  Why do children learn some words before others? Understanding individual
variability across children and also variability across words, may be
informative of the learning processes that underlie language learning. We
investigated item-based variability in vocabulary development using lexical
properties of distributional statistics derived from a large corpus of
child-directed speech. Unlike previous analyses, we predicted word trajectories
cross-sectionally, shedding light on trends in vocabulary development that may
not have been evident at a single time point. We also show that whether one
looks at a single age group or across ages as a whole, the best distributional
predictor of whether a child knows a word is the number of other known words
with which that word tends to co-occur. Keywords: age of acquisition;
vocabulary development; lexical diversity; child-directed speech;
