Intro

[00:00:00] David: [00:00:00] Welcome to episode 14 of STEMology

[00:00:02] Sophie: [00:00:02] A podcast sharing some of the interesting fun, and sometimes just patently bizarre news in science, technology, engineering, or maths.

[00:00:11] David: [00:00:11] Your hosts are Dr. Sophie Calabretto and Dr. David Farmer.

[00:00:14]Sophie: [00:00:14] Today, we’ll be talking about stone-age ravers, singing whales

[00:00:18]David: [00:00:18] infected ants and weird dreams

Stone age ravers

[00:00:31] Sophie: [00:00:31] So, Dave, you seem like the kind of man who would like to go to raves a lot, is that true?

[00:00:36]David: [00:00:36] Yeah, that’s true. I was about in the nineties with one of my little fishermen hats and my whistle tuning and Mo and Joe off. That was me.

[00:00:43] Sophie: [00:00:43] Well, it turns out Dave, that you’ve got a lot in common with people from the late Mesolithic era.

[00:00:49]David: [00:00:49] You mean the late stone age?

[00:00:50]Sophie: [00:00:50] I do. Yeah. So around 8,000 years ago, people were ravers, but instead of whistles, they made rattles out of elk teeth, apparently.

[00:01:00] David: [00:01:00] That’s right. And so this paper that we’re talking about this week is actually evidence for   the practice of raving by elk tooth, rattler stone age people.

[00:01:08] Sophie: [00:01:08] This was one of my, you know, I get delighted by science every so often. And everything about this was delightful. Like the purpose, the processes that were use to work these things out. But yeah, so they discovered to paint. Basically. There are, um, now I had to look up some Russian pronunciation, so everyone listening at home who can speak Russian, please don’t tell me how badly I’ve done.

[00:01:28] But the letters are things I’m not used to. So it was there Uzhniy Oleniy Ostrov burial sites in Russia. And so apparently there are about 177 burials of men, women, and children. and  we’ve got these burial sites they’ve been intact for, quite a while. There were lots of things in them. So there’s, you know, I think in the past, when they bury people you put in goods for the afterlife, there were sort of bones and antlers and stone tools, but there were also ornaments that were made of, what they then deduced were elk teeth. And so this particular paper was a study of sort of what those  elk teeth ornaments were used for. Um, and it turns out that, probably they were sewn into clothes and turned into ornaments for long raves  because of the rattling sound that they make when you dance with them.

[00:02:19] David: [00:02:19] Yeah, so that’s right. to clarify, so we’re talking about a graves of a few hundred people, but thousands and thousands of teeth found in these grave sites

[00:02:26] So 6,000 teeth, about four and a half thousand are the incisors of the Eurasian elk.

[00:02:31]Sophie: [00:02:31] Which, Dave,  is a moose?

[00:02:33]David: [00:02:33] Is it, it’s not an Alcatel. Why an elk is a mousse

[00:02:36] Sophie: [00:02:36] Yeah. So in, uh, Europe, it’s an elk. North America. It’s a moose, it’s just a

[00:02:41] different name. I thought they were different animals.

[00:02:43] David: [00:02:43] So did I

[00:02:44] Sophie: [00:02:44] So when I’ve eaten both elk and moose, in fact, I’ve only eaten elk and moose. I haven’t eaten elk AND moose. I’ve eaten both at the same time in different countries.

[00:02:53]David: [00:02:53] It’s like meters and feet.

[00:02:55]Sophie: [00:02:55] Yeah, exactly. Um, anyway, sorry. Yes.

[00:02:57]David: [00:02:57] Yeah, so four and a half dozen of incisors and no molars or pre-molars for some reason. but there were some other ones, about 1200 of the Eurasian Beaver.

[00:03:08] Uh, 170, are canines of the Brown bear and some dog teeth, some gray wolves, some wild reindeer, and some wild boar were also present, but the vast bulk of them, I mean, 75% of them were incisors of the Eurasian elk. And what they found was that they were arrayed and these really close patterns within the grave. So they were all found together and they didn’t find them connected together with a string, but they hypothesized that the reason they’re all close together in a row is because they were on a kind of a chain together and that they were being used to rattle against one another for the purpose of making music and dancing.

