Language-general biases and language-specific experience contribute to phonological detail in toddlers' word representations.

Although toddlers in their 2nd year of life generally have phonologically detailed representations of words, a consistent lack of sensitivity to certain kinds of phonological changes has been reported. The origin of these insensitivities is poorly understood, and uncovering their cause is crucial for obtaining a complete picture of early phonological development. The present study explored the origins of the insensitivity to the change from coronal to labial consonants. In cross-linguistic research, we assessed to what extent this insensitivity is language-specific (or would show both in learners of Dutch and a very different language like Japanese), and contrast/direction-specific to the coronal-to-labial change (or would also extend to the coronal-to-dorsal change). We measured Dutch and Japanese 18-month-old toddlers' sensitivity to labial and dorsal mispronunciations of newly learned coronal-initial words. Both Dutch and Japanese toddlers showed reduced sensitivity to the coronal-to-labial change, although this effect was more pronounced in Dutch toddlers. The lack of sensitivity was also specific to the coronal-to-labial change because toddlers from both language backgrounds were highly sensitive to dorsal mispronunciations. Combined with results from previous studies, the present outcomes are most consistent with an early, language-general bias specific to the coronal-to-labial change, which is modified by the properties of toddlers' early, language-specific lexicon.