Psychology of the Senses : Documentary on Sensation and Perception (Full Documentary)
Summary
TLDRThis program delves into the fascinating world of perception, exploring how our brains are tricked by visual illusions and the complexities of sensory processing. From the remarkable abilities of different species to the intricate workings of the human brain, the script uncovers the mechanisms behind our perceptual experiences, highlighting the role of bottom-up and top-down processing in creating a stable and meaningful interpretation of the world around us.
Takeaways
- 🎨 Visual illusions can trick the brain due to the way our perception system processes and interprets visual information.
- 🧠 Perception is a critical survival tool that allows us to make contact with our environment and gather essential information.
- 👀 Our sensory abilities are measured by the absolute threshold, which is the weakest level of a stimulus that can be detected half the time.
- 🌆 Perception involves both bottom-up processing, where raw data from sensory receptors is sent to the brain, and top-down processing, which adds our prior knowledge and context to the interpretation.
- 🔍 The brain performs complex transformations to interpret sensory information, such as eliminating confusing signals and giving objects three dimensions.
- 🏥 The occipital lobe in the brain is primarily responsible for processing visual information, while other lobes handle different types of sensory input.
- 🐦 Different species have developed specialized sensory apparatuses for survival, such as the keen vision of eagles or the sonar of bats.
- 🤔 Perceptual constancy allows us to perceive objects as relatively stable despite changes in the sensory input, such as size or brightness.
- 👁️ The visual system breaks down visual stimulation into millions of bits of information and recombines them into a coherent image that we recognize.
- 🤹♂️ Our brain can sometimes create phantom patterns or subjective contours, where we perceive a boundary or edge that doesn't physically exist.
- 🏈 Adaptation to altered perception, such as wearing glasses that displace visual feel, requires the brain to learn new arm-eye coordination, demonstrating the brain's plasticity.
Q & A
How does the brain get tricked by visual illusions?
-The brain gets tricked by visual illusions because it performs an instantaneous analysis of visual information, making assumptions based on past experiences and the context of the situation. These assumptions can lead to misinterpretations, such as perceiving size or shape incorrectly.
What is the role of perception in our interaction with the environment?
-Perception is our way of making contact with our environment, discovering what's happening outside our body. It is crucial for survival as it allows us to gather essential information through our senses and respond appropriately to our surroundings.
How do different species develop sensory apparatus for survival?
-Different species develop special sensory apparatus to gather information essential for their survival. For example, eagles have extremely accurate vision, dogs can smell in much lower concentrations, and bats use sonar to track and catch insects.
What is the absolute threshold in sensory perception?
-The absolute threshold is the weakest level of a stimulus that can be accurately detected at least half the time. It varies for different senses and is a measure of our sensory abilities.
How is visual information processed in the brain?
-Visual information is processed in several stages. It starts in the retina, then moves through the optic nerve to the brain, where it is further processed in the occipital lobe and other cortical areas. The visual cortex is responsible for interpreting the information and forming a coherent image.
What are the roles of the rods and cones in the retina?
-Rods and cones are photoreceptor cells in the retina that detect light and color. Rods are sensitive to low light conditions, while cones are responsible for color vision and function best in bright light.
How do the brain's transformations of visual information help in perceiving the real object?
-The brain transforms the visual information by eliminating confusing signals, filling in gaps, and giving the image three dimensions. It corrects the upside-down image and puts everything in perspective to determine the true nature of the actual object, known as the distal stimulus.
What is the significance of perceptual constancy in visual perception?
-Perceptual constancy allows us to perceive the actual size, shape, orientation, and brightness of an object as relatively constant, even when there are variations in the retinal image. This helps us maintain a stable perception of our environment despite changes in viewing conditions.
How does the brain use context to influence perception?
-The brain uses context to interpret sensory information by comparing it with what we already know and expect. This top-down processing adds meaning to our perceptions, allowing us to see things in a way that makes sense given the situation.
What is the concept of subjective contours in visual perception?
-Subjective contours are phantom patterns that the brain perceives even when they are not physically present. They occur when the brain detects a boundary or edge and extends that difference across a surface, creating the illusion of a complete shape or pattern.
