Taste, also known as gustation, the sense that enables an organism to detect flavors. Probably all animals possess this sense in some form. In some fishes the taste organs are located in the skin, and in certain insects they are present on the legs or antennae. In man and most other vertebrate animals the taste organs, called taste buds, are located in the mouth. Although some are present on the soft palate and in the throat at birth, only the taste buds on the tongue remain useful at maturity.
For all animals that have been tested, there are four basic tastes: sweet, sour, bitter, and salt. All other flavors are combinations of the basic tastes and are often influenced by other senses, particularly the sense of smell. For example, to a person with a head cold a cup of coffee may seem hot but flavorless. The characteristic coffee flavor is missing, because it consists mostly of odors and the head cold has impaired the person's sense of smell. The sense of touch is also an important part of taste, and the tastes associated with many oils and spices are actually combinations of taste and touch. Mustard and pepper, for example, stimulate the heat receptors in the tongue, as well as the taste buds.
The number of taste buds varies according to age. Adults have about 10,000 taste buds, and children have slightly more. A taste bud consists of a tiny group of special cells that are embedded in the tongue and are connected with the surface through a tiny pore. Each cell, called a taste cell, is long and slender and has a hairlike extension that projects through the pore. When taste cells are stimulated, they send nervous impulses to the taste centers of the brain. Taste cells can be stimulated only by a substance in a liquid form. A solid substance must become dissolved in saliva, the watery fluid secreted by glands in the mouth.
Although all taste buds in vertebrate animals are similar in structure, they vary slightly in function, some being more sensitive to a particular taste than others. The taste buds most sensitive to salt are scattered over most of the tongue's surface, but the taste buds most sensitive to the other three basic flavors are limited to small areas. The taste buds that are most sensitive to sweet are located chiefly at the tip of the tongue, and those most sensitive to sour are located mainly along the sides. The taste buds that are stimulated most strongly by bitter substances are mostly at the back of the tongue.
Crustaceans, insects, and many other invertebrate animals have organs serving the sense of taste on their legs or on paired appendages near the mouth. A sea anemone can taste objects that come into contact with its tentacles.