Perception seems to proceed in two major ways. In bottom-up processing, we analyze information starting at the "bottom" with small units (features) and build upward into a complete perception (Goldstein, 1984). The reverse also seems to occur. Many experinces are organized using one's knowledge of the world. This is called top-down processing. In this case, pre-existing knowledge is used to rapidly organize features into a meaningful whole.
Another good example of top-down processing is found in perceptual expectancies. A runner in the starting blocks at a track meet is set to respond in a certain way. Likewise, past experience, motives, context, or suggestion may create a perceptual expectancy that sets you to perceive in a certain way. If a car backfires, runners at a track meet may jump the gun. As a matter of fact, we all frequently jump the gun when perceiving. In essence, an expctancy is a perceptual hypothesis we are very likely to apply to a stimulus--even if applying it is inappropriate. Perceptual sets often lead us to see what we expct to see. For example, let's say you are driving across the desert. You are very low on gas. Finally, you see a sign approaching. On it are the worlds FUEL AHEAD. You relax, knowing you will not be standed. But as you draw nearer, the words on the sign become FOOD AHEAD. Most people have had smilar expxeriences in which expectation altered their perceptions. Perceptual expectancies are frequently created by suggestion.......
[Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989. Chapter: Perceiving]
R E F E R E N C E S
Expectation n. 1. the act of expecting. 2. the state of expecting: to wait in expectation. 3. an expectant mental attitude. 4. something expected: a thing looked forward to. 5. Often, expectations. a prospect of future good or profit: to have great expectations. 6. the degree of probability of the occurrrence of something: there is little expectation that he will win. 7. Statistics. See mathematical expectation. 8. the state of being expected. [< L expctátión- (s. of expctátió] an awaiting = expectát(us) (ptp. of expectáre to EXPECT] + -ión- -ION]
-Syn. 2. expectancy, anticipation, hope, trust.
Expect v.t. 1. to look forward to; regard as likely to happen; anticipate the occurence or the coming of: to expect guests; to expect a hurricane. 2. to look for with reason or justification: We expect obedience. 3. Informal, to suppose or surmise: I expect that you are tired from the trip. -v.i. 4. to be pregneant. [< L ex(s) pect(áre) (to) lookout for, await = ex- EX1 + spectáre to look at; see Spectacle] -Syn. 1. Expect, Anticipate all imply looking to some future event. Expect implies confidently believing, usually for good reasons, that an event will occur: to expect a visit from a friend. Anticipate is to look forward to an event and even to picture it: Do you anticipate trouble?
Expectancy n. 1. the quality or state of expecting; expectation; anticipatory belief or desire. 2. the state of being expected. 23. an object of expectation; something expected . . .
[Urdang, Laurence, ed. Random House Dictionary of The English Language. New York: Random House, 1968.]
R E F E R E N C E S
[Merriam-Webster's Collegiate Dictionary, 10th Edition. Springfield, MA, USA: Merriam-Webster, Inc. 1995.]
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