a picture of Hector the Tickle Robot. You'll find a lot of AI slop of people who are interested in the concept of a tickle robot for reasons that are their own business. But any who this guy he's doing his job, there's nothing untoward. Everybody everybody has consented to the foot tickling and it's been done scientifically. And studies using Hector found that this response happened so quickly within 300 milliseconds of a love science tickle onset. We see this. Yeah. Tio, we see breathing changes. The circumference of the chest, they were measuring that that changes within 300 milliseconds. We see the facial expression of a genuine smile,

21:18you know, you know, the whole face smiling those happen. And then within 500 milliseconds, people actually start laughing. This seems to the robot was doing the tickling. I apologize. It doesn't have to be the robot is doing it's not okay. The robot is doing the tickle. Got it. Got it. Got it. Got it. Showing me. Yes. They are concurrently measuring all of these things. Got it. Okay. People are hooked up to many devices, including a tickle robot. And yeah, they also found that 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 be in tickled right now. Right. One other really interesting thing I learned that I invested, I tried this morning for science was that, okay, so we know that you can't tickle yourself,

22:22except in very rare cases. So researchers looking at how that works found that if you are tickling yourself while someone else tries to tickle you, you feel less tickled. Be kind of that today 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, you know, not to get into two darker 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 averse reaction to being tickled. So it's morning, I said to my husband, I said, Oliver, I need to try something for science. And I thank you all. I tickled myself and I said, okay, do what you will. And it was genuinely more tolerable for me.

23:27And 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 took on myself with 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 and your armpit. That might be enough to 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 this study found that 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 often be kind of a learned behavior because we do see that people are more like glitter port that they overtly liked tickling when they were children than they do

24:32as adults. So people, yeah, 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, 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 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 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 is 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 tickle zone, 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.

25:36Thank you, and 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, what a ride. I actually broke up with somebody in high school for many reasons, but one of the top 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, those first couple of seconds. And then when it's like, okay, I'm having some trouble breathing. Yeah. Like it, you know, yeah. So we should, we share that a little bit. Yeah. I honestly, I would say that multiple times is like tickled me too much. Yeah. Yeah. 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, 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 psychosomatically, like, I've been itching a little bit during this

26:36whole 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, oh, wow, confirmation that I should 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, 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 is having a really good time. And I should probably facilitate that. So reading these studies also made me

27:38be like, yes, what that book was talking about was tickling for like a long time while you're screaming. That's not exactly. But humans are so funny. We do weird stuff. We have a little rhyme in Tamil. It goes like, none divided, the tail divided, the none divided, you do that little babies. And it literally means, well, it sounds a bit scary if I translate it because it would mean opian is coming and or something. And it's tropical stuff that you know, yeah. 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, yeah, you know, but I'm their nine months old. They absolutely love it. Yeah, it's a daily massage bath and a little bit of tickle time, you know, it sets your day. Yeah, yeah, absolutely. Yeah.

28:44And I love, again, like how universal it has 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. There was a rhyme for it. You know, even yeah, yeah, and rhyme would make my son smile. 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 anticipation coupled with like, you have no control over exactly what's going to happen. 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. Remember when you were a kid and summer meant freedom, freedom from homework, from teachers from school? Well, as an adult, summer can still mean freedom thanks to mint mobile summer sale. Right now, all of Mint's plans are just $15 per month, even unlimited.

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30:58Okay, we're back and Laura let's talk about some IT's IT's 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 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

32:00we would have gotten to the tagging it just would have been like tell me everything you've ever read about these eyeball teeth. 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, which is just again completely fascinating and I don't know maybe that won't stop everybody in their tracks. Maybe I'm just weird, but it's it completely derailed and the end of an interview for me a couple weeks ago. Yeah, before we get in too much to 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. They're maximum, they're complete maximum isn't well known, but they can grow again as largest 60 feet in way about 11 tons. They're mostly found across the Atlantic Pacific and Indian oceans in the tropics,

33:01but 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, round Florida, 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 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 balean 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. And dermal denticles themselves aren't just exclusive to the eyes. Obviously you see the word derm in there, which indicates skin, and they are found on several shark species and cover their bodies kind of along with the scales. They're small, V-shaped, and they sort of, they help decrease

34:07drag 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 little bite out of them. When it comes to the whale shark's 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 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 lura thing, because they don't have eyelids, and their eyes are also positioned on either sides of their head, either size 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

35:12squid 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 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 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 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 it teeth and that retraction might be helpful in shielding their eyes from, you know, just from elements, and it could also indicate something

36:16interesting about the whale sharks evolution and survival. 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 mistake an 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 used smell in 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 it 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.

