Gaps in factorial typology: The case of voicing in consonant clusters

In many languages, a voiceless obstruent cannot occur after a nasal. In some languages such a sequence is avoided through voicing assimilation, but in others through deletion of the nasal or of the obstruent, or changing the nasal into an oral stop. This variety of responses can be expressed in OT through different constraint rankings. Other ways of avoiding such a sequence, such as epenthesis or metathesis, are not attested. These patterns correspond to rankings that are unattested. It is shown that such gaps in factorial typology are pervasive, and cannot be addressed through ad hoc revisions of the constraints or representations. It is argued that the attested rankings correspond to patterns that arise through simple sound changes from phonetic patterns, while the unattested rankings cannot have such an origin. This approach suggests phonetics influences not only markedness in phonology, but also constraint ranking.