Pre-aspiration and the problem of zeroes: Phonological rules can be variable

Pre-aspiration can be defined as a period of glottal friction, [h], which is found in the sequences of sonorants and phonetically voiceless obstruents, as in map [ma^hp^h] (e.g. in Welsh English, Hejná 2015). This chapter problematises the default approach to pre-aspiration shown in a number of studies, which assume that unless pre-aspiration applies obligatorily it is subject only to phonetic constraints rather than, at least potentially, both phonetic and phonological constraints. As a result, instances where pre-aspiration reaches the duration of 0 ms, i.e. where it does not apply (mat [mat^s]), are typically included in the analyses of its phonetic conditioning. This can be problematic in cases where zero values reflect a variable phonological rule rather than the output of solely phonetic constraints as such an approach may obscure our understanding of the constraints on pre-aspiration.