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.
a /eɪāayeɪāayeɪāayˈˈˈˈˈˈˈˈˈ/ > /əəəəəəəəə/
to /tttttttttuo͞oueuo͞oueuo͞oueˈˈˈˈˈˈˈˈˈ/ > //tə//
for /fffffffffoōohoōohoōohˈˈˈˈˈˈˈˈˈrrrrrrrrr/ and /fffffffffɔôawɔôawɔôawˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /fffffffffɚûrurɚûrurɚûrur/
or /oōohoōohoōohˈˈˈˈˈˈˈˈˈrrrrrrrrr/ and /ɔôawɔôawɔôawˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /ɚûrurɚûrurɚûrur/
our /ɑʊowowɑʊowowɑʊowowˈˈˈˈˈˈˈˈˈɚûrurɚûrurɚûrur/ and /ɑʊowowɑʊowowɑʊowowˈˈˈˈˈˈˈˈˈrrrrrrrrr/ > /ɑäahɑäahɑäahˈˈˈˈˈˈˈˈˈrrrrrrrrr/