http://downloads.bbc.co.uk/podcasts/worldservice/forum/forum_20141018-0900b.mp3

This is a download from the BBC.

Welcome to The Forum, a world of ideas, from the BBC World Service, with me, Bridget Kendall.

What explains the miracle of bird migration? How is it a tiny song bird knows where to head for when flying thousands of kilometers? And how does that compare with how we humans find our way through a landscape?

Natural navigation is our subject today, not the way we use maps or satellite-based navigation systems on mobile phones or in cars, but how we use our senses and the world around us to judge distance and know where we are.

Around the Forum table today, leading British bird-watcher, Tim Birkhead, who spent decades unraveling the mysteries of avian behavior; writer and explorer, Tristan Gooley, who's one of the few to have sailed and flown single-handedly across the Atlantic; and joining us from the United States, neuro-scientist Jennifer Groh, whose experiments investigate how our brains create our sense of location. Welcome to all three of you. And can I start by asking you each to sum up, very briefly, why you are interested in natural navigation ... Jennifer, what about you?

Well, I'm interested in all the different ways that our senses and motor systems work together to gather the fundamental information that we need to do simple things that involve space. Everything that we need to know to be able to recognize faces, recognize any kind of visual stimulus, recognize objects, uh, how we use the auditory system to localize sounds and tell where cars are coming from when we cross the street ... all these things get put together to allow us to navigate within our immediate environment and to travel ... ultimately to travel longer distances.

OK. Well, that's one type of navigation. What about you, Tim? / I'm interested in animal behavior. I teach animal behavior to undergraduate students. And the focus of my courses, over the years, has been in an area called behavioral ecology, which is about the adaptive significance of behavior. And, relatively recently I realized that we've been ignoring more mechanistic aspects of behavior, so I started beoming interested in animal senses, and was just completely consumed by them, fascinated by the fact that so few people had really studied the senses of birds. So, I kind of set out to try and rectify that in my course.

Tristan, what about you? / Well, natural navigation became my passion because I'd undertaken some quite long journeys, and what I discovered about 16 years ago is that we can get that sense of excitement we had as a child over a very very short jorney if we don't stare at all the kit we've got used to, whether it's paper maps or electronic maps. If we use the natural clues, then a very short journey becomes like an exciting big mission. / So, looking at the world around us? / Exactly.

Let's start with you, Tim Birkhead, and your work. You're a professor of behavioral ecology, as you said, at University of Sheffield here in the UK. And, amongst your work on bird behavior, for over 40 years, your life-long interest has been in the study of guillemots on a small island off the coast of Wales in the UK. The island's called Skomer ... and every year, some 25 thousand guillemots come back to exactly the same spot to breed and nest. Tell us a bit about these sea birds. Why ... why have they held your attention for so long? What ... what do they look like?

(3:20)

OK. They look like a little penguin, they can fly ... about, uh, 30 centimeters high, and weigh about a kilo. And although there are 25 thousand pairs of guillemots on Skomer now, uh, when I first started in 1972, there were just two thousands. They're desparately vulnerable to oil polution. But things have kind of got better. There is still a long way to go from where they were in the 1930's, when there were hundred thousand pairs on Skomer.

ギルモットは、見た目はペンギンに似ているが、飛ぶことができる。体高は 30cm ほど、体重は 1kg ほど。今、スコーマー島には 25,000 組のつがいがいる。1972 年に調査を開始したときはたったの 2,000 組しかいなかった。ギルモットは石油による汚染にとても弱い。状況は良くなったが、1930 年代のレベル（100,000 組）まで戻すには、まだ道のりは遠い。

Uh, but I spent longer studying guillemots than any other bird that I studied, and I'm passionate about them. ... It's like watching people. They are just fantastic.

You can see you are passionate. You're grinning broadly. And you describe, in your latest book, Bird Sense, what it's like to be a bird, how you rather precariously climbed down the cliff to ring some of the birds with geo-locators, and, this is tracking technology, isn't it, which has, well, really revolutionized what we know about birds' migration patterns.

Completely. There are ... we are undergoing a most incredible revolution in terms of our understanding. For hundred years, people have put metal rings on birds and hoped that some of them, that died, might be found dead, and, from that you would try to piece together where the birds had gone. That ... it's a very, kind of, biased view, as soon as you get geo-locators your impression of what these birds do just changes completely. So, one of the bizarre things that bird-watchers do is something called sea-watching. I've never been a fan of this. You sit on some remote god-forsaken headland watching bird stream pass, and you say, "Huh, a hundred guillemots flying left, three flying right, ... for hours and hours and hours / like train-spotting? / But worse. ... And nobody had a clue what was going on.

