Chapter 2, page 37
classified as an H. In the sensory register, the word “HAT” is not the word hat or the letters H-A-T but
rather a series of lines and curves that have not yet been interpreted. As information moves to working
memory, it is classified, so that the H is now recognized as an H, and H-A-T is now the word hat.
Attention refers to focusing working memory on particular information. When people attend to some
information, they do so at the expense of other information. Attention is limited. Although there is debate
on this issue, recent evidence suggests that information that is not attended to does not enter working
memory (Lachter, Forster, & Ruthruff, 2004).
Classification involves two interacting forms of processing, called bottom-up processing and top-
down processing (Brewer & Lambert, 2001; Chinn & Malhotra, 2002a; Rock, 1985a, 1985b). When you
classify a stimulus that you observe, you use both the information in the stimulus (bottom-up processing)
and your own prior knowledge (top-down processing) to classify what you are observing. Bottom-up
processing is driven by the features of what you are observing. As an example, consider the word HAT.
You do not misperceive the word as CAT or BAT. The pattern of three intersecting lines in the H cannot
be mistaken for a C or a B. You respond to the pattern that you see. The information from the stimulus (at
the “bottom” of the system) is passed up through the system until you inevitably classify the three lines as
an H and as the first letter in the word HAT.
In top-down processing, prior knowledge plays a central role in influencing what is perceived. To
use an example similar to the previous one, read this word:. You no doubt read the first letter
as an H and read the word as HAT. Now read this word:. You probably read this as CAT. But
notice that the H in HAT and the A in CAT are exactly the same configuration of lines:. Whether
you interpret these lines as an A or as an H depends on the context. In the first case, you use your prior
knowledge about words (your knowledge is the “top” of the perceptual system) to form expectations that
the word is HAT, and so you interpret the as an H. In the second case, you form expectations that the
word is CAT, which induces you to interpret the as an A. This is top-down processing because your
expectations move from your prior knowledge (the “top” of the system) about words to influence how you
interpret the lines on the page (these stimuli are at the “bottom” of the system).
In this instance, the stimulus is ambiguous, but top-down processing also influences perception even
when the stimulus is not ambiguous. For one thing, top-down processing expedites the perception process.
For instance, if you know you are going to be looking at pictures of farm scenes, you will probably
identify a cow as a cow faster than if you mistakenly expect that you will be looking at urban scenes but
are instead shown a picture of a cow (cf. Delorme & Rousselet, 2004). We will discuss perceptual
processing, including top-down and bottom-up processing, in more detail in Chapter 5 (Prior
Conceptions).
Whereas perception is a process by which information moves into working memory, rehearsal is
the active repetition of information so that it stays in working memory. Rehearsal is simply saying
information over and over to keep it from dropping out of working memory, as when you repeat a phone
number to yourself to keep from forgetting it until you have dialed the number. Rehearsal by itself does
not move information into long-term memory; is simply keeps information cycling within working memory
so that it does not drop out of working memory.