Lexical exceptions in stress systems: Arguments from early language acquisition and adult speech processing

The occurrence of lexical exceptions in languages with fixed stress is subject to several crosslinguistic generalizations. These typological facts are explained within a framework of early language acquisition and its consequences for adult speech processing. Under the assumption that lexical exceptions to stress rules can only occur in a language if its native speakers can perceive stress contrasts, it is argued that the presence of lexical exceptions depends upon the age at which infants discover the stress rule of their language. If the stress regularity is easy to infer from the surface speech stream, then it will be acquired very early, and stress will not be encoded in the phonological representation of words in the mental lexicon; as a consequence, stress contrasts are not well perceived by adult speakers and lexical exceptions are excluded. If, by contrast, the regularity is difficult to infer, then it will be acquired relatively late, after the format of the phonological encoding of words has been fixed. That is, stress will be redundantly encoded in the mental lexicon, and lexical exceptions can thus be stored and processed by adult speakers. This proposal is supported by experimental psycholinguistic data, showing that native speakers of some but not all languages with purely phonological stress rules fail to perceive foreign stress contrasts. Finally, it is shown that within metrical phonology, it is hard to accommodate all the data explained in the proposed acquisition & processing account.