Figure 2.

Combined histograms and density plots for autism spectrum disorder–associated behaviors at 12 and 24 months. The leftmost distributions (enclosed by dashed box) were modeled using Poisson and negative binomial regression, whereas the rightmost distributions were modeled using linear regression. Blue density curves identify variables for which high scores reflect atypical behaviors; red density curves identify variables for which high scores reflect typical behaviors. CSS, calibrated severity score; IJA, initiation of joint attention; Rit/Same, ritualistic and sameness behaviors; RRB, restricted interest and repetitive behavior; V12, 12-month visit; V24, 24-month visit.