Chances are you saw it in school: a drawing of a tongue divided into neat zones, with sweet at the tip, bitter at the back, and salty and sour along the sides. Some classes even tested it with little paper strips. It looked so official. There was just one problem.
The tongue map is wrong. Every taste can be detected by all regions of the tongue. Some spots may pick up certain tastes a hair sooner than others, but those differences are tiny, and how strong a taste feels doesn't change from one area to the next.
Where the Map Came From
The story starts in 1901, when a German scientist named David P. Hänig published a paper on the psychophysics of taste. He measured how much of a flavor it took before people could detect it on different parts of the tongue. He found only minute differences.
In 1942, Harvard psychologist Edwin Boring included a translation of Hänig's work in a book. Boring replotted and normalized the original graphs. Other authors then misread the new versions. Where a curve dipped, they assumed there was no sensation at all, and where it peaked, they assumed maximum sensation. In reality, the gap between the two was very small.
That misunderstanding hardened into the idea that each part of the tongue tastes exactly one basic flavor. Textbooks picked it up, and a little difference in sensitivity got turned into a big difference in sensation.
A Classroom Classic
Into the late 1990s, the tongue map was a staple of high school biology. Students received paper strips soaked in different tastes and were told where each one should be strongest. They touched the strips to different spots on a lab partner's tongue and recorded the result they were supposed to get.
If your own results never quite matched the chart, now you know why. Your tongue was working perfectly. The diagram wasn't.
How Taste Really Works
Your tongue is covered with thousands of small bumps called papillae, which you can see in a mirror. Many of them hold taste buds, and you have somewhere between 2,000 and 5,000 taste buds on the front and back of your tongue. More are tucked away on the roof, sides, and back of your mouth, and even in your throat. Each taste bud contains 50 to 100 taste receptor cells.
What we call flavor is a team effort. Taste combines with your sense of smell and with nerves that register texture, temperature, and even pain. That's why food can seem bland when your nose is stuffed up.
The Taste the Map Forgot
The classic map covered four tastes, but scientists now recognize five: sweet, sour, salty, bitter, and savory, also known as umami. In 1908, Kikunae Ikeda of the University of Tokyo identified umami while studying a broth made from kombu seaweed. He traced its rich taste to glutamate.
A year later, Ikeda helped found the company Ajinomoto, which introduced the world's first umami seasoning, monosodium glutamate, better known as MSG. Even so, scientists debated umami for decades before it was formally recognized as the scientific term for that savory taste in 1985.
So the next time you lick an ice cream cone, go ahead and use any part of your tongue you like. The tip, the sides, and the back are all invited to the party, and every one of them can tell you it's sweet.
