[From Coon, Introduction to Psychology, Exploration and Application] - You are surrounded by sights, sounds, odors, tastes, and touch sensations. Which are you aware of? The first stage of perception is attention, the selection of incoming messages. There is little doubt about the importance of attention.
Selective attention refers to the fact that we give some messages priority and put others on hold (Johnston & Dark, 1986). Psychologists have found it helpful to think of selective attention as a sort of bottleneck, or narrowing in the information channel linking the senses to perception (Reed, 1988). When one message enters the bottleneck, it seems to prevent others from passing through. This may be why it is very difficult to listen to two people speaking at once. Typically, you can "tune in" one person or the other, but not both.
Divided attention often arises from our limited capacity for storing and thinking about information. At any moment, you must divide your mental effort amohng tasks, each of which requires more or less attention. However, as skill becomes more automatic, it requries less attention. Are some stimuli more attention-getting than others? Yes. Very intense stimuli usually command attention. Stimuli that are brighter, louder, or larger tend to capture atention: A gunshot in a library wuld be hard to ignore. Big, bright cars probably get more tickets than small, dull ones. Loud, irritating comedian Don Rickles ahs made a career out of the first principle of attention. Repetitious stimuli are also attention-getting. A dripping faucet at night makes little noise by normal standards, but because of repetition, it may become as attention-getting as a single snd many times louder. This effect is used repeatedly, so to speak, in television and radio commercials. Attention is also frequently related to contrast or change in stimulation. The contrasting type styles draw attention because they are unexpected. Norman Mackworth and Geoffrey Loftus (1978) found that people focus first adn longest on unexpcted objects. Change, contrast, and incongruity are perhaps the most basic sources of attention. We quickly habituate (respond less) to predictable and unchanging stimuli.
B. Habituation. Adaptation decreases the actual number of sensory messages sent to the brain. When messages do reach the brain, the body makes a sort of "What is it?" reaction known as the orientation response (OR). An OR is characterized by enlarged pupils, brain wave changes, a short pause in breathing, increased blood flow to the head, and turning toward the stimulus (Dember & Warm, 1979). Have you ever seen someone do a duble take? If so, you have observed an orientation response.
At first a new album holds your attention all the way through. But when the album becomes "old," a whole side may play without your really attending to it. When a stimulus is repeated wihtout change, the OR habituates, or decreases.
C. Motives. Motives also play a role in attention. If you are riding in a car adn are hungry, you wil notice restaurants and billboards picturing food. If you are running low on gas, your attention will shift to gas stations. Advertisers, of course, know that their pitch will be more effective if it gets your attention. Ads are therefore loud, repetitious, and intentionally irritating. They are also designed to take advantage of two motives that are widespread in our society: anxiety and sex---to advertise everything from mouthwash to automobile tires. In addition to directing attention, motives may alter what is perceived. And, an emotional stimulus can shift attention away from other information.
D. Perceptual Expectancies. 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. This is esepcially true of perceiving other people. For example, a psychology professor once aranged for a guest lecturer to teach his class. Half the students in the class were given a page of notes that described the lecturer as a "rather cold person, industrious, critical, practical, and determined." The other students got notes describing him as a "rather warm person, industrious, critical, practical, and determined" (Kelley, 1950; italics added). Students who received the "cold" description perceived the lecturer as unhappy and irritable and didnÍt volunteer in class discussion. Those who got the "warm" description saw the lecturer as happy and good-nataured, and they actively took part in discussion with him.
E. Categories. Psychologist Jerome Bruner used a tachistoscope--a device for projecting pictures for very short periods) to flash pictures of cards on a screen. He found that observers misperceived cards that did not fit thier knowledge and expectations. For instance, a red six of spades would be mispercieved as a normal six of hearts (Bruner & Postman, 1949). Bruner believes that perceptual learning bulds up mental categories. Experiences are then "sorted" into these categories. SInce observers had no category for a red six of spades, tey saw it as a six of hearts. Categories such as "punk," "mental patient," "queer," 'honky," "bitch," and so on, are particularly likely to distort perception. Perceptual categories, espcially those defined by labels, do made a difference, This is espcially true in perceiving people, where even trained observers may be influenced. Fore example, in one study, psychotherapists were shown a videotaped interview. Half of the therapists were told that the man being interviewed was applying for a job. The rest were told that the man was a mental patient. Therapists who thought the man was a job applicant perceived him as "realistic," "sincere," and "pleasant." Those who thought he was a patient perceived him as "defensive," "dependent," and "impulsive" (Langer & Abelson, 1974).
[Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989. Chapter: Perceiving.]