[00:03:43] Oh, and this would be exciting because this would be groundbreaking from the perspective of sound archeology, which is a thing, because there’s been no evidence of such instruments in the past, in this population. And according to ethnomusicologists, which is apparently also a thing, strong rattles of shells, bones, teeth, hooves, and beaks can be considered to be among the earliest musical or sound instruments known to have been used by human beings.

[00:04:08] So this is a really big deal.

[00:04:09] Sophie: [00:04:09] Yeah it’s huge. And so what I love is that there was sort of, it seems from what I can tell those a two-stage process. So to start off, they had all these teeth and they had to work out what kind of teeth these were. So they picked four graves that contained around a hundred teeth in total. And they actually all turned out to be elk teeth, but to match them, they got 180 fresh animal teeth from licensed tons as in Finland and Russia. And they also got some from the Finnish museum of natural history and the Russian Academy of science and they match them. But they looked at these  these fresh teeth microscopically before, and then what they did is they sort of did various experiments to work out what kind of patents would form when these teeth were sort of knocked together in various ways and then tried to match those to the old teeth. So what they did, they got these new teeth and they did things. They scrape them, they retouch them, they grind them and, you know, use things like Flint and slate tools, but then they also turn them into portable pendants and they were tied to the arms, hips and thighs of the researcher and worn on daily chores, including walking and light jumping for a period of one month for about two hours a day.

[00:05:12] And then. Dave, my favorite thing that has ever happened in science and I quote ” the wearing experiment reached its climax with a stone age-ish disco where 160 tooth pendants on the researcher was subjected to intense dancing and jumping for a period of six hours”.

[00:05:32]David: [00:05:32] six hours.

[00:05:34]Sophie: [00:05:34] Yeah. this was part of a sound installation bone garden at the new performance Turku festival in Turku, Finland in August, 2015.

[00:05:43] So this disco also served artistic purposes. And so they did this and then they went back and they looked at the teeth microscopically and looked at the grooves and went, you know, they’re not as deep and stuff as these other ones, but these other ones would have been worn for significantly longer. But I just like, it was beautiful.

[00:05:58] So the research had danced for six hours with elk teeth attached to see for science. And then they’ve talked to her and what I really like is just some of the quotes are beautiful in this, Dave. So ornaments Composed of elk teeth suspended for almost sewn onto clothes, and may allow a rattling noise when moving, wearing such Rattlers while dancing makes it easier to immerse yourself in the soundscape, eventually letting the sound and rhythm take control of your movements. It is as if the dancer is led in the dance by someone.  I just, this is the best kind of science. And so, yeah, as you said, this is kind of groundbreaking in the sense that we looked at these like rattling instruments from 8,000 years ago.

[00:06:39] And Dave, I know that you saw it. There’s a video online Tell us about the videotape.

[00:06:45] David: [00:06:45] So there’s a video and they’ve got these elk teeth arrayed on  a piece of leather that’s being worn and they’re kind of, you know, demonstrate it in a demonstrative way, jumping up and down and various ways to show what the sound is. And it’s like, Oh, cool. Yeah, and it makes a very dramatic sound then to show you the kind of detailed movements of the bones, they do it in slow motion, but they slow the music down as well.

[00:07:08] So. Listeners go into the show notes and go into the supplemental materials of this because, and listen to it because the noise of these slow motion, bones battering, one another will haunt your dreams. It’s it’s absolutely staggering. The noise that it makes.

[00:07:22] Sophie: [00:07:22] do you know what it reminded me a bit of? Do you remember those rain sticks?

[00:07:26]David: [00:07:26] Oh yeah, yeah, yeah,

[00:07:27] Sophie: [00:07:27] my brother used to have one and I was so jealous as a child. And for the life of me, I can’t work out why I wanted one of these things so badly, but yeah it really reminded me of like an aggressive rain stick.

