Table 2. Study 2: Stability of language across age by groups.

Numbers before the slashes represent correlations controlling for child age only (to control age variation within waves); numbers after the slashes represent correlations controlling for child age, nonverbal intelligence, sociability, and maternal age and education. Correlations of 0.10, 0.30, and 0.50 correspond to small, medium, and large effect sizes, respectively (78).

	6 months → year 1	Year 1 → year 2	Year 2 → year 3	Year 3 → year 7	Year 7 → year 8	Year 8 → year 9	Year 9 → year 13	Year 13 → year 15
Typical (n = 4111)	0.36/0.25	0.68/0.57	0.55/0.48	0.23/0.21	0.60/0.44	0.62/0.52	0.79/0.75	0.48/0.30
Moderate-late preterm (n = 435)	0.33/0.16	0.69/0.55	0.59/0.47	0.34/0.31	0.64/0.49	0.65/0.56	0.83/0.80	0.48/0.35
Very preterm (n = 51)	0.48/0.40	0.81/0.62	0.66/0.54	0.27/0.28	0.55/0.38	0.66/0.53	0.64/0.66	0.50/0.25
Dyslexia (n = 322)	0.37/0.20	0.68/0.48	0.54/0.46	0.27/0.24	0.51/0.39	0.50/0.44	0.82/0.82	0.26/0.24
Autism (n = 89)	0.32/0.12	0.70/0.48	0.65/0.58	0.53/0.49	0.70/0.62	0.71/0.66	0.85/0.81	0.53/0.40
Hearing impairment (n = 221)	0.38/0.26	0.72/0.55	0.58/0.50	0.27/0.27	0.54/0.42	0.58/0.54	0.77/0.80	0.37/0.25