Hockenbury Discovering Psychology 5th txtbk

The Chemical and Body Senses105Can Snakes Hear? Snakes have functionalinner ears, but they don’t have outer ears.So how do snakes hear? With their jaws.When a desert viper rests its head on theground, a bone in its jaw picks up minutevibrations in the sand. From the jaw, thesevibrations are transmitted along a chain oftiny bones to the cochlea in the inner ear,allowing the snake to “hear” the faintfootsteps of a mouse or other prey (Freidel& others, 2008). Similarly, in some speciesof salamanders, frogs, toads, and lizards,vibrations in the air are picked up by thelungs and transmitted to functional innerears.Both frequency theory and place theory are involved in explaining our discriminationof pitch. Frequency theory helps explain our discrimination of frequencieslower than 500 hertz. Place theory helps explain our discrimination of higherpitchedsounds. For intermediate frequencies or midrange pitches, both place andfrequency are involved.The Chemical and Body SensesSmell, Taste, Touch, and PositionKey Theme• Chemical stimuli produce the sensations of smell and taste, while pressureand other stimuli are involved in touch, pain, position, and balancesensations.Key Questions• How do airborne molecules result in the sensation of an odor?• What are the primary tastes, and how does the sensation of taste arise?• How do fast and slow pain systems differ, and what is the gate-controltheory of pain?• How are body sensations of movement, position, and balance produced?The senses of smell and taste are closely linked. If you’ve ever temporarily lost yoursense of smell because of a bad cold, you’ve probably noticed that your sense of tastewas also disrupted. Even a hot fudge sundae tastes bland.Smell and taste are linked in other ways, too. Unlike vision and hearing, whichinvolve sensitivity to different forms of energy, the sensory receptors for taste andsmell are specialized to respond to different types of chemical substances. That’swhy smell, or olfaction, and taste, or gustation, are sometimes called the “chemicalsenses” (Mombaerts, 2004).People can get along quite well without a sense of smell. A surprisingly largenumber of people are unable to smell specific odors or lack a sense of smell completely,a condition called anosmia. Fortunately, humans gather most of their informationabout the world through vision and hearing. However, many animal speciesdepend on chemical signals as their primary source of information.Even for humans, smell and taste can provide important information about theenvironment. Tastes help us determine whether a particular substance is to besavored or spat out. Smells, such as the odor of a smoldering fire, leaking gas, orspoiled food, alert us to potential dangers.Smell, Taste, and the Eight Million DollarNose According to Dutch winemaker IljaGort, “Tasting wine is something you dowith your nose, not your mouth.” Wineconnoisseurs are keenly aware of the factthat the senses of smell and taste areclosely intertwined. Specialized receptorsin the nasal passages are able to detectthe subtle aromas that differentiateamong fine wines (Simons & Noble, 2003).After hearing about a man who lost hissense of smell in an auto accident, Dutchwinemaker Ilja Gort approached Lloyd’sof London about insuring his nose—for$8 million. After a thorough examination,Lloyd’s agreed, but with a few conditions.Gort is not allowed to box, ride a motor -cycle, or have his moustache trimmed byanyone other than an experienced barber.