[00:07:37] David: [00:07:37] Yeah. It’s like  an aggressive, heavy metal rain stick

[00:07:41] Sophie: [00:07:41] Yeah, it was just, it was great. So, I mean, yeah, well done University of Helsinki. This has to be my favorite thing of the year so far. And yeah definitely, as Dave said, check out the show notes and watch that video because it is sensational

[00:07:54]David: [00:07:54] stone ages, disco.

[00:07:56]Sophie: [00:07:56] yeah. I want in

Singing Whales

[00:08:09]David: [00:08:09] So from bone disco to whale song, Sophie, we’re talking about the blue whales, blue whales are gigantic, but they’re also rare. It’s estimated that lesson’s 0.15% of them have survived the human practice of whaling. And today we’re talking to Tracy Rogers from the university of new south Wales who has been listening to them using hydrophones used by the comprehensive nuclear test ban treaty organization.

[00:08:33] Tracy, thank you so much for coming. How did you come to be listening to these hydrophones and how did you hear whales on them?

[00:08:42] Tracey: [00:08:42] Well, we don’t actually listen to them. We find them with algorithms. We’re looking for the signal of their sounds. And why we were listening for whales, is that what we do is we look for changes of environmental signals and how over long periods of time, different animals respond to the changing environment.

[00:09:02] And. We have this fabulous underwater sea noise data set from the nuclear test ban treaty data system where there’s this series of hydrophone arrays all around the world and they just keep collecting all this lovely underwater sea noise. And so that noise. Which is looking for bombs, nuclear bombs actually also holds the signals of whale calls. And what we do is it would be lovely to sit there and listen to sound, but at each one of these points, we’ve got like up to 18 years worth of data. So it’d be, you know, I’m old as it is. I really think so. Um, what we do is we, we write little algorithms to look for the kind of signal that the whales make.

[00:09:42] And my colleague Manu Emmanuelle, she went actually look at these signals. These are different to the ones we were looking for other kinds of blue whales. And she went, I think this is something different. So we went looking through yeah. The 18 years on one side and 14 years on the other side of this archipelago and went, wow, these are these, these sounds are here all the time.

[00:10:04] They’re moving backwards and forwards and they look just like a blue whale, but a different kind of blue whale. And then we reached out to, um, some colleagues and one colleague who’d recorded the same sounds around blue whales up in Sri Lanka. And then we found those same blue whale sounds again, off the coast of Australia.

[00:10:25] Um, the Kimberley. So it appears that there’s, uh, quite a big population of, of Pygmy blue whales that’s gone completely missed, right in, in the center of the central Indian ocean up near the equator.

[00:10:38] Sophie: [00:10:38] Yeah. And so with these pygmy blue whales, from my understanding, the idea is they all have each of these populations have very specific songs that they sing.

[00:10:47] And so this is, is it the fifth? Population. This was this a fifth unknown population of pygmy blue whales that you’ve found. But I said a question about, so when you’re analyzing the audio, so it should, you’re not listening to song, but you, are you looking specifically for the kinds of patterns in this audio specific to whales?

[00:11:08] Were you just looking for whales in general? And if you were looking for other animals, would you be analyzing the audio in a different way?

[00:11:15] Tracey: [00:11:15] Yeah. So for each, each different, as you say, there’s those five different, uh, pygmy blue whale populations now in the Indian ocean, each one of them, their song has a different acoustic features.

[00:11:28] So we create a detector looking for that particular song. So Manu was just sitting, looking at the not listening, but looking at the sounds below our hearing actually. And she went, whoa, look at the structure of that. That’s a different structured call. So each one of these whales how they change in frequency.

[00:11:49] And the structure of the coal is completely different. Sort of like we have different dialects. They have these different songs structures between these different populations.

[00:11:59] David: [00:11:59] And with regards to that, you’re on the record of saying that humpback whales are like jazz singers and blue whales are more traditional. Would you care to elaborate a little bit on that for our listeners?

[00:12:09] Tracey: [00:12:09] Sure so humpback whales, their songs evolve all the time. That between each year, sometimes they, they change a little bit each year. Sometimes they completely change like, uh, like a new singer comes on and they they’ve moved from jazz to rap.

