Lexical viability constraints on speech segmentation by infants

The Possible Word Constraint limits the number of lexical candidates considered in speech recognition by stipulating that input should be parsed into a string of lexically viable chunks. For instance, an isolated single consonant is not a feasible word candidate. Any segmentation containing such a chunk is disfavored. Five experiments using the head-turn preference procedure investigated whether, like adults, 12-month-olds observe this constraint in word recognition. In Experiments 1 and 2, infants were familiarized with target words (e.g., rush), then tested on lists of nonsense items containing these words in ââ"šÂ¬Ã…"possibleââ"šÂ¬Ã‚ (e.g., ââ"šÂ¬Ã…"niprushââ"šÂ¬Ã‚ [nip + rush]) or ââ"šÂ¬Ã…"impossibleââ"šÂ¬Ã‚ positions (e.g., ââ"šÂ¬Ã…"prushââ"šÂ¬Ã‚ [p + rush]). The infants listened significantly longer to targets in ââ"šÂ¬Ã…"possibleââ"šÂ¬Ã‚ versus ââ"šÂ¬Ã…"impossibleââ"šÂ¬Ã‚ contexts when targets occurred at the end of nonsense items (rush in ââ"šÂ¬Ã…"prushââ"šÂ¬Ã‚Â), but not when they occurred at the beginning (tan in ââ"šÂ¬Ã…"tanceââ"šÂ¬Ã‚Â). In Experiments 3 and 4, 12-month-olds were similarly familiarized with target words, but test items were real words in sentential contexts (win in ââ"šÂ¬Ã…"windââ"šÂ¬Ã‚ versus ââ"šÂ¬Ã…"windowââ"šÂ¬Ã‚Â). The infants listened significantly longer to words in the ââ"šÂ¬Ã…"possibleââ"šÂ¬Ã‚ condition regardless of target location. Experiment 5 with targets at the beginning of isolated real words (e.g., win in ââ"šÂ¬Ã…"windââ"šÂ¬Ã‚Â) replicated Experiment 2 in showing no evidence of viability effects in beginning position. Taken together, the findings suggest that, in situations in which 12-month-olds are required to rely on their word segmentation abilities, they give evidence of observing lexical viability constraints in the way that they parse fluent speech.