Some critical developments in acquiring native language sound organization during the first year.

Although infants are born with rather sophisticated capacities for discriminating and categorizing speech sounds, they still must learn about the sound organization of their native language. Before 6 months, infants show relatively little sensitivity to native language versus non-native language sound organization. Shortly thereafter, infants recognize which sounds and sound sequences and rhythmic patterns are likely to appear in native language words. Knowledge of these features plays a critical role in how and when infants segment words from fluent speech. Word segmentation abilities develop rapidly between 7.5 and 10.5 months. Initially, English-learners segment words using stress cues. Soon after, they learn to use other potential cues to word boundaries. As their lexicons develop during the second year, they begin to use information about known words in segmenting and learning new words.