Perceiving is Believing: Crash Course Psychology #7
Summary
TLDRThis script explores the fascinating world of perception, explaining how our brain organizes sensory data to create meaningful experiences. It discusses the influence of expectations, context, and cultural norms on our perceptions, highlighting the concept of perceptual set. Through examples like optical illusions and depth cues, the video illustrates how we interpret shapes, colors, motion, and depth. Ultimately, it underscores the brain's crucial role in constructing our reality, showing how perception helps us navigate and make sense of the world.
Takeaways
- 🌹 Not all roses have thorns, and various common sayings can be misleading.
- 👀 Perception is heavily influenced by expectations, experiences, moods, and cultural norms.
- 🧠 Our brain organizes and translates sensory data into meaningful perceptions.
- 👩👦 Without perception, familiar faces and scents would be meaningless shapes and smells.
- 🧩 Perceptual set theory explains how context, expectations, and emotions shape what we see.
- 🔄 The figure-ground relationship helps us distinguish objects from their backgrounds.
- 🏞️ Depth perception allows us to perceive the world in three dimensions using both eyes.
- 🎨 Monocular cues like relative size, linear perspective, and texture gradient help judge distance.
- 🏃 Motion perception lets us gauge speed and direction of moving objects.
- 🔍 Perceptual constancy helps us recognize objects despite changes in distance, angle, or lighting.
Q & A
Why is the statement 'Every rose has its thorn' not always true according to the script?
-Because in reality, several varieties of roses do not have thorns.
What role does perception play in how we interpret sensory information?
-Perception allows us to make meaning out of our senses and experience the world around us by organizing and translating sensory data into meaningful information.
How does the brain deal with upside-down faces, according to the script?
-The brain struggles with upside-down faces because it is not used to them and tries to piece the data together, often resulting in a distorted perception.
What is 'perceptual set' and how does it influence our perception?
-Perceptual set refers to the psychological factors that determine how we perceive our environment, influenced by expectations, experiences, moods, and cultural norms.
How does context affect our perception, as illustrated by the duck-bunny image?
-Context affects perception by influencing which image we see based on surrounding cues, such as associating the image with Easter eggs making us see a bunny.
What is the 'figure-ground relationship' in form perception?
-The figure-ground relationship is how we organize scenes into main objects (figures) and their backgrounds (ground), such as seeing either two faces or a vase in the classic illusion.
How do binocular cues contribute to depth perception?
-Binocular cues use the slightly different images received by each eye (retinal disparity) to help judge the distance of objects.
What is 'retinal disparity' and how does it help in perceiving depth?
-Retinal disparity is the difference between the images seen by each eye, which the brain uses to judge the distance of nearby objects.
What are some examples of monocular cues used in depth perception?
-Monocular cues include relative size, linear perspective, texture gradient, and interposition, which help judge distances and scale of objects.
How does motion perception influence our understanding of moving objects?
-Motion perception helps us infer the speed and direction of moving objects, using cues like shrinking objects appearing to retreat and enlarging objects seeming to approach.
Outlines
🌹 Perception and Reality
This paragraph explores how perception can differ from reality. Common sayings are challenged, emphasizing that our understanding is shaped by expectations, experiences, and cultural norms. The brain's role in interpreting sensory data is highlighted, illustrating how perception gives meaning to our experiences. The paragraph uses examples, like the upside-down face illusion, to demonstrate how our brains construct what we see, influencing our beliefs and experiences.
👥 Grouping and Depth Perception
This section discusses how the brain organizes sensory information using rules like proximity, continuity, and closure. It explains how we perceive groups based on these principles and the importance of depth perception in understanding the world in three dimensions. The text describes both binocular and monocular cues, such as retinal disparity and linear perspective, which help us judge distance and scale.
Mindmap
Keywords
💡Perception
💡Perceptual Set
💡Form Perception
💡Figure-Ground Relationship
💡Depth Perception
💡Binocular Cues
💡Monocular Cues
💡Motion Perception
💡Perceptual Constancy
💡Optical Illusions
Highlights
Several varieties of roses do not have thorns, challenging common sayings.
Both the good and the bad can die young, debunking the phrase 'only the good die young.'
Fast and steady often beats slow and steady, contrary to the common belief.
Our perceptions are heavily influenced by expectations, experiences, moods, and cultural norms.
Perception allows us to make meaning out of our senses and experience the world around us.
The brain plays a critical role in perception, organizing raw sensory data into meaningful experiences.
Expectations and context can influence what we perceive, as shown with the duck-bunny illusion.
Perceptual set theory shows that believing can also lead to seeing.
Emotions and motivations also affect our perception, as demonstrated by the hill steepness example.
