Essay 15.1 Scientific Urban Legend—The Bogus Tongue Map

One of the “facts” that experts have been unable to purge from many textbooks is the notion that sweet is perceived at the tip of the tongue, bitter at the back, sour on the sides, and salty all over. In the case of this myth, we know roughly when and where it began and we have some idea about what has maintained it in the face of determined efforts by experts to stamp it out.

The origin is most likely a book written by Harvard University’s Edwin Boring in 1942. Boring, in addition to his own work, chronicled the history of sensation and perception. He described a study conducted by Hänig in the laboratory of Wilhelm Wundt in 1901 (Hänig, 1901). Hänig wanted to show that the four basic tastes were mediated by different receptor mechanisms (something we take for granted today). He reasoned that if taste thresholds varied with tongue locus, then one would have to conclude that the receptor mechanisms varied as well. Hänig selected points on the oval distribution of taste buds around the perimeter of the tongue and laboriously measured thresholds for substances representing each of the four basic tastes. The variation in thresholds was small but the patterns across the four tastes were different; Hänig had made his point. Boring apparently misunderstood the concentration units in Hänig’s study and failed to appreciate just how small the variations in thresholds really were. Thus, Hänig’s result that sweet thresholds were slightly lower on the front of the tongue and bitter thresholds were slightly lower on the back was misconstrued and turned into the notion that we taste sweet on the front of our tongues, bitter on the back, etc.

Since the tongue map became a common laboratory demonstration, generations of students have had reason to doubt the map. Asked why they could not observe it, one group of students said that they “must have done the experiment wrong.” It is worth remembering that textbooks are not always correct. Nonetheless, you can believe us here: receptors for all four of the basic tastes are distributed over the entire tongue.

References

Boring, E. G. (1942). Sensation and Perception in the History of Experimental Psychology. New York: Appleton-Century-Crofts.

Hänig, D. P. (1901). Zur Psychophysik des Geschmackssinnes. Philosophische Studien 17: 576–623.