How morphological structure affects phonetic realisation in English compound nouns

Many studies have shown that syntagmatic and paradigmatic aspects of morphological structure may have an impact on the phonetic realisation of complex words (e.g. Cohen 2014a,b; Kuperman et al. 2007; Lee-Kim et al. 2013; Lõo et al. 2018; Plag et al. 2017; Schuppler et al. 2012; Smith et al. 2012; Sproat and Fujimura 1993; Zimmermann 2016, among many others). The majority of these studies have been concerned with affixes, often focusing on the acoustic properties of segments at a morphological boundary. The present study extends this line of investigation to compounds, exploring the extent to which consonant duration at compound-internal boundaries in English is dependent on morphological structure. Three competing hypotheses about the relationship between fine phonetic detail and morphological structure are tested. According to the Segmentability Hypothesis, greater morphological segmentability, i.e. a stronger morphological boundary, leads to acoustic lengthening (Ben Hedia and Plag 2017; Hay 2003; Plag and Ben Hedia 2018). The Informativity Hypothesis, on the other hand, states that higher informativity leads to lengthening (e.g. Jurafsky et al. 2001; van Son and Pols 2003). Finally, the Paradigmatic Support Hypothesis says that stronger paradigmatic support leads to lengthening (Cohen 2014b; Kuperman et al. 2007). To test these hypotheses, an experimental study was carried out using 62 compound types taken from the British National Corpus. The compounds were spoken by 30 speakers, yielding more than 1500 acoustic tokens overall. The data provide no support for the Segmentability Hypothesis, and only limited support for the Informativity Hypothesis. In contrast, the Paradigmatic Support Hypothesis makes correct predictions: consonant duration at compound-internal boundaries is positively correlated with the probability of the relevant consonant following the first noun, and the duration of compound-internal geminate consonants is negatively correlated with the family size of the first noun. In other words, longer durations are associated with lower paradigmatic diversity.