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(soft rock music)
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A lotta people ask me "What does my dog see?"
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We could guess what a dog sees, but we can't
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really tell you what its brain is processing.
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Their sensory worlds are not like our sensory world.
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They're living in a world that we would probably
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love to occupy for a little while, but it's not like ours.
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Vision doesn't play the role in their lives
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that it plays in ours, they don't have the kind
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of sharp detail vision that we have,
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so they don't see the fine structure of things
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that we're able to see, and their color vision
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is somewhat simplified compared to ours.
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So they don't see anything in the reds,
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so their vision is concentrated in blue and green.
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And frankly, they don't care much about color.
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It's just not important to them.
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They care about brightness and motion and shape.
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They have better vision at night
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than we have, probably, if you take a photograph
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of your dog, you'll often get some eye shine back.
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So there's a layer behind the retina
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and its function is basically to return light
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back through the photoreceptors.
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So, it provides a second chance for any light
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that wasn't absorbed on the first passage
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to be absorbed on the second passage
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as it bounces back out through the eye.
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For example, you can find animals,
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often by using a headlight, and you'll see the eyes
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of animals looking at you, and it's because it's
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reflective lighting on the back of the eye.
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(soft music)
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You see a lot more eye shine in something like a cat
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than you do in a dog.
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I mean, a cat probably can see in light
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about half as bright as we can,
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which might not seem like a big change,
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but, in fact, that takes them into a whole range of vision
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where we're not seeing anything
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and they're seeing things reasonably well.
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You'll see often, these sort of night camera views
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of a cat looking for prey, and I think
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it's not completely unreasonable,
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as to what they might, at least be able to pick out
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that we would miss entirely, even looking
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at exactly the same thing, with the same lighting,
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it's not gonna be the same for a cat's eyesight.
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In general, predators have anteriorly placed eyes.
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So if you look at any of the cats,
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any of the dogs, you're gonna see eyes
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in the front of their faces.
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They're predators, they're looking forward,
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they're looking for prey.
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Prey animals have laterally placed eyes,
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and the benefit of a laterally placed eye
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is it gives the animal full, 360 degree coverage
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of the horizon at all times.
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If a predator occurs anywhere, they don't want to miss it.
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So the best way to do that is to have good vision
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in the regions where you expect a predator to be.
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If you're a prey animal, you're normally
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in an environment where the horizon's fairly flat.
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You're in some kind of open country,
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and you're looking at the horizon.
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Predators are gonna appear somewhere on the horizon.
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If they're near to you, if you're unlucky,
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maybe far away, but wherever they're gonna be,
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they're gonna be at your level.
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So, how do you solve the problem
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of looking in all directions?
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Well, on most animals, that have eyes built like ours,
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have a part of the retina that's adapted
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for the highest quality of vision.
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We have a thing called a fovea at the back of the eye.
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Fovea means a hole or a dimple, that's our fovea.
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And in there are the cone cells
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that are adapted for best vision.
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Prey animals have what's called a strip fovea.
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The fovea actually extends along the back of the retina
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in a line reaching almost from one side to the other,
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and so, as it looks at the horizon,
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it's seeing good detail at all points
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along the horizon level, so anything
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that occurs in there that's moving,
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or that doesn't look right, it can pick out very quickly,
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and therefore take evasive action.
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If we're talking about eyes that have really
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excellent acuity, then we have to turn to the birds,
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because the birds have eyes
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that are the most adapted for high quality vision.
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Birds have incredibly variant ecologies,
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they dive, they are fruit eaters,
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they are predators.
(bird shrieks)
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The ones that always capture human imagination
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are the raptors, and the reason is
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because they do, in fact, have the best vision
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of any animal, with the highest acuity
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of any animal that we know of.
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Raptors also have a fovea, but it is deeply indented
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into the eye, much more deeply
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than ours is, and so that has much greater surface area
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than just a cup shaped fovea has.
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So as light enters this deep pit,
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it actually diverges and magnifies the image
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to a small extent, so it's like having binoculars.
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A very small patch, but with extremely high acuity.
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So to have, like, a peregrine falcon,
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the eyes are almost the same size as ours
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in an animal that's immensely smaller than us,
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and its acuity is about five to seven times ours,
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and so when a peregrine is flying,
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a thousand meters high in the sky,
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it's still capable of picking up movement on the ground
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at great distances, and to locate prey
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and to decide which are useful to attack
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and which ones are not worth attacking.
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(string music)
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Let's talk about owls for just a minute.
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Owls have eyes that are sort of tubular shaped,
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in other words, the eye is not
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a perfect sphere like our eyes are.
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And by making it tubular, the animal is essentially
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disposing of part of the volume of the eye in the head,
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and can make more of that volume available
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for frontal vision as a result, so the two eyes
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can be packed relatively close to each other,
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but they can still have really large magnifications,
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which means that the image is large on the retina,
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which means that the owl has good detail vision.
