We each have a parent or a teacher who has proudly told us: we perceive the sweetness on the tip of the tongue, the saltiness on the sides, the acidity, a little further back and the bitterness, close to the throat… Yet this assertion, which can still be read here and there, in France, on the website of an academy or a teacher's blog, is false.
It is the result of an imprecision published in a book in 1942, itself interpreted lightly.
The famous “language map” has since been widely denied, again this year in a scientific journal, but probably not enough to avoid word of mouth.
Example of a language map.
The story begins in 1901 when a German scientist named David P. Hänig published the results of an experiment conducted with a handful of colleagues.
In these volunteers, it stimulated the taste buds located on the edges of the tongue.
From their feelings, he concludes that the sensitivity to four flavors (sweet, salty, acid, bitter) varies according to the zones, without however being mutually exclusive.
Looking at his diagrams, we understand that they can be seen almost everywhere and that the differences are quite subtle.
The perception of sweet, salty, sour and bitter according to David P. Hänig.
Three decades later, a historian of psychology at Harvard, Edwin Boring, resumes in a book the raw data of Hänig.
It translates them into a line chart.
But does not include any ordinate scale to quantify the sensitivity of the different tips of the tongue to different flavors.
So much so that we could interpret the diagram in an erroneous way: without an indication of the lowest level reached by the sweet curve, for example, we will quickly conclude that certain regions of the tongue are insensitive to sweets.
Image taken from the book Sensation And Perception In The History Of Experimental Psychology.
Misleading tannins
This is how Hänig's work will be overused for decades and a legend, perpetuated until today.
The language map born of the Boring chart appears in popular magazines, such as Scientific American in the 1950s, as well as in scientific literature and textbooks.
Researchers will challenge this pseudo-discovery, but quietly.
In 1974, the American psychologist Virginia B. Collings dealt him a serious blow.
She notes, like Hänig, variations between the different regions of the language, judging them however insignificant.
It demonstrates that flavors can be felt anywhere on the tongue, but also on the palate or glottis.
In 1978, his colleague Linda Bartoshuk found the origin of the controversy by linking the myth of the tongue map to the book published by Boring, 36 years earlier.
"The apparent simplicity of the tongue map has made it a popular laboratory demonstration in children's biology classes," wrote the psychologist in 1993. "The popularity of this laboratory demonstration is all the more amazing because it must fail to produce the expected results regularly enough.
Because this is the originality of this legend: anyone who performs the experiment himself with a sorbet or a piece of crisps will certainly find it disappointing!
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We would have guessed it: bitter is the most tenacious taste.
While refuting the tongue map, two researchers, Emma Louise Feeney and John E. Hayes, wrote in 2014 that they observed that the perception of this flavor was "significantly greater" in the posterior part of the organ, so near the throat.
Asked, Charles Spence, a researcher at Oxford and author of a study published in 2022 around the myth, has an explanation: "The location of taste in the oral cavity is often determined by tactile cues, such as the astringency of tannins in woody red wine and tea", these tannins being "bitter".
The received idea, however, seems to have had its day.
In a memoir published four years ago, Manuel Zenger, now a neurobiologist and teacher in Vaud, Switzerland, argued that books for the general public no longer dare to present the map of language.
However, having surveyed 144 secondary school students and future teachers in the sector on their knowledge of this theory, he had reached a result that leaves you wondering: 59.3% of those questioned, with an average age of 23, had replied that he had already heard of it.
Of which more than 60% on school benches...