The contrastive hierarchy in phonology 2009 Dresher.pdf - CUNY ...

The only minimal pairs are {i, e} and {o, u}; the features [back] and [round]
double each other for every vowel except /a/, making each other logically
redundant, but not leaving behind enough features to make a contrast between
/i, u/ and /e, o/, and leaving /a/ without any contrastive feature.
The same point applies a fortiori with the simple three-vowel system /i, a,
u/. If we confine ourselves to two features, say [high] and [round], the vowels
fall into minimal pairs and the pairwise method can assign them distinct
representations.
(2.20) Three-vowel system, features [high], [round]
a. Full specifications
i a u
high + – +
round – – +
b. Specifications according to the pairwise method
i a u Minimal pairs
high + – {i, a}
round – + {a, u}
Adding one more feature, say [back], wipes out the minimal pairs (2.21),
causing the pairwise method to fail to distinguish them.
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