[00:12:25] Like it completely changes. So whereas with the blue whales, what they do is they have incredibly. It’s very stylized, basically very boring. Now songs that they repeat again, pulse, pulse, pulse, pulse, and there might be slight variation or there’s different variations, but they’re very, very, um, stylize now within any year, just like what the humpback whales do.

[00:12:49] All the whales in that population will be singing the same song and the blue whales change. But only just shifting in frequency, a tiny amount, whereas the humpbacks completely mix it up. They throw in all these different kinds of sounds and, and they change up the tempo and then they mix it around. Um, so yeah, they’re, they’re incredibly different versions of the same idea of song basically can be very simple and boring or it can be  really innovative.

[00:13:19]Sophie: [00:13:19] So in, in looking into this story, from what I could tell originally, it was thought that maybe that fifth population was just a variant of one of the other populations. So how did you deduce it this is in fact a completely different population?

[00:13:34] Tracey: [00:13:34] So why would they thought it was a variant on that another population was the Abigail in Sri Lanka had recorded that sound being made by blue whales up off Sri Lanka, where they make one that’s one of the other groups, the Sri Lankan blue whale. And so they only heard a couple of those sounds being produced  along with this Sri Lankan calls and they thought, oh, well this is just a young, a young whale.

[00:14:03]Hasn’t quite got the right song yet. And like, by the birds, you know, birds, how they practice the young birds, don’t quite get it right, mammals do the same thing. Kids, it babbling you babble and you do different kinds of sounds.

[00:14:15]So we’re just really wanting to get lots of calls from Antarctic blue whales and you know, different kinds of whales. They’re the Australian type blue whale. And it’s like this, this is actually looks. A lot like that one that’s just meant to be like little, it was just a note, like a variant of this Sri Lankan.

[00:14:32] And it’s there all the time through 18 years on the Southern side of the a shagger soccer Pedago and 14 years on the, the Western side and it’s moving backwards and forwards and it’s across to Australia. It was like, oh my God, this is actually a whole population. This isn’t some crazy young kid. This is a thing, this is a whole other group. And with other colleagues, we found another group of blue whale sounds that that population is up into the Amman sea. So up on the other side of the Indian ocean. So it’s like turf wars really that you have all these different groups. Singing these different songs from these different areas and that they, but what I think is really exciting is that they intersect with one another and sometimes they’re in the same places at the same time, but they all retain those same song patterns. So they are true to their true to their songs.

[00:15:24] What were you doing for raves or something? So they’re keeping, they’re keeping those, those song structures. Now, were they born with them or that? Did they learn them? That’s what I’d love. I’d love to know that except what we we’re doing now is them working out, we’re using their presence. And when they turn up in different areas, along with environmental data, to look at that there’s been changes with migration patterns, with changes in an oceanographic features. But I do like the song stuff. I think it’s fantastic.

[00:15:55] Sophie: [00:15:55] I was just interested in what the, sort of the discovery of this new population means for this, the endangered status of, of these blue whales.

[00:16:03]Tracey: [00:16:03] so that’s an excellent question. Their population is still incredibly low. They haven’t recovered from whaling, like, you know, the hump humpback whales and.

[00:16:13] Like everywhere.  And they’re doing fantastically well, but the blue whale is still incredibly, incredibly depleted compared to their original numbers. So any new population is fantastic. That that’s a whole, wow. Here’s another group of animals we didn’t know were there. However, this increase, isn’t the kind of, you know, it’s, it’s not going to change their endangered status. That they’re still, the numbers are still very, very low. But it’s, it’s so encouraging that there are more animals out there

[00:16:42] David: [00:16:42] And they’re making their presence known by singing away

[00:16:45] Tracey: [00:16:45] and they sure are!. But what I find is really cool is that this data set.

[00:16:51] is really for peace, it’s for finding nuclear bombs. But we’re using it for science. So we’re things where international infrastructure that’s been put together by a whole stack of dudes in, in rooms that ends up being used for peace and for science is got to be a good thing. Rather than just making money.