Form perception involves organizing visual stimuli into meaningful patterns using rules like proximity, continuity, and closure.
Depth perception helps us judge the distance and shape of objects using binocular and monocular cues.
Motion perception allows us to infer the speed and direction of moving objects.
Perceptual constancy helps us recognize objects regardless of changes in distance, angle, motion, or illumination.
The brain constructs our perceptions from sensory data, building a model of the world.
Understanding perception helps us comprehend how we navigate and interpret the world around us.
Transcripts
Every rose has its thorn. Only the good die young. Slow and steady wins the race.
And what you see is what you get. Except that in
reality, several varieties of roses do not have thorns;
both the good and the bad, on occasion, tragically die young; fast and steady beats slow and steady
every time; and what you see is, well... Our perception, or how we order the cacophonous
chaos of our environment, is heavily influenced, biased even, by our expectations, experiences,
moods, and even cultural norms. And we can be pretty good at fooling ourselves. In the last two
lessons, we've learned how we see shapes and colors, hear sounds, and smell and taste the
world's chemical concoctions, but our senses
mean little without our brain's ability to organize
and translate that data into meaningful perceptions.
Without perception, your mother's face is just a
combination of shapes. Without the ability to interpret scent, we couldn't differentiate the
smell of toast from a grease fire. Our perception is the process that allows us to make meaning
out of our senses and experience the world around us. it's what makes life understandable,
but also it means that sometimes what you see is not actually what you get.
[INTRO MUSIC]
So that was awesome, right? Upside-down, I look like me. Right-side-up, I look like some
kind of terrifying monster. Your brain isn't used to upside-down faces, so it's basically
just doing its best to put the pieces together. But it knows exactly what a right-side-up face
should look like, and that is not it. Just one of thousands of examples proving that your brain
does all the work of perception, and your eyes really are just feeding raw data. It's important
data, but it isn't actually what we see. What we see is the realm of the mind, not the eye.
What kind of bird do you see right now? A duck, right? But if I said, "What kind of mammal do you
see?" a bunny probably would have popped out at you. Now, you should be seeing both of them
popping back and forth, but likely your brain wants to perceive the image related to
whichever cue you first heard, or whichever image is more familiar to you. By cueing
"mammal" or "bird," I influenced your expectations and you saw what I wanted you to see. Pretty cool!
Your expectations are just one factor in your perceptual set: the psychological factors that
determine how you perceive your environment. Sometimes, seeing is believing, but perceptual
set theory teaches us that believing is also seeing. Context is another factor in your
perceptual set. If the duck bunny thing was pictured with easter eggs all around it,
you'd think bunny right away -- which is kind of weird, considering that of ducks
and bunnies, one is actually much more likely to be near an egg (it's not the bunny).
And that's an example of how culture is also an important part of our perceptual set.
As much as our perceptions are affected by context and expectations, they're also
swayed by our emotions and motivations. People will say a hill is more steep if they're
listening to emo by themselves than if they're listening to power pop and walking with a friend.
Most of the time, your personal perceptual set leads you to reasonable conclusions, but sets
can also be misleading or even harmful. They're
the basis of tons of entertaining optical illusions.
These two tables, for example, are the same size,
but the positions of their legs make that impossible
for you to believe until I lay them over each other.
And while all the fooling of our visual perception
can be fun, it also helps us understand how it works.
Our minds are given a tremendous amount of
information, especially through the eyes, and we need
to make quick work of it. Turning marks on a paper
into words; blobby lumps into the face of a friend;
seeing depth, color, movement, and contrast;
being able to pick out an object from all the other
clutter around it seems so simple, but we've come
to discover that it is quite complicated. So complicated
that we have a name for it: form perception. Take a neat
little dynamic called the "figure-ground relationship."
It's how we organize and simplify whatever scene
we're looking at into the main objects or figures and the surroundings or ground that they stand
out against. The classic "faces or vases" illusion is an example. Is it two faces against a white
background, or a vase against a black background?
If you look long enough, you'll see that the relationship
between the object and its surroundings flip back and forth, continually reversing, sometimes white
is the figure and black is the ground. That figure-ground
dynamic, though, is always there. The concept applies
to non-visual fields as well. Say you're at a party,
holding up the wall and creeping on your crush
across the room, trying to casually listen in on what
they're saying. As the focus of your attention, that voice
becomes the figure, while all the other voices jabbering
about sports and beer pong and Sherlock and everything
that doesn't have to do with that one beautiful person
all becomes the ground. Now that your mind has
distinguished figure from ground, it has to perceive
that form as something meaningful. Like for one,
that large shape on the couch is a person, and
further, that person isn't just any person, but the
specific unique person of your dreams. One way our minds shuffle all of these stimuli into
something coherent is by following rules of grouping,
like organizing things by proximity, continuity, or closure.