How can our expectations and biases affect our perception?
-Our expectations, interests, and biases can influence our perception by predisposing us to see what we expect to see or not see what we do not expect. This can lead to misinterpretations or overlooking certain details in our environment.
Outlines
🎨 Visual Perception and Illusions
This paragraph delves into the fascinating world of visual perception, exploring how our brains can be deceived by visual illusions. It starts with an introduction to the program's funding and purpose, then transitions into an interactive demonstration at the Exploratorium in San Francisco, where the presenter manipulates perception to appear larger or smaller. The discussion explains how our brains use visual information and past experiences to make instantaneous judgments about size and shape, often leading to misperceptions. The paragraph also touches on the importance of perception in survival, the absolute threshold of sensory detection, and the various sensory apparatuses developed by different species.
👀 Understanding Sensory Perception
The second paragraph provides an in-depth look at how sensory information is processed by the human brain. It explains the role of specialized receptors in detecting physical energy, such as light and sound waves, and converting these into neural impulses. The journey of these impulses from the sensory organs to the brain's cortex is detailed, highlighting the分工 of different cortical regions in processing various senses. The paragraph further discusses the primary sensory centers, the thalamus as a relay station, and the abstract information processing that occurs in the cortex. It also touches on the Nobel Prize-winning work of David Hubel and Torsten Wiesel on receptor cells in the visual pathway and the complexity of early vision processes.
🤖 The Complexity of Visual Processing
This paragraph examines the intricate process of visual information processing, from the initial reception of light by the retina to the recognition of objects. It describes how the visual system breaks down an image into millions of bits of information, using computer graphics to illustrate the point. The discussion includes the role of edge and line-detecting neurons in identifying object boundaries and the concept of constancies and simplicity in object recognition. The paragraph also explores the idea of motion perception and rigidity, using examples of rotating squares and crosses to demonstrate how the brain interprets motion. The importance of perceiving motion and the challenges of creating a seeing robot are emphasized, highlighting the complexity of visual perception.
🏈 Perception in Action and Adaptation
The fourth paragraph discusses the practical applications of perception, particularly in the context of sports, such as American football. It describes how a quarterback uses perception to calculate distance, angle, and velocity for passing the ball. The paragraph also introduces an experiment with glasses that distort visual perception, demonstrating how the brain adapts to new visual information and the consequences when perception returns to normal. The discussion extends to the concepts of bottom-up and top-down processing, explaining how our prior knowledge and context influence our perceptions. The paragraph concludes with examples of perceptual constancy and the active role our minds play in shaping our perceptions of reality.
🔍 The Active Nature of Perception
This paragraph explores the active nature of perception, emphasizing that our brains constantly select and process only a small part of the available sensory information. It discusses how context can significantly influence perception, using examples of a square appearing darker against a lighter background and the size comparison of three men. The paragraph also touches on the speed and efficiency of perception, highlighting the importance of edges and boundaries in conveying information about an object. The discussion includes the concept of subjective contours, where the brain registers patterns that do not exist, and the influence of our expectations, interests, and biases on perception.
🕵️♂️ Perception and the Limits of Understanding
The final paragraph addresses the limitations of perception and the role of our brain in organizing and interpreting sensory information. It discusses how our expectations and experiences can sometimes lead us astray, causing us to see things that aren't there or fail to see things we don't expect. The paragraph presents various visual paradoxes and illusions, such as the impossible triangle and the bouncing ball animation, to illustrate the conflict between analytic and holistic ways of seeing. It concludes with a reminder of the sophistication of our sensory apparatus and the software of our brain, which, despite occasional discrepancies, usually work together effectively to make sense of the world around us.
Mindmap
Keywords
💡Perception
💡Visual Illusions
💡Sensory Apparatus
💡Absolute Threshold
💡Neural Impulses
💡Cortex
💡Distal Stimulus
💡Perceptual Constancy
💡Bottom-Up Processing
💡Subjective Contours
💡Eyewitness Testimony
Highlights
The brain is tricked by visual illusions due to its reliance on past experiences and expectations to interpret sensory information.
