For me, the best part of the 2009 Star Trek movie was the scene where Kirk tries to pick up Uhara in a bar. After she says he probably doesn’t know what Xenolinguistics is, he replies:
The study of alien languages. Morphology, phonology, syntax. Means you’ve got a talented tongue.
Well. Four out of five isn’t bad. Linguists know about language, not the languages themselves–so tongue talents are a skill that linguists only develop tangentially. (Although, of course, a lot of linguists do end up learning the languages they work on.) But knowing about tongues is still pretty useful. For example, it helps explain why tongue twisters are so hard.
Basically, your tongue is a muscle like any other muscle, and it has certain limits. For example, there’s just a certain upper limit to how fast you can type, knit or eat, you can only produce recognizable words so fast. In addition to speed, however, there are certain motions that are difficult to make. Linguists often refer to correctly producing a given sound as “hitting an articulatory target”, and that’s a useful metaphor. For each sound in your repertoire, your tongue (and other parts of your articulatory system) have to be in certain positions.
Exercise time! Try saying “s sh s sh s sh” and “t k t k t k”. In the first, the tip of your tongue should move from that little ridge in your mouth (just behind your front teeth) to behind that ridge. In the second, the “t” sound should be made with the tip of your tongue against the roof of your mouth, and the “k” with the very back of your tongue. (I’m assuming that you have the “sh” sound in your native language, otherwise this exercise might have been a little fruitless for you. Sorry.)
You might have noticed that it was a little easier to make the “t k” sound than it was the “s sh” sound. That’s because you’re using two different parts of your tongue to make the “t k” pair, so while one is making a sound, the other is preparing to and vice versa. On the other hand, if your only using the very tip of your tongue, you have to finish one task before you can move onto the next, so your rate of making sounds is much lower. It’s the same reason that assembly lines are so much faster–you don’t have the additional time it takes to switch tasks. (BTW, that’s why, if you play a wind instrument, you can tongue faster with “t k t k” than “t t t t”.)
Ok, so we have two pressures working against your ability to produce tongue twisters. The first is that your tongue can only move so fast. You can train it to move faster, but eventually you will (barring cybernetic implants) reach the limits of the human body. Secondly, you have limited resources to make sounds, and when sounds that draw on the same resources are produced too close together, they both become more difficult to produce, and the speed at which you can produce them is reduced even further.
And that wraps it up for tongues, because the dirty secret of tongue twisters is that they’re mainly actually brain twisters. But I’ll cover that in part two. That’s right: brraaaaaaains.