The psychological status of a constraint on Japanese consonant alternation

The Japanese consonant alternation known as rendaku is a nonautomatic process whereby morphemes with an initial voiceless obstruent in isolation sometimes occur with an initial voiced obstruent as the second element of compounds or stem-affix formations. A putative phonological constraint known as Lyman's Law states that the initial consonant of a morpheme never undergoes rendaku if that morpheme already contains a voiced obstruent. There are only a handful of exceptions to this constraint in the existing vocabulary, but the experimental results presented here indicate that it is psychologically real only for a small minority of speakers. Since Lyman's Law appears to have been a part of Japanese for centuries, these results raise the problem of accounting for its persistence.