Transitional probabilities and positional frequency phonotactics in a hierarchical model of speech segmentation.

The present study explored the influence of a new metrics of phonotactics on adults' use of transitional probabilities to segment artificial languages. We exposed French native adults to continuous streams of trisyllabic nonsense words. High-frequency words had either high or low congruence with French phonotactics, in the sense that their syllables had either high or low positional frequency in French trisyllabic words. At test, participants heard low-frequency words and part-words, which differed in their transitional probabilities (high for words, low for part-words) but were matched for frequency and phonotactic congruency. Participants' preference for words over part-words was found only in the high-congruence languages. These results establish that subtle phonotactic manipulations can influence adults' use of transitional probabilities to segment speech and unambiguously demonstrate that this prior knowledge interferes directly with segmentation processes, in addition to affecting subsequent lexical decisions. Implications for a hierarchical theory of segmentation cues are discussed.