Sensory Science

The Tongue Map: A Common Misunderstanding

Everyone has seen the tongue map, that diagram of the tongue with different sections for different tastes: sweet in the front, salty and sour on the sides, bitter at the back. It’s an iconic image in the study of taste, but it’s wrong.

Taste Receptors: How They Work

Taste receptors are not confined to specific areas of the tongue. Instead, they are distributed all over its surface. These receptors detect the four basic tastes: sweet, salty, sour, and bitter. Umami, the savory taste of glutamate (found in monosodium glutamate, or MSG), is now recognized as a fifth basic taste.

Thresholds for Taste Perception

The sensitivity of taste receptors varies around the tongue. The tip and edges are particularly sensitive because they contain many taste buds, the sensory organs that detect taste. However, the differences in sensitivity are subtle, and all areas of the tongue can perceive all tastes.

The Origin of the Tongue Map

The tongue map originated in a 1901 study by German scientist David P. Hänig. Hänig measured the thresholds for taste perception around the edges of the tongue. His results showed that different parts of the tongue had slightly lower thresholds for certain tastes.

However, Hänig’s graph of his measurements was more of an artistic interpretation than an accurate representation. It made it appear as though different parts of the tongue were responsible for different tastes.

In the 1940s, Harvard psychology professor Edwin G. Boring reimagined Hänig’s graph in his book Sensation and Perception in the History of Experimental Psychology. Boring’s version had no meaningful scale, leading to the creation of the tongue map as we know it today.

Scientific Evidence Against the Tongue Map

Numerous experiments have refuted the tongue map. For example, studies have shown that all areas of the mouth containing taste buds, including the tongue, soft palate, and throat, are sensitive to all taste qualities.

Damage to the chorda tympani nerve, which supplies taste sensation to the front of the tongue, does not eliminate the ability to taste sweet. In fact, subjects with chorda tympani damage may experience an enhanced ability to taste sweet.

Molecular Biology and Taste Receptors

Modern molecular biology also contradicts the tongue map. Researchers have identified receptor proteins on taste cells that are responsible for detecting taste molecules. Sweet receptors are found throughout the mouth, not just in the front. Similarly, bitter receptors are found in all taste areas.

The True Test

The best way to debunk the tongue map is to conduct a simple experiment. Brew a cup of coffee, open a can of soda, and touch a salted pretzel to the tip of your tongue. You will quickly realize that your tongue can perceive all tastes, regardless of its location.

Despite the scientific evidence, the tongue map persists in common knowledge and is still taught in many classrooms and textbooks. It is a testament to the power of visual representations and the difficulty of dislodging misconceptions once they become entrenched.