function of years of perceptual training to see the world right side up and to
perceive faces in their usual orientation.
Identification and Recognition Processes
You can think of all the perceptual processes described so far as providing rea-
sonably accurate knowledge about physical properties of the distal stimulus—
the position, size, shape, texture, and color of objects in a three-dimensional
environment. With just this knowledge and some basic motor skills, you would
be able to walk around without bumping into anything and manipulate objects
that were small and light enough to move. However, you would not know
what the objects were or whether you had seen them before. Your experience
would resemble a visit to an alien planet where everything was new to you;
you wouldn’t know what to eat, what to put on your head, what to run away
from, or what to date. Your environment appears nonalien because you are
able to recognize and identify most objects as things you have seen before and
as members of the meaningful categories that you know about from experience.
Identification and recognition attach meaning to percepts.
Bottom-up and Top-down Processes
When you identify an object, you must match what you see against your stored
knowledge. Taking sensory data into the system and sending it upward for
extraction and analysis of relevant information is called bottom-up processing.
Bottom-up processingis anchored in empirical reality and deals with bits of in-
formation and the transformation of concrete, physical features of stimuli into
abstract representations. This type of processing is also calleddata-drivenpro-
cessing, because your starting point for identification is the sensory evidence
you obtain from the environment—the data.
In many cases, however, you can use information you already have about the
environment to help you make a perceptual identification. If you visit a zoo, for
example, you might be a little more ready to recognize some types of animals
than you otherwise would be. You are more likely to hypothesize that you are
seeing a tiger than you would be in your own back yard. When your expect-
ations affect perception, the phenomenon is called top-down processing.Top-
down processinginvolves your past experiences, knowledge, motivations, and
cultural background in perceiving the world. With top-down processing,
higher mental functioning influences how you understand objects and events.
Top-down processing is also known as conceptually driven(or hypothesis-
driven) processing, because the concepts you have stored in memory are af-
fecting your interpretation of the sensory data. The importance of top-down
processing can be illustrated by drawings known asdroodles(Price, 1953/1980).
Without the labels, these drawings are meaningless. However, once the draw-
ings are identified, you can easily find meaning in them (see figure 7.35).
For a more detailed example of top-down versus bottom-up processing, we
turn to the domain of speech perception. You have undoubtedly had the expe-
rience of trying to carry on a conversation at a very loud party. Under those
circumstances, it’s probably true that not all of the physical signal you are pro-
ducing arrives unambiguously at your acquaintance’s ears: some of what you
had to say was almost certainly obscured by coughs, thumping music, or peals
176 Philip G. Zimbardo and Richard J. Gerrig