Your sense of taste not only lets you enjoy delicious foods, but it also helps keep you alive and healthy. If it were not for taste, you might not consume the calories needed to grow and function. Also, your sense of taste helps warn you of poisonous substances, which are likely to have an unpleasant taste.
Most people are familiar with the “tongue map” from grade school. The tongue map is a picture of the tongue displaying areas of taste sensitivities. According to the map, we detect sweetness on the tip of our tongue, bitterness at the back, and saltiness and sourness along the sides. This map led many people to believe that there are different types of taste buds on different areas of the tongue, each with the ability to detect one of the four basic tastes. However, most scientists now believe that taste buds can detect all tastes, and the sensitivity differences along the perimeter of the tongue are of probably no significance.
Evidence for the Health Claim
In 1901, the German scientist Herr Hanig published his PhD thesis in Philosophische Studien , in which he presented a diagram summarizing his research on the distribution of taste sensitivity around the perimeter of the tongue.
Hanig’s diagram indicated that sensitivity to sweet tastes was highest on the tip of the tongue, sensitivity to bitter tastes was highest at the base, and sensitivity to sour tastes was highest on the edges. He found that saltiness was perceived equally on all areas of the tongue’s perimeter.
In 1942, researcher Edwin Boring discussed Hanig’s data in his book, Sensation and Perception in the History of Experimental Psychology . Boring performed calculations that supported Hanig’s findings, indicating variations in taste sensitivity among different regions of the tongue.
Hanig’s and Boring’s diagrams led to the labeling of tongue maps. Upon looking at tongue maps, many people mistakenly assumed that sweet tastes can only be detected on the tip of the tongue, bitter on the base, and so on.
Evidence Against the Health Claim
A 1974 study by researcher Virginia Collings, published in Perception and Psychophysics , re-examined the differences in taste perception across the tongue. She found that there were variations along the perimeter of the tongue in detecting sweet, sour, and salty tastes, but concluded that the variations were small and of no practical significance.
Why has Hanig’s work been misinterpreted for so long? Probably because the diagrams were meant to serve as visual representations of the variations in taste sensitivity in different areas of the tongue, not describe how meaningful the variations were.
Scientists now believe that all taste buds can detect the basic tastes: salt, sweet, sour, bitter, and umami (a taste in protein-rich foods). When you eat a food, enzymes in your saliva break it down into chemicals. When these chemicals come in contact with your taste buds, which are located in most of the bumpy papillae on your tongue, they set off different reactions. Depending on the reaction, a signal is sent along nerve fibers from your tongue to your brain, which distinguishes the tastes.
While your taste buds are busy sensing the food you have just eaten, these same chemicals travel up to your nose and trigger olfactory signals, which also reach your brain and considerably enhances your overall sensation of flavor. This is why foods tend to taste bland when your sensation of smell is absent or diminished.