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Voiceover: Let's look at
the difference between
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top-down and bottom-up processing.
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So, what is bottom-up processing?
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Bottom-up processing basically
begins with the stimulus,
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so let's imagine that
we're looking at something,
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or let's say I'm looking at a banana.
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The banana is sitting there and
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it influences what we perceive.
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So, stimulus influences what
we perceive, our perception.
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So, if I know absolutely
nothing about something,
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then the stimulus or whatever
it is I'm looking at,
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yet I don't know anything
about, I've never seen it,
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I don't have any preconceived
cognitive constructs
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about what it is I'm looking at.
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The stimulus basically is
influencing my perception.
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So, for example let's imagine that
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I'm looking at a cockpit of a plane.
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I'm not a pilot, so I'm not really
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too familiar with everything and
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everything kinda looks fairly confusing.
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So, basically all the different stimuli,
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so this stimulus, a bunch of gauges,
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and this rudder-looking thing,
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I'm basically looking at all the different
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little parts of something
that is new and novel to me,
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and trying to kind of comprehend
what it is I'm looking at.
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So, this is bottom-up.
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This is when you start
with no preconceived idea
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of what it is that you're looking at,
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and allow the stimulus to influence
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your perception of what it
is that you're looking at.
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So, bottom-up processing is data-driven,
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and your perception of what
it is that you're looking at
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directs your cognitive
awareness of the object.
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So, in contrast, top-down processing
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basically uses your background knowledge,
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so uses your background knowledge
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to influence perception.
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So, let's look at this example over here.
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So, what we're actually
seeing are a bunch of circles,
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they are just a bunch of circles and then
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inside the circle there are
a couple of lines drawn.
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So, we are looking at this set of circles,
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these white circles with
lines drawn inside of them.
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We are creating this cube.
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We're basically taking
these lines and then
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putting them together in
order to create a cube.
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Even though the stimulus itself,
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which is the circles with the lines,
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actually doesn't draw a cube because
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there are these black spaces over here,
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and there is absolutely
nothing in the black spaces,
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but our brains are basically
taking this information
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and using our knowledge of cubes
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and what they're supposed to look like,
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we're recreating a cube despite a lack of
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a cube actually being
present in the image.
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So, that's top-down processing.
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It's using your background information,
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your background knowledge, your learning,
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your expectations, in order to influence
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what it is that we're perceiving.
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So, in other words, it's theory-driven.
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We look at this and we assume that
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they're trying to represent a cube,
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even though one's not
actually drawn there,
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and we're using that theory in order to
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shape our cognitive understanding
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of what it is that we're looking at.
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So, our perception, our behavior
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is influenced by our expectations,
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which is top-down processing.
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So, we're using what's
already in our heads
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in order to perceive what
it is that we're looking at,
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whereas in bottom-up
processing we're using
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the stimulus itself in order
to drive our perception.
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So, another good example of top-down
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processing would be "Where's Waldo?"
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So, in "Where's Waldo?", we have a
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mental idea of what we're trying to do,
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which is to find Waldo amidst this
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really jumbled mess of a picture.
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So, if we were using bottom-up processing
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in order to look at this we would just
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be seeing a whole bunch of little people,
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and we wouldn't really be goal-driven,
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we wouldn't be trying to do anything,
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but with top-down
processing we have a goal,
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and we're able to look
through here to find Waldo.