Invitation to Psychology

208 Chapter 6 Sensation and Perception

can have as few as 500 or as many as 10,000 taste

buds (Miller & Reedy, 1990).

The taste buds are commonly referred to,

mistakenly, as the receptors for taste. The actual

receptor cells are inside the buds, 15 to 50 to a

bud. These cells send tiny fibers out through an

opening in the bud; the receptor sites are on these

fibers. New receptor cells replace old ones about

every 10 days. However, after age 40 or so, the to-

tal number of taste buds (and therefore receptors)

declines. Interestingly, the center of the tongue

contains no taste buds. However, as in the case of

the eye’s blind spot, you will not usually notice the

lack of sensation because the brain fills in the gap.

Four tastes are part of our evolutionary heri-

tage: salty, sour, bitter, and sweet, each produced by

a different type of chemical. Their receptors are

tuned to molecules that alert us to good or danger-

ous tastes: Bitter tastes detect poison; sweet tastes

attract us to biologically useful sugars, such as those

in fruit; salty tastes enable us to identify sodium, a

mineral crucial to survival; and sour tastes permit

us to avoid acids in concentrations that might in-

jure tissue (Bartoshuk, 2009). Although you may

have heard that your tongue has a distinct zone

for each of these four tastes, that’s a myth. All of

the basic tastes can be perceived at any spot on the

tongue that has receptors, and differences among

the areas are small. When you bite into an egg or

a piece of bread or an orange, its unique flavor is

composed of some combination of these tastes.

Some researchers believe that there is a fifth

basic taste, umami, the taste of monosodium gluta-

mate (MSG), which is said to permit the detection

of protein-rich foods. Umami was identified by

Japanese chemists in the early 1900s as a flavor

enhancer. (The word has no exact English transla-

tion, but the closest is “delicious” or “savory.”) The

findings from umami research, which has largely

taste buds Nests of
taste-receptor cells.

You are about to learn...

•    the basics of how we taste, smell, and feel.

•    why saccharin and caffeine taste bitter to some

people but not to others.

•    why you have trouble tasting your food when

you have a cold.

•    why pain is complicated to understand and

treat.

•    how two senses inform us of the movement of

our own bodies.

Other Senses

Psychologists have been particularly interested in

vision and audition because of the importance of

these senses to human survival. However, research

on other senses is growing rapidly, as awareness of

how they contribute to our lives increases and new

ways are found to study them.

Taste: Savory Sensations

Lo 6.19, Lo 6.20

Taste, or gustation, occurs because chemicals stim-

ulate thousands of receptors in the mouth. These

receptors are located primarily on the tongue,

but some are also found in the throat, inside the

cheeks, on the roof of the mouth, and, incredibly,

as we will see, in your gut. If you look at your

tongue in a mirror, you will notice many tiny

bumps; they are called papillae (from the Latin for

“pimples”), and they come in several forms. In all

but one of these forms, the sides of each papilla

are lined with taste buds, which up close look a

little like segmented oranges (see Figure 6.9).

Because of genetic differences, human tongues

papillae [pa-PiLL-ee]
Knoblike elevations on
the tongue, containing
the taste buds. (Singular:
papilla.)

Papilla

Taste buds

Nerve

bers

Taste receptor cell

Supporting cell

Taste bers

containing

receptor sites

Figure 6.9 Taste receptors

The illustration on the left shows taste buds lining the sides of a papilla on the tongue’s surface.

The illustration on the right shows an enlarged view of a single taste bud.