“…Studies of language development in typically developing children find significant differences in the quantity and quality of caregiver speech children receive (e.g., Bee, Van Egeren, Streissguth, Nyman & Leckie, 1969; Farian & Haskins, 1980; Hart & Risley, 1995; Hoff, 2003; Huttenlocher, Vasilyeva, Waterfall, Vevea, & Hedges, 2007; Rowe, Pan & Ayoub, 2005), which are often correlated with background characteristics, such as socioeconomic status (SES). These input differences appear to be related to vocabulary growth (Hart & Risley, 1995; Huttenlocher, Haight, Bryk, Seltzer, & Lyons, 1991; Pan, Rowe, Singer & Snow, 2005) and growth in sentence length (Barnes, Gutfreund, Satterly, & Wells, 1983) and complexity (Huttenlocher et al, in prep).…”