Daniel Wolpert: The real reason for brains

342,104 views ・ 2011-11-03

TED


Dvaput kliknite na engleske titlove ispod za reprodukciju videozapisa.

Prevoditelj: Senzos Osijek Recezent: Katarina Smetko
00:15
I'm a neuroscientist.
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Ja sam neuroznanstvenik.
00:17
And in neuroscience,
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A u neuroznanosti,
00:19
we have to deal with many difficult questions about the brain.
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moramo se baviti mnoštvom teških pitanja o mozgu.
00:22
But I want to start with the easiest question
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No, želim početi s najlakšim pitanjem,
00:24
and the question you really should have all asked yourselves at some point in your life,
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pitanjem koje ste trebali postaviti sami sebi u nekom trenutku svojeg života,
00:27
because it's a fundamental question
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jer to je temeljno pitanje
00:29
if we want to understand brain function.
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ako želimo razumjeti funkciju mozga.
00:31
And that is, why do we and other animals
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A to pitanje jest: zašto mi i neke druge vrste
00:33
have brains?
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imamo mozak?
00:35
Not all species on our planet have brains,
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Nemaju sve vrste na našoj planeti mozak,
00:38
so if we want to know what the brain is for,
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pa ako želimo saznati za što nam mozak služi,
00:40
let's think about why we evolved one.
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razmislimo prvo zašto smo ga uopće razvili tijekom evolucije.
00:42
Now you may reason that we have one
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Možete tvrditi da nam je potreban
00:44
to perceive the world or to think,
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kako bismo mogli spoznati svijet ili razmišljati,
00:46
and that's completely wrong.
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no to je potpuno krivo.
00:48
If you think about this question for any length of time,
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Ako razmislite o tom pitanju malo duže,
00:51
it's blindingly obvious why we have a brain.
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nevjerojatno je očito zašto imamo mozak.
00:53
We have a brain for one reason and one reason only,
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Imamo mozak iz jednog jedinog razloga:
00:56
and that's to produce adaptable and complex movements.
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da bismo mogli izvoditi primjerene i složene pokrete.
00:59
There is no other reason to have a brain.
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Nema drugog razloga zašto imamo mozak.
01:01
Think about it.
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Razmislite o tome.
01:03
Movement is the only way you have
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Kretnje su jedini način na koji možete
01:05
of affecting the world around you.
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utjecati na svijet oko vas.
01:07
Now that's not quite true. There's one other way, and that's through sweating.
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Dobro, to nije u potpunosti točno. Postoji jedan drugi način, a to je znojenje.
01:10
But apart from that,
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No, osim toga,
01:12
everything else goes through contractions of muscles.
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sve ostalo ide preko mišića.
01:14
So think about communication --
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Dakle, razmislite o komunikaciji –
01:16
speech, gestures, writing, sign language --
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govor, geste, pisanje, znakovni jezik –
01:19
they're all mediated through contractions of your muscles.
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sve to omogućavaju pokreti vaših mišića.
01:22
So it's really important to remember
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Zato je vrlo važno imati na umu
01:24
that sensory, memory and cognitive processes are all important,
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da su osjetila, pamćenje i kognitivni procesi važni,
01:28
but they're only important
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ali važni su samo
01:30
to either drive or suppress future movements.
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kako bi u budćnosti potaknuli ili potisnuli kretnje.
01:32
There can be no evolutionary advantage
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Nema evolucijske prednosti
01:34
to laying down memories of childhood
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u pohranjivanju sjećanja iz djetinjstva
01:36
or perceiving the color of a rose
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ili percepciji boje ruže,
01:38
if it doesn't affect the way you're going to move later in life.
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ako to neće utjecati na naše kretanje kasnije u životu.
01:41
Now for those who don't believe this argument,
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Za one koji ne vjeruju ovim argumentima --
01:43
we have trees and grass on our planet without the brain,
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drveće i trava na našem planetu nemaju mozak,
01:45
but the clinching evidence is this animal here --
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no ključni je dokaz ova životinja ovdje --
01:47
the humble sea squirt.
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skromni morski plaštenjaci.
01:49
Rudimentary animal, has a nervous system,
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Rudimentarna životinja, koja ima živčani sustav,
01:52
swims around in the ocean in its juvenile life.
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pliva oceanom u prvom razdoblju svog života.
01:54
And at some point of its life,
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U jednom trenutku u životu,
01:56
it implants on a rock.
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usadi se u kamen.
01:58
And the first thing it does in implanting on that rock, which it never leaves,
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A prva stvar koju učini kad se usadi u stijenu, koju više nikad ne napušta,
02:01
is to digest its own brain and nervous system
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jest da probavi svoj mozak i živčani sustav
02:04
for food.
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kao hranu.
02:06
So once you don't need to move,
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Dakle, jednom kad se više ne trebate kretati,
02:08
you don't need the luxury of that brain.
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posjedovanje mozga nepotreban je luksuz.
02:11
And this animal is often taken
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Ova životinja često se uzima
02:13
as an analogy to what happens at universities
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za usporedbu s onim što se događa na sveučilištima
02:15
when professors get tenure,
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kad netko postane redoviti profesor,
02:17
but that's a different subject.
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no to je druga tema.
02:19
(Applause)
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(Pljesak)
02:21
So I am a movement chauvinist.
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Dakle, ja sam šovinist pokreta.
02:24
I believe movement is the most important function of the brain --
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Vjerujem da je kretanje najvažnija funkcija mozga –
02:26
don't let anyone tell you that it's not true.
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neka vas nitko ne uvjeri kako to nije istina.
02:28
Now if movement is so important,
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Ako je pokret toliko važan,
02:30
how well are we doing
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koliko dobro mi uopće
02:32
understanding how the brain controls movement?
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razumijemo kako mozak kontrolira pokrete?
02:34
And the answer is we're doing extremely poorly; it's a very hard problem.
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Odgovor je da nam ide vrlo loše, to je prilično velik problem.
02:36
But we can look at how well we're doing
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No, možemo vidjeti kako nam dobro ide
02:38
by thinking about how well we're doing building machines
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ako razmislimo koliko dobro razvijamo strojeve
02:40
which can do what humans can do.
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koji mogu raditi ono što i ljudi rade.
02:42
Think about the game of chess.
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Razmislite o igri šaha.
