Perceptionand the

Mwahahahaha!!

AAAAAAAAAAAH!Not more sensory cues!!!

senses

Perception

sensesand the

Based on the bbc 4 radio programme ‘in our time’

edited and illustrated by Louisa Hadjipetrou

1

“Barry Stein’s laboratory at Wake Forest University in the United States found that the shape of a right angle drawn on the hand of a chimpanzee starts the visual part of the brain working, even when the shape has not been seen. It has also been discovered that babies learn by touch before they can properly make sense of visual data, and that the senses of smell and taste chemically

combine to give us fLavour.

Perception is a tangled web of processes and so much of what we see, hear and touch is determined by our own expectations that it raises

the question of whether we ever truly perceive what others do.

What governs our perception of the world? And are we correct to distinguish between sight, sound, smell, touch and taste when they

appear to infLuence each other so very much?”

Indroduction

2

I think there’s something in

my eye...

3

4

“we call that perception, meaning that the brain is adding a vast amount of information to the information received by the senses,

it’s enriched tremendously and if you think about it the eyes have little tiny

pictures like postage stamps...”

“and from those tiny pictures only the centers of which have any sort of

sharpness to them anyway, we see this incredible richness of

the world.”

5

So what’s this FIlm

about then?

“we see objects as solid, as useful, as frightening, as beautiful, as sexy, all these rich qualities which come from

our knowledge of the world which are projected into the world from

the brain.”

So what’s this FIlm

about then?

6

“So we sort of project into the world perceptually as we receive signals through the senses, the eyes, the ears, which are then

transmitted to the brain and I think the essential point about perception is that even directly it is related

to the external world.”

7

“we seem to be directly aware of things around us or both in the world continuously, actually the brain is locked away in this little black box not of course receiving any light. Although we see light, light never enters into the brain.”

8

Hey! It’s dark in here...

.--. . .-. -.-. . .--. - .. --- -. / .- -. -.. / - .... . / ... . -. ... . ..

Errrrr...??

9

10

“All the brain gets are signals like Morse code, dots and dashes from the senses which it has

to decode. It has to interpret, it has to read from knowledge with lots of rules and it constructs the world

around us. It’s really constructed by an active brain.”

11

“well in the eye itself we have of course the retina which has 120 million receptors which

are like little tiny photoelectric cells which accept photons and then produce signals- we call

these transducers it’s an engineering term, it converts the photons energy entering the eye into signals which are little pulses of electricity.”

12

I’m a clever

chap i am!

“so it receives these pulses of electricity which are essentially the same for all the senses. Also, incredibly, very much the same as any sort of signal working the muscles, these are called action potential. Discovered at the beginning of the 19th century by lord Adrian. He discovered

wonderful coding of the nervous system.”

13

I can see what you se

e!

Highest form of anim

al my arse!

I wish I had my glasses...

I can see what you se

e!

Highest form of anim

al my arse!

14

“it starts of with these separate kinds of processing for

different kinds of creatures of the world and yet we experience one

homogenous world of objects from all this mish-mash…”

15

“the brain creates hypothesis of the external world which are rather like hypothesis in science. It’s got bits and

pieces of data coming in, pretty inadequate actually, vast amounts of knowledge stored from the past and then its got those rules

by which it handles the data, very much how science works and then it creates stories...”

hypothesis, predictive hypothesis of the external world and that is

our inner reality.”

If the size of the molecules is related to the rate of diffusion as they pass through a membrane, then smaller molecules will flow through at a higher rate.

16

17

We’re so awesome!

Oh I know...

18

“and then the same process of transduction takes

place within the inner ear leading to the generation of

nerve impulses.”

“but the difference between the senses actually starts at the outer

part, in the eye and the ear. So whereas we have photons stimulating the retina, in the auditory system we have energy, mechanical transformations in the air

which then set up mechanical changes in the ear...”