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(birds chirp)
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Now, interestingly enough, eyes like that of an owl
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turn up in one other place in the world,
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and that is in the deep sea.
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Deep sea fishes often have tubular eyes.
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A good example is the hatchetfish.
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Hatchetfish have gorgeous tubular eyes.
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This is adapted for restricting the visual field
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to just looking overhead of the fish.
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If you're in the deep sea, the best place
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to look for something is directly overhead,
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because that's where the light field is.
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The light is compressed by the refraction
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at the waters' surface into a circle of light
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straight up over the fish.
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And that circle of light can have prey in it,
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or it could have predators in it,
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and so these animals often will build eyes
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that can just see that little bit of the world,
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looking straight up and look for prey in that part.
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And hatchetfishes hunt by looking up
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and then striking from below.
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The big advantage of vision, and the reason
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why it comes up again and again in animals,
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is it gives you fairly quick information, and it gives you
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extraordinarily good directional information,
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much better than any other sense does.
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So, that's why it's evolved over and over again in animals.
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Making an eye is ridiculously easy, evolutionarily,
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it turns out, it's not at all complicated.
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The simplest thing you could have is just a photoreceptor.
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It detects light, tells the creature
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whether the light's present or absent,
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which is useful, 'cause even that can tell an animal
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something weird is going on,
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the light suddenly dipped really quickly.
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I don't think they're thinking this, but the evolution
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is saying, this is a good time to get outta here.
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So the next step is to take that cell and multiply it
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times 10 or a hundred, or a thousand,
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and then lay out an array of these cells
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that can see a little bit of information
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about shape and direction of things.
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It doesn't necessarily see anything,
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but it can respond to things.
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If you look at a flatworm, like a thing called planaria,
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and each of those little eyes is a black pigment,
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which is what you see, and within that pigment
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there's a group of photoreceptor cells,
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and those creatures are then sampling
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a little region of space with each eye,
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and it can tell them which way to swim
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or which way to go if the light changes suddenly
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or if they're, they wanna go towards the light,
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they can orient their body so they head towards that light.
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From there, the obvious thing is to add more receptors,
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a step that every animal has gone through
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at some point in its ancestry is to add additional receptors
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until you get a large number, maybe a hundred,
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in this eye cup that you've got.
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There's no optics there, to speak of,
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except for the shape of the eye.
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So, what do you do?
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Well, one solution is to restrict where light
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comes to that receptor array, and so an animal
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can build what's called a pinhole eye,
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basically close down the opening to that cup
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so it's smaller and smaller, which means
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that the image formed becomes sharper and sharper.
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There's only one really good example
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that can be illustrated today,
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that's the nautilus, which is a deep sea creature.
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You would never expect that would be the one place
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to find a pinhole eye, because deep sea creatures
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don't get much light, and pinhole eyes
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are inherently very insensitive
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because they have a very small opening,
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so not much light gets into an eye of that type,
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and they don't focus it beyond restricting an aperture.
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So the image is extremely dim,
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and why a nautilus, which is a pretty big animal,
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with at least moderately complicated behavior,
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has been happy to sit around with an eye like this
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is kind of a mystery, but nautiluses
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do what they have to do, they don't seem to mind.
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So, nautilus is a real outlier there.
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I think the main thing is the more that I work with animals,
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and the more that I work with marine creatures
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is that these creatures have their own lives
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and that their lives are so utterly different from ours
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that their experience of the world is truly alien.
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(eerie music)
So there are jellyfish,
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it's kind of terrifying to think this,
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there's lethal jellyfish out there,
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jellyfish that can kill a person
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who have eyes that have beautiful, perfect lenses in them.
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They look like a small version of our eye,
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a tiny version of our eye, and they work the same way.
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Now, jellyfish don't have brains,
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they have a ring of nerves that run around the body
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that analyze something, and these creatures
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can make directed responses, they can move towards shadows
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or move towards light, depending on what's motivating them.
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Why they have these insanely complicated eyes
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is not obvious.
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Their experience of the world is truly alien.
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I don't think that we could find anything more alien
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in another galaxy than we find right here on our planet,
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in terms of the way in which it interacts
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with its world and what it needs to know from its world
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and what is important to it.
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Scallops go off in a totally new direction.
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Scallops have about 60 eyes, arranged around the edge
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of their mantle, the part that we don't eat.
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These eyes look around all the margins of the shell
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in all different directions.
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Each eye sees a patch of the world,
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and sees enough detail to tell the scallop
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what's going on in its part of the world.
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The scallops don't even have much of a brain,
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in fact, it'd be hard to define the brain of a scallop.
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They have a bunch of ganglia, which are cell groups.