02:44
How well are we doing determining what piece to move where?
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Koliko dobro možemo odrediti kamo koju figuru trebamo pomaknuti?
02:47
If you pit Garry Kasparov here, when he's not in jail,
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Kada bi se suočili Gary Kasparov, ako nije u zatvoru,
02:50
against IBM's Deep Blue,
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i IBM-ov Deep Blue,
02:52
well the answer is IBM's Deep Blue will occasionally win.
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odgovor je da bi IBM-ov Deep Blue ponekad pobijedio.
02:55
And I think if IBM's Deep Blue played anyone in this room, it would win every time.
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Mislim da bi IBM-ov Deep Blue, kad bi igrao šah bilo s kim od vas u ovoj prostoriji, pobijedio svaki put.
02:58
That problem is solved.
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Taj je problem riješen.
03:00
What about the problem
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Što je s problemom
03:02
of picking up a chess piece,
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podizanja šahovske figurice,
03:04
dexterously manipulating it and putting it back down on the board?
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spretne manipulacije i spuštanja natrag na ploču?
03:07
If you put a five year-old child's dexterity against the best robots of today,
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Kada biste spretnost petogodišnjaka usporedili sa spretnošću najboljeg robota,
03:10
the answer is simple:
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odgovor je jednostavan:
03:12
the child wins easily.
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dijete bi ispalo spretnije.
03:14
There's no competition at all.
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Djetetu robot uopće nije neka konkurencija.
03:16
Now why is that top problem so easy
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No, zašto je gornji problem toliko jednostavan,
03:18
and the bottom problem so hard?
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a donji toliko težak?
03:20
One reason is a very smart five year-old
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Jedan razlog je taj što bi vam vrlo pametan petogodišnjak
03:22
could tell you the algorithm for that top problem --
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mogao reći algoritam za prvi problem –
03:24
look at all possible moves to the end of the game
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razmotriti sve moguće pokrete do kraja igre
03:26
and choose the one that makes you win.
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i odabrati onaj kojim bi pobijedio.
03:28
So it's a very simple algorithm.
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Algoritam je vrlo jednostavan.
03:30
Now of course there are other moves,
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Naravno, postoje i druga dobra rješenja,
03:32
but with vast computers we approximate
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no s dobrim računalom možemo
03:34
and come close to the optimal solution.
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otprilike odrediti optimalno rješenje.
03:36
When it comes to being dexterous,
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Kad je u pitanju spretnost –
03:38
it's not even clear what the algorithm is you have to solve to be dexterous.
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nije jasno ni koji se algoritam treba riješiti da bismo bili spretni.
03:40
And we'll see you have to both perceive and act on the world,
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Vidjet ćemo da morate i percipirati i djelovati na svijet,
03:42
which has a lot of problems.
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u kojem ima mnogo problema.
03:44
But let me show you cutting-edge robotics.
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No, pokazat ću vam najsuvremeniju robotiku.
03:46
Now a lot of robotics is very impressive,
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Velik dio robotike vrlo je impresivan,
03:48
but manipulation robotics is really just in the dark ages.
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no manipulativna robotika kao da je u srednjem vijeku.
03:51
So this is the end of a Ph.D. project
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Ovo je proizašlo iz jednog projekta za doktorat
03:53
from one of the best robotics institutes.
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iz jednog od najboljih instituta robotike.
03:55
And the student has trained this robot
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Student je izvježbao ovog robota
03:57
to pour this water into a glass.
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za nalijevanje vode u čašu.
03:59
It's a hard problem because the water sloshes about, but it can do it.
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Ovo je težak problem jer se voda i prolijeva, ali ipak uspijeva.
04:02
But it doesn't do it with anything like the agility of a human.
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Ali ne radi to ni s približnom spretnošću koju ima čovjek.
04:05
Now if you want this robot to do a different task,
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Želimo li da ovaj robot obavlja neki drugi zadatak
04:08
that's another three-year Ph.D. program.
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to je još jedan doktorski program od 3 godine.
04:11
There is no generalization at all
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Nema nikakve generalizacije
04:13
from one task to another in robotics.
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između različitih zadataka u robotici.
04:15
Now we can compare this
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To možemo usporediti
04:17
to cutting-edge human performance.
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s najboljom ljudskom izvedbom.
04:19
So what I'm going to show you is Emily Fox
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Pokazat ću vam kako je Emily Fox
04:21
winning the world record for cup stacking.
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pobijedila na svjetskom prvenstvu u slaganju čaša.
04:24
Now the Americans in the audience will know all about cup stacking.
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Amerikanci u publici znat će o čemu je riječ.
04:26
It's a high school sport
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To je srednjoškolski sport
04:28
where you have 12 cups you have to stack and unstack
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u kojem imate 12 čaša koje morate slagati
04:30
against the clock in a prescribed order.
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u određenom roku po propisanom redu.
04:32
And this is her getting the world record in real time.
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A ovo je snimka kako postiže svjetski rekord u realnom vremenu.
04:39
(Laughter)
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(Smijeh)
04:47
(Applause)
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(Pljesak)
04:52
And she's pretty happy.
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I prilično je sretna.
04:54
We have no idea what is going on inside her brain when she does that,
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Nemamo pojma što se događa u njezinom mozgu dok to radi,
04:56
and that's what we'd like to know.
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a to je ono što bismo željeli saznati.
04:58
So in my group, what we try to do
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U mojoj grupi pokušavamo raditi
05:00
is reverse engineer how humans control movement.
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obrnuti inženjering kontrole pokreta kod ljudi.
05:03
And it sounds like an easy problem.
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To zvuči kao jednostavan problem.
05:05
You send a command down, it causes muscles to contract.
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Pošaljete naredbu, ona prouzrokuje stezanje mišića.
05:07
Your arm or body moves,
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Vaša ruka ili tijelo pokreće se,
05:09
and you get sensory feedback from vision, from skin, from muscles and so on.
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a dobivate povratnu informaciju iz osjetila - preko vida, iz kože, mišića itd.
05:12
The trouble is
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Problem je što
05:14
these signals are not the beautiful signals you want them to be.
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ovi signali nisu onako lijepi kako biste vi to željeli.
05:16
So one thing that makes controlling movement difficult
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Primjerice, jedna stvar koja otežava kontrolu pokreta
05:18
is, for example, sensory feedback is extremely noisy.
