Phonemes: Lexical access and beyond

Abstract

Phonemes play a central role in traditional theories as units of speech perception and access codes to lexical representations. Phonemes have two essential properties: they are 'segment-sized' (the size of a consonant or vowel) and abstract (a single phoneme may be have different acoustic realisations). Nevertheless, there is a long history of challenging the phoneme hypothesis, with some theorists arguing for differently sized phonological units (e.g. features or syllables) and others rejecting abstract codes in favour of representations that encode detailed acoustic properties of the stimulus. The phoneme hypothesis is the minority view today. We defend the phoneme hypothesis in two complementary ways. First, we show that rejection of phonemes is based on a flawed interpretation of empirical findings. For example, it is commonly argued that the failure to find acoustic invariances for phonemes rules out phonemes. However, the lack of invariance is only a problem on the assumption that speech perception is a bottom-up process. If learned sublexical codes are modified by top-down constraints (which they are), then this argument loses all force. Second, we provide strong positive evidence for phonemes on the basis of linguistic data. Almost all findings that are taken (incorrectly) as evidence against phonemes are based on psycholinguistic studies of single words. However, phonemes were first introduced in linguistics, and the best evidence for phonemes comes from linguistic analyses of complex word forms and sentences. In short, the rejection of phonemes is based on a false analysis and a too-narrow consideration of the relevant data.

Keywords: Access codes to lexicon; Lexical access; Lexical representation; Phonemes; Phonological form; Speech perception; Speech segmentation; Units of speech perception.

Fig. 1

a Hickok’s (2014) neurocognitive model of speech processing (adopted from Hickok, , with minor modifications) recruits phonemes only on the speech production route, whereas speech perception and lexical representations are assumed to operate at the level of (demi-)syllables. b Phonemes as postaccess codes model (Morton & Long, ; Warren, 1976), in which lexical representations are accessed via (allo)phones, with phoneme representations activated after a lexical representation has been retrieved. In both models, the red dotted box includes representations involved narrowly into speech perception/word identification, whereas a blue solid box includes representations available more broadly for language comprehension, including higher-level morphosyntactic and semantic computations (not shown). (Colour figure online)

Fig. 2

A pathway for processing a speech signal en route to word identification, exemplified for the example input camel. While many sources of information are extracted from the acoustic signal in parallel (see text), phonemes serve as access codes to words and morphemes