Perception and the Senses
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Transcript of Perception and the Senses
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