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jest to što osjetilna povratna informacija ima mnogo šumova.
05:21
Now by noise, I do not mean sound.
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Kad kažem "šumovi", ne mislim na zvuk.
05:24
We use it in the engineering and neuroscience sense
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Koristimo tu riječ u inženjeringu i neuroznanosti
05:26
meaning a random noise corrupting a signal.
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u smislu nepravilnog šuma koji remeti signal.
05:28
So the old days before digital radio when you were tuning in your radio
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To je kao s radijima prije digitalnog – kad ste namještali stanicu
05:31
and you heard "crrcckkk" on the station you wanted to hear,
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i čuli onaj ''khrkrhhrkkk'' na stanici koju ste željeli čuti –
05:33
that was the noise.
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to je bio taj šum.
05:35
But more generally, this noise is something that corrupts the signal.
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No, općenito, taj je šum nešto što remeti signal.
05:38
So for example, if you put your hand under a table
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Primjerice, ako stavite ruku pod stol
05:40
and try to localize it with your other hand,
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i želite locirati tu ruku drugom rukom,
05:42
you can be off by several centimeters
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možete pogriješiti nekoliko centimetara
05:44
due to the noise in sensory feedback.
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zbog šuma u osjetilnoj povratnoj informaciji.
05:46
Similarly, when you put motor output on movement output,
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Slično tome, kad postavite motorički izlaz na izlaz za kretnje,
05:48
it's extremely noisy.
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signal je pun šumova.
05:50
Forget about trying to hit the bull's eye in darts,
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Prestanite pokušavati pogoditi metu u pikadu,
05:52
just aim for the same spot over and over again.
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samo neprestano ciljajte jednu te istu točku.
05:54
You have a huge spread due to movement variability.
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Imate ogromne pomake zbog varijabilnosti pokreta.
05:57
And more than that, the outside world, or task,
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Pored toga, vanjski svijet ili sam zadatak
05:59
is both ambiguous and variable.
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dvosmislen je i varijabilan.
06:01
The teapot could be full, it could be empty.
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Ovaj bi čajnik mogao biti i pun i prazan.
06:03
It changes over time.
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Mijenja se tijekom vremena.
06:05
So we work in a whole sensory movement task soup of noise.
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Dakle, radimo motoričke pokrete pod skupom šumova izvana.
06:09
Now this noise is so great
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Šumovi su toliko veliki
06:11
that society places a huge premium
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da društvo iznimno cijeni
06:13
on those of us who can reduce the consequences of noise.
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one koji mogu reducirati posljedice šumova.
06:16
So if you're lucky enough to be able to knock a small white ball
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Ako imate dovoljno sreće da možete ubaciti malu bijelu lopticu
06:19
into a hole several hundred yards away using a long metal stick,
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u rupu koja je udaljena nekoliko stotina metara koristeći dug metalni štap,
06:22
our society will be willing to reward you
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naše će društvo biti spremno nagraditi vas
06:24
with hundreds of millions of dollars.
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stotinama milijuna dolara.
06:27
Now what I want to convince you of
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Želim vas zapravo uvjeriti
06:29
is the brain also goes through a lot of effort
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da mozak također ulaže puno truda
06:31
to reduce the negative consequences
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kako bi se smanjile negativne posljedice
06:33
of this sort of noise and variability.
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ovakvih šumova i varijabilnosti pokreta.
06:35
And to do that, I'm going to tell you about a framework
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Kako bih to učinio, predstavit ću vam radni okvir
06:37
which is very popular in statistics and machine learning of the last 50 years
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koji je vrlo popularan u statistici i strojnom učenju u zadnjih 50 godina,
06:40
called Bayesian decision theory.
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a zove se Bayesova teorija odlučivanja.
06:42
And it's more recently a unifying way
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To je u novije vrijeme ujedinjenje načina
06:45
to think about how the brain deals with uncertainty.
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razmišljanja o tome kako se mozak bavi nesigurnošću.
06:48
And the fundamental idea is you want to make inferences and then take actions.
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Temeljna je ideja da pokušavamo donijeti zaključke i onda djelovati.
06:51
So let's think about the inference.
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Razmislimo malo o zaključivanju.
06:53
You want to generate beliefs about the world.
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Želite stvoriti uvjerenja o svijetu.
06:55
So what are beliefs?
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A što su to uvjerenja?
06:57
Beliefs could be: where are my arms in space?
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Uvjerenje bi moglo biti: gdje su moje ruke u prostoru?
06:59
Am I looking at a cat or a fox?
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Gledam li mačku ili lisicu?
07:01
But we're going to represent beliefs with probabilities.
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No, predstavit ćemo uvjerenje kao vjerojatnost.
07:04
So we're going to represent a belief
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Predstavit ćemo uvjerenje
07:06
with a number between zero and one --
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kao broj između 0 i 1 –
07:08
zero meaning I don't believe it at all, one means I'm absolutely certain.
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gdje 0 znači "ne vjerujem uopće", a 1 znači "apsolutno sam siguran".
07:11
And numbers in between give you the gray levels of uncertainty.
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Brojevi između označavaju zonu nesigurnosti.
07:14
And the key idea to Bayesian inference
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Glavna ideja Bayesovog zaključivanja
07:16
is you have two sources of information
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jest da postoje dva izvora informacija
07:18
from which to make your inference.
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iz kojih se mogu donijeti zaključci.
07:20
You have data,
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Imamo podatke –
07:22
and data in neuroscience is sensory input.
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a podaci u neuroznanosti jesu informacije iz osjetila.
07:24
So I have sensory input, which I can take in to make beliefs.
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Dakle, imamo informacije iz osjetila, pomoću kojih možemo doći do uvjerenja.
07:27
But there's another source of information, and that's effectively prior knowledge.
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No, postoji još jedan izvor informacija, a to je prethodno znanje.
07:30
You accumulate knowledge throughout your life in memories.
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Znanje skupljate kroz život u obliku sjećanja.
07:33
And the point about Bayesian decision theory
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A svrha Bayesove teorije odlučivanja
07:35
is it gives you the mathematics
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jest da pomoću nje izračunate
07:37
of the optimal way to combine
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optimalni način kombiniranja
07:39
your prior knowledge with your sensory evidence
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prijašnjeg znanja i osjetilnih podražaja
07:41
to generate new beliefs.
