Modeling the role of distributional information in children's use of phonemic contrasts

Between the first and the second year of life, children improve in their ability to use phonemic contrasts when learning label-object pairings. This improvement may be related to children's experience with the distribution of phonemes across lexical forms. Because phonemes typically occur in different lexical frames (e.g., /d/ and /t/ in “doggy” and “teddy” rather than “doggy” and “toggy”), familiarity with words makes similar phonemes more distinct through acquired distinctiveness. In a series of simulations, we demonstrate that English input has the distributional characteristics necessary to facilitate use of phonemic contrasts as a function of increasing familiarity with the lexicon. Further, these simulations support a novel prediction: that less common phonemes should take longer to be used productively. We tested this prediction with children between 18 and 25 months, and found that the relatively infrequent /s/ and /z/ contrast takes longer to emerge than frequent contrasts such as /b/-/d/ or /d/-/t/.