The Development of Anticipatory Smiling in Infants At Risk for Autism Spectrum Disorders

Background:  Infant-initiated joint attention (IJA), which typically emerges during the first year of life, is an important precursor of later social competence.  IJA is impaired in children with Autism Spectrum Disorder (ASD) and may be impaired in their high-risk siblings.  However, there are multiple types of IJA that may be impacted differently by high-risk status.  IJA can occur with smiling in anticipation of the social partner, smiling in reaction to the social partner, or no smiling.  IJA with anticipatory smiling—the current study’s focus—occurs when an infant looks at an object, smiles, and then turns the smile toward a social partner, communicating preexisting positive affect to a partner. In typically developing infants, anticipatory smiling behavior within IJA increases from 8 to 12 months of age and is uniquely associated with later social outcomes.  Fewer early anticipatory smiles may be a specific IJA deficit in children at risk for an ASD with implications for later social competencies.

Objectives:  Determine whether there are deficits in IJA with anticipatory smiling, reactive smiling, or IJA with no smiling in infant siblings of children with an ASD (high-risk siblings) compared with infant siblings of typically developing children (low-risk siblings).

Methods:  High-risk (n = 56) and low-risk (n = 26) infant siblings were administered the Early Social Communication Scales (ESCS) at 8, 10, and 12 months of age.  During the ESCS, IJA episodes (in which the infant gazes at the social partner to share information about an event or object) were coded for smiling behavior.  IJA was coded as involving an anticipatory smile (gaze at object, smile, turn while smiling to gaze at examiner), reactive smile (gaze at object, gaze to examiner, then smile), or no smile (no smile during gaze to examiner).

Results:  Hierarchical linear modeling was used to examine group differences based on high-risk status in the development of frequency of IJA with anticipatory smiling, reactive smiling, and no smiling.  The best fit model for IJA with anticipatory smiles included risk group status as a predictor at the intercept, χ² = 6.19, p = 0.01.  High-risk siblings produced fewer IJA with anticipatory smiles than low-risk siblings (β₀₁ = -1.88, t(79) = -2.58, p = 0.01).  Linear (β₁₀ = 5.54, t(80) = 4.39, p < 0.001) and quadratic (β₂₀ = -2.34, t(80) = -3.97, p < 0.001) coefficients did not differ by status.  There was no significant effect of risk group status on IJA with reactive smiling or IJA with no smiling.

Conclusions:  High-risk siblings produced fewer IJA with anticipatory smiling between 8 and 12 months than low-risk siblings, indicating that communicating positive affect may be a specific impairment in children at risk for developing an ASD.  We are currently investigating whether this apparent impairment predicts later diagnostic and social outcomes.