And then, suddenly, we put these geo-locators on, and they ... they allow you to plot the position of your bird every ten minutes for a year or up to five years. / Because they measure ... / measures light and dark, and from that, you can estimate roughly where it is on the globe.

(5:05)

And what this showed was that birds from Skomer, uh, at the end of breeding season in July, swim, uh, because they are molting and lose all their feathers ... they swim to the Bay of Biscay, which must be quite a rich ... / .... which is off the coast of Spain. / Yeah, which must be quite a rich feeding ground. And then, by that time / down / feathers are grown, and then, to my absolute amazement, they fly up somewhere near the Faeroe Islands between Scotland and Iceland, and then, a few weeks after that, they fly back to the Bay of Biscay, and then, by the beginning of the breeding season next March, they've come back to Skomer.

スコーマー島で繁殖するギルモットは、７月に繁殖期が終わると、ビスケー湾に渡ります。換羽期のため羽がすっかり抜けてしまっているので、泳いで渡ります。ビスケー湾はよほど良い餌場なのでしょう。次に、羽が生えそろうと、フェロー諸島のあたりまで飛んで渡ります。その数週間後には、またビスケー湾に飛んで戻ってきます。そして、３月に繁殖期が始まるまでに、スコーマー島に帰ってきます。

So they ... that explains those lovely north-south movements that they, sea-watchers saw, ... suddenly it makes sense.

So, now we know about the patterns of migration, and bigger questions are, how and why do birds do this? Um, one factor is what's called migratory restlessness, isn't it, which is, the urge to migrate and the instinct of which way to fly, and one way that we've been able to measure that is something called an Emlen funnel. Tell us how that works.

OK. Well, migratory restlessness really refers to the kind of behavior little birds might do in captivity. It was discovered in the 1690's by people who kept nightingales and there was a guy who wrote a book about this and he said, "You might think your nightingale is sick, uh, but it will get over it.", and what people was actually recording was migratory restlessness as the bird fluttered against the cage. And he realized what that was.

Later, people realized that there was a kind of directionality to migratory restlessness. So, in the, ... in the spring, birds hopped in the northery direction, and in the autumn they hop in the southerly direction. And then, in 1960's, a colleague of mine, Steve Emlen, invented the so-called Emlen funnel, which is a cone, uh, about, uh, 18 inches in diameter, of blotting paper, ... at the base there's a little circular ink pad, and then you put a wire mesh on top of it, and you can pop a bird you catch on migration into this Emlen funnel for half an hour or an hour, and it will hop in the direction it want to migrate. / on the blotting paper / feet on the ink, and then it leaves a trace, and, the direction and the amount of ... of hopping gives you a really good index for the migratory, kind of, urge, if you like. And, so, birds that migrate a long way, um, hop for a long time, and birds that don't migrate very far hop for a very short time. People have now used this, using Emlen funnel, as an assay of migratory behavior. And it's revolutionized the way we understood migration. And I always think it's slightly paradoxical that we are using birds in little cages to understand how they traverse. / These thousands of kilometers and miles, yeah.

And, but then, the next question is, well, you know, how do they navigate? And what's the latest thinking on that?

Well, birds have a series of navigational aids, which is a really sensible thing for natural selection to have done, because, if ... if you are a night migrant, uh, you would use the stars, but if it's cloudy, you ... you don't just stop. You ... the next one kicks in, and then you might use your sense of the Earth's magnetic field. If you are a diurnal migrant, you might use the sun __ __ sun compas. And, of the various methods that birds use to navigate, the most controversial, and difficult to study, has been this sense of the Earth's magnetic field. That's partly because there's no magnetic organ. So, if, you know, if you're depending on vision, you've got eyes, if you're depending on olfaction you've got a nose, but where is the magnetic organ? And there've been lots of controversy over that. ... Starting at about 1950, um, people showed that, if you had a bird completely in the dark, sometimes they could navigate perfectly well in the direction they should go. And the only explanation was that they were using the Earth's magnetic field ... you design an experiment where you use a huge magnet to reverse the Earth's magnetic field, and the bird changes direction.

So, that seems pretty conclusive. / That ... that was the evidence. Now the question is, how do they do it? / And where is this little compas?

