Maier Hartman, R. 1 , Schwab, J. 2 , Lew-Williams, C. 2 & Fausey, C. 1
1 University of Oregon
2 Princeton University
Hearing isolated words can potentiate language learning (Brent & Siskind, 2001; Lew-Williams et al., 2011). In everyday speech, do infants encounter isolated words haphazardly or do natural conversations yield structure correlated with isolated word use? In a very large corpus of child-directed speech (English CHILDES ages 0-3 years), we identified three patterns of noun use: isolated (only word in utterance), clustered (used at least three times within six utterances), and isolated-within-clusters (at least one isolated utterance in a cluster). Notably, isolated nouns were used again in the same interaction with fewer intervening utterances (M=3.14) than non-isolated nouns (M=8.82), p<.001. Isolated nouns were also more likely to be clustered than expected by chance (Cramer?s V=.07, p< .001). Finally, MCDI nouns encountered as isolated-within-clusters were more likely to be produced by 24-month-old children than those without this profile (t(374)=4.56, p<.001; controlling for frequency). We suggest that "isolated" is a misnomer, in both characterizing the input as well as the learning mechanism. When children hear a noun in isolation, they often have heard it recently or will again soon. Isolation and repetition together may create moments of local coherence that prove especially helpful in supporting vocabulary growth.