Figure 1.

Box-and-whisker plots for key variables. N = 119 except 109 for Test de Vocabulario en Imágenes Peabody: Adaptación Hispanoamericana (TVIP; Dunn et al., 1986) and N = 115 and 116 for mother response percentage at Visits 1 and 2, respectively. The box includes scores from the 25th to the 75th percentile. The whiskers indicate the lowest and highest scores that are not extreme. Extreme scores, defined as any 1.5 times the interquartile range below the 25th or above the 75th percentile, are indicated with circles (Tukey, 1977). MLU = mean length of utterance; NDW = number of different words; MTL = mean turn length (higher values indicate less turn-taking). Children's mean ages at Visits 1 and 2 were 2.5 and 3.6 years, respectively.