And, where is it? We don't know. But the most likely idea, remarkably, is that it's in the eye. And some researchers have suggested it's just in the right eye, which is even more mind-boggling. As I say, it's controversial, it's still ongoing research. We don't know. But it looks as though there's an interaction between light and particular receptors in the eye and the Earth's magnetic field. And, the way I like to think about it is a little bit like seeing an after-image, after you've been looking at a bright light, that's super-imposed on what you are looking at that presumably allows the bird to see the Earth's magnetic field and to help it navigate and find its way.

And, presumably, these receptors must have something like iron in them to respond.

No. That's ... well, no... that's the other idea that there are particles, tiny tiny particles of magnetite in the upper part of the bird's beak. That's the alternative, uh, hypothesis, for which there seems to be less evidence now. So, looks as though the eyes are crucial thing.

I can see you are listening very intently, Tristan, as a man who's interested in human navigation tools ... the way the birds do it. Well, they have one up on us, don't they?

Well, they do, but there they've been such an ispiration, and everything Tim said is really resonating very strongly with me, from the migratory restlessness, which is a wonderful expression I haven't heard before, but I just instantly relate to because I was that kid who would see a hill and think it might be more fun at the top than the bottom, and then the hill became mountains ... but, more recently, I've taken a lot of inspiration from the birds, and I led a two-man expedition from Scotland up into the Arctic Circle, and what I was trying to do is to prove that the ... the viking references to animals. In particular, birds could be used as what in modern terms, we might think of as radar. So, if you count ten or more birds in a random 5-minute window, there's a very high probability that land is within 40 nautical miles, and if you count two or fewer, there's a very low probability that the land is within 40 nautical miles.

But maybe the probability ... I find that a bit surprising, though, if you think about how far birds can fly when they migrate. __ some of them it could be as long as a week, right?

Often the small birds are doing it at night, so you wouldn't see those, and often they are very high. So, I can relate to that, exactly.

We used modern technology to prove very old methods. So, we would use GPS to work out how far from land we were, so had a very accurate figure on that, and then use viking methods, i.e. just looking out to see, and we found there was a very strong relationship between not just bird numbers but whales, dolphines, jerryfish ... even less beautiful things like rubbish. The amount of rubbish you see in the sea is actually quite a good measure of where you are relative to land.

But, do you think, Jennifer, ... I mean, as far as we know, as Tim said it, human beings don't have this magnetic sense. ... So, do the birds have one up on us on that, or is there something else that we have that could, sort of, compensate for that?

Well, they certainly seem to have something that we don't have, and many animals that have senses that we can't even conceive of. For example there are fish are sensitive to electric fields, and snakes are sensitive to ranges of light that we can't see. ... It really tells us, you know, that our senses are special and are limited, and we can't see what's outside the range that our sensors are able to detect.

Although in some ways I guess we can ... you know, as you've been saying, Tristan, we can learn from these creatures because another skill that birds use, Tim, is echo-location, kind of clicking and then hearing the sound reverbrate back.

There's ... there're a small number of spieces that can, uh, echo-locate, like bats or oilbirds that breed in Central and South America and some cave swiftlets. They breed in these caves with absolutely no light, and they manage to find their way around. And, uh, I was intrigued by this when I was doing the research for bird senses / I'd read that / blind people could often echo-locate. So, I decided I would test myself on this. And there was a room in the University, where, as I opened the door, I scraped on the floor, and I could tell from the echo of that scrape whether there was anybody in the room or not without being able to see. So, over a period of eight months I __ tested myself every time. And I got to point where I was 80% correct. If you, kind of, consciously try to do that ... we know that the brain will readjust itself, and, so, in a way, it's not surprising that you get better at something like that.

I ... yes. Again, this is, um, I'm getting very excited because these are experiments I do when I'm running natural navigation courses is I ... I get people to walk towards a wall in silence, I stop them / ask / how far __ think they are from the wall, and I get them to repeat the experiment / whilst making a constant noise / I say, "You are going to feel silly __ la la la la, and ... and, they can genuinely pick up where the wall is. And I was just absolutely stunned by the brilliance of ... some blind people can work out where furniture is just by picking up the way the carpet tension changes. If you walk over a carpet in bare feet or socks, (靴を履かずに) it will feel different as you get near to furniture.

That's amazing. / That is extraordinary. That's a whole area for research for you, Jennifer. / Yes. I'm taking notes.