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i pomoću njih stvorite nova uvjerenja.
07:43
And I've put the formula up there.
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Stavio sam ovdje gore formulu.
07:45
I'm not going to explain what that formula is, but it's very beautiful.
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Neću objašnjavati tu formulu, ali baš je lijepa.
07:47
And it has real beauty and real explanatory power.
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Ima istinsku ljepotu i pravu moć objašnjavanja.
07:50
And what it really says, and what you want to estimate,
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A ono što zbilja govori i što želite procijeniti
07:52
is the probability of different beliefs
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jest vjerojatnost različitih uvjerenja
07:54
given your sensory input.
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s obzirom na vaše informacije iz osjetila.
07:56
So let me give you an intuitive example.
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Dat ću vam intuitivan primjer.
07:58
Imagine you're learning to play tennis
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Zamislite da učite igrati tenis
08:01
and you want to decide where the ball is going to bounce
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i želite procijeniti kamo će loptica odskočiti
08:03
as it comes over the net towards you.
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dok dolazi preko mreže prema vama.
08:05
There are two sources of information
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Postoje dva izvora informacija,
08:07
Bayes' rule tells you.
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po Bayesovom pravilu.
08:09
There's sensory evidence -- you can use visual information auditory information,
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Imamo osjetilni dokaz – možete koristiti vidne ili slušne informacije,
08:12
and that might tell you it's going to land in that red spot.
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i zaključiti da će pasti na crvenu točku.
08:15
But you know that your senses are not perfect,
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No, znate da vaša osjetila nisu savršena
08:18
and therefore there's some variability of where it's going to land
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i zato postoje varijacije mjesta kamo će loptica pasti -
08:20
shown by that cloud of red,
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to pokazuje ovaj crveni dio –
08:22
representing numbers between 0.5 and maybe 0.1.
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predstavlja brojeve između 0,5 i možda 1.
08:26
That information is available in the current shot,
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To su informacije dostupne tijekom trenutnog napucavanja lopte,
08:28
but there's another source of information
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no postoji još jedan izvor informacija
08:30
not available on the current shot,
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koji nije dostupan u trenutku kada lopta putuje prema vama,
08:32
but only available by repeated experience in the game of tennis,
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nego tek nakon ponovljenog iskustva igranja tenisa -
08:35
and that's that the ball doesn't bounce
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a to je da loptica neće odskočiti
08:37
with equal probability over the court during the match.
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s jednakom vjerojatnošću na cijelom igralištu tijekom meča.
08:39
If you're playing against a very good opponent,
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Ako igrate protiv vrlo dobrog protivnika,
08:41
they may distribute it in that green area,
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može ju usmjeriti na neki od ovih zelenih dijelova,
08:43
which is the prior distribution,
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koji će zbog prethodno odigranog poteza,
08:45
making it hard for you to return.
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biti vama teško dohvatljiv dio.
08:47
Now both these sources of information carry important information.
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Oba ova izvora informacija donose važne informacije.
08:49
And what Bayes' rule says
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Bayesovo pravilo kaže nam
08:51
is that I should multiply the numbers on the red by the numbers on the green
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da bismo trebali pomnožiti brojeve na crvenoj površini s brojevima na zelenoj površini
08:54
to get the numbers of the yellow, which have the ellipses,
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kako bismo dobili brojeve na žutoj boji – to su elipse –
08:57
and that's my belief.
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i to je moje uvjerenje.
08:59
So it's the optimal way of combining information.
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Tako da je to optimalan način kombiniranja informacija.
09:02
Now I wouldn't tell you all this if it wasn't that a few years ago,
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Ne bih vam rekao sve ovo da nismo prije nekoliko godina
09:04
we showed this is exactly what people do
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dokazali da je upravo to način na koji ljudi
09:06
when they learn new movement skills.
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uče nove motoričke sposobnosti.
09:08
And what it means
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A to znači
09:10
is we really are Bayesian inference machines.
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da zbilja i jesmo strojevi koji rade po Bayesovom zaključivanju.
09:12
As we go around, we learn about statistics of the world and lay that down,
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Idemo kroz svijet učeći statistike o svijetu i pohranjujemo ih,
09:16
but we also learn
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ali isto tako učimo i
09:18
about how noisy our own sensory apparatus is,
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koliko šumova ima u našim osjetilnim putovima
09:20
and then combine those
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pa ih stoga kombiniramo
09:22
in a real Bayesian way.
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na pravi Bayesovski način.
09:24
Now a key part to the Bayesian is this part of the formula.
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Ključni dio Bayesovog zaključivanja jest ovaj dio formule.
09:27
And what this part really says
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Ono što ovaj dio zapravo govori
09:29
is I have to predict the probability
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jest da moram predvidjeti vjerojatnost
09:31
of different sensory feedbacks
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različitih osjetilnih povratnih informacija
09:33
given my beliefs.
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s obzirom na svoja uvjerenja.
09:35
So that really means I have to make predictions of the future.
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To zapravo znači da moram pretpostaviti budućnost.
09:38
And I want to convince you the brain does make predictions
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Želim vas uvjeriti da mozak zaista daje pretpostavke
09:40
of the sensory feedback it's going to get.
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osjetilnih povratnih informacija koje će dobiti.
09:42
And moreover, it profoundly changes your perceptions
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I osim toga, duboko se mijenja percepcija
09:44
by what you do.
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onoga što činite.
09:46
And to do that, I'll tell you
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Kako bih vas u to uvjerio, reći ću vam
09:48
about how the brain deals with sensory input.
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kako se mozak nosi s informacijama iz osjetila.
09:50
So you send a command out,
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Dakle, šaljete naredbu iz mozga,
09:53
you get sensory feedback back,
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dobivate povratne informacije iz osjetila,
09:55
and that transformation is governed
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i tom transformacijom upravlja
09:57
by the physics of your body and your sensory apparatus.
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fizika vašeg tijela i funkcioniranje osjetilnog aparata.
10:00
But you can imagine looking inside the brain.
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Možete zamisliti da gledate u unutrašnjost mozga.
10:02
And here's inside the brain.
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Ovo je unutrašnjost mozga.
10:04
You might have a little predictor, a neural simulator,
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Možda je tu mali predviđač, neuralni simulator
10:06
of the physics of your body and your senses.
