A prospective longitudinal study of language development in late talkers.

This longitudinal investigation charted the course of cognitive and language development from the prelinguistic period to multiword productions in 19 typically developing (TD) toddlers and 4 toddlers who were subsequently identified as having late onset of expressive language. Assessments were conducted at 3-month intervals over a 21-month period, with 12 months of prospective assessment data comparing the TD and late talker (LT) subjects (mean CA: 13 to 25 months) and 9 months of follow-up data (mean CA: 25-34 months) on the 4 subjects who were identified as late talkers at age 2. Three different developmental profiles were identified, and predictors of expressive language outcomes for the LT subjects were evaluated.