Let's come on to you, Tristan Gooley, um, talk a bit more about human navigation. You are a writer, navigator and explorer, and author of The Natural Navigator and The Walkers' Guide to Outdoor Clues and Signs. And, in particular, you are interested in these ideas of natural navigation where we don't use those aids like GPS or map or compas, and, in fact, you studied the navigational methods of traditional peoples like the Tuareg of North Africa and the Arab Bedoins, and the Dayak people of Borneo, as well as having flown solo and single-handedly across the Atlantic. I guess you used navigational aids for that （それには GPS とかを使ったのでしょうね？）.

I did, yes. My philosophy is not about making things difficult. (そうそう。別に、わざわざ難しくしたいわけじゃありませんから。) It's about trying to make things interesting. And, we can have the best of both worlds these days. We can use the technology that's available to make things safer. But we shouldn't think that our map or GPS is ... is the world, because every second we spend looking at even a wonderful map, is a second that we're not looking at the richness of the world around us. And that's something that really proved to me, spending time with ... with people like Dayak and Tuareg is / they see detail that the technology-obsessed, you know, traveller just wouldn't even think to look for, let alone, spot.

So, for example, walking across the Sahara with the Tuareg nomads, What did you learn from them?

For example, anywhere you are on ... on Earth, once you understand the relationship between the wind and that place, it doesn't matter if you are in the center of a city or in a very remote region. If you understand the relationship between the wind and the land or the sea, you can start to find your way. So, in the case of the desert, the Tuareg were absolute experts at understanding that a prevailing wind will scalp the sand in certain shapes. It will be firmer on the side the wind has come from and softer and slightly steeper on the downwind side. So, what looks like a ... a pile of sand, you quickly appreciate, is a compass, and a fascinating one.

So, just as the, uh, birds might not just use the sun and the moon and the stars but resort to their magnetic sense if they are flying in the dark, you are saying the Tuareg would look at the shape of the sand.

Yes. The most exciting thing for me is, all of these techniques, every single one of them, can be brought much closer to home wherever home is. So, for example, wherever you see any small particles that have been blown into a little hill / So, it can be a sandy beach near home / but / it can be equally / can be little bits of leaves / blown into a pile ... once you understand the simple relationship between wind and the things that the wind carries ... sand, snow, leaves and dust, we find these little compases literally all over the world.

I read that, when it comes to modern urban setting, you'd identified 14 natural clues that could help us orientate ourselves and get around.

Yes. They are almost limitless. And each day, I'm delighted to say, they grow. I mean, I think I'm up to about 19 different ways we can use ... religious buildings / OK / You can use modern techology in an old-fashioned way. So, TV satellite dishes show trends. And, wherever you are in the world, once you understand which way they point ... it's, broadly speaking, towards the Equator, but, uh, in different parts of the world you get different trends there. ... We can use nature itself. So, lichens are very sensitive to light and moisture, quite a few other things, but ... / These ... these are mosses that grow on trees and things like that / Well, mosses ... mosses are one family. And lichens are another, and you can have a lot of fun without getting too scientific just by noting trends. If you notice that one side of a building, you know, near you, is covered in something, ... you don't have to be able to name it, you just have to spot it, and then you see the other side isn't, you are at the beginning of quite an exciting journey of being able to navigate without any instruments in a town.

What you are talking about really is kind of taking us back to an earliest stage in our, kind of, evolution ... these people you've talked about crossing the desert, it was a matter of life and death to notice those kind of things, so, natural selection weeded out the duffers that couldn't do it, and the survivors survived, and, living in our current urban environment, ... none of that matters to us, does it, but I think what you are doing is kind of allowing us to ... to re-invent that and re-experience. I think it's wonderful.

Tristan is, sort of, saying the same things that you are saying but in a more scientific way, isn't it, Jennifer, that this is absolutely crucial to ... / Absolutely. / ... where we are as humans /

I think absolutely so. And, another thought that I'm having while listening to what Tristan was describing is that he was giving me insight into why, where I live now, I feel more confused about how to navigate around than I have in some other places that I've lived. There are no mountains, there are no view of the oceans or anything that often provide / sort of, anchoring framework for knowing where you are. And that's what I tend to lack. I have a harder time being able to point to where the north is then, uh, than I have in some other place I have lived.

