HM 4-4 Top-down processing essentially refers to the effect that meaning, familiarity, or context has in determining our perceptions (Goldstein, 2002). Several examples of top-down processing can be presented fairly easily in class. Reversible figures can provide a good example of top-down processing if you generate and expectation in students before you show the figures.

HM 4-4 For example, make copies of HM 4-3 and give a third of your class the top picture (rat), a third of your class the bottom picture (man), and a third of your class no picture. Then, show the entire class TM 4-4 and ask them to record what they saw. The third of the class who saw no prior picture will serve as you “control group” to determine what portion of students see the TM as a rat or a man.

HM 4-4 The third who previously saw the rat picture should be more likely to perceive the TM as a rat; those who saw the man’s picture should be more likely to perceive the TM as a man. Thus, students are likely to perceive what they have been lead to expect and to have a difficult time in reversing the figure.

HM 4-4 Biederman (1981) described research that provides another good example of top-down processing. Participants were asked to look at a particular location on a screen where a picture was to be flashed and to identify the object that appeared at that location. Biederman found that people were less accurate when the object was shown in an unusual or atypical position (for example, a fire hydrant placed on top of a mailbox). Participants’ knowledge about the objects affected their perception of those objects.

HM 4-4 Although the pervious examples of top-down processing have shown examples of bias in perception, top-down processing can also occur in ways that are beneficial to us. To demonstrate this effect, prepare copies of HM 4-4 for your students. Give each student a copy and ask them to attempt to decode the “meaningless” sentences. Most students should do fairly well at this task because of their prior knowledge about how words and sentences are composed.

HM 4-4 Thus, prior knowledge drives their performance on this task – top-down processing. If you have international students for who English is a second language, they may perform more poorly at this task because their- expectations would not be as strong as native English speakers.

HM 4-4 HM 4-4 answers: – MARY HAD A LITTLE LAMB HER FLEECE WAS WHITE AS SNOW. – THE SUN IS NOT SHINING TODAY. – SOME WORDS ARE EASIER TO UNDERSTAND THAN OTHERS.

HM 4-4 Bottom-up processing assumes that our perceptions are built on the component parts of the object or scene that is presented to us. As the text points out, the discovery of physiological cells that function as feature detectors supports the notion of bottom-up processing. An example that you can use to illustrate bottom- up processing in class is provided on TM 4-5 (the word WIN).

HM 4-4 The stimulus is composed of elements that stimulate various types of receptor cells and receptive fields. These messages must then be brought together and integrated in order for perception to occur (another example is the cow transparency provided in the Wadsworth generic transparency set). Students may note that bottom-up processing seems more difficult, but remind them of the difficulty they had during the top-down demonstrations.

HM 4-4 In is hard to make the reversible figures reverse when you have been primed to expect one image.