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fizike vašeg tijela i osjetila.
10:08
So as you send a movement command down,
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Dok šaljete zapovijed za kretnju na periferiju,
10:10
you tap a copy of that off
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uzmete kopiju toga
10:12
and run it into your neural simulator
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i unesete je u svoj neuralni simulator
10:14
to anticipate the sensory consequences of your actions.
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kako biste predvidjeli koje će posljedice vaše radnje imati na osjetila.
10:18
So as I shake this ketchup bottle,
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Dakle, ako protresete bocu kečapa,
10:20
I get some true sensory feedback as the function of time in the bottom row.
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dobit ćete prave osjetilne informacije kao funkciju vremena u donjem redu.
10:23
And if I've got a good predictor, it predicts the same thing.
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Ako imamo dobrog predviđača, on će predvidjeti istu stvar.
10:26
Well why would I bother doing that?
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Zašto se uopće gnjavimo time?
10:28
I'm going to get the same feedback anyway.
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Ionako ćemo dobiti jednake povratne informacije.
10:30
Well there's good reasons.
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Pa, postoje dobri razlozi za to.
10:32
Imagine, as I shake the ketchup bottle,
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Zamislite da dok ja tresem bocu kečapa,
10:34
someone very kindly comes up to me and taps it on the back for me.
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netko ljubazno dođe do mene i malo ju udari.
10:37
Now I get an extra source of sensory information
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Sada imam dodatni izvor osjetilnih informacija,
10:39
due to that external act.
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koji je nastao zbog vanjskog djelovanja.
10:41
So I get two sources.
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Imam dva izvora.
10:43
I get you tapping on it, and I get me shaking it,
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Vi je lagano udarate, a ja je tresem,
10:46
but from my senses' point of view,
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ali moja osjetila to doživljavaju
10:48
that is combined together into one source of information.
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kao djelovanje koje se ujedinjuje u jedan izvor informacije.
10:51
Now there's good reason to believe
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Postoji dobar razlog zašto biste željeli
10:53
that you would want to be able to distinguish external events from internal events.
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razlučiti vanjska djelovanja od unutarnjih.
10:56
Because external events are actually much more behaviorally relevant
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Zato što su vanjska djelovanja mnogo relevantnija za ponašanje
10:59
than feeling everything that's going on inside my body.
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od osjećaja što se sve događa unutar mojeg tijela.
11:02
So one way to reconstruct that
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Jedan način da to rekonstruiramo
11:04
is to compare the prediction --
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jest da usporedimo predviđanje,
11:06
which is only based on your movement commands --
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koje je utemeljeno samo na našim motoričkim naredbama,
11:08
with the reality.
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sa stvarnošću.
11:10
Any discrepancy should hopefully be external.
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Svaka razlika trebala bi biti pod utjecajem vanjske sile.
11:13
So as I go around the world,
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Dakle, dok hodam uokolo,
11:15
I'm making predictions of what I should get, subtracting them off.
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izrađujem predviđanja o tome što bih trebao dobiti ulaganjem motoričkih naredbi.
11:18
Everything left over is external to me.
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Sve ostalo prepoznajem kao vanjsku silu.
11:20
What evidence is there for this?
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Kakvi dokazi postoje za ovo?
11:22
Well there's one very clear example
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Postoji jedan vrlo jasan primjer,
11:24
where a sensation generated by myself feels very different
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u kojem je osjećaj koji se stvara u meni vrlo različit
11:26
then if generated by another person.
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od osjećaja koji se stvara pod utjecajem druge osobe.
11:28
And so we decided the most obvious place to start
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I tako smo odlučili početi s očitim -
11:30
was with tickling.
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sa škakljanjem.
11:32
It's been known for a long time, you can't tickle yourself
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Već je dugo poznato da ne možete poškakljati sami sebe
11:34
as well as other people can.
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kao što vas mogu poškakljati drugi.
11:36
But it hasn't really been shown, it's because you have a neural simulator,
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No, to nije zaista dokazano, jer posjedujete neuralni stimulator
11:39
simulating your own body
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koji simulira vaše vlastito tijelo
11:41
and subtracting off that sense.
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i poništava taj osjet.
11:43
So we can bring the experiments of the 21st century
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Možemo eksperimente dovesti u 21. stoljeće
11:46
by applying robotic technologies to this problem.
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koristeći robotske tehnologije.
11:49
And in effect, what we have is some sort of stick in one hand attached to a robot,
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Imamo nekakav štap u jednoj ruci pričvršćenoj na robota,
11:52
and they're going to move that back and forward.
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i to će se micati naprijed-nazad.
11:54
And then we're going to track that with a computer
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Zatim ćemo to pratiti računalom
11:56
and use it to control another robot,
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i koristiti za upravljanje drugim robotom,
11:58
which is going to tickle their palm with another stick.
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koji će poškakljati dlanove osobe drugim štapom.
12:00
And then we're going to ask them to rate a bunch of things
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Onda ćemo ih zamoliti da ocijene razne stvari,
12:02
including ticklishness.
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uključujući i razinu škakljanja.
12:04
I'll show you just one part of our study.
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Pokazat ću vam samo jedan dio našeg istraživanja.
12:06
And here I've taken away the robots,
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Ovdje smo uklonili robote,
12:08
but basically people move with their right arm sinusoidally back and forward.
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i zapravo osoba miče desnu ruku sinusoidno naprijed-nazad.
12:11
And we replay that to the other hand with a time delay.
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Mi tu kretnju prenesemo na drugu ruku s vremenskim odmakom.
12:14
Either no time delay,
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Ili bez vremenskog odmaka,
12:16
in which case light would just tickle your palm,
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pri čemu bi osobi samo lagano zagolicao dlan,
12:18
or with a time delay of two-tenths of three-tenths of a second.
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ili s vremenskim odmakom od dvije ili tri desetinke sekunde.
12:22
So the important point here
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Dakle, važno je
12:24
is the right hand always does the same things -- sinusoidal movement.
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da desna ruka cijelo vrijeme čini istu kretnju – sinusoidni pokret.
12:27
The left hand always is the same and puts sinusoidal tickle.
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Lijeva je ruka uvijek u istom položaju i prima sinusoidno škakljanje.
12:30
All we're playing with is a tempo causality.