[00:17:13] David: [00:17:13] Yeah.

[00:17:13] Everyone professor Tracy Rogers from the university of new south Wales. Thank you so much for being with us.

[00:17:21] Tracey: [00:17:21] Thank you.

Ant Story [00:17:31] Sophie: [00:17:31] Dave, from very big animals to very small animals that live forever when filled with parasites.

[00:17:38] David: [00:17:38] I know. So if I was to say to anyone, you’re about to be parasitized, do you think you’ll live longer or a shorter amount of time? Like most people are going to guess a shorter amount of time. I’m being parasitized and being taken advantage of that’s going to be bad for me, but not so for the German and Temnothorax Nylanderi

[00:17:58] Sophie: [00:17:58] It’s a beautiful name. And I tried to Latin that one up and that ones. So Temno means despise is what I found. Thorax racks is like a thorax and then I couldn’t work out this Nylanderi, but it turns out that’s actually a Swedish name from Dutch, which means dweller on new land. So I don’t know if that’s completely irrelevant, but, um, that’s what I got excited about when I look

[00:18:19] David: [00:18:19] at this

[00:18:19] This is, um, Intrepid ants of some kind, and they are the intermediate hosts of a tape worm, which for some reason, when it infects these ants increases their lifespan perhaps as much as 10 fold.

[00:18:33]Sophie: [00:18:33] Yeah. And so, I mean, we know that we’ve talked about ants before, and we know that we have our queen ant and she’s just hanging out. She’s making babies, she’s got all that ant health care people like waiting on her and foot. She doesn’t need to go outside the ants nest so, you know, tend to live for a very long time.

[00:18:48] But then these poor work ants, the female worker ants that, you know, they, she gets to do. Her bidding. They go out, they get messed up there. You know, they live for not very long and usually at most about sort of like two years old. And it turns out in this particular sort of ant at least, but yet it turns out that being infected with this type of tape worm means that these worker ants can live for Yeah lifespans of maybe the queen. And they think there’s perhaps a couple of reasons behind that. Right, Dave?

[00:19:18]David: [00:19:18] Yeah, that’s right. So what they talk about is the queen, like you say, so it’s safe to be inside the nest. And apparently like if you’re a worker and it’s worse than having to go outside. So when you’re inside, you start off as a nurse, what’s called a nurse, which is like, you look after the babies and you look after the queen and then the older you get.

[00:19:36] The more likely it is that you get sent out to become what’s called a forager, which is where you go outside of the nest to go and do outdoor stuff, to look for food and stuff like that. So the older you are, the more dangerous your life is, and therefore the less likely you are to live. So there’s this kind of in-built social structure. That means that the older you are, the less likely you are to live for a long time, but it’s not just that there seem to be some genetic and physiological things that happen. To the ants that mean they live for a longer time. So what these researchers did was they looked at a parasite infected nests of ants at non-parasite infected nest of ants.

[00:20:16] And they look to exactly this. And what they found was that the animals that were parasitized, tended to be looked after a bit better by the uninfected individuals around them. but that didn’t explain everything. There had to be some epigenetic or some physiological changes in the ants that extended their lifespan as well.

[00:20:34]Sophie: [00:20:34] Yeah. And so what I found really interesting just to start off with was apparently, a single ant, can be infected by up to 70 parasitic larvae.

[00:20:43] David: [00:20:43] How do you feel 70 anything in there

[00:20:45]Sophie: [00:20:45] Yeah. They’re like two to three millimeters, these ants, and you’re just like, God, there’s a small larvae. but yeah, so apparently like a bunch of different things happen.

[00:20:52] So the parasites actually survive in the hemo lymph, which I learned is the equivalent of blood in most invertebrates. So it’s kind of like just the body fluid in like this insect.  and what they’ve found is that there are a lot of physiological changes in these ants. So you can actually even detect them by sight these infected ants, because there are lighter of yellow color, than their Brown uninfected pals.

