|MadSci Network: Medicine|
I think from the way you asked this question, you already have a pretty good idea of the answer. What I really want you to do is prove the answer to yourself. I'm going to give you some instructions for a taste experiment. Try it, and see what YOU find out. If you feel you have to see my answer, look here.
First, what I'd like for you to do is find a mirror and stick out your tongue. Look closely, and you'll see it is covered by lots of little bumps. These are called papillae. Inside many of these papillae are taste buds. The taste buds have cells in them which allow you to taste whatever is dissolved in your saliva. You also have taste buds in the roof of your mouth, in your checks, and in your throat. Other animals have taste buds in other places. Some fish have taste buds on the outside of their bodies, and some insects have taste buds on their feet. Scientists now believe that a human tongue is capable of detecting 4 different types of taste; sweet, sour, salty and bitter.
So, which goes where?
Here is what I'd like you to do:
Get four glasses and fill them with 1/4 cup of distilled water. Add a teaspoon of salt to the first glass, a teaspoon of sugar to the second glass, a teaspoon of lemon juice to the third glass, and a teaspoon of unsweetened tonic water to the fourth glass (alternatively use a teaspoon of unsweetened cocoa or instant coffee). Mix them up well. These sorts of stimuli worked pretty well when I did the experiment, but you might need to change them a little, depending on your subject's taste sensitivity. Have You'll also need some distilled water for rinsing. Make sure everything is at room temperature.
Now, get some of your classmates, and have them rinse their mouths with distilled water until they feel it has no taste. Keep the glasses hidden from your classmates. Put a cotton swab into one of the solutions. Take it out and drain off the excess. Now, have a friend stick out their tongue, and place the swab on a part of their tongue. Ask them what they taste (sweet, sour, salty, bitter or nothing). Remove the swab and record the result. Keep repeating this, using different solutions on different parts of the tongue. Be sure to have the subject rinse out their mouth between each application. With these sorts of stimuli, you will probably find you can taste some of them regardless of where they are placed on your tongue, but some spots should be much more sensitive to particular tastes than other spots. So, you should be able to make a rough map of which parts of the tongue taste which flavors. If you want to improve this experiment, you can fool around with the concentrations until you can just taste them when they are placed on their sensitive taste spot, then make the map again.
Here's a question: can you taste anything on the center of your tongue?
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