Perception is a crucial survival tool that allows us to make contact with our environment and understand what's happening around us.
Different species have developed unique sensory apparatuses, such as eagles' sharp vision and dogs' heightened sense of smell.
Psychologists focus on visual perception, which is processed in the occipital lobe and involves multiple stages of neural activity.
The absolute threshold measures the weakest level of a stimulus that can be detected half the time, highlighting the sensitivity of human senses.
Sensory receptors convert physical energy into neural impulses, which the brain's cortex interprets into various psychological experiences.
The primary visual cortex processes visual information, which is initially an upside-down, distorted image on the retina.
The brain performs transformations to eliminate confusing signals and give depth and perspective to the visual information received.
David Hubel and Torsten Wiesel's research on receptor cells in the visual pathway won them a Nobel Prize, shedding light on how we see.
The visual system breaks down visual stimulation into millions of bits of information, reassembling them into a coherent image.
Perception involves both bottom-up processing, which detects external stimulation, and top-down processing, which adds context and meaning.
Perceptual constancy allows us to perceive objects as relatively constant despite changes in the sensory input they project.
Our expectations and biases can lead to different perceptions, as seen in the varying interpretations of ambiguous figures.
Subjective contours demonstrate how the brain can create perceived edges even where there are none, influenced by surrounding context.
Eyewitness testimonies can be unreliable due to the brain's quick reactions that may outpace its ability to accurately process visual information.
Visual paradoxes challenge our understanding of what is possible, as our brain uses both analytic and holistic ways of seeing to make sense of objects.
The program explores the sophisticated interplay between our sensory apparatus and the brain's software for processing information and making sense of the world.
Transcripts
funding for this program is provided by
anenberg cpb to advance excellent
[Music]
teaching how is our brain tricked by
visual
Illusions what makes a Star Quarterback
misjudge an Easy Pass
why does this rotating Square appear to
expand and
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contract sensation and perception this
time on discovering
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[Applause]
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psychology
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lights camera
perception when you were little and some
big kids pushed you around did you ever
fantasize about becoming bigger all of a
sudden
well I did and now I can at the
Exploratorium San Francisco's Science
Museum how did I do it the easy way by
manipulating your perception when you
first saw me I appeared to be normal
size because you couldn't see the rest
of the room but as the lights came up
and the camera pulled back your brain
performed a new instantaneous analysis
it now saw me as small it added up all
all the visual information it had about
my size and the size and shape of the
room and then it added in everything it
knew from experience about the usual
shape of rooms that they're rectangular
and have right
angles so when I walked over here your
brain was convinced I was growing
incredibly large because there was no
other perceptual explanation even though
it wasn't
logical let's look at it again only this
time from a different perspective the
room is not rectangular at all it's
totally distorted there are no right
angles anywhere so that makes this clock
which is large and oval look the same as
that clock which is small and circular
from your other perspective the floor
slopes upward as you can see the ceiling
slopes
downward so I'm not getting larger at
all you're just miss perceiving my size
because you think that you're the same
distance from me when I'm over here as
you are from me me when I'm over
there but in fact I'm twice as far
away it's always more fun to have a
vivid example of
misperception but the truth is our
perception is usually very accurate it
has to be we couldn't survive if it
weren't perception is our way of making
contact with our environment of
discovering what's happening outside our
body and our
brain all species have developed special
sensory apparatus to gather information
essential for
survival Eagles and other birds of prey
have astonishingly accurate
Vision dogs can smell things in
concentrations a 100 times lower than we
can and bats can use sonar to track and
Capt tiny fast moving
insects psychologists study all sensory
processes hearing smell taste and so on
but their major focus and ours is on
visual perception our sensory abilities
are usually measured by the absolute
threshold the weakest level of a
stimulus that can be accurately detected
at least half the
time for you humans that includes a
candle flame seen at 30 m on a dark
clear
night the tick of a watch under quiet
conditions at 20
ft one teaspoon of sugar in 2 gallons of
water one drop of perfume diffused in
the space of a three room
apartment the wing of a bee for rolling
on your cheek from a distance of 1
