The vowels in words change depending on stress. When a word is not stressed, a vowel may become a schwa greatly changing its pronunication. In many cases, changes in stress can cause words to incorporate reduced vowels like the schwa. For example, the word a in English is likely to change from a diphthong to a schwa in a sentence when it is not stressed:
I want a new book.
Additionally, the word could change back to a diphthong, if the stress shifts to that word. (e.g., I don't want a stack of books. I just want a book!)
The reduced vowels are a weakened form. In speech, vowels often become more central. In other words the tongue moves less forward, back, up, or down and instead goes to a more central or mid-height. This requires less time and energy. It also changes the acoustic production to a new vowel sound. For cuers, this means that the vowels /ɪĭiɪĭiɪĭi/ an /əəəəəəəəə/ will be used with even greater frequency at the phrase and sentence level.
A common reponse to "how-to" questions in our community is to tell someone "this is how I cue it." However, that is how one might cue a word in that moment and in that context. In reality, we all cue words differently differently based on what is important in that moment.
Take, for example, the word them. If someone were to ask how the word is cued, most word demonstrate using the chin. That is a common pronunciation for the word in isolation. However, in a running sentence where the stress is placed on another word, the vowel may change. The vowel may become a schwa:
No, I want them now!
In the sentence above, the stress is likely to fall on the word no or on now. Because of this shift in stress, the word them may weaken to a schwa.
/eɪāayeɪāayeɪāayˈˈˈˈˈˈˈˈˈ/ > /əəəəəəəəə/
/tttttttttuo͞oueuo͞oueuo͞oueˈˈˈˈˈˈˈˈˈ/ > /tttttttttəəəəəəəəə/
/fffffffffoōohoōohoōohˈˈˈˈˈˈˈˈˈrrrrrrrrr/ and /fffffffffɔôawɔôawɔôawˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /fffffffffɚûrurɚûrurɚûrur/
/oōohoōohoōohˈˈˈˈˈˈˈˈˈrrrrrrrrr/ and /ɔôawɔôawɔôawˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /ɚûrurɚûrurɚûrur/
/ɑʊowowɑʊowowɑʊowowˈˈˈˈˈˈˈˈˈɚûrurɚûrurɚûrur/ and /ɑʊowowɑʊowowɑʊowowˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /ɑäahɑäahɑäahˈˈˈˈˈˈˈˈˈrrrrrrrrr/
Even native English speakers are sometimes surprised by the realization that they use reduced vowels in their everyday communication. Sometimes speakers view these pronunciations as lazy, aberrant, or just plain wrong. Cuers may feel that cueing the full vowel, rather than it's reduced form, may actually provide a better (or perhaps clearer) version on English to deaf children. In fact, caregivers may use more full vowels with hearing infants. Parents use a specialized form of "parentese" speech with many full and elongated vowels. This is only temporary, of course, and some reduced vowels can still be idenitified in samples of parentese speech.
Redced vowels are incredibly common among native English speakers and cuers. They are a fact of English language use. If one were to cue the word to only as /tttttttttuo͞oueuo͞oueuo͞oue/ and never as /tttttttttəəəəəəəəə/, it would likely be perceived by others as less natural. As an experiment, try producing the sentence, I want to go to the store, but use only full vowels. So the word to is /tttttttttuo͞oueuo͞oueuo͞oue/ and the word the is /ðt͟htHðt͟htHðt͟htHiēeeiēeeiēee/.
The sentence above is somewhat stilted by its being separate words pulled from the dictionary. However, even in running conversation, the use of full vowels is likely to give the perception to others that the speaker (or cuer) is non-native. In other words, the use of full vowels is like a foreign accent. In fact, a common feature of many foreign accents is the lack of reduced vowels. By not cueing reduced vowels to deaf cuers, one would essentially foorce upon them an artifical dialect of English.
If speech is a goal for deaf cuers, reduced vowels are essential for natural rhythm, stress, and pronunication. Reduced vowels should be used in everyday interactions, just as one would use with hearing children as they acquire language.
Another important consideration is that deaf children often grow up and teach others to cue. The natural acquisition of reduced vowels helps deaf cuers see, understand, and passively acquire the patterns of English so that they can teach cueing accurately to others.