In the second assignment, we're trying to address a myth in the field; whether there is a taste map on our tongue. There's a lot of dispute about that. So let's see whether we would be able to address what, actually, is a taste map. Now, in this assignment, we have roughly 2,500 students participating. So, we are asking students to put on their tongue, in different region, with different solutions, no matter is salty, sour, sweet or bitter. And we ask students to give a score whether, when they put that solution on the tongue, they would have some level of intensity on that specific sensation. So let's look at the result. The first group is using the salty solution. So we expect that the student to find the solution salty. The interesting thing is that, when we look at all the reporting, we find that, no matter where when we put the solution at the position A, B, C, and D, that means from the back of the tongue, to the tip of the tongue, in every single part, majority of students from 80 to 90 percent of them they would be able to tell us that that's a salty solution. Now, there are few things I would like you to pay attention to. Interestingly, we find that the solution is salty, yet there are students who reported that they sense from sourness, sweetness, and bitterness For example, in position A; the same thing happened in the other positions, too. So suggesting that there's a lot of false input or the perception that the students sense, and it may not be related to the actual taste. The second thing is that when you comparing different positions, in position C, which is on the lateral side closer to the front of the tongue, this salty solution of salty sensation, in fact, gave a higher intensity, is 2.83 compared with the sensation level in the other area, which is from 2.0 something or 2.5 something, suggesting that, in position C, the sensation of saltiness actually is strongest. Now a very similar type of observation is made when we are trying the second group using the sour solution. The same thing happened is that no matter is in position A, B, C, and D. The sensation of sourness was detected. And for the same observation, if you look at position B, which is on the more anterior side on the lateral part of the tongue, the sensation of sourness gave you a stronger intensity, 2.8 something, as compared to 2.1 something or 2.4 something in the other regions. When we come down to the thirds test, the sweet solution, the same was observed. That means no matter is in position A, B, C, and D, students were able to sense the sweetness. Although, if you look at position D, which is the tip of the tongue you'll find that the strength of this sensation goes up to 3.13, way higher than the other, which is at the level of 1.9 to 2.3 something. Now, when you look at the fourth solution, which is the bitter solution, a very similar observation is made, that is, if you try A, B, C, and D position, every single part they would be able to sense that bitterness. On the other hand, at position A, you'll find that the intensity of that sensation is the strongest. Now, when you look at that, essentially, it tells you two things. In the general understanding, we always thought that, or we were taught in the past, there is a taste map suggesting that one part of your tongue is sensing a particular sensation - sweetness, saltiness, sourness, or bitterness. On the other hand, this exercise clearly tells you that, in fact, all these four tastes they can be sensed on every single part of our tongue. Why? Because these tastes need to be perceived because of the presence of certain taste receptors. And these receptors are distributed all over your tongue and so, therefore, no matter where you put this solution,you would be able to sense that taste. On the other hand, if you look at the intensity of the response, again, which is related to the lumber of receptors available in a particular region, you will find that there are regions which give a stronger sensation, a perception, for a specific taste. Such as in the position A you find that the strongest sensation will be detected for the bitterness, and in position D, which is at the tip of the tongue, in fact, the sensation of sweetness is highest. So, what it tells you is that, yes, these receptors, they are widely distributed on the tongue, however, the density are different. And of course, based on input from our students and there are various reports in the forum, we noticed that some students also say that, well, they detect a different strength, different intensity, and sometimes, students even don't detect certain tastes when solution are put in certain area. What it tells you is that in fact, no single person is identical and there's no fixed answer of a fixed taste map. It varies from person to person; but as a whole, as a big population that we have tested, certainly, the distribution and the density of this receptor for specific taste, they are not even throughout entire tongue. There are some regions with more bitter receptor, there are some regions with more sour receptor, salt receptor, and sweet receptor. And so having that, next time when you try any meal you may notice that it really depends on where you put the food item onto your tongue. It may trigger a different intensity or sensation. And so we should learn about that. So that in the future you try the food in a very different way.
