Late-talking toddlers: MLU and IPSyn outcomes at 3;o and 4;o

Expressive language outcomes measured by MLU and the Index of Productive Sy ntax (IPSyn) at ages 3;0 and 4;0 were investigated in 34 late talkers with normal receptive language identified between 2;0 to 2;7 and 16 typically de veloping comparison children matched on age, SES, and nonverbal ability. La te talkers made greater gains than comparison children between 3;0 and 4;0 in both MLU and IPSyn raw score. However, when age-standardized x-scores we re analysed, the late talkers were about 2.5 Standard deviations below comp arison children on both measures at both ages. At 3;0, 41 % of the late tal kers had MLUs above the 10th percentile based on Scarborough's (1990) bench mark sample; by 4;0, 71 % did so. Using the IPSyn, a more stringent measure , 34% scored above the 10th percentile at 3;0 and only 29 % did so at 4;0. MLU was significantly correlated with the IPSyn at both ages for the late t alkers, but only at 3;0 for the comparison children. A converging set of re gression analyses indicated no group differences in the predictive relation ship between MLU and IPSyn, suggesting that the late talkers were delayed o n both measures but not deviant in their development.