UNIT IV Sensation and Perception

A chapter opener titled “Sensation and Perception” shows two girls belonging to different ethnicities eating watermelon on a beach.

MODULES

“I have perfect vision,” explains acclaimed writer and teacher Heather Sellers. Her vision may be perfect, but her perception is not. In her memoir, You Don’t Look Like Anyone I Know (2010), she tells of awkward moments resulting from her lifelong prosopagnosia—face blindness.

In college, on a date at the Spaghetti Station, I returned from the bathroom and plunked myself down in the wrong booth, facing the wrong man. I remained unaware he was not my date even as my date (a stranger to me) accosted Wrong Booth Guy, and then stormed out. . . . I do not recognize myself in photos or videos. I can’t recognize my stepsons in the soccer pick-up line; I failed to determine which husband was mine at a party, in the mall, at the market.

“Voice blind” people with phonagnosia—an inability to recognize familiar voices—may make similar mistakes. One man flirted on the phone with someone he presumed was his wife, not realizing it was a different woman (Spiegel, 2010).

To avoid being perceived as snobby or aloof, Sellers sometimes fakes recognition. She often smiles at people she passes in case she knows them. Or she pretends to know the person with whom she is talking. (Similarly, those of us with hearing loss often fake hearing.) But, Sellers points out, there is an upside: When encountering someone who previously irritated her, she typically feels no ill will—she doesn’t recognize the person.

Unlike Sellers, most of us have (as Module 18 explains) a functioning area on the underside of our brain’s right hemisphere that helps us recognize a familiar human face as soon as we detect it—in only one-seventh of a second (Jacques & Rossion, 2006; Rossion & Boremanse, 2011). This remarkable ability illustrates a broader principle: Nature’s sensory gifts enable each animal to obtain essential information. Other examples:

Human ears are most sensitive to sound frequencies that include human voices, especially a baby’s cry.
Frogs, which feed on flying insects, have cells in their eyes that fire only in response to small, dark, moving objects. A frog could starve to death knee-deep in motionless flies. But let one zoom by and the frog’s “bug detector” cells snap awake. (As Kermit the Frog said, “Time’s fun when you’re having flies.”)
Male silkworm moths’ odor receptors can detect one-billionth of an ounce of chemical sex attractant per second, released by a female one mile away (Sagan, 1977). That helps explain why there continue to be silkworms.

In this unit, we’ll look at what psychologists have learned about how we sense and perceive our world. We begin by considering some basic principles that apply to all our senses.

Unit IV Overview Video