19

“in reality we’re not just simply looking at a single auditory cue like a tone and a fLash of light and

the brain has to decide whether those things arise from the same object or not, but the more usual cases are as you

walk through your environment your brain is bombarded by multiple sensory cues arising from lots of different objects.

So its had to evolve some rules by which it can decide whether more than one sensory cue arises from one object or multiple ones and two cues it has learned that give us information about where these signals are coming from are proximity in time and space. So by and large we know when things occur in time and are arising from the same location

they tend to be coming from the same object.”

AAAAAAAAAAAH!Not more sensory cues!!!

Mwahahahaha!!

20

You should be ki

ssed

and often and by

someone who know

s how.

21

“when you’re looking at a movie, when you’re in the cinema looking at a movie, looking at people talking we think: yes they

are talking, that person is saying those words before my very eyes and it’s happening on the screen in front of me on the little moon of my existence in the universe… but we know the sound is coming from the sides, sometimes from

the back, sometimes from the ceiling …”

“typically when you have multiple senses they sense which is the most easily localizable in

this case for us humans that’s vision, the other sense will be misallocated towards the visual

cue because it’s the most persuasive…”

You should be ki

ssed

and often and by

someone who know

s how.

Where’s the sound coming from?

22

... and this is my good friend vincent! Say

hello vincent...

Ah shut up!

23

24

“and more to do with the fact that the persuasiveness of

the time course of the dummy’s lips and mouth movements that he moves in time with his speech shifts your perception of the sound and speech away from the ventriloquist and

towards the dummy.”

“so this is the basis, not only of you sitting in the cinema and perceiving that the sound is actually coming from

the speakers on the screen in front of you even though it’s not it’s in the surround sound at the back but also on the basis of the ventriloquist illusion which has

less to do with the ventriloquists ability to throw his voice...”

25

“the same cells which recognize correspondence between

different senses are also able to detect incongruence so things which are just slightly slicked

out of time perhaps are spatially disparate or perhaps even the

content doesn’t match...”

“for example if you’ve watched a foreign movie and

they dub English over the natural language that the

speakers are mouthing it will actually hamper your ability to hear what’s being said.”

A toast to the queen!

A piece of toast for the queen!

“Mἱα φρυγανἱα γιἀ τἠν βασἰλισσα!”

26

27

“I think in a way when studying the mind, illusions are

like test tubes in a chemistry set, isolated from the physical world

because perception has departed from the physics, departed from the actual world of objects and you either get distortions or complete fIctions.”

All by my se

eeeeelf,

don’t wanna

be all

by my seeee

lf anymore..

.

28

All by my se

eeeeelf,

don’t wanna

be all

by my seeee

lf anymore..

.

29

“the brain is quite capable of creating ghosts, completely fIctional objects which do not exist and there are rules and laws for producing ghosts, it’s not just

unlawful, it’s not just random and roughly what’s happening is that the brain adopts all sorts of strategies for making effective use of rather limited information on the basis of

past experience ...”

“so when you’ve got a situation which in some way is similar to the past but in another subtle was different, it’ll process it as though it’s a typical situation. It’ll then produce artifacts, errors.”

AAAAAAAAAAAH!! A Ghost!!Oh wait they don’t exist... my bad!

BOO!!

30

31

I’m actually hol

low,

didn’t know that no

w did you?!

32

“a very nice example is looking at a hollow face, a hollow mask and you see it just sticking out, the nose sticking

out although it’s really sticking in simply because all the faces ones seen in ones life have had

sticking out noses...”

“and its got your information, it is a face, the shape of the eyes and nose and so on. It might be a cartoon indeed illustrating your face and then the brain FIlls in all sorts of information from past experience which happens to be

down right wrong.”

NOW YOU DON’T

NOW YOU

SEE US.

..

33

34

“now I fInd illustrations incredibly interesting, I think there are many kinds of

distortions, complete fIctions and there are also ambiguities which are terribly interesting when

perception FLips from one thing to another although the input is fIxed, is the same with no change

whatsoever, it’ll entertain if you like, different hypothesis and so you see the activity of the brain trying out possibilities actively even from the same input, for example there’s a famous illustration again involving faces where you draw a vase and the outside of the vase forms two faces looking at each other and sometimes you see the vase and other times you see the two faces with no change

whatsoever in the object or the drawing.”