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We suspect that these ridiculously complicated eyes
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are probably mostly there just to tell the scallop
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when it's time to either close its shell
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or possibly initiate an escape response.
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Scallops are really interesting because they're a mollusk.
258
00:12:40,350 --> 00:12:41,830
Mollusks have the greatest diversity
259
00:12:41,830 --> 00:12:44,798
of eyes of any group of animals.
260
00:12:44,798 --> 00:12:47,090
They go from extraordinarily simple eyes
261
00:12:47,090 --> 00:12:50,120
that can just barely see whether a light's on or off,
262
00:12:50,120 --> 00:12:51,800
to eyes like the eyes of a giant squid,
263
00:12:51,800 --> 00:12:53,500
which is the biggest eye that
264
00:12:53,500 --> 00:12:55,600
we know of that's ever evolved.
265
00:12:55,600 --> 00:12:58,840
Other mollusks are things like octopuses and squids,
266
00:12:58,840 --> 00:13:01,140
and octopuses are interacting with their world all the time,
267
00:13:01,140 --> 00:13:02,340
they're looking for things to eat,
268
00:13:02,340 --> 00:13:04,976
they're particularly alert for predators,
269
00:13:04,976 --> 00:13:08,570
being soft bodied creatures, they're very vulnerable
270
00:13:08,570 --> 00:13:12,880
to predation by anything with teeth or claws,
271
00:13:12,880 --> 00:13:15,210
so it's necessary for them to be aware
272
00:13:15,210 --> 00:13:16,810
of what's happening around them.
273
00:13:18,080 --> 00:13:21,505
Octopus have good vision, they have large eyes,
274
00:13:21,505 --> 00:13:24,271
they have good optics, beautiful optics,
275
00:13:24,271 --> 00:13:26,580
so they can see quite clearly.
276
00:13:26,580 --> 00:13:29,160
So they probably have a sense of vision
277
00:13:29,160 --> 00:13:31,913
that is not so totally different from ours,
278
00:13:33,150 --> 00:13:37,072
but, of course, what an octopus sees
279
00:13:37,072 --> 00:13:38,987
depends on what an octopus needs to see,
280
00:13:38,987 --> 00:13:41,993
and I'm not really able to tell you that.
281
00:13:44,140 --> 00:13:48,114
We give volition to all kinds of things.
282
00:13:48,114 --> 00:13:51,440
But what they're doing is what they do. (laughs)
283
00:13:51,440 --> 00:13:54,403
It's not necessarily what we interpret them doing.
284
00:13:55,460 --> 00:13:58,210
Take the shark, for example, sharks are impressive animals,
285
00:13:58,210 --> 00:14:01,700
they're beautiful animals, but it's difficult
286
00:14:01,700 --> 00:14:04,843
to imagine a shark that's anything other than a machine.
287
00:14:07,970 --> 00:14:10,610
I don't think anybody would say that a shark
288
00:14:10,610 --> 00:14:13,040
is thinking about things, it's doing things.
289
00:14:13,040 --> 00:14:15,767
If you could talk to a shark, it would just say,
290
00:14:15,767 --> 00:14:20,767
"Fish, danger, friend, enemy, mate."
291
00:14:21,800 --> 00:14:26,800
That's kind of the whole world of a shark's existence.
292
00:14:26,800 --> 00:14:31,800
It doesn't sit there and say, "Why did God make me a shark?"
293
00:14:32,100 --> 00:14:35,757
or "Why do Chinese people want to eat my fins?"
294
00:14:35,757 --> 00:14:38,793
It doesn't, that's not its world.
295
00:14:39,700 --> 00:14:41,660
We know a lot about their vision.
296
00:14:41,660 --> 00:14:44,260
Sharks are vertebrates, they're related to us.
297
00:14:44,260 --> 00:14:46,060
Their eyes are related to our eyes,
298
00:14:46,060 --> 00:14:49,319
they're extremely good eyes, they're acute,
299
00:14:49,319 --> 00:14:53,020
they have a lot of receptors, they have cone cells
300
00:14:53,020 --> 00:14:55,470
and rod cells, so they can see color,
301
00:14:55,470 --> 00:14:58,010
as well as shades of brightness and darkness.
302
00:14:58,010 --> 00:15:01,300
So the quality of the eye in a shark
303
00:15:01,300 --> 00:15:04,860
is comparable to our eyes, and possibly
304
00:15:04,860 --> 00:15:07,254
even better than our color vision.
305
00:15:07,254 --> 00:15:10,060
(bubbles gurgle)
306
00:15:10,060 --> 00:15:12,329
Fish have beautiful color vision,
307
00:15:12,329 --> 00:15:14,410
they have better color vision than humans have.
308
00:15:14,410 --> 00:15:17,650
In fact, most fishes have a higher dimensionality
309
00:15:17,650 --> 00:15:19,331
of color than we have.