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Igramo se učincima promjene tempa.
12:32
And as we go from naught to 0.1 second,
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Kako mijenjamo od 0 do 0,1 sekunde,
12:34
it becomes more ticklish.
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počinje sve više škakljati.
12:36
As you go from 0.1 to 0.2,
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Povećavajući kašnjenje od 0,1 do 0,2 –
12:38
it becomes more ticklish at the end.
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dodatno se povećava škakljivost.
12:40
And by 0.2 of a second,
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I na kraju – od 0,2 s pa nadalje –
12:42
it's equivalently ticklish
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jednako će vas škakljati
12:44
to the robot that just tickled you without you doing anything.
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kao i robot koji vas je upravo poškakljao dok vi niste ništa radili.
12:46
So whatever is responsible for this cancellation
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Što god je odgovorno za izostanak osjećaja škakljanja
12:48
is extremely tightly coupled with tempo causality.
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vrlo je usko vezano s učincima promjene tempa.
12:51
And based on this illustration, we really convinced ourselves in the field
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Na temelju ovih ilustracija, uvjerili smo se
12:54
that the brain's making precise predictions
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da mozak čini precizna predviđanja
12:56
and subtracting them off from the sensations.
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i odvaja ih od osjeta.
12:59
Now I have to admit, these are the worst studies my lab has ever run.
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Moram priznati da su ovo najgora istraživanja provedena u mojem laboratoriju.
13:02
Because the tickle sensation on the palm comes and goes,
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Budući da osjećaj golicanja na dlanu dolazi i odlazi,
13:04
you need large numbers of subjects
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potreban vam je ogroman broj ispitanika
13:06
with these stars making them significant.
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kako bi istraživanje bilo značajno.
13:08
So we were looking for a much more objective way
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Dakle, tražili smo neki mnogo objektivniji način
13:10
to assess this phenomena.
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istraživanja ovog fenomena.
13:12
And in the intervening years I had two daughters.
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U međuvremenu sam dobio dvije kćeri.
13:14
And one thing you notice about children in backseats of cars on long journeys,
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Nešto što uočite kod djece na stražnjem sjedištu auta tijekom dužih vožnji –
13:17
they get into fights --
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započinju tučnjave --
13:19
which started with one of them doing something to the other, the other retaliating.
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što počne tako što jedna napravi nešto drugoj, pa ova vrati.
13:22
It quickly escalates.
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To brzo eskalira.
13:24
And children tend to get into fights which escalate in terms of force.
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Djeca su sklona tučnjavama u kojima se koristi sve više sile.
13:27
Now when I screamed at my children to stop,
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Kad bih viknuo na njih da prestanu,
13:29
sometimes they would both say to me
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ponekad bih od obje dobio odgovor
13:31
the other person hit them harder.
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da je ona druga jače udarila.
13:34
Now I happen to know my children don't lie,
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Slučajno znam da moja djeca ne lažu
13:36
so I thought, as a neuroscientist,
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pa mi je zato, kao neuroznanstveniku,
13:38
it was important how I could explain
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bilo važno dokazati
13:40
how they were telling inconsistent truths.
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kako su obje nedosljedno govorile istinu.
13:42
And we hypothesize based on the tickling study
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Napravili smo hipotezu na temelju studije o škakljanju,
13:44
that when one child hits another,
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da kad jedno dijete udari ono drugo,
13:46
they generate the movement command.
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stvaraju naredbu pokreta.
13:48
They predict the sensory consequences and subtract it off.
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Djeca predviđaju osjetilne posljedice i zanemaruju ih.
13:51
So they actually think they've hit the person less hard than they have --
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Tako da zapravo misle da su udarili osobu slabije nego što zaist jesu --
13:53
rather like the tickling.
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kao što je slučaj i sa škakljanjem.
13:55
Whereas the passive recipient
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A pasivni primatelj
13:57
doesn't make the prediction, feels the full blow.
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ne predviđa posljedice udarca, nego osjeća punu jačinu.
13:59
So if they retaliate with the same force,
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Dakle, ako se uzvrati istom mjerom,
14:01
the first person will think it's been escalated.
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druga će osoba to jače osjećati.
14:03
So we decided to test this in the lab.
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Tako da smo odlučili to testirati u laboratoriju.
14:05
(Laughter)
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(Smijeh)
14:08
Now we don't work with children, we don't work with hitting,
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Ne radimo s djecom, ne udaramo se,
14:10
but the concept is identical.
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ali koncept je isti.
14:12
We bring in two adults. We tell them they're going to play a game.
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Dvije odrasle osobe. Kažemo im da će igrati neku igru.
14:15
And so here's player one and player two sitting opposite to each other.
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Ovdje dva igrača sjede na suprotnim stranama.
14:17
And the game is very simple.
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Igra je vrlo jednostavna.
14:19
We started with a motor
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Počeli smo s motorom
14:21
with a little lever, a little force transfuser.
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s malom polugom, mali pretvarač sile.
14:23
And we use this motor to apply force down to player one's fingers
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Koristimo taj motor kako bismo primjenili silu na prste prvog igrača
14:25
for three seconds and then it stops.
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na tri sekunde i zatim popustili.
14:28
And that player's been told, remember the experience of that force
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Tom je igraču rečeno da zapamti jačinu te sile
14:31
and use your other finger
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i da svojim drugim prstom
14:33
to apply the same force
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primijeni jednaku silu
14:35
down to the other subject's finger through a force transfuser -- and they do that.
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na prst drugog igrača preko pretvarača sile - i onda bi to učinili.
14:38
And player two's been told, remember the experience of that force.
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Drugom je igraču rečeno da zapamti jačinu te sile
14:41
Use your other hand to apply the force back down.
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i da primijeni jednaku silu drugom rukom.
14:44
And so they take it in turns
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Tako su oni naizmjence pokušavali
14:46
to apply the force they've just experienced back and forward.
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odgovoriti jednakom silom na podražaj.
14:48
But critically,
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No, važno je naglasiti
14:50
they're briefed about the rules of the game in separate rooms.
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da su s pravilima igre upoznati u odvojenim prostorijama.
14:53
So they don't know the rules the other person's playing by.
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Tako da ne znaju po kojim pravilima igra druga osoba.
14:55
And what we've measured
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Ono što smo mi mjerili
14:57
is the force as a function of terms.
