Psychology: Sensation

Sensation

Katie Callahan has three secrets: “I don’t like choco-late. I don’t like coffee. And I don’t like beer. They all taste like burnt dirt to me.”

“But when I tell people this, they think I’m prissy, or boring, or anorexic,” says Katie. “It really throws a wrench in your social life. And so I learned in college to keep my food aversions to myself.”

In her late twenties, Katie figured out why her friends’ cravings left her gagging: She’s a supertaster. While her friends savor chocolate, cheese, and chilies, to her they taste like dish soap, salty baby oil, and acid.

“My tongue has about 100 times more taste buds than normal tasters’,” Katie explains, and she’s not alone. According to one estimate, 25% of Americans are supertasters, while 50% are normal tasters. The remaining 25% are nontasters, who cannot sense certain bitter chemicals. While nontasters live in a pastel world of taste, supertasters live in a neon world, says Linda Bartoshuk, a psychologist who studies supertasters. Bartoshuk, a nontaster, confesses that she regularly sweetens her wine with sugar.

Genetics research suggests that Katie owes her sensitive tongue to her parents. They both dislike strong flavors, although neither has dietary displeasures as severe as their daughter’s. The strength of Katie’s aversions suggests that she received a double dose—one from each parent—of the allele that codes for supertasting.

Because the insides of their mouths are easily overwhelmed, supertasters tend to eat less sugary and fatty food. This often keeps them thin and lowers their risk of heart disease. But supertasters also tend to eat fewer vegetables with cancer-fighting flavonoids (which taste too acrid to them), so they may be more vulnerable to certain cancers. How can our tiny taste buds so powerfully shape our behavior and potentially our health? The first step in tackling this question is to ask how our tongues—or, more broadly, our sense organs—funnel the outside world into our bodies and minds. These questions are central to the psychology of sensation.

Katie’s case also reminds us that our senses shape our daily existence. Of course, someone who’s blind can have a full, rich life—but nonetheless, walking down a hall-way or crossing a street are much more challenging than for someone sighted, and some activities (like driving) are out of the question. Likewise, deaf people live per-fectly normal lives in most respects; but they can’t respond to the smoke alarm’s shriek or the wail of a police siren, and they can converse with only a limited number of peo-ple. (Roughly 2 million people are proficient in American Sign Language worldwide; but compare that to, say, the world’s 400 million English speakers.) Things are more extreme for individuals lacking other senses—including people who can’t sense pain. As we’ll see, these people are at risk for many injuries, including biting their tongues while chewing or leaning on a hot stove without realizing it.

Our dependence on the senses raises a question: How reliable are they? You’ve likely had the experience of spotting a friend in a crowd—only to discover that the person is someone else altogether. You’ve probably heard someone calling you, but then realized you imagined it. And surely at some point you’ve failed to hear someone speaking to you. Is it possible that our sensory experiences are often inaccurate or incomplete—so that the world we sense differs from the world as it is?

The world certainly poses a challenge for our sensory apparatus: This is now in front of your eyes—but you also see your hands, others in the room, the table surface, and more. Your eyes take in a wealth of information from each of these objects—and your eyes and brain constantly collect, encode, interpret, and act upon what you see, even as you simultaneously make sense of an influx of other sensory information.

We’ll examine how our senses function, beginning with the ques-tions that launched scientific inquiry in this domain: How accurate and complete are our sensory experiences? And how objective is our perception of the world? We’ll then turn to psychologists’ methods for addressing these questions. With that base, we’ll survey the senses, starting with properties they all have in common and then consider-ing each sense separately.