37:17So it's possible that they evolved these denticles because vision is more important to their survival than it is with other sharks. So it's just kind of like 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 like it's just kind of one of those, 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 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 could ask questions all day. If you could be any shark

38:18species for a day, which one would you be and why? I'll give you a minute. 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. Yes. Yeah. So those are cool, but I think if I was going to be one, I don't remember which shark is the one that's just like, I don't think the mouth is just open. The basking sharks. Maybe. Let me think. Yeah. Yeah. Oh, that one also has a big wide open mouth. It is not the one I was thinking. Oh, that's scary looking. Yeah. Hammerhead Sharks, but that's my aunt. Well, that's, oh, oh, 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 to love him. I just they're so cool.

39:18They're so cool looking and yeah, the way that they move you. I have so many of them for my kids because I love that. Yeah. Yeah. Yeah. We had a researcher on talking about Hammerhead Sharks. I'll have to link to that episode in our article for this one. Just incredible. I think, okay, I think the one I'm thinking of is the mega mouth 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-feeling 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. Yeah. It just seems very they seem really calm. Yeah. But if I wanted to really scare someone, it would be the frilled shark because those look frightening. Freaky little guys. It's I mean, I would say whale shark even beyond doing this story,

40:23but 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 the point where one of my nieces now whenever she sees something with a shark on it will say, but I don't 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 what that was even before I knew about the eyeball teeth. Also, I just looked up a picture of a whale shark and realized that's the shark I was thinking of. I was thinking really? 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 mouth. They're like, they're really great. Now I have the right name for the shark. I so thank you for that. All right, we're going to take one more break and then we will back with some more facts. Okay, we're back. And let's talk about some spices and how they

41:32work in the brain. Why do they make our brains buzz? Please tell me more. Let's spice up our lives, shall we? 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 Spies is that I look at several prickly ash varieties all the way from West Africa by a goa, the Nepal, China, Japan, and Korea. 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.

42:34Oh, 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. So let's go through prickly ash first and then I'll jump on to chilies and then let's consider what happens when we put them together in our mouth, say in a plate of Maputafu. So most people know prickly ash as Sichuan pepper as we just talked and they've probably tasted it in a Chinese restaurant serving Sichuanese fare. A plate of Maputafu 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 the dried outer covering or botanically speaking the berry carp of the fruits of several santa-silent species. And this biodiversity of prickly ash is truly spectacular. It belongs to the citrus family like wow in lemons and oranges and mandarins which probably explains its various citrus aroma.

43:37Yeah, right? Yeah. 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 I bought a few bundles and the lady's called a tepple 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 if the fine spray of very potent citrus extract and that exploded inside my head. There was like this warm, numping 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, the tender and it's a

44:41whole other experience to the dried berries that you may have used for cooking which is what it binds to the markets 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. Actually, Rachel, when you were talking about 50 herds, I remember a study I had read a couple of years ago and it was by researchers led by Nobuhiro Hagura and Patrick Hagard at the Institute of Cognitive Neuroscience at the City College in London and they measured the tingling sensation caused by Sichuan peppers to be perceived at approximately 50 herds in a study that they did in 2013. Wow. It's so interesting and that distinctive sensation actually comes from a large group of compounds called sandshuz, particularly one called hydroxy alpha-sensual. So instead of producing this

45:45straightforward burning sensation of chilies, what sandshuz does is it goes in the series, it starts with this tingle which moves on to become a buzz and then you start feeling things vibrating and then there's a numping sensation. So there's a curious trick to this. Yeah. And I think it's because our century 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. Sandshuz does is it comes in and it interferes with some of these potassium channels and particularly one that scientists have called as Tresk or TRESK. What Tresk does is it changes the neuron's electrical balance,

46:51making it easier for the sensory neuron to become active. And so the neuron becomes very excited. But here's the extraordinary part. Sandshuz 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 small pepper barrier. 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 this evaporation. And this happens, not if you just place it in your tongue, you have to chew it to like activate to kind of say it. Exactly. And that releases this whole thing because what, yeah, you know, it's the oil glands that rupture. So when you eat sishwani peppers, your tongue isn't actually or literally vibrating. It's that sensation. Your neurons are sending your brain a pattern of electrical signals

47:57that your brain experiences as vibration really. And I think what happens is when you can, you know, when you keep digging into your maputofu, for example, that is, let me put it scientifically, this continued stimulation at pain sensing machinery in those neurons, they become less responsive, temporarily. 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. And that begins to shift how we register taste that follow. Hightening them in, man. So, you know, food begins to taste delicious because only all these taste buds are more open, more receptive. And so go ahead, spice your food with

48:59some prickly ash and it will taste delicious. This probably explains, you know, the use of Chinese spice salts like jaoyan, Cantonese seasoning blend, which literally means pepper salt, jao meaning three peppers in the blend, there's sishwani 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 are used in a lot of Cantonese style 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. Yeah, I have a jar of that that I use all the time. It is a great easy hack to just make most food taste. Exactly, there you go. It's such a classic and simple thing that you can easily make at home actually. So there's a recipe for that in the book as well. Just as spice also showcases so many flavors of prickly ash. So you know, this