310
00:15:19,331 --> 00:15:22,240
In addition to the receptors that are much like ours,
311
00:15:22,240 --> 00:15:25,560
blue, green and red, they have ultraviolet
312
00:15:25,560 --> 00:15:28,360
sensitive photoreceptors yet, so they can see in the UV.
313
00:15:29,290 --> 00:15:31,950
Many coral reef fishes have a receptor set
314
00:15:31,950 --> 00:15:34,050
very much like this, so they're seeing colors
315
00:15:34,050 --> 00:15:35,891
that we don't even know about.
316
00:15:35,891 --> 00:15:40,060
So color vision in humans is important and good,
317
00:15:40,060 --> 00:15:43,020
but it's nothing extraordinarily special.
318
00:15:43,020 --> 00:15:45,310
(birds chirp)
Now, insects,
319
00:15:45,310 --> 00:15:47,663
they actually have more color classes of receptors
320
00:15:47,663 --> 00:15:51,040
than we have, they actually see basically four primaries,
321
00:15:51,040 --> 00:15:53,890
two kinds of UV, blue and green,
322
00:15:53,890 --> 00:15:55,550
and they put those together somehow,
323
00:15:55,550 --> 00:15:58,690
and can interpret that as a color signal.
324
00:15:58,690 --> 00:16:00,546
They all have compound eyes.
325
00:16:00,546 --> 00:16:04,460
Compound eye consists of many many essentially identical
326
00:16:04,460 --> 00:16:08,620
units that sample the world point by point,
327
00:16:08,620 --> 00:16:12,690
and the whole image is sometimes called a mosaic image.
328
00:16:12,690 --> 00:16:15,980
Each unit sees one point in space.
329
00:16:15,980 --> 00:16:17,550
It doesn't see an image of that point,
330
00:16:17,550 --> 00:16:19,360
it just sees how much light there is
331
00:16:19,360 --> 00:16:22,160
and how much color there is at that point.
332
00:16:22,160 --> 00:16:25,326
Their acuity is extremely poor,
333
00:16:25,326 --> 00:16:29,930
only maybe 1/100 of our acuity.
334
00:16:29,930 --> 00:16:32,270
So they're seeing, when we see a face,
335
00:16:32,270 --> 00:16:34,940
they're just seeing a blob with maybe a couple of dark areas
336
00:16:34,940 --> 00:16:36,340
where the eyes would be, that's about
337
00:16:36,340 --> 00:16:37,690
all they're gonna pick out.
338
00:16:40,040 --> 00:16:43,220
Their motion vision is fantastically good,
339
00:16:43,220 --> 00:16:45,680
because they have to fly through spaces and not crash
340
00:16:45,680 --> 00:16:48,913
into things, so they have almost unbelievable motion vision.
341
00:16:50,010 --> 00:16:51,513
They have a much simpler nervous system,
342
00:16:51,513 --> 00:16:54,390
so things are processed really quickly,
343
00:16:54,390 --> 00:16:55,660
and everything's more compact,
344
00:16:55,660 --> 00:16:57,789
which makes everything faster.
345
00:16:57,789 --> 00:17:02,750
So their vision is very fast, and it's very reflexive,
346
00:17:02,750 --> 00:17:06,859
so they're able to see a motion extremely early
347
00:17:06,859 --> 00:17:09,560
and make a decision about what it means
348
00:17:09,560 --> 00:17:10,393
(tape squeals)
349
00:17:10,393 --> 00:17:12,563
and where it's coming from, and then evade.
350
00:17:13,870 --> 00:17:17,030
Now, insects have an infinite arrangement,
351
00:17:17,030 --> 00:17:20,380
just almost uncountable arrangement of ecological roles.
352
00:17:20,380 --> 00:17:22,461
They can be down in the grass,
353
00:17:22,461 --> 00:17:24,010
they can be flying, they can be living in trees,
354
00:17:24,010 --> 00:17:26,980
they can be out hunting, they have many many different ways
355
00:17:26,980 --> 00:17:30,130
of making a living, and there's so many possible choices
356
00:17:30,130 --> 00:17:32,860
that each demands an eye that's specialized
357
00:17:32,860 --> 00:17:35,850
to be best at that job, in fact,
358
00:17:35,850 --> 00:17:38,876
the world's most efficient aerial hunter
359
00:17:38,876 --> 00:17:42,307
is not a hawk, it's a dragonfly.
360
00:17:42,307 --> 00:17:46,890
Dragonflies can successfully capture prey
361
00:17:46,890 --> 00:17:49,870
on up to 90% of their predatory attacks.
362
00:17:49,870 --> 00:17:52,130
It's pretty fabulous.
363
00:17:52,130 --> 00:17:55,710
What they're doing, is they're visually inspecting space
364
00:17:55,710 --> 00:17:58,299
above them for small dots that are flying.
