Genetic and environmental contributions to video-referenced ratings of reciprocal social behavior in toddler twins

Reciprocal social behavior (RSB; the capacity to engage in social behaviors with others) is a primary deficit among individuals with autism spectrum disorders (ASDs). The video-referenced Rating of Reciprocal Social Behavior... [ view full abstract ]

Reciprocal social behavior (RSB; the capacity to engage in social behaviors with others) is a primary deficit among individuals with autism spectrum disorders (ASDs). The video-referenced Rating of Reciprocal Social Behavior (vrRSB) was designed to quantify variability in RSB among toddlers at an age prior to most ASD diagnoses by having caregivers watch a 3-minute video of a typically-developing 19-month-old interacting with an adult and then rate their own child’s RSB in comparison to the videotaped scoring anchor. Exploratory factor analysis (EFA) of the 13-item vrRSB with a community-based singleton sample (n=1563, M=19.3 months at caregiver rating) yielded a two-factor solution with boys and girls combined (preliminary analyses indicated comparable factors across sex). Factor 1 was interpreted as “affective engagement” (Eigenvalue=5.73) and Factor 2 as “functional communication skills” (Eigenvalue=1.24), with an inter-factor correlation of 0.52. We applied this factor structure to confirmatory factor analysis (CFA) with a general-population toddler twin sample (both members of MZF=63, MZM=63, DZF=51, DZM=50, and DZO=90 pairs; 2 individuals without cotwin rating; M=18.5 months at caregiver rating). We extracted individual factor-scores from the CFA, and examined genetic and environmental contributions to variance in and covariance between these latent constructs. Bivariate Cholesky analyses indicated significant A on both factors for girls (a²=0.45–0.51) and boys (a²=0.81–0.88), but significant C only for girls (c²=0.35–0.37). For girls, covariation between factor scores was attributable to A, C, and individual-specific factors (E; r_A=0.81, r_C=1.00, r_E=0.52). For boys, covariation was attributable to both A and E (r_A=0.89, r_E=0.73). Given that the vrRSB can capture heritable variability in RSB among toddlers at an early stage of verbal development, the vrRSB could provide an important tool for the assessment of response to treatment in ASD-focused early-interventions.