Phonemic Categorization and Phonotactic Repair as Parallel Sublexical Processes
Phonemic perception exhibits coarticulation sensitivity, phonotactic sensitivity and lexical sensitivity. Three kinds of models of speech perception are found in the literature, which embody different answers to the question of how the three kinds of sensitivity are related to each other: two-step models, one-step models and lexicalist models. In two-step models (Church, 1987), phonemes are first extracted, and phonotactic repairs are subsequently made on the obtained phoneme string; both phonemic categorization and phonotactic repair are sublexical, and coarticulation sensitivity should only affect initial (pre-phonotactic) phonemic categorization. In one-step models (Dehaene-Lambertz et al., 2000; Dupoux et al., 2011; Mehler et al., 1990), phonemic categorization and phonotactic repair are sublexical and simultaneous; phonotactic repairs themselves depend on coarticulation cues. Such models can be implemented in two different versions: suprasegmental matching, according to which a speech signal is matched against phonotactics-respecting suprasegmental units (such as syllables), rather than phonemes, and slot filling, according to which a speech signal is matched against phonemes as fillers for slots in phonotactics-respecting suprasegmental units. In lexicalist models (Cutler et al., 2009; McClelland & Elman, 1986), coarticulation sensitivity and/or phonotactic sensitivity reduce to lexical sensitivity. McClelland & Elman (1986) claim a lexicalist reduction of phonotactic sensitivity; Cutler et al.'s (2009) make a claim implying lexicalist reductions both of phonotactic sensitivity and of coarticulation sensitivity. This thesis attempts to distinguish among those models. Since different perceptual processes are assumed in these three models (whether sublexical units are perceived, or how many stages are involved in perceptual processing), our understanding of how speech perception works crucially depends on the relative superiority of those three kinds of models. Based on the results available in the past literature on the one hand, and on the results of perceptual experiments with Japanese listeners testing their coarticulation sensitivity in different settings on the other, this thesis argues for the superiority of the slot filling version of one-step models over the others. According to this conclusion, phonemic parsing (categorization) and phonotactic parsing (repair) are separate but parallel sublexical processes.