365
00:17:58,299 --> 00:18:01,420
(insects buzz)
And they spot a dot
366
00:18:01,420 --> 00:18:04,793
of appropriate speed and appropriate size,
367
00:18:04,793 --> 00:18:07,595
their little dragonfly brains say,
368
00:18:07,595 --> 00:18:11,133
that's prey, that's an insect, I can catch that,
369
00:18:12,470 --> 00:18:14,929
and they'll make a quick, flying ascent
370
00:18:14,929 --> 00:18:17,580
and snatch that prey out of the air.
371
00:18:17,580 --> 00:18:19,100
And the way that they can see this
372
00:18:19,100 --> 00:18:20,870
is that the whole top part of the eye
373
00:18:20,870 --> 00:18:25,850
is adapted for seeing overhead with extreme detail.
374
00:18:25,850 --> 00:18:28,447
They can see very very well looking up,
375
00:18:28,447 --> 00:18:30,700
and see rather poorly looking in front,
376
00:18:30,700 --> 00:18:32,880
and they see very poorly looking down,
377
00:18:32,880 --> 00:18:34,900
but looking up they have excellent vision,
378
00:18:34,900 --> 00:18:37,598
especially up at slightly in front of them,
379
00:18:37,598 --> 00:18:38,450
so they try to place their prey item
380
00:18:38,450 --> 00:18:41,700
in that part of the visual field and chase it down
381
00:18:41,700 --> 00:18:44,909
with a very quick flying attack.
382
00:18:44,909 --> 00:18:47,002
(insect crunching)
383
00:18:47,002 --> 00:18:48,110
So that's an insect eye that's really adapted
384
00:18:48,110 --> 00:18:51,130
for that job, of pursuit and prey capture.
385
00:18:51,130 --> 00:18:53,180
But there's other ones like that's for other jobs,
386
00:18:53,180 --> 00:18:55,877
so if we think about something like a honeybee,
387
00:18:55,877 --> 00:19:00,200
honeybee eyes are adapted primarily for finding flowers
388
00:19:00,200 --> 00:19:02,520
and for finding their way around.
389
00:19:02,520 --> 00:19:03,720
They'll always know where they are,
390
00:19:03,720 --> 00:19:06,572
because as they fly, they look at the sky
391
00:19:06,572 --> 00:19:09,850
and they monitor either the position of the sun
392
00:19:09,850 --> 00:19:12,590
or the position of a field of light
393
00:19:12,590 --> 00:19:14,020
called the polarized light field
394
00:19:14,020 --> 00:19:17,000
that we don't see, but that honeybees see very well.
395
00:19:17,000 --> 00:19:20,410
And use that information to orient what direction
396
00:19:20,410 --> 00:19:21,900
they're traveling.
(bees buzz)
397
00:19:21,900 --> 00:19:24,820
And so, doing that, they can tell what direction
398
00:19:24,820 --> 00:19:26,420
they're flying, and by monitoring
399
00:19:26,420 --> 00:19:29,180
their speed through the air, they can tell how far
400
00:19:29,180 --> 00:19:31,500
they've flown so they know pretty much where they are
401
00:19:31,500 --> 00:19:32,820
all the time.
(bees buzz)
402
00:19:32,820 --> 00:19:35,340
Bess have ultraviolet vision, and they use it
403
00:19:35,340 --> 00:19:38,950
for identifying flowers and for looking for patterns
404
00:19:38,950 --> 00:19:42,264
of flowers that guide them to where the nectar is.
405
00:19:42,264 --> 00:19:44,535
And if they encounter a patch of flowers,
406
00:19:44,535 --> 00:19:46,659
they can return to the hive,
407
00:19:46,659 --> 00:19:48,700
'cause they've been keeping track of where they are,
408
00:19:48,700 --> 00:19:50,920
using the sun and the sky the whole time.
409
00:19:50,920 --> 00:19:53,547
They can use that same information to get back home again.
410
00:19:53,547 --> 00:19:57,640
And once they get home, they use that very same information
411
00:19:57,640 --> 00:20:01,623
to then do this waggle dance that bees are so famous for.
412
00:20:01,623 --> 00:20:04,340
And tell other bees in the hive
413
00:20:04,340 --> 00:20:07,283
that food can be found at a given distance,
414
00:20:07,283 --> 00:20:11,120
in a given direction, so they'll tell other bees
415
00:20:11,120 --> 00:20:13,924
if you fly three degrees left of the sun
416
00:20:13,924 --> 00:20:18,924
and you fly for 200 meters, there'll be flowers there.
417
00:20:20,150 --> 00:20:21,957
Go there and get some food.
