This is one of those things you just need to know. It actually came up in a conversation at a party a few weeks ago, but nobody was certain of the answer, and we were left in that unsatisfying condition of speculation… the sort of thing that drove us all straight home to Google. Well, that’s true in my case, anyway; the rest of the people at the party probably have lives.
Into whichever camp you might fall, the addicted-to-google, or the having-a-life, you can spare yourself from our embarrassing fate! Read on for the fascinating answer to the question: what are the four taste sensations?
Students of science may recall that the tongue can identify only a few basic tastes, and that the rest of what we call “flavor” is comprised primarily of smell (olfaction) and, to a lesser degree, tactile sensation within the mouth. Here are the four taste sensations most folks can recite, if they were paying attention in 7th grade rather than chucking paper wads out the window when the teacher’s back was turned:
Students endowed with robust memories might even recall that specific areas of the tongue are sensitive to each of these four sensations, as illustrated by this nifty interactive taste-region map.
If you didn’t remember the four sensations, or the taste regions of the tongue, don’t feel bad… all the people who did remember were incorrect anyway.
Yes, that’s right: the arcane knowledge they dredged up from the depths of grade-school memory is inaccurate in two respects; worse, it was known to be incorrect at the time those folks’ textbooks were written. (By the way, this is one of the ways I justify my feeble powers of recall — I figure most of the stuff I’ve forgotten was wrong to begin with.)
Here is the straight scoop: scientists now recognize a fifth taste sensation, which at the party I remembered vaguely by saying, “And what’s that fifth one, they have it in Japan…” which shed about .00015 yocto-watts of illumination on the topic, even though my comment was historically accurate.
The sensation is called umami; it was discovered and named by Japanese scientist Kikunae Ikeda in the early 1900s. The chemical that causes umami — that is, the substance that triggers the taste receptors that transmit the message “this isn’t bitter, salty, sour, or sweet, but something else, and by the way I’m kind of enjoying it” to the brain — is glutamic acid, or, essentially, MSG.
What a coincidence, you might wonder, that a known flavor enhancer (monosodium glutamate) would contain the precise chemical that triggers this umami flavor! It is in fact no coincidence at all: Kikunae Ikeda invented MSG.
Finally, in stark contradiction to the taste map referenced above, no less an authority than Scientific American has this to say: Taste researchers have known for many years that these tongue maps are wrong. The maps arose early in the 20th century as a result of a misinterpretation of research reported in the late 1800s. The article is entitled, unambiguously, The Taste Map: All Wrong.
So there you have it: five taste sensations, not four, and no spatial segregation of sensitivities across the tongue. The only other thing you might need to know about the sensation of taste is that there is early evidence of a sixth sort of receptor, the existence of which is demonstrated by a friend of mine who can often be heard to say, “That tastes like ass!” I don’t think anyone has researched that particular component of gustation yet though.