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cm our sensory knowledge of these
stimuli comes from the many millions of
specialized receptors spread throughout
our
bodies in Our Eyes Ears Nose tongue skin
muscles our joints and tendons our inner
ear and even certain parts of our
digestive
tract each receptor is designed to
detect certain types of physical energy
such as light waves or sound waves this
stimulation is then converted into a
special code electrochemical signals
called neural impulses which the nervous
system transmits to the brain's
cortex the cortex has the job of putting
all the sensory information together and
acting upon it different regions of the
cortex translate different neural
impulses into different psychological
experiences such as melody or
touch visual information is first
processed in the occipital lobe area in
the rear of the brain hearing and smell
in the temporal lobe speech perception
in the frontal lobe and body senses in
the parietal lobe these primary sensory
centers then project the results of
their activity to a relay station the
thalamus which in turn sends the
information to a succession of areas in
the
cortex it's believed that this is where
more abstract information processing
takes place and where we connect new
information with old information stored
in our
memory visual perception for instance
takes place in three areas in the retina
or the back surface of the eye in the
pathways through the brain and in the
part of the cortex at the back of the
brain resp responsible for visual
processing the visual
cortex this is the way an image or
rather a pattern of stimulation is
formed on the retina it's upside down
flat distorted full of holes out of
focus and obscured by blood vessels in
fact it's amazing that we see as well as
we
do now remember that the task of all
perception is to determine what the real
object in the environment is another
term for this object is the distal
stimulus the thing out there but the
only way to find out what that is is by
using information derived from the
object stimulation of a sensory receptor
in the body this stimulation is called
the proximal stimulus in this case an
image formed on the retina the brain
knows only the image but what it must
discover is the true nature of the
actual object the distal stimulus
so here's where the brain earns its keep
it must eliminate confusing
signals fill in the
blanks give it three
dimensions and straighten out the upside
down image to put it all in
perspective these Transformations occur
instantly and
continually David Yubel of Harvard won a
Nobel Prize with his colleague Toren
visel for mapping the action of receptor
cells along the visual path of a primate
from the retina to the cortex receptor
cells usually in a v in the visual
pathway mean the cells that take in the
energy and turn them it into electrical
signals and in the retina those are the
rods and cones there are 125 million
rods and cones in each retina so in the
case of the visual pathway you start
with the retina the output put is the
optic nerve which contains a million
fibers they end up in a certain region
in the
brain that region or there really two or
three regions that they end up in uh
each of those sends a cable of fibers of
the order of maybe a million to other
regions and they connect to other
regions and in the case of the cortex
you have separate areas of Cortex each
one connected to one or more other areas
and this whole thing is a pathway in the
cortex for example the primary visual
cortex which is about seven stages
Beyond The receptors in the retina those
cells uh react to visual stimula only if
the if a line falls on the retina and
the line has to be a particular
orientation can be a bright line or a
dark line or an edge between bright and
light any kind of line really generally
works but the position of the line and
the orientation are terribly important
and if they're not just right any
individual cell doesn't doesn't
respond in this experimental footage a
bright vertical line stimulates a small
number of neurons in the visual cortex
of a cat the crackling sound is the
electrical activity of these neurons as
they respond to this retinal image by
listening to the intensity of this
electrical activity the researchers can
determine the correct orientation of the
line
but when the line is moved to a diagonal
or horizontal position the amount of
stimulation decreases
dramatically we're only at a very
Elementary stage when it comes to
understanding something like how you
recognize a face or something like that
the the general region of the brain is
known where where things like that go on
but we don't have the slightest idea of
what's happening at the level of single
cells for that particular problem but
for more Elementary problems for the the
very first uh processes of vision we do
have a very good understanding what
happens at the very beginning so it's
just a
start Misha Pavel of Stanford University
is studying the successive stages of
information processing that take place
continually as we perceive the world
using computer Graphics he has
demonstrated how the visual system
breaks down VIs ual stimulation into
millions of bits of information and
recombines them into a coherent image
that we recognize seeing something is
seems such an effortless activity that
it's hard to imagine for us the
complexities and difficulties that are
