Two-year-old children's processing of two-word sequences occurring 19 or more times per million and their influence on subsequent word learning.

We know that 8-month-old infants track the statistical properties of a series of syllables and that 2- and 3-year-old children process familiar phrases more efficiently than unfamiliar phrases, but less is known about the intermediary level of two-word sequences. In Study 1, 2-year-olds (N = 45, mean age = 651 days) heard two-word sequences consisting of a prime word followed by a noun, with two pictures appearing on the screen (depicting the noun and a distractor). Eye tracking showed that children looked more quickly at the noun picture for two-word sequences occurring an average of 19 times per million and 206 times per million in child-directed speech than for novel sequences. In Study 2, corpus analyses showed that 2-year-olds' noun learning increased in line with the frequency of the two-word sequence that preceded it in caregiver speech utterances. This effect holds even after controlling nouns for frequency in caregiver speech, phonemic length, neighborhood density, phonotactic probability, and concreteness and after removing nouns produced in isolation by caregivers and nouns produced by children before being produced by caregivers. These studies show that young children's language processing is facilitated by known two-word sequences, allowing children to focus on more novel aspects of the utterance. Such efficiencies are far-reaching because nearly two thirds of child-directed utterances contain two-word sequences with frequencies of 19 or more per million.