[00:21:14] Um, and that results from their, yeah, their cuticles just become less pigmented. They have metabolic rates and, lipid levels similar to those in younger ants. So it seems like these ants remain in a sort of a permanent juvenile stage. And they’ve said that’s likely due to the tape worm larvae altering the expressions of ant genes that affect aging, but also the parasites release of proteins containing antioxidants into this like ants, body fluid.

[00:21:41]David: [00:21:41] It’s amazing. And, another thing I really enjoyed in the study, so they looked at the survival of ants. They looked at just how long they lived. Like you say, one of the ways they did that was by wire marking ants so they would go in and find nurses and foragers and they would label them by something called wire marking, which I looked up it’s literally taking a tiny piece of wire and wrapping it around the thorax or abdomen of the ant so that you can identify it later. Like that is some top drawer nontransferable skills brought to you by the field of biology.

[00:22:14] Sophie: [00:22:14] I reckon that person who did that as great at the game operation, like I think you’d have to be really steady. And, you know, because the thing is, if you just do that slightly too hard, you’ve just probably like bisected your ant, right? Like if you mess it up, you’re just like, I’m just trying to mark this one. Oh I accidentally cut it in half with my small piece of wire.

[00:22:32]David: [00:22:32] and just, another thing that I find buried in the methods for anyone that thinks that science has really cut and dried and dull, there’s a lot of intrigue and a lot of mystery here. So we’ve got during the three years, 16.8% of marked young workers, 21% of marked foragers and 15.3% of marked infected workers disappeared with no corpses found.

[00:22:54]So where are these ants?

[00:22:55]Sophie: [00:22:55] um, yeah, no, those are the magical types. That’s a different type of tape them that they’re infected with. And they’re the ones that can just apparate and disapparate as per Harry Potter. But yeah, so what they’ve found is over these are the three years, more than 95% of the uninfected workers had died right after the three years.

[00:23:16] But at that point in time, over half of the infected workers were still alive. And I did like a little bit more digging. So as you said before, like eventually these parasites want to end up in a woodpecker, right? They’re there for the woodpecker, they’re in the ant and then the woodpecker eats the ants and there’s other studies that they’ve done on these ants  cause these ants live in sort of, um, I think sort of logs.

[00:23:36] And I think one of the things was like acorns, which I think adorable. I imagine like that would be a cute cartoon where you had like a little ant population in an acorn. And what they did is they simulated the breaking of the acorn by a woodpecker. And they found out that the majority of the uninfected ants fled.

[00:23:52]I think it was something I forgotten the number. It was like 80% or something. But in terms of the infected ads, there were like 2 to 3% of them escaped, which meant that when the woodpecker here comes like these like little lazy new Queens hanging out, being waited on hand and foot are literally there as amazing like food sources for the woodpeckers full of the parasite.

[00:24:12] So the parasites are literally like, it’s very clever. How clever is nature, dave?

[00:24:16] David: [00:24:16] That’s amazing. You actually answered one of my questions. Like I was wondering, like, why would they stay inside? If they’re going to be parasitized? Wouldn’t it be better if they went outside and left the nest, but no, they don’t need to because the woodpeckers going to go after the accorn.

[00:24:29] Sophie: [00:24:29] Yeah. And then another thing, just fun fact, apparently, um, one of the other physiological changes and it has to do with the layer of hydrocarbon chemicals on the cuticles means that they smell different. These ants smell different to their uninfected pals. but Yeah, I thought that was great. Cause I mean, my experience, uh, not my experience with tapeworm, I’ve had the tapeworm before, but whenever I hear tapeworm  I think back to, you know, when people used to take tapeworm pills to lose weight, turns out you can’t buy those pills on the net anymore, but they’re different types of tapeworms, Dave.

[00:24:59] So those are three tapeworms that we can be infected with that will make us lose weight in a very unhealthy way. And they’re not the same as these, uh, the tapeworms in the ants, cause also we are,  several orders of magnitude larger than the ants. So it would make sense that we would be infected with different types of tapeworms and you know, our, um, I don’t think our smell changes.

[00:25:17]David: [00:25:17] You smell a bit less bossy body positive?

