We’ve all probably heard something of some sort about “the tongue map” –the idea that different parts of our tongues are used to distinguish different basic tastes such as sweet, salty, and bitter. For example, the tongue ma below would suggest only the tips of our tongues are used to taste sweetness.
In fact, I remember a PSSA question in middle school that revolved around a story about dipping Q-tips in salt water and dabbing it around your tongue to see where you tasted salt.
What we know presently, however, is that the tongue map is a misconception. So how did the myth start and what does science tell us about the “the tongue map” today?
It turns out the theory of the tongue map began with something a lot of us know all too well: a miscommunication. Back in the very early 1900’s, a German scientist by the name of D.P. Hanig published research (Zur Psychophysik des Geschmackssinnes… say that 5 times fast) indicating that his participants could indeed detect a variety of tastes on all parts of the tongue. He also reported that different areas of the tongue seemed to have different sensitivities for the tastes, though these differences were small.
Flash forward about 40 years. That was when a prominent Harvard psychologist Edwin Boring took Hanig’s research and re-plotted it in a way so that those relatively tiny differences between sensitivities in different areas of the tongue seemed much larger than they actually were.
How did he do this? Take a look at the original graph by Hanig below:
Ignoring the fact that it’s in German, anyone who has had to make a graph in school knows this blatantly goes against the rules. Notice how the y-axis isn’t even labeled, let alone marked with a scale and units. Without a proper scale to go by, Boring just assumed the sensitivity thresholds at the bottom were equal to zero, when if he in fact looked through the mounds and mounds of German text he would have seen that these were not absolute sensitivities but relative sensitivities. Whoops.
Scientists and historians looked at Boring’s Sensation and Perception in the History of Experimental Psychology and the idea of the “tongue map” was born.
Also notice how both of these graphs had no error bars. Without them, anyone who looks at that graph will have no way of knowing if those clearly visible differences in height between the tastes are actually statistically significant. So if there’s anything to be learned from this (besides the myth of the tongue map of course), it’s to properly label your graphs and include error bars if necessary!
Though you may have had experiences in early education dealing with the tongue map, research to disprove it was being conducted as early as the 1970’s. Virginia Collings conducted one of the more important studies at that time. She essentially re-proved the same concept that Hanig did originally- that the differences in sensitivities of taste around the tongue were trivial.
Countless studies have since been published that disprove the “tongue map” concept. Here’s what we know about tastes on the tongue today. The main areas you can taste on the tongue are where the lingual papillae are located, since they contain your taste buds. This includes fungiform papillae on the front and sides of your tongue, foliate papillae on the back sides, and circumvallate papillae on the very back of the tongue (as you can see from this image)
All of our taste buds contain taste receptor cells, which are capable of distinguishing all five basic tastes (and possibly a sixth, but more on that later).
So even decades after the tongue map has been disproven, why are we still talking about it? It could very well be that people simply enjoy the idea of a map, since it’s visually appealing. It would be nice to think that each taste has their own specific area on the tongue, and it doesn’t deviate from that. We like things that are divided into neat, clear categories, and for a while it appeared that the tongue and basic tastes were one of those things.
It’s also quite easy to fool yourself with expectations, like with top-down processing. For example if you have the expectation that a bitter compound is going to taste stronger, you may rate it as such without really thinking about it (even though it may be just as intense as a sweet-tasting compound).
And as for a true “tongue map?”
Here you go:
Yes indeed, these colored areas, where the concentrations of papillae are highest, are where all of the basic tastes can be detected.