50:01white arug 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 prickly ash berries. Let me tell you what happened. So when you crush them between your fingers, they're raised oil glands rupture. And this is, you know, you can try them in your kitchen with dried store-bought Sichuan peppers, good quality prickly ash berries. The fruits release a very heady citrusy scent and the old friend, depending on which ones you're trying. So Sichuan tepo, which is sparkles like, I think like calamansi,

51:04the Timur and Thingie which grow in the the Sabhimali and Ranges and that region, they have a more honey, vergamo kind of smell. And Teppel, 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 the essential can smell some warm orange peel, bit of resin and maybe even a bit of spice like huzu. So very very different citrus smells from different varieties of prickly ash. And all of this also then depending on whether they are fresh or dried, right? Not just the smell, it's also of the tongue. There's 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 tendent of prickly ash. It comes in.

52:10It comes in. But the buzz varies. And there's my experience and I will have to hear if at all any of you tasted what would your sensations were, Indonesian and Aliman is quick and very prickling. The Teppel from Nepal was more woodsy and the buzz creeps in slowly maybe because it's more to chew, you know. But Wajau, which is Sichuan peppercorns, they linger, but they linger on the lip. Right. Yeah. So there are these different zones they were activating, which I thought was very fascinating. I find the ones that when it lasts on the lips, that's the heart. I personally, that's always the one that's the the most difficult. I guess that's maybe more sensitive. Maybe there are more interventions. But that's the one that always like, you know, if I don't like a spice, it's usually because of like that little lip linger. Yeah. And then I learned that altitude, soil and climate affect what is known as the alchemyde levels in these fruits.

53:16So I believe these taste so different. 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 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, you know, these prickly ash spices in your in your grocery, you can look at you can look at these for quality. And now let's move on to chilies, which was the other spice we were constrained. And with chilies, capsicin is the molecule that makes chili feel hot. Right. But it doesn't actually make your mouth hotter. What it does is it activates a heat sensing protein called trip V1, which you would dispel it. It would be TRPV1, we just call it trip V1, on your sensory nerves. Your nerves normally

54:23use trip V2 detect dangerous heat. Right. And so when capsicin switches it on, your brain receives this message, that's hot. Even both, isn't actually a rise in temperature. Whereas capsicin finds trip V1 on our pain sensing nerve endings. And it's you know, trip V1 is basically an eye on channel. Think of it as a as a doorway, a tiny, tiny molecule or doorway in the cell membrane of a nerve. So when capsicin opens its door, all the positively charged sodium and calcium ions can rush into the cell. And that makes the neurons electrical charge less negative because they were positively charged. And this process is what neuroscientists call as depolarization, sort of like a plane 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

55:27interprets that activity as burning heat. Got it. Except that there isn't any fire. And it has simply hijacked one of our body's detection systems in a way. So your nervous system is being percuated to believe that it's getting hotter. And scientifically speaking, it has sort of changed the electrical state of your new sensory neuron. Yeah. That's crazy to think about it. That is I know. So discrete and it happens and you experience it all the time. Yeah. 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 of the heat, which is more about why does eating more chili eventually make the burning more bearable? You know, 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 capsized in you eat,

56:31the more your nervous system would scream, stop it. Right. Right. happening. Chili has this built in paradox in a way that the molecules that initially make the spin sensing neurons fire and with continued exposure, eat more and more, basically make that same neuron less responsive. So you keep upgrading those trippy 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. I'm done. I'm done. Yeah. And that's one reason that the first bite of a very hot chili can feel absolutely theroshes if I make food there. But while several bites later, you may find yourself thinking, yeah, you know what? Actually, I can handle this. Yeah. And that makes me think, you know, when you watch all these shows, if people come to eat super spicy chili, I was like, that's how people get to come out once. And then there's a spot around watching all of that stuff.

57:34I wonder if they actually eat some super hot chilies kind of just condition their mouth. Yeah. Because there is something about how convenient and how easy they make it look. I'm sure there's a lot of pain bearing going on, but there could be something behind the camera. There's a green room chili eating speed. Or like, is there, is there like a doping scandal like 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. Exactly. Yeah. So well, this is just my hypothesis. That could be to be. I have been invited. I have not been invited to eat any chilies in any contest. And I don't think I'm a contender for that at all. 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,

58:41as a sensory machinery becomes temporarily less responsive, which is actually the neurophysiology that's going on. That's what's your brain. Okay. Here's the thing about chilies. They come in a very wide range of capsized in content. So you have very mild chilies or you even have bell peppers which have zero sizes, moving all the way up the scale to coast peppers and things that have way more heat than that. And you know, midpoint maybe can, which is super common in most people's kids. It's a standard stuff. Moderate heat. And you also have the more popular hot varieties like there's the habanero and the scotch bunnets 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? Inspised there is a chapter on chili. So every spice is a chapter. The chapter of chilies is arranged in the increasing order of their heat. So you start with traditional recipes with, say,