[00:25:21] Sophie: [00:25:21] Yeah that’s right

[00:25:22] David: [00:25:22] It’s basically your scent becomes less body positive and grim.

[00:25:25]Sophie: [00:25:25] Yeah. It’s really interesting. So I think, yeah, it basically, it’s just a story about how these parasites are epically good at what they’re designed to do. And that is getting a woodpecker by just like trick thing up an ant population.

[00:25:36] David: [00:25:36] Yeah. And also if you can trigger an epigenetic change of some kind in an ant that makes it live for much longer than there some kind of fountain of youth type thing to be had there for everyone?

[00:25:47] Sophie: [00:25:47] I mean, maybe as I said, why don’t we just start ingesting tapeworms again and see what happens? Um, for everyone listening at home, that wasn’t a real suggestion. Don’t tape worms  it was a joke please. It’s very, it’s bad for your health. They eat your nutrients, exercise and a good diet, I believe is the best way to weight loss in people

Weird dreams [00:26:14]

[00:26:14]So, Dave, Yeah.

[00:26:15] let’s talk about dreams.

[00:26:16]David: [00:26:16] Yeah.

[00:26:17] Sophie: [00:26:17] why do we dream, Dave? tell me right now. Why do we dream?

[00:26:20] David: [00:26:20] Well, that’s a really good question which experts are still debating. And that is in fact exactly the subject of a paper we’ve read this week, which is all about a new idea of why we dream called the overfitted brain hypothesis.

[00:26:35] Sophie: [00:26:35] Yes. So apparently, there are many contemporary theories of dreams. Um, I hadn’t heard of any of them, but for example, there are, you know, dreams are for emotional regulation. They’re for memory consolidation there for selective forgetting, uh, they’re preparation for real-world problems, dreams can benefit predictive processing by refining regenerative modules.

[00:26:56]But apparently Dave, that might not be true. We don’t know, but this is a new theory and actually has weird ties to deep neural networks.

[00:27:06]David: [00:27:06] Yeah, so deep neural networks are networks that have kind of brain-like properties because they have an inverted commas, neurons that have weights, and basically they have an input and an output. And what you do is you train it based on some input, to identify say a picture of a dog and then you say yes, that’s right. if it’s right, then if it’s wrong, you say, no that’s wrong. And it adjust it’s weights. And then that way it learns to identify dogs. Now, one of the problems with these networks I learned this week is that they can become over fitted to the input that you give them.

[00:27:38] So if you have a training dataset for them, They can become far too good at identifying things in the training data set such that when you present them with a new picture of a dog, say they can’t identify anything because all they can do is identify that one dog in the training dataset.

[00:27:54]Sophie: [00:27:54] we do talk about artificial intelligence and things a little bit on this podcast. And that is, that’s a theme that I have noticed. It’s when we, train things on our data, we also train them on our biases. And as you said, if your data set is not sort of broad enough, then. It won’t be able to recognize your dog, but there are things that data scientists can do to sort of mitigate these particular effects.

[00:28:15]and so they sort of introduce a kind of chaos. There’s apparently a bunch of different ways that you can kind of regularize these processes so that you’re not getting, um, sort of overfitting. And so one of them that’s the most relevant to this particular thing that we looked at is called dropout, where you basically just you take some of the data out. So some of the data’s randomly ignored, but then I learned about things called L one and L two regularization. So L one tries to estimate the median of the data. L two tries to estimate the mean of the data and that’s to avoid overfitting. They use data augmentation.

[00:28:47] They use a process called early stopping. So there’s all these different techniques that people use in the regularization of deep learning. And it’s this dropout one that best striking resemblance to dreams.

[00:29:00]David: [00:29:00] Yes. So this is where it gets a little bit wild. So what Eric Hoel at the Allen Discovery Center at Tufts University is proposing is that dreams because they are hallucinatory and a bit wild, but yeah, I think he uses the word fabulous.

[00:29:17]  in the paper and because they are wild and fabulous and not representative of everyday life, that they are a way of making sure the brain doesn’t become over fitted to day-to-day life.

