Sensation

Objectives

• Understand the different sensory systems involving vision, hearing, taste, smell, and touch
• Explain how the visual sensory system converts light into images
• Review the way in which the ear responds to sound waves
• Explore the pleasurable senses of taste and smell
• Understand the workings of the somatic sensory system involved in touch, pressure, temperature, and pain

absolute thresholds

auditory nerve

cochlea

endorphins

gate control theory

perception

pheromones

photoreceptors

receptors

retina

sensory adaptation

sensory coding

somatic receptors

visual cortex

Background

Students constantly use their sensory systems—their sight, hearing, and senses of smell, taste, and touch—but seldom think about or appreciate them. However, these senses are of paramount importance, since they provide people with a way to experience and interact with their environment and to gain and process information from the world around them.

Through this chapter, students learn how sensory systems work and the specific processes involved in how human beings perceive. They start with a basic concept: each sensory system has receptors that are activated by stimuli they pick up and convey to the brain in the form of neural impulses, or sensations it can interpret. After students review this basic process, they learn more about the specific functions and issues involved in seeing, hearing, smelling, tasting, and feeling.

Students first discover the workings of the visual sensory system, the nature of light, and the different factors involved in seeing "color." Next, students learn about hearing and sound, including a definition of sound, its characteristics, how sound waves are converted in the ear, and what happens in deafness. They find out that perceiving is actually done in the brain—and not in the eye, ear, mouth, nose, or on the skin.

Students next learn how smell and taste occur and how somatic receptors of the skin feel sensations like touch, pressure, temperature, and pain. They find out how and why people feel pain. A variety of chapter features—diagrams of the eye and ear, explanatory tables, research notes on pheromones, a sidebar on managing pain, and a critical thinking feature on sensory deprivation—help students to appreciate their senses and ways in which they affect their lives.

Further Resources

Ackerman, Diane. A Natural History of the Senses. New York: Random House, 1990.

Schiffman, H. R. Sensation and Perception.New York: Wiley & Sons, 1982.

For Discussion

Review

1. What are the five sensory organs and to what kinds of stimuli do their receptors respond?

2. What is the difference between rods and cones?

3. What are three parts of the ear and the three characteristics of a sound?

4. What are the three types of deafness?

Critical Thinking

1. Which of your five senses—sight, sound, smell, taste, and touch—do you think is most important for your quality of life? least important? Why?

2. If your taste buds lost their sensitivity and you put a hot pepper in your mouth, what would it taste like? Why?

3. If you had a choice between feeling pain or not feeling pain for the rest of your life, which would you choose? Why?

4. Why do you think pheromones are more common with animals than humans?

Activities

1. Tracking the Five Senses

Divide students into groups of five with each member representing one of the five senses. Challenge members to come up with various activities (i.e., eating pizza, going to a movie) and take turns discussing how each sense is functioning during the specific activity.

2. What It's Like to Be Blind

Ask students to choose partners and have the partners take turns pretending to be blind. Each "blind" student should attempt to do something in class (i.e., sharpen a pencil) and note the issues, feelings, and altered sensations involved in the experience. Encourage a discussion of how the person's other senses functioned during the exercise.

3. Internet: Psychology Research on Sensory Systems

Direct the students to locate psychology research Web sites that discuss sensory systems. Ask them to print out site pages that are particularly interesting and to summarize what they find in short reports.

4. Special Sources: Sensory Depravation

Using the library or Internet, have students research information, articles, or experiments on sensory deprivation that either support or refute the findings of John Lilly in this chapter. Analyze the similarities, differences, and issues involved, including the notion that humans create "alternative realities" to cope when their senses are deprived.