I’ve mentioned in the past that I currently work for Purdue’s Oral English Proficiency Program, where we train international teaching assistants for the classroom. International grad students who have TA funding and whose TOEFL scores are below a certain cut score take a test that was developed internally here at the university, and which grad students (like me) and a few permanent employees rate. Those below a certain point on that scale attend a semester or two of small-group classes and tutoring, so that they can move on to teach our undergrads. It’s a great program to teach for; teaching grad students is a joy, and I learn a tremendous amount about my students’ research interests, as they are evaluated on presentations and mock classes that are dedicated to their area of specialty. It’s also a good opportunity for me to study the oral language-literacy interface, which is a research interest of mine.
I spend a lot of time, as most anyone who tutors or teaches oral English does, working on a particular consonant sound. Or a pair of sounds, to get technical– the voiced and voiceless interdental fricatives, the sounds typically identified by “th” in the Latin orthography and represented as ð and θ, respectively, in the International Phonetics Alphabet. (When you hear the word “voiced” in phonetics, think of vibration– say “this” and then “thing,” and note the way your tongue vibrates against your teeth with the former and not with the latter. That’s the difference between voiced and voiceless.) These sounds are notoriously hard for many learners of English.
It’s not unusual for second language learners to have difficulty with producing particular sounds; many native speakers of Western languages have despaired at ever faithfully reproducing the tonal systems common to Chinese languages and dialects, for example. What’s unusual about the interdental fricatives is that they are so difficult for such a large variety of learners– they’re hated in equal measure by learners from France, and from Russia, and from Iran, and from China. Oftentimes, language learners struggle with sounds that are not found in their home languages. Speakers of many eastern Asian languages, for example, have a well-known difficulty with distinguishing the lateral liquid consonant /l/ from the rhotic liquid consonant /ɹ/. (Despite the popular understanding, this error is actually less common in the initial position, like the contrast between “lice” and “rice,” and much more common in medial positions, like substituting “armost” for “almost.”) These difficulties are understandable: minimal pairs, or the smallest differences in sound that can distinguish between different meanings for a given language, are thought to imprint themselves on native speakers by six months old.
It’s the diversity in language background of the many people that struggle with these particular sounds that makes them unusual. There’s just very few languages that utilize the interdental fricatives. Perhaps that’s sensible, given the name: “interdental,” after all, comes from the fact that the tongue is stuck fully between the teeth to produce the sound. That’s a somewhat precarious position, making biting your tongue much more likely, and it isn’t unexpected that many languages would have evolved to avoid this tendency. Very often, non-native English speakers actually end up producing a /z/ sound. This is a result of what we sometimes call “cheating;” the speaker does not fully commit to putting the tongue all the way through the teeth, but will leave it just short of the opening of their teeth. The space for air to pass between the teeth and open the tongue creates the characteristic “z” sound.
I’ve found that, unlike some other pronunciation difficulties like vowel substitutions, most learners can actually produce this sound fairly easily– they just have to stop and think to do it. Unfortunately, stopping and thinking is a major impediment to actual oral communication, which relies on speed and fluency to maintain a natural speech rate. I had a French student once, very dedicated and smart young woman, who would pronounce the sound reliably when she was practicing with me, but when she would take a practice TOEFL test, would collapse into a long series of “ze”s instead of “the”s. Once her mental attention was on the other aspects of the test, rather than on the production of that sound, she lost it. I’m not saying that students can’t improve on this articulation; I’ve seen it myself. It just takes constant repetition and the development of muscle memory, as is involved in a lot of language learning. But this one is particularly widespread and particularly problematic, in no small part because it is so deeply ingrained in our functional vocabulary (then, than, the, this, these, those, them….).
For this reason, some phonologists and historical linguists suspect that these sounds will eventually disappear from English. I searched and searched and I can’t find a convenient citation for you guys (if you know of one, send it along). For me it’s more of a matter of picking it up from people I meet at school and at conferences, etc. It’s an interesting question. World Englishes is a potentially rich field. There is no doubt that English is expanding its domain, and there is, I think, very legitimate cause to worry about the demise of traditional languages that are part of what gives the human species its diversity, our great strength. But we should also recognize that as we internationalize English, English is internationalized, and there’s no way that the hundreds of millions of Chinese learners of English (to pick one example) won’t make their own mark on what “standard” English consists of. There are some sounds that pretty much have to exist in a given language, just as there are some grammatical distinctions that we can’t wish away. (Singular “their” is not really a problem, but the “your/you’re” distinction can’t be done away with nearly as easily.) But the interdental fricatives? We could survive with them being replaced by /z/ or /d/. I almost never misunderstand my students thanks to this sound substitution, which is certainly not the case for others.
I won’t live to see the demise of the “th,” at least not here in the States. If I did, I’m sure I would miss it. I am a living language believer– I think prescriptivists just misunderstand how language works, in a basic sense. At the same time, I also think that those who argue against prescriptivists end up falling into a prescriptivism of their own, which is to in effect argue that language must be the way that they perceive it to be changing into. Old meanings may change, but they only do because people acquiesce to them changing. Language is personal, intrinsic, even existential, and you’ve got to let people mourn what they grew up with. I’d miss the “th.” But my grandkids or great-grandkids? I wouldn’t be surprised if they grow up into a world where nobody is foolish enough to stick their tongue between their teeth when they speak.