[00:29:30] So if the tasks you do day to day are very similar, there’s a danger that the brain can become over adapted to dealing with only those things. So if something unexpected happens, you’re unable to adapt to it and deal with it. So if you have weird dreams that kind of perturb the model that you have of the world and the way that you’ve learned how to do tasks, you’re then better able to generalize and to deal with the unexpected.

[00:29:52] Sophie: [00:29:53] Yeah.

[00:29:53] Yeah. Cause I think most of my dreams are quiet weird and that makes me, so the idea is that makes me better at everyday life. And there’s be, I don’t know, Dave, I don’t know about you, but I found that this paper had a lot of words in it, but apparently there is evidence in neuroscience that does support this overfitted brain hypothesis. So there’s things like the most reliable way we know to prompt dreams about something is to repeatedly do that thing IRL or in real life. and then this means that then you dream about it. So they’ve got an example, uh, which was like extensive playing of games, like Tetris or ski simulators lead to dreams involving those learnt  tasks, but in a way that you don’t get the same repetitions and it’s not replay of something that you’ve done in your memory.

[00:30:36] David: [00:30:36] So, yeah, so they talk about one of the alternative hypothesis about dreaming is memory consolidation, you mentioned. So they said if that was true, it’d be much more likely that if you learn how to do a new task repetitively, and that provokes a dream, because apparently doing a repetitive task a lot is one of the best ways to provoke dreaming, um, which I didn’t realize, um, if it was true that it was all about memory consolidation, it would be much more likely that you’d see

[00:31:00]just replays of things you’d done in real life.  rather than these fabulous versions of them is what they kind of argue. And yet they also talk about, memory consolidation in terms of making electrical recordings of activity in the brain. So when you create connections between neurons, what tends to happen is they start to fire together.

[00:31:19] And that’s what happens when you learn a task. And when you create a new memory of how to do that task, and what they say is that when you learn how to do a task, you see firing on two different parts of the brain, um, happening at the same time. And yes, when you dream you’ll see that same pattern of firing, but you also happen to see it when the animal’s not dreaming and when the animals quietly awake.

[00:31:41] So they kind of say, If dreaming really had to do with memory consolidation, you wouldn’t see these patterns of activity across, you would see them just during dreaming and not all the time.   So that’s, yeah. They’re kind of arguing that it’s these fabulous versions of things that are perturbing and perturbing are our day-to-day understanding of what’s going on and therefore making us better able to deal with unexpected things

[00:32:04] Sophie: [00:32:04] yeah. So I’ve got a question for you, Dave. Cause there was some, you know, they went through sort of all of these different ways that neuroscience research supports this new hypothesis. And there were a few things that they sort of refer to, which, from what I could tell, basically suggested that sleep improves performance in certain things.

[00:32:20] And like, how can you tell that? It’s just not because you’re well rested.

[00:32:24] David: [00:32:24] Well, that’s an absolutely valid question. So, um, I learned some things about sleep in this paper. Sleep is not something I’m an expert in, but apparently there’s a thing called glymphatic drainage,

[00:32:34] which is something that, yeah, it’s basically a clearing mechanism. So when you go to sleep, there’s this drainage of the cerebral spinal fluid through the blood brain that removes metabolites and things like that.

[00:32:45] That’s apparently one of the reasons that we sleep and that’s a fairly recent finding.

[00:32:49] That’s something we’ve learned fairly recently. So yeah, definitely separating the effects of sleep deprivation from that regard and separating the effects of sleep deprivation from the point of view of you weren’t asleep so you didn’t dream is a difficult thing, but they poses something really interesting, which is that if it’s true, that going through these fantastical versions of everyday events is good for us being able to generalize things and be able to deal with the, unexpected. Then you might be able to give people dream-like experiences that would do the same thing without sleep.

[00:33:18] So they talk about showing people um videos or giving them virtual reality experiences of the sort that might rejuvenate them. So they give the example of like a pilot who’s been flying for eight hours and is maybe over fitted to the task of flying. So then you give them a VR headset and for an hour or something you put the plane on autopilot and give them some hallucinatory, fabulous experience.