Covert contrast in the acquisition of second language phonology

This paper reports results on the acquisition of the English /s/ – /z/ phonemic contrast by native speakers of Spanish. The central finding is that some of the research participants exhibited a covert contrast between these segments in their interlanguage productions. Acoustic analysis revealed that four of the participants produced a statistically reliable distinction between English [s] and [z], however, this difference was not perceived by the transcribers who were phonetically trained, native speakers of English. The existence of a stage of covert contrast in L2 phonology is eminently plausible, given the progressive nature of phonological acquisition, and brings the learning of second-language contrasts into conformity with findings in the areas of L1 acquisition and phonologically disordered speech.