The predictive power of optimality theory for phonological treatment.

The phonology and clinically induced learning patterns of a female child with a phonological delay (age 4;11) were examined from the analytical perspective of Optimality Theory. The analysis revealed that a Consonant Harmony error pattern affected alveolar stops from two different sources-from underlying lexical representations and from representations derived by an interacting error pattern of Deaffrication. The implications of that analysis for the selection of treatment targets were explored in a treatment study. It was found that treatment aimed at the derived source of Consonant Harmony resulted in the suppression of both Consonant Harmony and Deaffrication. The explanation for these results was attributed to a fixed ranking among certain constraints.