Perception

Objectives

• Understand what perception is and the psychological and physical factors that influence it
• Identify the different perceptual constancies
• Review theories of how the brain organizes perception
• Discover how the brain and the eye perceive motion and the different aspects of illusions

binocular cues

constructionist view

difference threshold

figure-ground

gestalt

illusions

induced movement

monocular cues

perception

psychophysics

signal-detection

theory

Background

Like all humans, students depend upon their perceptions to make sense of the world.

Yet despite great advancements in the study of human perception, the complexity of the brain and sensory systems continues to elude scientists, making the natural workings of human perception an ongoing mystery. Nevertheless, scientists have been able to determine that we perceive through receptors in our sensory organs, which pick up and transform stimuli from our environment and send them to the brain in the form of electrical neural impulses which it can "perceive" and make meaningful.

In this chapter, students discover the many psychological and psychophysical factors that affect perception, such as an individual's uniqueness and varied experiences, memories, tastes, and expectations. They find out that perception also is greatly influenced by prior knowledge of the world, or perceptual constancies—like size, shape, brightness, and color—which continue to help humans to make sense of their physical environments and to survive.

How exactly does the brain form a picture of the world based on the images, sounds, smells, tastes, and other sensations it receives? Students learn about the constructionist view of perception, which theorizes that the brain constructs a perception from a great many individual sensations. They also evaluate the Gestalt theories of perception, which hold that the brain perceives a stimulus as a whole and not as individual sensations. The Gestalt laws of perceptions are well detailed (and scrutinized) in this chapter.

Students next learn about ways in which people perceive depth through bodily depth cues and pictorial depth cues. They also find out how people perceive motion in the eye and in the brain.

Students next consider illusions and try their luck with graphic presentations of five illusions often used by psychologists—the Muller-Lyer illusion, the Ponzo railroad track illusion, the Necker cube, the Boring figure, and the Ames room. They learn that what they believe they are seeing is not necessarily accurate. Finally, they consider the critical thinking question of whether or not some people have extrasensory perception (ESP).

Further Resources

Heil, J. Perception and Cognition. Berkeley, Calif.: University of California Press, 1983.

Rock, Irvin. The Logic of Perception.Cambridge, Mass.: MIT Press, 1983.

For Discussion

Review

1. What are the four perceptual constancies?

2. What are the four most important "laws of perception" held by Gestalt psychologists?

3. What are the three bodily depth cues and the seven pictorial depth cues?

4. What are five illusions often used by psychologists?

Critical Thinking

1. In perceptual terms, what explanation can you offer for the difference in how teenagers and older people react to rock music?

2. What do you think that life would be like if the brain did not have perceptual constancies?

3. How and why are three-dimensional films illusions?

4. In what ways is the study of perception helpful or beneficial in the work of psychologists?

Activities

1. Playing with Perceptual Constancies

Divide students into pairs and challenge them to use materials and objects within the class to experiment with size, shape, brightness, and color perceptual constancies. Encourage students to openly discuss the "changes" that occur when moving and manipulating these unchanging objects.

2. Drawing Illusions

Following the chapter examples, challenge students to draw simple pictures that deceive or manipulate our perceptions. Have students present their illustrations to the class for students to consider and figure out. Discuss what is happening in our minds in perceptual terms.

3. Internet: Exploring Perceptions

Direct the students to research Web sites devoted to the study of perceptions. Have students look for new information or studies that will broaden their understanding of perceptual constancies, organization, depth cues, motion, and illusions.

4. Special Sources: Experiments in Perception

Divide students into pairs and research recently published psychological experiments dealing with perception. Have each pair select one experiment to evaluate and present to the class for discussion, scrutiny, and debate.