Longitudinal Relations Between 2-Year-Olds' Language and 4-Year-Olds' Theory of Mind

Maternal reports of child vocabulary, utterance length, morpheme usage, and sentence complexity and experimenter-assessed receptive and expressive language were obtained at the end of the 2nd year for European American middle-class toddlers (N = 27). Maternal verbal intelligence and socioeconomic status were also measured. At 48 months of age, children's false-belief understanding and verbal intelligence were evaluated. Individual differences in child language at 24 months and child verbal IQ at 48 months predicted unique variance in performance on the false-belief tasks at 48 months, although only the early language factor findings were statistically significant. These findings demonstrate previously unobserved relations between early language and later acquisition of complex concepts related to mind.