Abstract
Early vocabulary knowledge and speed of word processing are important foundational skills for the development of preschool and school-age language and cognition. However, the variance in outcomes accounted for by parent-reported receptive or expressive vocabulary is generally modest. Recent research suggests that directly assessed, decontextualized vocabulary predicts developmental outcomes, including general language ability and kindergarten readiness, accounting for additional variance above and beyond parent-reported vocabulary. The current research extends this finding by exploring prediction from both decontextualized vocabulary and speed of word processing at 2 years of age to vocabulary during the preschool period. At age 2, children completed a two-alternative forced-choice task that yielded a measure of decontextualized vocabulary (number of correct touch responses) and two measures of speed of processing: latency to fixate the target (visual response latency) and latency to touch (haptic response latency). Results reveal that age 2 vocabulary and visual response latency, but not haptic response latency, independently predict vocabulary at ages 3 and 4. Furthermore, only decontextualized vocabulary remains a significant predictor when controlling for speed of processing, but not vice versa. This suggests that the number of early, stable word-referent associations and the efficiency with which these are processed are important to vocabulary outcomes. However, it also suggests that decontextualized vocabulary may be a more robust unique predictor of downstream outcomes.