The rule of proximity, for instance, simply states that
we like to group nearby figures together. So instead of
seeing a random garble of partygoers, we tend to
mentally connect people standing next to each other.
Like, there's the hockey team over there, and the debate team over there, and then you've got the
band geeks -- why are all these people at the same party? We're also drawn to organize our world with
attention to continuity, perceiving smooth, continuous
patterns, and often ignoring broken ones. We also like
closure -- and not just after a breakup. Visually, we want
to fill in gaps to create whole objects. So here, we see
an illusory triangle breaking the completion of these
circles on the left. But just add the little lines, close up
the circles, and you stop seeing the triangle. Form
perception is obviously crucial to making sense
of the world, or, y'know, a moderately interesting party.
But imagine trying to navigate the world without
depth perception. As you gaze upon your one true love,
the image hits your retina in two dimensions. Yet somehow,
you're still able to see the full three-dimensional
gloriousness of their form. You can thank your
depth perception for that! Depth perception is what helps us estimate an object's distance
and full shape. In this case, a nice shape that is
currently too far away from you. It is at least partially
innate -- even most babies have it. We're able to perceive
depth by using both binocular and monocular visual cues.
Binocular cues, as the name gives away, require the use
of both eyes. Because your eyes are about 2.5 inches apart,
your retinas receive ever-so-slightly different images.
You know, camera one, camera two. So when you're
looking with both your eyes, your brain compares the two images to help judge distance. The closer
the object, the greater the difference between the two images, also known as the retinal disparity.
Retinal disparity is pretty easy to see, you just hold
your fingers up, and then you look past them, and
suddenly you have four instead of two fingers. Because those left and right images vary only
slightly, retinal disparity doesn't help much when it comes to judging far-off distances.
For that, we look to monocular cues to help us determine the scale and distance of an object.
These are things like relative size and height, linear
perspective, texture gradient, and interposition.
Relative size allows you to determine that your crush is not supporting a tiny newborn chihuahua
on their shoulder, but rather, there's a full-grown
chihuahua behind them in the back of the room.
In the absence of a chihuahua (or like object), you
can also judge distances using your linear perspective.
If you've ever made a perspective drawing in art class,
you'll remember that parallel lines appear to meet
as they move into the distance. Just like the tiled floor,
the sharper the angle of convergence, and the closer
the lines together, the greater the distance will seem.
And if you've ever looked out at a mountain range
or a Bob Ross painting, you'll understand texture gradient as the cue that makes the first ridge
appear all rocky and textured, but as your eye follows the ridges into the distance, they become
less detailed. And finally, our interposition, or overlap,
cue tells us when one object, like this oaf here,
blocks our view of something else, your crush, we perceive it as being closer. And in this case,
especially annoying. So all these perceptual concepts can be demonstrated with a fixed
image, but of course, life involves a lot of movement. At least if you're doing it right.
We use motion perception to infer speed and direction of a moving object.
Like, your brain gauges motion based partly on the idea that shrinking objects are
retreating and enlarging objects are approaching. The thing is, your brain
is easily tricked when it comes to motion. For instance, large objects appear to move
much more slowly than small ones going the same speed. And in addition to organizing
things by form, depth, and motion, our perception of the world also requires consistency. Or as
psychologists call it, constancy. Perceptual constancy is what allows us to continue
to recognize an object, regardless of its distance, viewing angle, motion, or illumination,
even as it might appear to change color, size, shape, and brightness, depending on the
conditions. Like, we know what a chihuahua looks like, whether it looks like this this,
this, or this. In the end, though, your perception
isn't just about funky optical illusions. It's about
how you understand the world and your place in it, both physically and psychologically.
Your sensory organs pull in the world's raw data,
which is disassembled into little bits of information
and then reassembled in your brain to form your own model of the world. It's like your senses
are just collecting a bunch of Legos and your brain
can build and rebuild whatever it perceives.
A party, your crush, a duck, or a chihuahua. In other words, your brain constructs
your perceptions. And if you were correctly constructing your perceptions this lesson,
you learned what forms your perceptual set, how form perception works, and the many
visual cues that influence your depth perception. Thank you for watching, especially to all of our
Subbable subscribers who make this whole channel possible. If you'd like to sponsor an
episode of Crash Course Psychology, get a copy of one of our Rorschach prints, and even be
animated into an upcoming episode, just go subbable.com/crashcourse. This episode
was written by Kathleen Yale, edited by Blake de Pastino
and myself, and our consultant is Dr. Ranjit Bhagwat.
Our director and editor is Nicholas Jenkins, the script supervisor is Michael Aranda who is
also our sound designer, and the graphics team is Thought Café.
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