It's very interesting, and I come across this a lot, and I can relate to it as well. If get lost, it's much more likely to be in an urban setting than a remote one ... um ... the desert is actually quite easy once you've ... once you've picked up a few fundamental skills, but cities remain wonderfully purplexing for a long period __ and quite often I find people ... exactly as you were saying earlier, Jennifer, is this use of different skills, complementary skills. So, something I say to people is, if you're finding the cardinal directions are a bit confusing, there are a lot of ways of ... a bit like the birds do, we migrate as well in town, so, if you're totally and hopelessly lost in a big city, if you go against the flow of people in the early morning, or, with the flow of people towards the end of the day, you find __ station quite quickly, which is a lateral solution, and there's no / north, south, east or west involved. It's just another way of solving the same problem, I suppose.

I love that idea, using the movement of people like some kind of natural ... natural flow. / Sounds potentially dangerous to me.

You've got a natural navigation school, haven't you, Tristan? You take people out in the countryside and give them tips on how to orientate themselves ... because I was wondering, if you felt that natural navigation is a kind of instinctive or genetic memory, or has to be learned, and, as you're telling us, has to be re-learned now by us, because it doesn't come naturally necessarily.

It's a slightly controversial area, and the debate rumbles on. And I think it will do for a very long time because there are, as Jennifer said, there are enough overlapping areas and techniques we can use here. So, I have yet to meet anyone who is infallible, uh, myself very much, you know, uh, included. Uh, but, the most interesting thing is, we can move a lot of the things that our ancestors used to do subconsciously into our ... into our conscious brain. So, a lot of people, hundreds and thousands of years ago, would have worked out which way, roughly, they were going without thinking about it, because they were aware of where the sun was, because they would be in real trouble if they weren't. What I'm doing in my course is, saying to people, if you choose to, mainly because it's fun and interesting, not because you are likely to get into trouble if you don't, this is how you do what our ancestors did.

I was gonna ask you about that whether you thought that this was, um, intuitive, you know ... people you crossed the desert with ... they don't have to think about it consciously. They just, kind of, already know, but, previously, about 20-30 years ago, there was somebody that imagined that we did have a magnetic sense and would have claimed that in ... even in an environment like this, if you took in, you know, 50 people and said "Which way do you think is home or north?", he would have claimed that they could have done that, you know, on average. Do you have a kind of view on that?

<20:57>

Yes. I found the most interesting clues to that, referring to the people who've held onto survival knowledge, and quite a few people talk about believing they have a sixth sense, but when you actually drill down what they were doing, they have just spent an awful lot of time outdoors, quite often in key periods of their life.

So, is it about knowledge, but maybe __ you absorb it / unconsciously / consciously, because I was thinking about using the sun to orientate yourself / because it depends on what time of year it is and where you are, doesn't it? It's not as simple as, you know, there's the sun.

No. You are absolutely right. And the thing that's really struck me and keeps me, sort of, passionately, sort of, driving these ideas forward is, the percentage of people in the world who know where the sun rises, even at their home, is dropping, I think, quite dramatically, and I even see that now when I visit some indigenous people, that, they quite often talk about how their parents knew things like how to use the stars and where the sun was at different times of the year, but even those people these days are losing those skills like us.

And one of the most remarkable things about bird navigation is their ability to adjust for the position of the sun. So, their ability is not just being able to use the sun, but also reckoning there's a clock inside the bird's brain that says, "Given that it's this time, this is the direction you can go", 「今の時間はこれこれだから君の進むべき方角はこっちだ」 and the same is true for the star compasses as well.

So, you are saying that, whereas ... if we are humans, 人間の場合は we need people like Tristan to remind us and teach us / for birds ... they don't need their parent birds to tell them how to do this?

No. There is ... there is some learning involved. Uh, so, uh, there's a very nice evidence that the duration and direction of your migratory restlessness is inherited, very strongly inherited. And young birds use that to get from where they are raised to where they've got to spend the winter. But then, when they've got to where they want to spend / the winter, they imprint on the landscape, and they use that learning then to subsequently refine where they are supposed to be. / Fascinating.

(22:50)

This is The Forum from the BBC. Today: natural navigation in birds and in humans. And how does our brain help us map out where we are and where to head for? But first, time for our 60-second idea to improve the world. And this week, it's from American experimental neuro-scientist, Jennifer Groh. And, Jennifer, your task is to win us over in just one minute ... that's me and my other two guests, British ornithologist, Tim Birkhead, and explorer, Tristan Gooley. So, off you go.

