New cuers frequently have difficulty distinguishing the vowels /ɑäahɑäahɑäah/ (as in cot) and /ɔôawɔôawɔôaw/ as in (caught). For many dialects in English, these two vowels are contrastive and can be used to make different words.
The vowel /ɑäahɑäahɑäah/ as in cot is cued as a side-forward movement. In spoken English, the vowel is open and the tongue is low and back. The position of the tongue for this vowel is why doctors ask patients to say "Ah!" when examining the throat. Producing the vowel makes the tongue move down and out of the way and provides a reletively unobstructed view.
The vowel /ɔôawɔôawɔôaw/ as in caught is cued at the chin placement. In spoken English, the jaw drops bringing the sides of the mouth slightly in. The tongue is generally positioned low (but likely higher than /ɑäahɑäahɑäah/) and the back in the mouth.
These vowels are highly interchangeable in many dialects. Many words may be pronounced either way – (hot/hot, Boston/Boston). In some cases, a cuer may even alternate between the pronunciations of certain words depending on where they occur in the sentence or whether they are stressed (e.g., off/off, on/on, honk/honk).
In some regions of the United States, the vowels /ɑäahɑäahɑäah/ and /ɔôawɔôawɔôaw/ have merged. For example, in parts of the west (like Utah and Idaho), these vowels have lost their distinction. Words like cot/caught are both pronounced with the vowel /ɑäahɑäahɑäah/ (side-forward).
In other regions, like the Northeast U.S. and Canada, the vowels have merged and are likely pronounced as /ɔôawɔôawɔôaw/ (chin placement). For them, the words cot/caught will both be cued with /ɔôawɔôawɔôaw/.
Instructors will sometimes encourage beginners to examine the word hotdog to decide if the vowels are the same in each syllable or different. For many, the vowels in this word are hot (side-forward) and dog (chin placement). But for others, the both syllables may be cued with a side-forward movement or at the chin placement.
In general, substitution errors by new cuers of /ɑäahɑäahɑäah/ and /ɔôawɔôawɔôaw/ have relatively little impact as an error would reflect a possible pronunciation in Engish even if that pronunciation is incorrect for that cuer. Sometimes, these vowels are also confused with /æăaæăaæăa/ like hat (throat placement). Confusion with this vowel is a more serious priority since cat is not likely to be pronounced like caught in any dialect.