This paper analyzes the asymmetric vowel coalescences pattern and palatalization of Okayama Japanese within the framework of Optimality Theory. The coalescence pattern of Okayama Japanese is similar to that of the Bingo dialect of Hiroshima Prefecture.
However, the emergence of a fused vowel like [tja:], [tsa:], [tjo:], [tso:], [dja:] and [djo:] is specific to this dialect. Most Japanese dialect studies tend to describe the phonological characteristics of a target dialect based on Hattori's (1951, 1960, 1979) phonemic system, especially /t/ and /c/. This tendency is shown in the previous studies for Okayama Japanese vowel coalescence. However, Hattori's system presents several problems in terms of distinctiveness and distribution.
I will account for the emergence of [tja:], [tsa:], [tjo:], [tso:], [dja:] and [djo:] by assuming input /t/, and by postulating morphologically privileged constraint and OO correspondence constraint, both of which prohibit affrication.