Video transcript
Voiceover: Let's look atthe difference between top-down and bottom-up processing. So, what is bottom-up processing? Bottom-up processing basicallybegins with the stimulus, so let's imagine thatwe're looking at something, or let's say I'm looking at a banana. The banana is sitting there and it influences what we perceive. So, stimulus influences whatwe perceive, our perception. So, if I know absolutelynothing about something, then the stimulus or whateverit is I'm looking at, yet I don't know anythingabout, I've never seen it, I don't have any preconceivedcognitive constructs about what it is I'm looking at. The stimulus basically isinfluencing my perception. So, for example let's imagine that I'm looking at a co*ckpit of a plane. I'm not a pilot, so I'm not really too familiar with everything and everything kinda looks fairly confusing. So, basically all the different stimuli, so this stimulus, a bunch of gauges, and this rudder-looking thing, I'm basically looking at all the different little parts of somethingthat is new and novel to me, and trying to kind of comprehendwhat it is I'm looking at. So, this is bottom-up. This is when you startwith no preconceived idea of what it is that you're looking at, and allow the stimulus to influence your perception of what itis that you're looking at. So, bottom-up processing is data-driven, and your perception of whatit is that you're looking at directs your cognitiveawareness of the object. So, in contrast, top-down processing basically uses your background knowledge, so uses your background knowledge to influence perception. So, let's look at this example over here. So, what we're actuallyseeing are a bunch of circles, they are just a bunch of circles and then inside the circle there area couple of lines drawn. So, we are looking at this set of circles, these white circles withlines drawn inside of them. We are creating this cube. We're basically takingthese lines and then putting them together inorder to create a cube. Even though the stimulus itself, which is the circles with the lines, actually doesn't draw a cube because there are these black spaces over here, and there is absolutelynothing in the black spaces, but our brains are basicallytaking this information and using our knowledge of cubes and what they're supposed to look like, we're recreating a cube despite a lack of a cube actually beingpresent in the image. So, that's top-down processing. It's using your background information, your background knowledge, your learning, your expectations, in order to influence what it is that we're perceiving. So, in other words, it's theory-driven. We look at this and we assume that they're trying to represent a cube, even though one's notactually drawn there, and we're using that theory in order to shape our cognitive understanding of what it is that we're looking at. So, our perception, our behavior is influenced by our expectations, which is top-down processing. So, we're using what'salready in our heads in order to perceive whatit is that we're looking at, whereas in bottom-upprocessing we're using the stimulus itself in orderto drive our perception. So, another good example of top-down processing would be "Where's Waldo?" So, in "Where's Waldo?", we have a mental idea of what we're trying to do, which is to find Waldo amidst this really jumbled mess of a picture. So, if we were using bottom-up processing in order to look at this we would just be seeing a whole bunch of little people, and we wouldn't really be goal-driven, we wouldn't be trying to do anything, but with top-downprocessing we have a goal, and we're able to lookthrough here to find Waldo.