418
00:20:21,957 --> 00:20:26,790
(bees buzz)
(birds chirp)
419
00:20:28,770 --> 00:20:31,660
The animal that I started my research on,
420
00:20:31,660 --> 00:20:34,840
when I was working on visual physiology of marine animals
421
00:20:34,840 --> 00:20:37,521
was, strangely enough, an animal that has
422
00:20:37,521 --> 00:20:42,200
probably the most remarkable known visual system of all,
423
00:20:42,200 --> 00:20:44,040
and that's vision in mantis shrimps.
424
00:20:44,040 --> 00:20:48,060
Friend of mine calls them shrimps from Mars,
425
00:20:48,060 --> 00:20:50,580
and that's pretty much what they are.
426
00:20:50,580 --> 00:20:53,380
They have amazing eyes, unique to mantis shrimps.
427
00:20:53,380 --> 00:20:56,514
Each eye is actually three eyes in one,
428
00:20:56,514 --> 00:20:59,180
it has a top half and a bottom half,
429
00:20:59,180 --> 00:21:01,410
those are two of the parts, and they're pretty much
430
00:21:01,410 --> 00:21:04,265
like the compound eyes on bumblebee or a dragonfly.
431
00:21:04,265 --> 00:21:07,837
But in the middle of this regular split eye,
432
00:21:07,837 --> 00:21:10,235
there is a thing called a midband.
433
00:21:10,235 --> 00:21:14,890
And it's the midband that contains all of the receptors
434
00:21:14,890 --> 00:21:17,810
that are sensitive to the special properties of light.
435
00:21:17,810 --> 00:21:21,540
So, ultraviolet color receptors,
436
00:21:21,540 --> 00:21:24,100
and even some special polarized light receptors
437
00:21:24,100 --> 00:21:26,110
are all found just in the midband.
438
00:21:26,110 --> 00:21:29,885
The midband only sees a little strip of space.
439
00:21:29,885 --> 00:21:34,250
It's like you looking through a very very narrow slot.
440
00:21:34,250 --> 00:21:36,610
You can only see a little tiny bit of the world
441
00:21:36,610 --> 00:21:38,540
through that little narrow slot,
442
00:21:38,540 --> 00:21:39,730
so to see more of the world,
443
00:21:39,730 --> 00:21:41,110
you have to move that slot around,
444
00:21:41,110 --> 00:21:42,900
so mantis shrimps see the world
445
00:21:42,900 --> 00:21:44,880
by moving their eyes around a lot.
446
00:21:44,880 --> 00:21:47,320
That's how they manage to sample the world
447
00:21:47,320 --> 00:21:49,173
with this very narrow midband.
448
00:21:49,173 --> 00:21:51,090
Now the rest of the eye sees the whole world,
449
00:21:51,090 --> 00:21:55,470
but it doesn't see it in color at all.
450
00:21:55,470 --> 00:21:57,930
The midband adds a lot of information.
451
00:21:57,930 --> 00:22:00,212
So, basically the eye is being moved around
452
00:22:00,212 --> 00:22:04,640
on the world, to color in the world by these movements.
453
00:22:04,640 --> 00:22:07,750
What's special about their eyes besides all this stuff,
454
00:22:07,750 --> 00:22:11,312
and that is that they have more kinds of photoreceptors
455
00:22:11,312 --> 00:22:14,720
than any other animal that we know of today.
456
00:22:14,720 --> 00:22:16,990
They have eight classes of primary photoreceptors.
457
00:22:16,990 --> 00:22:19,550
Remember, we have three, we have red, green, blue.
458
00:22:19,550 --> 00:22:21,050
They have eight classes in the visible,
459
00:22:21,050 --> 00:22:22,820
so they have violet blue, blue green,
460
00:22:22,820 --> 00:22:25,220
green, green yellow, yellow and orange.
461
00:22:25,220 --> 00:22:28,050
They also have four more ultraviolet color classes,
462
00:22:28,050 --> 00:22:30,670
so they have a total of 12 color classes.
463
00:22:30,670 --> 00:22:32,370
So give them a great color vision,
464
00:22:33,715 --> 00:22:35,910
and it looks like, behaviorally, it's not necessarily
465
00:22:35,910 --> 00:22:39,030
as good as ours is, it's really hard to say for sure,
466
00:22:39,030 --> 00:22:43,064
but probably all this apparatus is there
467
00:22:43,064 --> 00:22:46,460
not to give them fabulous color vision
468
00:22:46,460 --> 00:22:50,800
but to give them a simple way of categorizing colors.
469
00:22:50,800 --> 00:22:53,220
So, that basically, they're making a decision
470
00:22:54,195 --> 00:22:55,028
about what color they're looking at,
471
00:22:55,028 --> 00:22:57,530
not by analyzing it with complicated machinery
472
00:22:57,530 --> 00:23:01,282
in the brain like we do, we don't know anything about color
473
00:23:01,282 --> 00:23:03,090
till the signal gets to the back of our head
474
00:23:03,090 --> 00:23:06,230
where it goes through a series of analytical stations,
475
00:23:06,230 --> 00:23:08,860
one of which extracts color from the stimulus.