Well, about eight years ago, I started learning to play the banjo. I found a teacher, and I practiced every day. I joined a band, and I was quickly making progress. But about five years in, I seem to stall. I just stopped gettting any faster. And speed is very critical for banjo music. So, my idea to improve my world and the world of people who play musical instruments is to have a brain pacemaker that would allow us to play faster. Just as a heart pacemaker uses electrical stimulation to alter heart rhythms, I'd like a device that would allow people to speed up activity in the motor cortex to make our fingers move faster. Humans are unusual in that we have control over how fast we talk and how fast we play music. We can choose to play a song slowly or quickly, whereas birds sing their songs at a particular stable tempo. We don't know how the brain controls the tempo of music and language, and we don't know how our brains get faster with practice. I guess you could say I'm looking for a shortcut to help us keep up.

That's lovely, Jennifer. Thank you so much. ... I must say, the idea of brain pace-maker ... I just find it a bit kinda creepy. It's ... it feels a bit terrifying to me, a device that could speed things up, including the rate of your fingers. You know, it reminds me of those fairy stories, where you have magic shoes that dance so fast and so long that the wearer's feet are torn to shreds. Maybe you should be careful what you wish for here.

Oh, well. That is a little creepy, yeah. I should say we are not very close to being able to do something exactly like this. But there are devices that are implanted in the brain, such as deep-brain stimulation for Parkinson's patients, or prosthetic devices implanted in the cochlear for correcting hearing loss. So, I'm thinking of something like that, but we don't know exactly where we should put it or what it should do.

What do you think about this, Tim, because, uh, Jennifer referenced birds who have this even tempo when they sing their bird song?

OK. Well, I sympathize with / your position. / I play the guitar. I've stagnated in terms of speed, and if you are a lead guitarist, you know, you are supposed to be fast. But also worry that, if you are too fast, then all those sounds merge together, and the human brain isn't very good at distinguishing those sounds, whereas bird brains are extremely good at separating out sounds that are very close together in time. Um, so, I'm ... I'm actually pretty happy with how fast I can play the guitar.

What about you, Tristan?

Um ... I find it a little bit scary, as you might imagine. If we can do that, I don't see why we can't go the next step, which is, we could go to a concert and, with our smartphone, we can actually change the speed of the musicians we are listening to. We'd have to have some sort of averaging system so that everybody in the audience was inputting and it would just get faster and slower until there was a sort of average everybody in the audience was quite happy with. But it's making me feel quite peculiar.

Well, lovely idea. Thank you, Jennifer, for your 60-second idea. And, there are more 60-second ideas, or, indeed, whole programs to download for free on our web site. Just go to bbcworldservice.com/forum.

Now, we've been talking about birds and humans, but let's talk a bit more about navigation and the human brain. And your work, Jennifer. You are a neuro-scientist at Duke University, North Carolina in the U.S.A., and you've got a particular interest in how the brain weaves together the information that it gets from our senses to figure out where we are and how to navigate our way through our daily lives. You've just rolled out a book about it, called "Making Space: How the Brain Knows Where Things Are", and, in fact, it goes even further to ask whether the brain systems for thinking about space may help us understand the systems of thought itself. ... But let's start with what you call the computational power of our brain needed to figure out the simplest details about spacial relationships. Can you give us an example?

Yes. So, one example is how we use eye movements to update our visual scene. So, as you experience your visual scene, it seems like a very stable visual image. But, in fact, what's happening on the retina, is changing constantly. And it's changing constantly because we are moving our eyes around, and we move our eyes about three times a second, and, they move at the speed of about 500 degrees per second. So, that's as if the eyes could go around the head one and a half times in the space of just one second. So, the computational power of the brain here is that it is combining information about what direction this, uh, the camera of our eyes is being aimed by these eye movements, uh, together with the image that the camera of the eye is receiving. And it's, kind of, rapidly stitching together these different snapshots to give us an experience of a stable visual scene where we can see clearly across the entire visual scene, even though, actually, we never experience that at any moment.

Well, I've found it particularly interesting, in reading about your work, though, that this isn't just about the senses. It's also about memory __ that you have to know where you were as well as where you are now, in order to make sense of it all. We are kind of aware of this from people who have degenerative diseases like Alzheimer's and lose the ability to remember, then they also lose their sense of where they are.

That's right. And it turns out that the brain systems for navigation and the brain systems for storing memories seem to share a common infrastructure. Um ... and, I think this is one reason why, when you go to a college reunion, for example. memories that have been dormant for, you know, for 20 years may come flooding back to you, because you're ... you're back in the places where you were ... and that seems to be a filing system that allows you to re-access that information.

