A few weekends ago my wife and I took a trip to Hershey's Chocolate World in Hershey's, PA (recommended). We paid for their "Chocolate Tasting Adventure" because we are both Sensory Scientists and couldn't resist.
And then it came up. The tongue map. I couldn't believe it.
You've all seen it, because somehow it persists. Yet sensory scientists have known for years that it is not only false, but terribly false. The receptors for taste - tiny specialized structures that perceive different tastes when they come in contact with food, are located all over your tongue for all different tastes.
I challenge you to a simple experiment. Mix together some simple syrup (sugar + water, 10% by weight) and find an eye dropper. Test the different areas of your tongue and see if you can taste the sweetness where the drop falls, being sure to drink plain water between. Unsalted "Saltines" are great for cleansing the palate also. You can repeat with lemon juice if you can stand to continue the experiment. At best you'll noticed reduced sensation in different areas.
Back at the Culinary Institute of America in Introduction to Gastronomy, we were not (thankfully) treated to this map. The class does, however, simplify the tongue to "five basic tastes": sweet, salty, sour, bitter and the new kid, umami.
Umami is the full mouth feeling meaty sensation elicited by glutamate, an amino acid and a building block of protein. Because glutamate is naturally negatively charged, in its stable form it is bonded with sodium in a way very similar to table salt (sodium + chlorine), hence "Mono-Sodium Glutamate." It makes sense that we have developed a taste for meat because typically it signifies protein, and for most of human history protein was hard to come by. The Japanese company Ajinomoto patented the process for making MSG 1909. It is amazing to me that American's ignored this fundamental taste until the 70s or 80s. New kid, right.
The whole idea of basic tastes has been turned on its head recently. Gray Kunz, of Cafe Gray fame in NYC notes upwards of 23 basic tastes that him and his colleagues came up with (see Elements of Taste) in response to the inability of his staff to accurately describe taste sensations. Wikipedia notes 7. So what are basic tastes, really? What distinguishes one sensation (say sweetness) being declared a basic taste, and another, such as "metallic", from not being elevated to one?
I think the concept of basic tastes in general is on its way out. It limits our own perception because we tend to default to "basic tastes" when describing flavor. Think beyond that. Texture, astringency, heat (from chilies), temperature, metallic, pungent, umami, electric and others. The tongue as a sense organ is way more magical and complex than that and we owe it to ourselves to think beyond such simplified perceptions when describing food.
"Essentially, all models are wrong, but some are useful." --George Box