Wherever you are at the moment, there are a lot of objects to see, but you’re only looking at one of them. There are probably a lot of sounds, too—the soft buzz of a neon light; the whirr of an overhead fan—that you hadn’t even noticed. There are pressures on your skin from your clothes or the chair in which you’re sitting that entirely escaped your attention. You perceive only a small slice of the world—that slice to which you pay attention. Attention is the process of bringing an idea or an external stimulus into conscious awareness.

Attention takes effort (Kahneman, 2011). Although some occurrences (e.g., a sudden loud noise) do “grab” your attention, often you have to exert effort to keep your mind from wandering. Even when you want to, it can be difficult to fix your attention on a rambling anecdote, a classroom lecture, or the pages of a textbook.

However, when you do exert effort, you find that you’ve got a mental power: selective attention. Selective attention is the capacity to choose the flow of information that enters conscious awareness, when more than one flow of information exists in the environment. Thanks to selective attention, if there are 3 people talking at once, or 8 people out on a dance floor, or 22 people running around a football field, you can “zoom in” mentally on any one of them. Researchers have explored people’s ability to attend selectively to sounds (auditory selective attention) and sights (visual selective attention), as we’ll see in the closing sections of this chapter.

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To study auditory selective attention, researchers ask participants to wear headphones that project different sounds—for example, speakers reading different passages of text—to the left and right ears. Participants are instructed to ignore the sounds in one ear while attending to the other. To ensure that they attend to the correct message, participants are asked to “shadow” it, that is, to repeat the material out loud. This simple experimental procedure produces three key research findings (Neisser, 1976; Treisman, 1969):

The study of visual selective attention began with a research paradigm devised by psychologist Ulric Neisser and his associates (Becklen & Cervone, 1983; Neisser & Becklen, 1975). A video displayed two overlapping events: two groups of visually overlapping basketball players running, dribbling, and passing basketballs. Participants had to attend to one team, counting the number of times its team members passed the ball. At one point in the film, an unexpected event occurred: A woman carrying an umbrella walked straight across the screen. Surprisingly, hardly anyone noticed her. Although her image on the screen—and thus on participants’ retinas—was prominent, she went unnoticed by the large majority of participants (see, e.g., Becklen & Cervone, 1983).

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Later researchers obtained similar results with an event even more unexpected: the intrusion of a gorilla (Simons & Chabris, 1999). While two teams of basketballers played, a gorilla—well, a research assistant dressed in a gorilla suit—walked directly across the screen while participants counted passes. Again, most people didn’t even notice.

TRY THIS!

Do these selective attention experiments sound familiar to you? They should—they are exactly the sort of research experience you had in our Try This! experiment, introduced earlier in this chapter. As you see now, that experiment was not designed merely to see if you could follow motion in a fast-moving event. It was designed to show how little information people pick up from a second event when attending to the first one—even though the second event is passing right before their eyes!

How could people miss a woman with an umbrella? Or a gorilla? Neisser (1976) explains that perception is guided by anticipations. People actively anticipate certain types of information. They search for the anticipated information and, if it’s there, pick it up. Unexpected information simply isn’t picked up.

Neisser’s argument underscores a general point about the material in this chapter. Perception is an active psychological activity. Your perceptions of the world reveal information about the world, and yourself.