LECTURE 23: PERCEPTION (CHAPTER 7)
•The “bottom-up” recognition achieved by the analysis of features, context also provides a
“top-down” way to bias the system for perceiving some items over others.
•Bottom means sensation
•Top is like the brain is already trained on that and that is how we perceive it.
•Memory affects the way we perceive things.
•Thus, a number of things may be crucial in our ability to figure out what things are, including:
The use of prototypes; Analysis of features; Contextual Support
•We expect some things to occur under the situation and some things not to occur under that
•Depth perception: figure out where an objects is, we need some way of judging depth in our
•We use a fairly large range of cues to help in our perception of depth, and the fall under two
-Some depth information can only be obtained when both eyes are viewing the world …
these types of information are termed
-binocular cues to depth. In contrast, monocular cues can be obtained using only one eye.
•Binocular cues (Convergence): Because the two eyes converge on an object when we are
viewing it, the brain can use the angle of convergence as a cue to how far away that object is.
For example: the larger the angel, the nearer the object, vice versa.
-Retinal Disperity: Whenever we are not focusing on an object, the image of that object
falls on different points of the two retinas.
-Amount of disparity (difference) between the two retinal images can be used as a cue
-Try holding up two fingers one in front of the other. Focus on the front one (you
should now see two images of the back one). Now move the back one away from, then
back towards you, while still focusing on the front one. What happens to the two
images you see as the back finger moves?