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jest sila ovisna o uvjetima.
14:59
And if we look at what we start with,
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Kad uzmemo u obzir da smo počeli s
15:01
a quarter of a Newton there, a number of turns,
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četvrtinom Newtona, i nakon brojnih ponavljanja,
15:03
perfect would be that red line.
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savršena bi bila ova crvena crta.
15:05
And what we see in all pairs of subjects is this --
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Kod svih smo parova primijetili
15:08
a 70 percent escalation in force
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da dolazi do 70%-tne eskalacije sile
15:10
on each go.
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u svakoj rundi.
15:12
So it really suggests, when you're doing this --
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To zapravo znači, da kad to radite –
15:14
based on this study and others we've done --
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na temelju ovog i drugih istraživanja koja smo provodili --
15:16
that the brain is canceling the sensory consequences
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mozak zanemaruje osjetilne posljedice
15:18
and underestimating the force it's producing.
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i podcjenjuje silu koju primjenjujete.
15:20
So it re-shows the brain makes predictions
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Dakle, to ponovno pokazuje kako mozak radi pretpostavke
15:22
and fundamentally changes the precepts.
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i na taj način temeljito mijenja percepciju.
15:25
So we've made inferences, we've done predictions,
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Donijeli smo zaključke, napravili smo pretpostavke –
15:28
now we have to generate actions.
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a sada trebamo djelovati.
15:30
And what Bayes' rule says is, given my beliefs,
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Bayesovo pravilo kaže da bi s obzirom na moja uvjerenja
15:32
the action should in some sense be optimal.
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radnja na neki način trebala biti optimalna.
15:34
But we've got a problem.
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No, imamo problem.
15:36
Tasks are symbolic -- I want to drink, I want to dance --
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Zadaci su simbolični – želim piti, želim plesati –
15:39
but the movement system has to contract 600 muscles
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no za to moram pokrenuti 600 mišića
15:41
in a particular sequence.
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u određenom slijedu.
15:43
And there's a big gap
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A postoji velika razlika
15:45
between the task and the movement system.
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između zadatka i sustava za kretanje,
15:47
So it could be bridged in infinitely many different ways.
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a mogla bi se premostiti na beskrajno mnogo različitih načina.
15:49
So think about just a point to point movement.
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Razmislite o pokretu od točke do točke.
15:51
I could choose these two paths
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Mogao bih odabrati ova dva načina
15:53
out of an infinite number of paths.
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od beskonačnog broja načina.
15:55
Having chosen a particular path,
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Nakon što odaberem određeni način,
15:57
I can hold my hand on that path
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mogu na njemu držati ruku
15:59
as infinitely many different joint configurations.
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u beskonačnom broju položaja zglobova.
16:01
And I can hold my arm in a particular joint configuration
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A u određenom zglobnom položaju,
16:03
either very stiff or very relaxed.
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mogao bih mišiće ruke ili čvrsto stisnuti ili opustiti.
16:05
So I have a huge amount of choice to make.
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Dakle, moram donijeti ogromnu količinu odluka.
16:08
Now it turns out, we are extremely stereotypical.
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Ispada da smo vrlo podložni stereotipima.
16:11
We all move the same way pretty much.
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Većinom se svi krećemo na isti način.
16:14
And so it turns out we're so stereotypical,
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Ispada da smo toliko stereotipni,
16:16
our brains have got dedicated neural circuitry
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da naš mozak ima određene neuralne krugove
16:18
to decode this stereotyping.
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kojima dekodira taj obrazac.
16:20
So if I take some dots
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Ako uzmemo ove točkice
16:22
and set them in motion with biological motion,
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i pokrenemo ih u biološkom načinu kretanja –
16:25
your brain's circuitry would understand instantly what's going on.
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vaš mozak će odmah razumjeti o čemu se radi.
16:28
Now this is a bunch of dots moving.
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Ovo je hrpa točkica koje se kreću.
16:30
You will know what this person is doing,
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No, vi ćete prepoznati što ta osoba radi,
16:33
whether happy, sad, old, young -- a huge amount of information.
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je li sretna, tužna, stara, mlada – ogromna količina informacija.
16:36
If these dots were cars going on a racing circuit,
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Da ove točkice predstavljaju aute koji kruže u utrci,
16:38
you would have absolutely no idea what's going on.
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ne biste imali pojma o čemu se radi.
16:41
So why is it
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Zašto se, onda, krećemo
16:43
that we move the particular ways we do?
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baš na ovaj način?
16:45
Well let's think about what really happens.
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Razmislimo o tome što se zaista događa.
16:47
Maybe we don't all quite move the same way.
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Možda se ne krećemo baš svi na jednak način.
16:50
Maybe there's variation in the population.
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Možda postoje varijacije u populaciji.
16:52
And maybe those who move better than others
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Možda oni koji se kreću bolje
16:54
have got more chance of getting their children into the next generation.
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imaju veću vjerojatnost dobivanja potomstva.
16:56
So in evolutionary scales, movements get better.
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Tijekom evolucije pokreti postaju bolji.
16:59
And perhaps in life, movements get better through learning.
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A vjerojatno tijekom života isto tako pokreti postaju bolji kroz učenje.
17:02
So what is it about a movement which is good or bad?
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Što je to u pokretu dobro ili loše?
17:04
Imagine I want to intercept this ball.
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Zamislite da želim presresti ovu loptu.
17:06
Here are two possible paths to that ball.
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Postoje dva različita načina na koje to mogu učiniti.
17:09
Well if I choose the left-hand path,
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Ako odaberem put s lijeve strane,
17:11
I can work out the forces required
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mogu proizvesti snagu potrebnu
17:13
in one of my muscles as a function of time.
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u određenom mišiću, kao funkciju vremena.
17:15
But there's noise added to this.
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No, tome trebamo pridodati šum.
17:17
So what I actually get, based on this lovely, smooth, desired force,
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Ono što zapravo dobivam na temelju ove željene glatke sile,
17:20
is a very noisy version.
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zapravo je verzija puna šumova.
17:22
So if I pick the same command through many times,
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Dakle, ako istu zapovijed pošaljem mnogo puta,
17:25
I will get a different noisy version each time, because noise changes each time.
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svaki ću put dobiti drugačiju verziju punu šumova jer se oni svaki put mijenjaju.
