This is a follow up to this answer were the OP makes the point that the schwa vowel (a.k.a. central or neutral vowel) is produced when other vowels are reduced to that sound. It makes perfect sense since the brain is just trying to pronounce the words in a very efficient way, with the minimum effort involved in the process.

But what about those languages that don't have a schwa vowel, isn't the brain adapted so the physiognomy, tongue and vocal folds work as little as possible to pronounce clear distinguishable words in those languages?

What do languages without a schwa vowel have in common so the brain is not able to take advantage of this shortcut?

  • 3
    You make it sound like vowel reduction is a braindead simple optimization with no downsides, but each bit of vowel reduction means the brain of the listener must work harder to retrieve the original context, so there's always a tradeoff.
    – jick
    Jul 27, 2017 at 23:09
  • @jick I understand your point, although it remains to see if the neuronal networks needed to distinguish those reduced vowels is considerable grater than the one needed to process non-reduced vowels, and whether that difference in energy consumption is comparable to the one required for the more vigorous movements involved when speaking without reduced vowels. But then we would end up speaking about speculative science.
    – rraallvv
    Jul 28, 2017 at 1:32

3 Answers 3


The basic tendency is that vowel tend to be less differentiated when they are shortened in some way (usually related to stress, of syllable structure), because it is harder to perceive and accurately produce subtle vowel distinctions with significantly reduced duration. But languages differ in terms of how extensive that reduction is: you might reduce all unstressed vowels to one vowel, or eliminate 3 out of 7 vowels. The thing that a vowel reduces to is partially a function of which distinctions are neutralized, and also what the vowel inventory is.

One language that fits the type that you're looking for is Makonde, where unstressed [e,o] become [a] (vowels=[aeiou]). There simply is no vowel schwa in anywhere in Makonde. Another language might be English, because although we have a phonetic schwa, it is in complementary distribution (in unstressed syllables) with the vowel [ʌ]. In the phonological sense, English doesn't have schwa (it does have wedge), although schwa is present phonetically. In talking about languages that "don't have schwa", you have to distinguish "languages with the phoneme /ə/" from "languages without the phone [ə]". Ojibwa is sort of like English (vowels reduce to schwa) except that in Ojibwa, vowel reduction is the only source of schwa.

A third example would be Russian, where unstressed non-high vowels (or at least /a,o/) become "[a]" which is apparently actually pronounced more like [ə] when the stress is 2+ syllables to the right. There is, in addition, some degree of vowel reduction of /u,i/, and the pronounced vowel depends in part on whether the preceding consonant is palatalized (the result being that /e/ and /i/ neutralize, we could say to i pronounced more like [ɪ]).

Catalan is sort of mixed. Unstressed /a,e/ reduce to [ə] which is not an independent phoneme of the language, but /o/ reduces to [u], which is a phoneme. In Chamorro, unstressed [e,o] become [i,u]: this is of interest compared to Makonde, because Chamorro has the vowel system /æɑeoiu/, basically one more vowel than Makonde, but a different output for reduction.

The brain doesn't actually adapt or change in any way: rather, the grammar (which is a set of mental principles allowing people to speak a given language) can be different between languages. There has not been enough research on the different kinds of vowel reduction that exist in human language to be able to explain when reduction of /e, o/ yields [ə] vs [a] vs. [i,u] or similar vowels.

It is also important to keep in mind that not every letter "ə" is actually pronounced [ə]. In Moroccan and Syrian Arabic, there is a vowel which can be the result of reduction, conventionally transcribed as "ə", but which is phonetically closer to [ɨ].

  • 1
    Analysing schwa and STRUT as allophones of the same phoneme is not unproblematic for all accents of English. Some people seem to feel that the adverb "just" always has schwa, not STRUT, even when stressed. Many American English speakers distinguish reduced schwa from word-final schwa, the "roses-Rosa's" distinction (word-final schwa is generally lower). Jul 27, 2017 at 23:14
  • I have the Roses/Rosas distinction, and my judgment is that the epenthetic vowel in the former is [ɨ]; anyhow, the uncertainty of transcription is one of the bigger problems in looking at vowel reduction cross-linguistically.
    – user6726
    Jul 28, 2017 at 0:17

"What do languages without a schwa vowel have in common so the brain is not able to take advantage of this shortcut?"

