Myth of the Tongue Map

The taste map: 1. Bitter 2. Sour 3. Salt 4. Sweet. MesserWoland via Wikimedia Commons, CC BY-SA

A persistent meme of misconception

It’s not what you know that gets you into trouble. It’s what you know that ain’t so.”

Mark Twain

The Problem

How do we know what is so and what ain’t so? Sometimes obsolete or debunked ideas still persist and circulate widely. Many people today still believe the misconception that your tongue has four separate taste regions, with each region specializing in tasting either sweet, sour, salty, or bitter.

This myth claims you will taste sweetness on the front of your tongue, for example, but not elsewhere. There is even a cool, colorful graphic of a tongue with the four regions labeled for handy reference. People have this mistaken belief because they learned it, either in school, at home, or from “the common knowledge that everyone knows.”

Many science textbooks from the elementary level up through the collegiate level still contain diagrams and information stating that different regions of the tongue are sensitive to particular tastes, says Steven Munger, a neuroscientist specializing in taste and smell at the University of Florida. A quick Google search of the phrase “classroom activities tongue mapping” generated 42,500 hits in half a second. Looking at the first ten results, showed that most of them were perpetuating the myth. Hopefully, many of the other 42,500 hits were trying to set the record straight.

The Science

Humans have about 8000 taste buds with each taste bud having 50 to 100 different receptors with a mix of receptors for each of the five tastes: sweet, sour, salty, bitter, and umami. The savory taste of umami was discovered after the tongue map went viral. Our taste receptors are evenly distributed on our tongues. Our sensation of any flavor is not localized in any specific region of the tongue. Recent research also finds that each of the five tastes has a particular receptor connected to the brain.

 Why, then, do so many people believe this misconception to be true?

Myth History

The problem comes from a misreading and a mistranslation. A study in 1901 by German perception researcher David Hanig started it all. He wanted to know whether every region of the tongue was equally sensitive to taste. Hanig was studying taste in general, not a specific taste, though he tested for all four tastes he knew. He found that the edges of the tongue are slightly more sensitive than the center. His research was not about finding zones for specific tastes on the tongue.

The problem came when he graphed his results for publication and didn’t include a scale to interpret his graphs. In the 1940s, Edwin Boring at Harvard University read this study and misinterpreted the results. Maybe he didn’t read carefully enough, maybe the translation he read was poorly done. Unfortunately, he included his misunderstood and misinterpreted conclusions in a book he was writing on the science of sensation and perception. Also, unfortunately, his book influenced many people, as this misconception flooded into the science taught in schools.

I feel sorry for generations of students who were told that the tongue map was true, and they would do an experiment to verify these results. Social pressure and confirmation bias helped support this misconception. I remember my own experience with this “experiment.” I did not taste sweet or salty or bitter where I was supposed to, although many of my classmates reported they did. I came away feeling that somehow my senses were wrong or that I wasn’t interpreting things correctly. And all of this was because a psychology professor didn’t understand what he was reading.

Persistence of a Misconception

Does a viral meme ever die? For a long time scientists and science educators have been trying to stamp out this misconception about taste and tongue maps. San Francisco’s famous science museum, The Exploratorium, has a professional development program for science teachers. I remember one of our first lessons in the introductory seminar was about the myth of tongue maps. Yet years later, I continue to meet science teachers who think that the maps represent scientific fact,.

All this goes to show that misconceptions, particularly those with a catchy meme, can be very hard to eradicate. This simple myth is easy to understand, seems reasonable, and is frequently repeated in so many places from obsolete-but-still-used science textbooks to internet prominence. It seems likely to continue for a long, long time. One can see the appeal of this idea. It claims to be based on a study, it’s clear, and it looks like an easy and fun school classroom activity.

The process of science catches errors like this by design. In 1974, Virginia Collins re-examined the original study, discovered Boring’s error, and laid the foundation for our modern understanding of taste. Collins and others corrected the error in science journals. Yet, almost 50 years later, so many people still believe a misconception based on a poorly graphed study and a poorly understood translation. Wouldn’t it be great to have a similar system to correct popular misconceptions, the common science beliefs that everyone knows but ain’t so?

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