476
00:23:08,860 --> 00:23:11,590
Mantis shrimps can do this right at the eye,
477
00:23:11,590 --> 00:23:14,300
and avoid the brain entirely, so what the brain gets
478
00:23:14,300 --> 00:23:17,730
is red, orange, yellow, green,
479
00:23:17,730 --> 00:23:21,713
whatever in that object they're looking at at that moment.
480
00:23:21,713 --> 00:23:26,220
So it's a way of making color sense operate very quickly
481
00:23:26,220 --> 00:23:28,960
and very simply without a lot of neural machinery.
482
00:23:28,960 --> 00:23:31,258
And we think that may be what's happening.
483
00:23:31,258 --> 00:23:35,981
They are spectacularly pugnacious, violent animals.
484
00:23:35,981 --> 00:23:39,670
They catch prey by having a pair of front arms
485
00:23:39,670 --> 00:23:43,973
that are especially modified for very high speed attacks.
486
00:23:43,973 --> 00:23:46,800
They can hit an object with the force
487
00:23:46,800 --> 00:23:50,330
of a 22 caliber bullet, they have one of the fastest
488
00:23:50,330 --> 00:23:53,550
movements ever recorded in animals, the force is huge.
489
00:23:53,550 --> 00:23:56,919
They can break an aquarium wall in a large species.
490
00:23:56,919 --> 00:24:00,320
They have to have good eyes to have an effective strike,
491
00:24:00,320 --> 00:24:01,610
otherwise it's useless to them.
492
00:24:01,610 --> 00:24:03,810
They have to know where their prey item is,
493
00:24:03,810 --> 00:24:07,060
how far away it is, and, importantly as anything,
494
00:24:07,060 --> 00:24:08,230
what is it?
495
00:24:08,230 --> 00:24:11,400
Is it something, like a rock, which is gonna break my arm,
496
00:24:11,400 --> 00:24:14,364
or is it actually something to eat, which is not.
497
00:24:14,364 --> 00:24:16,490
And, is it another mantis shrimp?
498
00:24:16,490 --> 00:24:17,830
'Cause that's really important.
499
00:24:17,830 --> 00:24:21,400
Another mantis shrimp can fight back and can kill you
500
00:24:21,400 --> 00:24:26,030
if you attack it, so it needs to know these things quickly.
501
00:24:26,030 --> 00:24:27,650
The other thing that pushes it is,
502
00:24:27,650 --> 00:24:29,860
in fact, they are dealing with other mantis shrimps.
503
00:24:29,860 --> 00:24:33,580
They have to mate, they need to defend their burrows,
504
00:24:33,580 --> 00:24:36,030
they need to get along in the world,
505
00:24:36,030 --> 00:24:38,763
and to do that, they have to know who they're dealing with.
506
00:24:38,763 --> 00:24:42,760
And so, mantis shrimps have evolved a really elaborate
507
00:24:42,760 --> 00:24:45,880
set of colored signals in many species.
508
00:24:45,880 --> 00:24:48,840
Those colored signals say to another mantis shrimp,
509
00:24:48,840 --> 00:24:53,840
I am your species or not, I am angry or not,
510
00:24:53,950 --> 00:24:58,843
I'm a female or a male, depending on who's doing it,
511
00:24:59,680 --> 00:25:03,200
I'm feeling pretty cheerful right now or not.
512
00:25:03,200 --> 00:25:05,350
All those things are signaled by colored signals
513
00:25:05,350 --> 00:25:06,986
that mantis shrimps use.
514
00:25:06,986 --> 00:25:10,570
But mantis shrimps have another pattern that we don't see,
515
00:25:10,570 --> 00:25:13,200
and that's their polarized light patterns.
516
00:25:13,200 --> 00:25:16,090
So they can reflect polarized light in ways
517
00:25:16,090 --> 00:25:18,600
that make it possible to have one part
518
00:25:18,600 --> 00:25:20,820
of their bodies stand off as being different
519
00:25:20,820 --> 00:25:24,470
from other parts, and they use that to talk to each other.
520
00:25:24,470 --> 00:25:27,500
And, in particular, some species use a little blue object,
521
00:25:27,500 --> 00:25:29,939
which is along one of their front appendages
522
00:25:29,939 --> 00:25:33,772
as a little part of it, it reflects blue polarized light.
523
00:25:33,772 --> 00:25:38,188
They use that, we believe, in communicating
524
00:25:38,188 --> 00:25:40,490
their sexual intentions to each other,
525
00:25:40,490 --> 00:25:43,560
so this little blue polarizer looks blue to us,
526
00:25:43,560 --> 00:25:45,940
but to another mantis shrimp, it looks like it's polarized,
527
00:25:45,940 --> 00:25:48,560
and that polarization seems to be important.