59:44Hungarian 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 but Nagar goes peppers and traditional dishes cooked with that. So this wonderful spectrum of recipes to cook with there. If I can just plum in back into the paprika, maybe you want to use it later on. Pepperica is so uniquely Hungarian. It arrived in Hungary in the mid-16th century with the Ottoman occupation. For a very long time it was little more than a botanical curiosity. The sweet peppers we know today grow across Hungary. But paprika is the spice, right? It comes particularly associated with two places in southern Hungary. Sigead and Kalloxa, which are on the flat fertile plains between the denobae and the Cesar rivers. We know that from historical records we know that there has been intensive breeding work in this

1:00:50region. What I find very fascinating is the first research institute for chili peppers. Wow. Yeah. The Pepper Research Institute of Kenya 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. I try to understand the breeding of chili plants 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 develop the variety. But I believe Europe is going to love this. But you know by the late 19th century we do have a lot of writing where we can see that farmers

1:01:52around this region had begun using mechanized tools in the production of paprika. So they had all machines. It was not no more a hand done activity by shredding 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 but here's the fun fact. A very big international debut movement came only when August Dyskoffia, the legendary French chef, in Africa from Sighed, into his gula shed Monte Carlo. Wow. That's what did it. That's what did it. And suddenly the intentionally 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 everything. 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

1:02:56and 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 paprika. Then put in the paprika. So the paprika is sizzling in the warm oil but it's not burning. Let's go fall that color into the oil. So you've colored the oil and the oil then colors everything else that you add to it. You could be your peppers. There's everything about that dish is so red but it's that oil and careful handling of paprika that is so important there. But anyway, when someone says paprika, there isn't just one flavor behind that word. There's just a variety there, right? There is the very mild ones which are called edas, literally meaning sweet. And then they progressively go adding seven or eleven varieties, including ira, which is the hottest variety. So remember the trip we won, the molecular doorway that Kepsisin opens, making a paint sensing no fire. And then you remember,

1:04:00Tresk, we talked about it with Prickly Ash, this potassium channel that's sensual 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? I mean, to me, I think that's neurologically extraordinary as a situation. Yeah. On paper, that's what it would be kind of just like a kind of yeah, that's what that's what Mala is, right? Yeah, exactly. But I don't, but what's going on in the brain? Right. Very complicated. Very complicated 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. These 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.

1:05:01So it's not just hotter, it's neurologically busier. So it's like hot, right, hot, and there's a lot going on. It's kind of like, you know, if you're tasting wine, it's like it's a more complex bouquet or something like that. So what I find fascinating and I highlight 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, Mamining, Nambiing and Tingling and Lamining hot and spicy, but you could see it repeat over and over again. It's a motive, it's a spice motive that comes again and again in a Goen Gassi stew or sprinkled on top of a Bhutanese cucumber and salty cheese salad. It's called Goen Hogue, or you should try this superbly spiced Nepali condiment called Timur Kho Chop.

1:06:05And several Sishwani's classics, of course, including some recipes for crispy chili oil that include both. Then you have the Indonesian sambal tuk-tuk, which is a Bhutanese classic. And even all the way in Japan, a classic Shichimi Togorashi would have that, both of them powdered into the seven spiced blend. So, you know, it's really fascinating how so many different cultures have clicked upon the same combination. Yeah, like tickling. Yeah, the tickling and the heat. And the heat is, I think it's, 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, right? Right. They use the facing heaven chilies, which is Chaotian Jao, which is mild. While in Indonesia, it's Chabera, but it's pretty sharp. Yeah. 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,

1:07:08combined whatever you want, but I think experience is this thrill, which is very, very fascinating. Yeah, it's so fascinating. And also, like, you know, as someone who loves, you know, this combo and this sensation in Sashwan food, I really, like now that you're saying it, I've definitely experienced 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, by too many kinds of prickly ash peppercorns and gilded berries. That's a fun experience. I love doing that. You know, just have varieties and then playing with it. I think that's the best part of working with ingredients. Yeah, absolutely. Well, thank you so much for coming on. This has been so fun and I'm really excited to check out your book and to start cooking some recipes from it.

1:08:12Thank you so much for joining us. Thank you so much Rachel and Laura for having me. The weirdest thing I learned this week is produced by all of our hosts, including me, Rachel Fultman, along with Jess Bodie, who also serves as our audio engineer and editor extraordinaire. Our theme music is by Billy Caden. Our logo is by Katie Belloff. If you have questions, suggestions, or weird stories to share, tweet us out weirdest underscores thing. Thanks for listening, Weirdos.