Mothers' use of infant-directed speech (IDS) may assist infants in decoding language input. IDS is characterized by exaggerated prosodic features (Fernald, 1989), shorter mean length of utterance (Cooper, 1997; Bernstein Ratner, 1996), repetition (Bernstein Ratner, 1996), and more highly clarified acoustic qualities (Bernstein Ratner, 1984; Malsheen, 1980) in comparison to speech directed to adults. However, it is not yet known to what extent such measures of maternal input have long-term impacts on language development. This thesis seeks to test the overarching hypothesis that children who receive more clarified speech input during the prelinguistic stage may be expected to have better language skills at an earlier age than children who receive poorer quality input.