Many school books once showed a "tongue map." It said that the tip of the tongue tastes sweet things and the back tastes bitter things.

But this map is wrong. It came from a mistake in reading an old study from 1901. That study found only small differences between parts of the tongue. In fact, you can taste all five basic tastes on every part of your tongue. Try it at home!

For many years, textbooks showed a tongue map in which sweetness was sensed at the tip, saltiness and sourness at the sides, and bitterness at the back. This map is a misunderstanding. In 1901, a German researcher tested how sensitive different parts of the tongue were to tastes. He found only small differences.

In 1942, an American psychologist turned this data into a graph that was easy to misread. People thought it meant each taste could only be sensed in one area. In 1974, another researcher confirmed that all tastes can be sensed everywhere on the tongue.

Today we know that receptors for different tastes are found in taste buds across the tongue. The old map also had no place for umami, discovered by a Japanese chemist in 1908.

For decades, students learned from a colorful diagram that divided the tongue into zones, with sweet at the tip, salty and sour along the sides and bitter at the back. The diagram is a textbook case of data being distorted as it is passed along. In 1901, the German researcher Hänig measured how weak a solution could be and still be tasted at different points on the tongue.

His thresholds varied only slightly from place to place, and every area detected every taste he tested. In a 1942 history of psychology, Edwin Boring presented these data in a graph whose scale was easy to misread. Readers seem to have concluded that each region handled a single taste. A "slightly more sensitive" area became the "only" area.

In 1974, Collings re-examined the question and confirmed that all tastes can be perceived throughout the tongue. Molecular research has since found receptors for sweet, umami and bitter tastes in cells spread among taste buds all over the tongue. Small regional differences in sensitivity are real. The regions simply do not divide up the work. The old map also had no zone for umami, which was identified in 1908.