involved only when you try to build a
robot that can actually see and
recognize objects do you realize how
complicated task this is people can must
do awful lot of processing in order to
see images and interpret them here is an
image of a cat as our eye and brain sees
it now let's look at what the visual
system goes through to enable us to see
this image when the light first reaches
the retina the image is slightly
defocused by the Optics of the eye then
it is broken up into millions of little
pieces each receptor sees just a
minuscule portion of the original image
and measures its brightness different
receptors in the retina are sensitive to
different colors of light and respond to
the amount of that color that they
see to discover objects the visual
system tries to find important
boundaries it uses Edge and line
detecting neurons whose characteristics
have been investigated by hubel and
visel here you can see the results of
the
red
green and blue edge detectors look at
the blue edges it is hard to believe
that there is a cat in
there what I like to show you now is the
kind of information that the brain uses
in order to make sense out of these
messy
images the things that the brain seems
to look for are constancies and
simplicity imagine that you are in your
visual system looking at this pattern of
active neurons but you can't recognize
the
pattern we can see it now because all
the points in the cat picture move
together this is an example of the brain
using rigidity to recognize moving
objects ambiguous perception of motion
can actually destroy the rigidity
percept in this case we have a rotating
rigid object a square but when its
Corners
disappear appear appear from view the
square appears to get
smaller when the cers reappear it gets
larger another example we thought that
the square loses its rigidity because
the visual neurons at each location can
see only a small proportion of the
entire picture and therefore can't
accurately perceive the direction of the
moving parts of the object if we rotate
the cross then the stationary Square
appears to be
rigid we can simultaneously compare
these two
situations the conclusion is that the
motion of the square is necessary to
lose rigidity the failure of rigidity in
this case helps scientists to study how
information from different retinal
locations is combined to form a single
percept this is one of many examples
where percep show phenomena can reveal
how our brain
works
every moment the brain must make an
endless number of perceptual decisions
it has to compute size and distance
relationships determine where boundaries
and edges exist identify figures within
backgrounds move us toward objects we
want and away from objects we need to
avoid many of these perceptual decisions
are made without any conscious awareness
of the processes involved
the brain is automatically Computing the
sensory feedback and guiding the body to
perform the necessary
tasks when a quarterback sees a receiver
for instance he automatically
unconsciously calculates distance angle
and velocity and the muscles in his hand
arm and shoulder adjust
accordingly but what if we distort his
perception of the receiver these glasses
will displace his visual feel by 20° in
other words the distal stimulus the real
object will be 20° off from where he
perceives it to
be if he continues to pass with the
glasses on he'll begin to adapt to the
new signals by compensating for the
misinformation his retina is sending to
his
brain he'll start throwing what seems to
him to be 20° off in order to hit the
receiver he has quickly learned a new
arm eye
coordination but return his vision to
normal and he'll start missing again in
the opposite
direction even though his retina is now
passing on accurate information about
the true location of the target his
brain hasn't caught up with the new
input his brain is still compensating
for the previous feedback from the
movements in his hand and arm
getting accurate information about the
world around us and not just the images
on a retina is the major task of our
visual system but to sense perceive and
understand our world we utilize two very
different processes first our sensory
receptors detect external stimulation
and send this raw data to the brain for
analysis we call this bottom up
processing then top down processing
enters the scene it adds what we already
know about such stimulation what we
remember about the context in which it
usually appears and how we label and
classify it in this way we give meaning
to our
perceptions when people walk towards us
we know that they're not getting larger
even though the image they cast on the
retina does get
larger and if a shadow falls on our
newspaper we know the paper isn't
turning darker
that's because the hallm mark of
perception is our ability to impose
stability on the constantly changing
flow of Sensations we
experience psychologists refer to this
phenomenon as perceptual constancy the
actual size shape orientation and
brightness of an object are perceived as
remaining relatively constant even when
there are extreme variations in the
image IT
projects
what we perceive is not just a passive
photograph of reality but an active
construction of reality we tend to see
what we expect to see we see things with
our minds as well as our
eyes we are constantly selecting only a
small part of the available sensory