And ... and this comes down to the area in the brain known as the hippocampus, doesn't it, which seems to be vital for our ability to find a way around, but also responsible for memory. What ... what is ... what is known, scientifically, now, about the link here, that ... that ... of what's going on in the brain, the connection that is being made between spatial navigation and memory?

Well, so, one of the first things that was known about hippocampus came from, uh, some tragic, uh, surgical cases from the 1950's. A famous patient, who later became known as H.M. had suffered a bicycle accident when he was a child, and had developed intractable epilepsy. And surgeons removed the hippocampus on both sides of the brain to try to cure this epilepsy. But what happened as a result of that was quite tragic, on its own right, and, that was, he was no longer able to form any new memories. So, he couldn't remember people he'd met or places he'd been, or anything new that had happened to him since that surgery. But the connection to navigation wasn't realized until somewhat later when experiments in rats revealed that neurons in the hippocampus are sensitive to the location of the rat in the environment. So, um, and this was discovered by John O'Keefe and several of his colleagues.

And he ... in fact, he's just been awarded a Nobel Prize for this, hasn't he?

That's ... that's right. And it's really amazing work. So, what happens is, if you study a rat in a laboratory setting, you allow the rats to wander around the laboratory, and you measure the activity of neurons in the hippocampus while the rat is doing this / you'll find that there will be a location in the laboratory setting / where a particular neuron might become active and other neurons are active when the rat is in other locations in the laboratory environment. And, altogether, the neurons in the hippocampus seem to form a representation of where the rat is located in space. And ... by the way, this representation is very sensitive to what are the stimuli that the rat can experience from these locations. And, if you make the laboratory setting very impoverished so that there aren't very many cues to where you are, but you put one, say, really big obvious cue like a big white flag on the wall or something ... if you rotate that flag when the rat can't see that you've moved it, and then bring the rat back in to the laboratory, his entire cognitive map in the hippocampus seems to shift to track this change in the landmark.

What does it make you think, Tristan? 'cause you've been thinking about navigation as a way of helping us to get around, but here, Jennifer is pointing out to us that it's not just about knowing where you are, it's about knowing where you were. ... It's about the past as well as the present.

Yes. Again, all of this is very exciting for me to hear because, out there in the field with, mostly walkers, but also __ teaching sailors as well ... sailors, for ... for centuries, have depended on something called "deduced reckoning" / which is as simple as / you knew roughly an hour ago or 24 hours ago, and ... and where you were earlier was really some of the most treasured knowledge on a boat for hundreds of years. The thing that I get, sometimes a little bit worked up about, in a good way, I hope, is that, I think sometimes the academic community assume that, particularly in a more wild setting, that there are a very small number of clues to location. For example, academics quite often talk about a mountain top in the distance, if there is the sun, if there is the moon, ... / and / part of what I'm tryinig to do is to point out there are all those things but also probably several hundred things. And I wonder whether those two ideas come together. Maybe the rats are picking up clues that aren't just flags but are very very subtle clues to location and direction.

Absolutely. I mean, one of the things that really made me think about this was that, we see the world in a very crude, massive pixel kind of way. Birds and other organisms see so much more we haven't even begun to understand the way animals perceive their environment, in exactly the way you've just described.

That's a rather profound comment, isn't it, Jennifer, for these sorts of experiments, because the conclusions you are drawing from them are conclusions through the perceptions of humans. Maybe something else is going on.

Yeah. It took a ... many decades of work after these hippocampal place cells were first discovered before people were really convinced that what was reflected in the activity patterns, was, what did the rat think about where it was? And, this is very consistent with what Tristan is saying, that there are many different ways that you can, in principle, know where you are. And, I think that the current thinking is that, you know, whatever it is that you are using, that's what your hippocampal place network is likely to reflect.

But we don't all orientate in the same way, do we? I mean, even different humans are different. For example, I have no problems making my way to a destination when I'm driving a car. I'm quite a good map-reader, I think I have a good sense of spacial awareness. But I'm absolutely terrible at distinguishing left from right. If I'm in the passenger seat and am navigating, and I tell the driver to turn left, I probably mean they should turn right.

Is it a problem of naming the direction, or of knowing what direction you should go?

I think it's probably in name, actually, because, if I use my hand, I say, "Go that way", then I get it right. But, if I say "Go left", I might very well get the wrong one.

That takes me, um, straight to my conversations with the Tuareg and the Dayak. If I ask them how they're doing things, the ... the conversation breaks down, I mean, even once we've got over the language hurdles. If I ask them "Can you point towards the village we are walking towards?", they will get it right. / and / (if) I say to them "How are you doing that?", they can't label it.