35

Three goa

ts and a

troll...??

36

WE GO TO SCHOOL“lip reading which is very

important for people who are hard of hearing but what’s less well recognized is that it’s also very important for people who

hear normally and we’re consciously lip reading all the time when we’re watching somebody talk particularly this can be

benefIcial in a situation where the auditory signal is degraded in some way and we can sort of use the lip reading to FIll in the

missing auditory signal.”

37

“a fascinating illusion in hearing, well it’s a cross modal illusion, is the so called mcgurk effect and I fIrst witnessed this at a

large convention center, there were 5000 people in the audience and the speaker asked us to close our eyes and she played a syllable which was pa and everyone heard pa and then she asked us to

open our eyes and there on the screen in front of us was a huge picture of somebody’s face and the visual stimulus was saying KA and immediately on the fIrst presentation of this everybody got the perception of either ka or ta but not pa and this huge gasp went up in the audience, it was

incredibly dramatic. So this shows the power of how vision can actually infLuence what we hear.”

“probably the more common example of the mcgurk effect is with the syllables ba and da; the auditory

is the ba and the visual is the da but what you actually hear is ga, a blend of the two neither one nor the other but a fusion. This demonstrates the infLuence of lip reading on your

auditory perception.”

Ba Ba Ba

Ga Ga Ga

Da Da Da

I better be getting

paid for this...

38

39

So we deduce that as an object falls, its

speed increases because it’s being pulled on

by gravity!

40

“this is a characteristic of children, I think children when they’re in a high chair throwing a mug on the fLoor and all the rest of it, they’re actually

carrying out experiments, they’re relating the signals coming to their brains to their eyes to the world of tangible objects which

can hurt them or reward them because they’re experimenting with the world actively and these experiments which you do in childhood

which are such a pain to everyone except the mother are really a child being a scientist

discovering the world.”

41

“hearing does begin in utero at about the 26th week or so of pregnancy and there’s been some reports that children when they’re born can recognize their mothers voices so there is some sort of learning going on

in there apparently.”

Oh please stop kicking me,

mummy’s uterus isn’t a football...

Oi! you talkin’ about me?!

42

woah...

JUST DO WHAT I DO!

43

44

“learning by natural selection, that is there is a change in the genetic

code according to what has been successful behavior, tends to get inherited

by natural selection and so knowledge gets inherited not directly by the brain but by the genetic code and this is what we mean by innate knowledge… it is in fact knowledge gained by experience but it’s experience through millions of generations so we actually start with

knowledge acquired by previous species.”

“if you talk to a behavioral geneticist they will say that

behavior is more inherited than physical attributes in some senses, that it has a

higher degree of heritability.”

45

AAAAAAH!!

WHY GOD WHY!!

“there is a whole science in psychology about intuitive physics, babies innate

assumptions about the world, experiments have been done on how babies experience falling

objects and if they don’t fall vertically they get a bit upset they sort of intuitively know that objects should fall down vertically… there’s a lot of evidence in the way babies

look, in the way they move their eyes that they immediately respond to people and that people are very special. They don’t of course recognize their mother at fIrst go but they do recognize a face, that is they prefer a picture of a simple cartoon

face to the same feature jumbled up…”

AAAAAAH!!

WHY GOD WHY!!

46

The End

A humorous accompaniment to the bbc 4 radio programme ‘IN OUR Time’. This edition focuses on

perception and the senses and is hosted by Melvin Bragg. Guest speakers are Richard Gregory, Senior Research Fellow in the Department of Experimental Psychology, Bristol University; David Moore, Director of the Medical Research

Council Institute of Hearing Research, University of Nottingham and Gemma Calvert, Reader in Cognitive Neuroscience, University of Bath.

edited and illustrated by Louisa Hadjipetrou