Our Sense of Taste

105
The Chemical Senses: Taste and Smell
infants are breastfed, they can discriminate their own mother’s odor from that of other
breastfeeding women and appear to be comforted by it (Porter, 1991). Recognizing
this odor may help establish the mother-infant bond discussed in the chapter on
human development.
Our Sense of Taste
FIGURE
3.17
Are You a Supertaster?
This photo shows papillae on
the tongue of a “supertaster.”
by
If you don’t mind a temporary
stain on your mouth and teeth, you can
look at your own papillae by painting the
front of your tongue with a cotton swab
soaked in blue food coloring. Distribute
the dye by moving your tongue around and
swallowing; then look into a magnifying
mirror as you shine a flashlight on your
tongue. The pink circles you see against
the blue background are papillae, each of
which has about six taste buds buried in its
surface. Get several friends to do this test,
and you will see that genes create wide individual differences in taste bud density.
doing
2
in review
learn
Our receptors for taste are in the taste buds, which are grouped together in structures
called papillae (pronounced “puh-PILL-ee”). Normally, there are about ten thousand
taste buds in a person’s mouth, mostly on the tongue but also on the roof of the mouth
and on the back of the throat.
The human taste system detects only a few basic sensations: sweet, sour, bitter, and
salty. Each taste bud responds best to one or two of these categories (Zhang et al., 2003)
but it also responds weakly to others. Research has also revealed two additional taste
sensations (Rolls, 1997). One, called umami (which means “delicious” in Japanese),
enhances other tastes and is produced by certain proteins, as well as by monosodium
glutamate (MSG; DuBois, 2004). The other, called astringent, is the taste produced by
tannins, which are found in tea, for example. About 25 percent of us are “supertasters”—individuals whose genes have given them an especially large number of papillae on their tongues (Bartoshuk, 2000; see Figure 3.17). Supertasters are more sensitive
than other people to bitterness, as revealed in their reactions to foods such as broccoli,
soy products, and grapefruit.
Scientists are learning more and more about how interactions between foods and
taste receptors signal various tastes (Small et al., 2003; Stillman, 2002), and they are
putting the information to good use. Understanding the chemistry of sweetness, for
example, has led to new chemicals that fit into sweetness receptors and taste thousands
of times sweeter than sugar. When used in products such as artificial sweeteners, they
offer new ways to enjoy good-tasting but low-calorie sweets. (“In Review: Smell and
Taste” summarizes our discussion of these senses.)
SMELL AND TASTE
Aspect of
Sensory System
Elements
Key Characteristics
Energy
Smell: volatile chemicals
Taste: chemicals in
solution
The amount, intensity, and
location of the chemicals
determine taste and smell
sensations.
Structures of
taste and smell
Smell: chemical receptors in
the mucous membrane of
the nose
Taste: taste buds grouped in
papillae in the mouth
Odor and taste molecules
stimulate chemical receptors.
Pathway to the
brain
Olfactory bulb and taste
buds
Axons from the nose and
mouth bypass the thalamus
and extend directly to the
olfactory bulb.
?
papillae Structures in the mouth on
which taste buds are grouped.
1. The flavor of food arises from a combination of
and
.
2. Emotion and memory are linked especially closely to our sense of
.
3. Perfume ads suggest that humans are affected by
that increase
sexual attraction.