information to attend to and
process one of the ways we perceive
something actively is by taking into
account its context this context can
even determine the nature of the
perception itself with the same object
looking very different in different
contexts take a look at this
Square notice how the square appears to
get darker as the background becomes
lighter or in other words as the context
changes now take a look at these three
men we see the figure on the right as
smaller than the one on the left in back
because we unconscious iously compare
him with the large figure but in fact
the two small figures are exactly the
same
size to be effective perception also has
to work fast and extract the minimal
amount of information necessary to form
an impression of the entire pattern
visual perception would be far too slow
we had to wait to experience every last
piece of
something edges and boundaries in
particular convey lots of information
about an object they provide a visual
shortcut which can help the brain fill
in the whole pattern from the fewest
identifying
Parts sometimes the brain will even
register a pattern that doesn't exist
these Phantom patterns are called
subjective
Contours a boundary or an edge can
powerfully influence the way we see
things in this example Le the left half
of the screen appears darker than the
right half but watch what happens when
we cover up the
boundary what happened is this your
brain detected a slight difference in
brightness in the center and then went
overboard and extending that difference
to the rest of the
surface given the complexity of the
world we try to understand and the
complexity of our minds it's small
wonder that what we perceive as out
there is subject to a great number of
influences some of which will lead us
astray we may see something that isn't
there because it's what we expect to see
or conversely we may not see something
because we don't expect to see it our
previous experience our
expectations interests and biases are
constantly giving rise to different
perceptions let's take a look at this
illustration
some of you will see a young woman and
some of you will see an old woman in
various studies it was found that
younger people tended to see the younger
face while older people tended to see
the older face without any hints about
what to look
for and then there's the ratman illusion
try to identify each drawing as soon as
you see
it now identify this
one let's try another
sequence again identify each drawing as
soon as you see
it now how about this
one in a number of studies it was found
that the first series of drawings of
animals LED most subjects to identify
this image as a
rat but when other subjects saw the
drawings of people they tended to
identify this drawing as an old man with
glasses their prior experiences created
very different ways of looking at the
same distal
stimulus sometimes however we have
trouble perceiving things not because of
our experiences or our expectations but
just the opposite there's just too much
unfamiliar information to absorb we're
taken by
surprise but surprise is what often
happens to
eyewitnesses watch the simulated bank
robbery again and try to tell who did
what
who shot
whom would you swear to it in
court let's show the film this time in
slow motion to see if you were
right the hand the arm even the whole
body can be quicker than the eye when
the brain isn't ready to do its
detective
work what happens when we have no
trouble seeing something but what we see
just doesn't Mak sense when we encounter
a visual
Paradox at first glance this is a solid
wooden
triangle but it can't be a triangle
because from my perspective it has two
right angles and that's impossible so
impossible I want you to watch this as I
slice my arm right through without
breaking it so now you know that it
can't be solid either changing the
perspective enables you to see it as it
really is we call this way of seeing an
object in terms of its parts the
analytic way of seeing which conflicts
with the holistic way of seeing the big
picture either of you Mak sense alone
but
together they create a
[Music]
paradox in this animation of a bouncing
ball the staircase appears to go up
[Music]
forever this Paradox all also works in
Reverse Although our senses put us in
touch with the world around us it's our
brain working from prior experiences
that tells us whether something is
impossible or possible organizing our
perceptions and telling us what's out
there and what we should think about
it and so each of us has incredibly
sophisticated Hardware in the form of
sensory
apparatus and software to process the
information and make sense of it both
perfected over millions of
years usually the two work together
extremely
well but sometimes they don't and so we
can never take perception for granted no
matter how well we do it in the normal
course of our
lives in our next program we're going to
look at another ability of ours that
shapes the way we look at the world and
that's our ability to learn to profit
from experience a tale of mice and men
and women next time I'm Philip
[Music]
zimbardo
[Music]
[Music]
[Applause]
[Music]
funding for this program is provided by
anenberg cpb to advance excellent
teaching
for information about this and other
anenberg cpb programs call one800
learner and visit us at
www.learner.org
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