Clinical Correlates of Social Affect in Early Infancy: Implications for Early Identification of Autism Spectrum Disorder

Background: Earlier intervention for infants and toddlers with autism spectrum disorder (ASD) enhances developmental gains (Rogers, et al. 2012) and necessitates ascertainment of early, reliable indicators of ASD. Diminished positive social affect, also termed social smiling, has been among the leading hypothesized risk factors for ASD in the prelinguistic period, between 6-12 months of age. However, research has resulted in mixed findings for the predictive value of social engagement in 6-9-month-old infants for the development of ASD. If abnormalities in infant social affect contribute to the early phenotypic expression of ASD, it is important to determine whether diminished social affect is a unique construct associated exclusively with social impairments or if it is, alternatively, an expression of normal variation in individual development better explained by temperamental style. 

Objectives: The current study sought to enhance the understanding of atypical social development in early infancy by investigating individual differences in social engagement. Positive social affect exhibited by 6-8-month-old infants during naturalistic parent-infant interactions was correlated with four dimensions of behavior relevant to early identification of ASD: social-communication, vocal production, and autism symptomology. Temperament was included as a control measure of individual behavioral style, often considered to be independent of developmental psychopathology.

Methods: Participants included 33 dyads of 6-8-month-old infants and their mother. Each dyad participated in a videotaped semi-structured face-to-face interaction that was later coded for infant expression of directed positive affect. Positive social affect was coded in ten-second intervals using a previously developed affect rating scale (Koegel et al., 2014). Time spent engaging in positive social affect was then correlated with clinical measures of social-communication (CSBS Social Composite and Mullen Receptive Language), vocal production (CSBS Speech Composite), autism symptomology (Autism Observation Scale for Infants), and temperament (Infant Behavior Questionnaire).

Results: Overall, the proportion of time infants spent exhibiting positive social affect ranged from .00 to .60 with an overall mean of .32 (SD=.18). Analyses revealed a positive association between positive social affect and receptive language (r=.428, p=.007). No significant relations were observed between positive social affect and other clinical measures, including vocal production (r=-.118, ns), autism symptomology (r=-.166, ns), or the three dimensions of temperament (Surgency: r=.042; Negative Affect: r=.098; Effortful Control: r=-.125). Age and gender were not significantly associated with the primary measure of positive social affect. Further, overall attention the caregiver’s face regardless of affect revealed no significant associations with clinical measures.

Conclusions: These results suggest that positive social affect in early infancy may be a uniquely meaningful indicator of social responsivity and perhaps social motivation. The lack of association between positive social affect and other clinical measures, including temperament, may suggest that this is a specific behavioral marker for low social responsivity and possibly ASD. Additionally, the lack of relation between total time looking to the caregiver's face and clinical measures suggests that overall social attention at this age is not indicative of social-communicative skills. Further research is needed to understand how diminished positive social affect in early infancy may impact later developmental outcomes, including development of ASD.