17:28
So what I can show you here
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Ovo što vam mogu pokazati
17:30
is how the variability of the movement will evolve
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jest kako će se varijabilnost pokreta razviti
17:32
if I choose that way.
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ako izaberem ovaj način.
17:34
If I choose a different way of moving -- on the right for example --
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Ako odaberem drugi način kretanja, primjerice ovaj s desne strane,
17:37
then I'll have a different command, different noise,
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tada ću imati drugačiju naredbu i drugačije šumove,
17:39
playing through a noisy system, very complicated.
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koji dolaze kroz sustav pun šumova, vrlo komplicirano.
17:42
All we can be sure of is the variability will be different.
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Jedino u što možemo biti sigurni jest da će varijabilnost biti drugačija.
17:45
If I move in this particular way,
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Ako se krećem na taj određeni način,
17:47
I end up with a smaller variability across many movements.
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pokreti će mi postajati manje varijabilni.
17:50
So if I have to choose between those two,
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Kad bih morao birati između ta dva načina,
17:52
I would choose the right one because it's less variable.
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odabrao bih desni način jer bi mi pokreti bili manje varijabilni.
17:54
And the fundamental idea
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Temeljna ideja
17:56
is you want to plan your movements
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jest da želite planirati svoje pokrete
17:58
so as to minimize the negative consequence of the noise.
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tako da se maksimalno smanje negativne posljedice šumova.
18:01
And one intuition to get
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Intuicija koju trebate steći
18:03
is actually the amount of noise or variability I show here
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jest zapravo da se količina šuma ili varijabilnosti koju pokazujem
18:05
gets bigger as the force gets bigger.
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povećava kako se povećava i sila.
18:07
So you want to avoid big forces as one principle.
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Želite izbjeći uporabu velike sile.
18:10
So we've shown that using this,
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Ovime smo pokazali
18:12
we can explain a huge amount of data --
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kako možemo objasniti ogromne količine podataka --
18:14
that exactly people are going about their lives planning movements
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ljudi u svom životu planiraju pokrete
18:17
so as to minimize negative consequences of noise.
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kako bi smanjili negativne posljedice šumova.
18:20
So I hope I've convinced you the brain is there
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Nadam se da sam vas uvjerio kako mozak postoji
18:22
and evolved to control movement.
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i kako se razvio da bi mogao upravljati pokretima.
18:24
And it's an intellectual challenge to understand how we do that.
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Intelektualni je izazov shvatiti kako to činimo.
18:27
But it's also relevant
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No, to je bitno
18:29
for disease and rehabilitation.
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i za mnoge bolesti i rehabilitaciju.
18:31
There are many diseases which effect movement.
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Postoje mnoge bolesti koje utječu na kretanje.
18:34
And hopefully if we understand how we control movement,
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Nadamo se, ako shvatimo kako kontroliramo pokrete,
18:36
we can apply that to robotic technology.
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da ćemo to znanje moći primjeniti i na robote.
18:38
And finally, I want to remind you,
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I, za kraj, želim vas podsjetiti
18:40
when you see animals do what look like very simple tasks,
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da kad vidite životinje kako vrše naizgled vrlo jednostavne zadatke,
18:42
the actual complexity of what is going on inside their brain
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imajte na umu da je složenost onoga što se događa u njihovom mozgu
18:44
is really quite dramatic.
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zapravo vrlo dramatična.
18:46
Thank you very much.
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Hvala vam.
18:48
(Applause)
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(Pljesak)
18:56
Chris Anderson: Quick question for you, Dan.
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Chris Anderson: Imam kratko pitanje za vas, Dan.
18:58
So you're a movement -- (DW: Chauvinist.) -- chauvinist.
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Rekli ste da ste pokretni.... /Dan: Šovinist./ - šovinist.
19:02
Does that mean that you think that the other things we think our brains are about --
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Znači li to da mislite da druge stvari za koje mislimo da naš mozak služi --
19:05
the dreaming, the yearning, the falling in love and all these things --
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kao što su sanjanje, čežnje, zaljubljenost i te stvari –
19:08
are a kind of side show, an accident?
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sve zapravo popratni sadržaj, slučajnosti?
19:11
DW: No, no, actually I think they're all important
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DW: Ne, ne, zapravo mislim da je to sve važno
19:13
to drive the right movement behavior to get reproduction in the end.
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kao utjecaj na kretanje koje će nam na kraju osigurati potomstvo.
19:16
So I think people who study sensation or memory
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Smatram da ljudi koji proučavaju osjete ili pamćenje,
19:19
without realizing why you're laying down memories of childhood.
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zapravo ne razumiju zašto pohranjujemo sjećanja iz djetinjstva.
19:21
The fact that we forget most of our childhood, for example,
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Činjenica da smo zaboravili većinu toga iz djetinjstva, primjerice,
19:24
is probably fine, because it doesn't effect our movements later in life.
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vjerojatno je u redu, zato što to nema utjecaja na naše kasnije pokrete.
19:27
You only need to store things which are really going to effect movement.
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Pohraniti trebate samo ono što će vam kasnije utjecati na kretanje.
19:30
CA: So you think that people thinking about the brain, and consciousness generally,
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CA: Dakle, vi mislite da bi ljudi koji razmišljaju o mozgu i općenito o svijesti
19:33
could get real insight
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mogli dobiti pravi uvid
19:35
by saying, where does movement play in this game?
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kad bi odgovorili na pitanje kakvu ulogu kretanje ima u cijeloj priči?
19:37
DW: So people have found out for example
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DW: Ljudi su otkrili, primjerice,
19:39
that studying vision in the absence of realizing why you have vision
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da je proučavanje osjeta vida bez shvaćanja zašto uopće imamo vid
19:41
is a mistake.
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pogrešno.
19:43
You have to study vision with the realization
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Vid se mora proučavati zajedno sa spoznajom
19:45
of how the movement system is going to use vision.
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kako će sustav za kretanje iskoristiti taj vid.
19:47
And it uses it very differently once you think about it that way.
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A koristi ga vrlo različito, jednom kad o tome počnete tako razmišljati.
19:49
CA: Well that was quite fascinating. Thank you very much indeed.
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CA: To je zaista fascinantno. Hvala vam puno!
19:52
(Applause)
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(Pljesak)
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