So, how do you explain these quirks in how the brain processes the spacial information, Jennifer?

There is a lot of individual differences that we haven't fully appreciated. Uh ... I was startled some years ago when my spouse and I was standing in our yard, and, we were looking at one of the windows. And I knew exactly what room it, the window, was from. But my husband didn't know. And I thought it was quite strange that his sense of location within the house didn't map on to his sense of location outside of the house, that these were, kind of, two distinct worlds for him.

It's ... it's really fascinating, all this. One other thing I was thinking about ... you were talking about the link between memory and spacial awareness. There ... there is a practice which was used in the ancient world, which was to have a "memory palace". So, if you wanted to try and retrieve an awful lot of information, you would imagine a palace and store the memories in different rooms, and then, in an imaginary way, walk through them in order to retrive the memory. And it sounds, from what you are saying, as though, maybe, ... phyciologically, in our head, this isn't surprising because these two processes are happening in the same part of the brain.

Correct. I think that's a way of, sort of, deliberately making use of the link between navigation and memory to try to, on purpose, remember a set of things that might otherwise be hard to remember.

There are lots of take-aways from program today. We've all got to go away and eke a location __ __ __ memory palaces. / and also

One thing I must ask you, Jennifer, is / that / intriguingly, you say / all this navigational work done by the brain you believe is so important that the brain's systems for thinking about space, may also help us understand the systems of thought itself. What do you mean by that?

Well, it was noticed by linguist, uh, George Lakoff and philosopher Mark Johnson some years ago, that there's a particular pattern to the language metaphors that we use for things that are not, in or of themselves, spacial. So, for example, you might refer to having a close friend, or a distant relative. And there you are using words that concern spacial relationships to describe things that are not themselves spacial. And this got me really thinking about the extensive networks concerning space in the brain, make this idea seem very plausible, that, uh, if we use a system that's completely distinct from our spacial systems in the brain, we really wouldn't have that much brain tissue to work with for these kind of things. So, I think it makes a lot of sense that you're going to use the kind of organizing principles that are probably the most important organizing principles that we have and we are gonna use those for some of the cognitive abilities and intelligence that makes us human.

(37:29)

It raises a very interesting question, which is, if so much of the brain is being used up with spacial processing, then does that mean that, if you use navigational aids like GPS and maps, which give you a kind of shortcut, does it free-up the brain from doing all this hard computational stuff, so you can do other things and think other thoughts? Or does it mean that the brain isn't getting the gym that it needs and it could atrophy because it really ought be doing all this stuff which Tristan has said that we ... we got out of the habit of doing? What do you think? Jennifer?

I think that's exactly the right question. And, the right way to think about it, it could be either of those. It could be both of those. Uh ... it probably depends on how you use the time that you would otherwise be spending, uh, carefully attending to how you get from one place to another. So, if you just zone out and don't do anything with it, um, then you ... maybe you are not flexing your brain as a muscle, and maybe there's ... those skills are atrophying. But if you are using that time to listen carefully to um, an interesting radio program, for example, then you might be able to use that spacial infrastructure for other kinds of thinking, uh, during that period of time.

Fair enough, Tristan? Would you think you should actually be doing the navigation rather than writing War and Peace or a new symphony?

No. I ... I think natural navigation is ... is really really rewarding. But the analogy I quite often come back to, is, cooking fine food. We don't ... most of us, want to be in the kitchen all day every day. Equally, we don' want to go our whole lives without having that joy of preparing our own food occasionally. So ... so, knowing how to do it, choosing to do it occasionally, but not feeling you have to do it all the time, is probably the best of all worlds.

Tim? / I'm a firm believer that, if you don't use it, your brain just goes to mush （脳みそは使わなければおかゆになる、というのが私の持論でね。）/

So, ornithology sat on the fence / but you think we should definitely hone our navigational skills? / Absolutely. Yes.

Follow the birds. That's a great way to end our program. Thank you so much to all three of you, Tim Birkhead, Tristan Gooley and Jennifer Groh. Next week: Entangling with robots. Are some of them becoming too cute for our own human good? The Forum travels to New York to hear from leading robotics designers about the latest interactions between man and machine. Until then, from me, Bridget Kendle and all of us here at The Forum, have a good week. And, for our bird song to end our program this week, given your life-long interest in guillemots, Tim, we've chosen a recording of them, perched precariously on the cliffs of Skomer island just off the coast of Wales.