528
00:25:48,560 --> 00:25:50,520
If you destroy the polarization
529
00:25:50,520 --> 00:25:54,400
of that little object on the front leg, male mantis shrimps
530
00:25:55,545 --> 00:25:57,695
find it much more difficult to find a mate.
531
00:25:59,760 --> 00:26:01,251
They're very interesting animals.
532
00:26:01,251 --> 00:26:03,648
They make great pets as long as you wanna keep one animal
533
00:26:03,648 --> 00:26:06,766
in an aquarium, because anything else that's in there,
534
00:26:06,766 --> 00:26:08,073
it will kill it.
535
00:26:09,206 --> 00:26:11,670
(dog pants)
You know,
536
00:26:11,670 --> 00:26:14,320
we've all been through our own evolutionary paths.
537
00:26:14,320 --> 00:26:17,740
We've all gotten our senses through millions of years
538
00:26:17,740 --> 00:26:20,750
of ancestors and the ancestors of dogs
539
00:26:20,750 --> 00:26:22,520
separated from the ancestors of humans,
540
00:26:22,520 --> 00:26:24,530
or of a cat or a mouse or a horse,
541
00:26:24,530 --> 00:26:27,828
or whatever your pet is, a parrot, even a better example.
542
00:26:27,828 --> 00:26:30,840
Their ancestors have separated from our ancestors
543
00:26:30,840 --> 00:26:33,330
by millions to tens of millions
544
00:26:33,330 --> 00:26:35,318
to hundreds of millions of years.
545
00:26:35,318 --> 00:26:38,600
I think that human vision is pretty darn good.
546
00:26:38,600 --> 00:26:41,770
The thing about humans is, we're not adapted.
547
00:26:41,770 --> 00:26:44,260
We're really generalist animals.
548
00:26:44,260 --> 00:26:45,810
We don't climb in trees very well,
549
00:26:45,810 --> 00:26:49,883
like our ancestors, we can't outrun a cheetah,
550
00:26:50,790 --> 00:26:53,420
some animal out there can excel us at anything,
551
00:26:53,420 --> 00:26:57,111
including vision, but we don't have to feel bad about that.
552
00:26:57,111 --> 00:26:59,600
I think we can, in general, say that human vision
553
00:26:59,600 --> 00:27:03,610
is, for what we need, it's probably more than enough.
554
00:27:03,610 --> 00:27:05,880
And it's one reason, probably, we depend on it so much
555
00:27:05,880 --> 00:27:07,540
is that it's so well adapted to do
556
00:27:07,540 --> 00:27:09,193
almost any kind of job we need.
557
00:27:11,010 --> 00:27:14,930
If I was an animal, I would like
558
00:27:14,930 --> 00:27:18,810
to be a lot of different animals for an hour each.
559
00:27:18,810 --> 00:27:21,000
I don't think I wanna be only one,
560
00:27:21,000 --> 00:27:23,360
I'd love to be a hawk and see what it's like
561
00:27:23,360 --> 00:27:27,150
to see prey from a mile high in the sky.
562
00:27:27,150 --> 00:27:30,210
I'd love to be an octopus and see what it's like
563
00:27:30,210 --> 00:27:32,898
to catch prey when I'm down in the water.
564
00:27:32,898 --> 00:27:33,920
(bubbles gurgle)
565
00:27:33,920 --> 00:27:35,790
I'd love to be a mantis shrimp
566
00:27:35,790 --> 00:27:37,920
and see what it's like to live in their colorful world,
567
00:27:37,920 --> 00:27:40,620
and a world that's full of polarized light
568
00:27:40,620 --> 00:27:43,150
and ultraviolet light, and just have a sense
569
00:27:43,150 --> 00:27:44,770
of what it is they see out there,
570
00:27:44,770 --> 00:27:46,770
but I must say, that if I put myself
571
00:27:46,770 --> 00:27:51,140
in the mind of a hawk or in the mind of a mantis shrimp,
572
00:27:51,140 --> 00:27:54,420
or in the mind of an octopus, I would have no idea
573
00:27:54,420 --> 00:27:56,970
what was going on, because they don't have minds
574
00:27:56,970 --> 00:27:59,228
like mine, and what they're sensing
575
00:27:59,228 --> 00:28:02,380
is something that I really can't comprehend.
576
00:28:02,380 --> 00:28:05,270
So, I'm afraid that it's something,
577
00:28:05,270 --> 00:28:07,479
as much as I would like to be able to do it,
578
00:28:07,479 --> 00:28:10,153
even in the world of virtual reality,
579
00:28:10,153 --> 00:28:12,007
it'll never really happen.
580
00:28:12,007 --> 00:28:14,424
(soft music)
47739
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