Electropalatographic (EPG) evidence of covert contrasts in disordered speech.

The phenomenon of covert contrasts has intrigued researchers and clinicians since it was first identified using instrumental data nearly 50 years ago. The term covert contrast refers to phonological contrasts that listeners do not readily identify and which therefore pass unrecorded in transcription-based studies. Covert contrasts are viewed as significant from theoretical and clinical perspectives. Although influential, there are relatively few instrumental studies of covert contrasts. The studies that do exist are limited to revealing contrasts that manifest in specific phonetic parameters or phonological processes. However, recent studies have provided convincing new evidence that covert contrasts are likely to be widespread in child speech. The purpose of this article is threefold: to review electropalatography (EPG) studies of covert contrasts; to provide EPG examples from the speech of individuals with speech disorders and to discuss the implications in child speech.