In Stampe's theory of Natural Phonology, human languages differ phonologically because they have in their histories made different choices about how the brain (and the rest of physiology) must be prohibited from taking advantage of such shortcuts. If a language has schwa among its sounds, speakers of that language must not have learned not to apply any of the "shortcuts" that would remove schwa, and the same goes for any other specific sound.

For instance, sometimes schwas can be lost by being deleted or assimilated to nearby sounds. If such processes are unconstrained, clearly no schwas can be pronounced.


I think the answer to your question actually lies in something you wrote, let me place the emphasis:

isn't the brain adapted so the physiognomy, tongue and vocal folds work as little as possible to pronounce clear distinguishable words in those languages?

The issue is that some languages are structured in such a way that makes it hard to distinguish words unless you can clearly hear all vowels.

Japanese is a great example of this phenomenon. Japanese does not have a schwa sound, it just has five vowels, "a,e,i,o,u". It has some reduction or shortcuts that happen in typical use, but there is no vowel reduction like in English. The reductions or shortcuts typical are of another nature, like leaving out syllables in certain words, or omitting certain vowels in certain syllables in a predictable pattern (i.e. "su" becomes just "s").

In Japanese, nearly all possible syllable combinations made of commonly-used sounds, produce real words. Furthermore, there is considerable overlap: some words are distinguished only by pitch accent, and some words are homonyms even with the pitch accent. It's not at all like in English where if you string together commonly-used sounds, you end up with mostly gibberish.

Because of this, if you slur a single vowel and it gets misheard, someone might hear you as saying a completely different word.

Japanese also does not have stress...it is a "mora-timed" language, meaning it consists of syllables in an equally spaced rhythm.

If you try to speak Japanese and mispronounce vowels by shortening them, Japanese speakers will not always hear the words the way you intend them. For example, I frequently hear English speakers mispronounce Japanese words shortening "a" into the schwa. But native Japanese speakers will sometimes hear the schwa as closer to the "o", depending on context. This can lead people to miscommunicate.

I also think the key or "interesting" characteristic here is not whether or not languages have a schwa sound, but whether or not things reduce unstressed vowels to a schwa sound. Mandarin Chinese has a staggering variety of vowels (far more than Japanese) but, like Japanese, it has tons of homonyms and you need to distinguish all the vowels in speaking because hearing a single vowel differently, will usually result in it sounding like a completely different word. There are vowels in Mandarin Chinese that are very schwa-like, including neutral vowels where you basically leave your mouth in the same shape used to pronounce whatever consonant they follow, and also ones that occur in dipthongs that are very close to the sound of the schwa in English. But they don't play the same role that the schwa does in English.

Also keep in mind, languages can shorten vowels to sounds other than a schwa.

For example, Turkish uses vowel harmony, but it isn't perfect in the sense that like, when you put a suffix on a word, the vowel gets reduced in a certain pattern. Turkish does have a schwa sound too, it is denoted with a dot-less "i", i.e. "I/ı". And sounds are sometimes reduced to this sound, but not always. For example, to make "Adam" into the direct object using the accusative case, it would be "Adamı", so the "a" vowel creates a schwa sound after it in the vowel harmony. But the "e" vowel creates an "i", so for example "Ekmek" becomes "Ekmeği", and the same pattern plays out with other words, like "Yer" (eat) becomes "yerim" (I eat).

If you start learning Turkish, you'll realize that the system of vowel harmony is pretty intuitive...when you speak fast, certain sounds wouldn't get distinguished, but others would.

Basically, I think the "interesting" question here is a little broader. Just having a schwa or not, isn't the same as reducing vowels. Languages can have no schwa-like vowel (like Japanese) and not reduce vowels. Or they can have a schwa-like vowel (like Mandarin) and also not reduce vowels. And they can have a schwa (like English) and reduce vowels to them a lot. Or they can have a schwa (like Turkish) and reduce them sometimes in a sort of predictable pattern in certain circumstances but not in the exact same pattern as English nor as often as English in situations where we would.

And I think, whatever happens, it comes down to the language needing to be understood as it is spoken.

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