Incremental word processing influences the evolution of phonotactic patterns

Listeners incrementally process words as they hear them, progressively updating inferences about what word is intended as the phonetic signal unfolds in time. As a consequence, phonetic cues positioned early in the signal for a word are on average more informative about word-identity because they dis-ambiguate the intended word from more lexical alternatives than cues late in the word. In this contribution, we review two new findings about structure in lexicons and phonological grammars, and argue that both arise through the same biases on phonetic reduction and enhancement resulting from incremental processing. (i) Languages optimize their lexicons over time with respect to the amount of signal allocated to words relative to their predictability: words that are on average less predictable in context tend to be longer, while those that are on average more predictable tend to be shorter. However, the fact that phonetic material earlier in the word plays a larger role in word identification suggests that languages should also optimize the distribution of that information across the word. In this contribution we review recent work on a range of different languages that supports this hypothesis: less frequent words are not only on average longer, but also contain more highly informative segments early in the word. (ii) All languages are characterized by phonological grammars of rules describing predictable modifications of pronunciation in context. Because speakers appear to pronounce informative phonetic cues more carefully than less informative cues, it has been predicted that languages should be less likely to evolve phonological rules that reduce lexical contrast at word beginnings. A recent investigation through a statistical analysis of a cross-linguistic dataset of phonological rules strongly supports this hypothesis. Taken together, we argue that these findings suggest that the incrementality of lexical processing has wide-ranging effects on the evolution of phonotactic patterns.