Evidence for an Infant Construct of Social Motivation and Predictive Validity for Autism Spectrum Disorder

Poster Presentation
Thursday, May 2, 2019: 5:30 PM-7:00 PM
Room: 710 (Palais des congres de Montreal)
N. Marrus1, K. Botteron1, L. Markson2, J. Pruett1, J. J. Jackson2, J. T. Elison3, J. Wolff3, A. Estes4, L. Zwaigenbaum5, S. Paterson6, H. C. Hazlett7, S. R. Dager4, R. T. Schultz8, J. Piven9, J. N. Constantino1 and .. The IBIS Network7, (1)Washington University School of Medicine, St. Louis, MO, (2)Washington University in St. Louis, St. Louis, MO, (3)University of Minnesota, Minneapolis, MN, (4)University of Washington, Seattle, WA, (5)University of Alberta, Edmonton, AB, Canada, (6)Department of Psychology, Temple University, Philadelphia, PA, (7)University of North Carolina, Chapel Hill, NC, (8)Center for Autism Research, Children's Hospital of Philadelphia, Philadelphia, PA, (9)*Co-Senior Authors, IBIS Network, University of North Carolina, Chapel Hill, NC
Background: According to the social motivation hypothesis, deficits in social motivation during infancy constrain early social learning, thereby contributing to canalization of atypical social development and the emergence of autism spectrum disorder (ASD). A major barrier to studying social motivation’s role in the ontogeny of ASD is the lack of measurement tools to assess individual differences in this important aspect of social behavior during early development.

Objectives: To investigate the evidence for a social motivation construct in infants, we leveraged existing data to 1) derive a parent-report index of social motivation in infants and 2) quantify the extent to which early social motivation accounts for variation related to ASD outcome at age 24 months.

Methods: Behavioral data were analyzed from over 400 participants in the Infant Brain Imaging Study, a prospective, multisite study of infants at high and low familial risk for ASD. High-risk infants have an older sibling with ASD; low-risk infants have no first-degree relatives with ASD. Participants were assessed at 6, 12, and 24 months of age, and items were selected from multiple parent-report measures, including the Vineland Adaptive Behavior Scales, First Year Inventory, Infant Behavioral Questionnaire-revised, and Macarthur-Bates CDI, based on face validity for indexing social motivation. Social motivation was operationalized as the disposition to preferentially orient to social stimuli; to seek, want, and like social interactions; and to exert effort to maintain social engagement (Chevallier, 2012). Item scores were uniformly weighted and summed to generate a “social motivation index” (SMI) score. A clinical-best-estimate procedure including the Autism Diagnostic Observation Schedule (ADOS) was used to diagnose ASD at age 24 months.

Results: The SMI demonstrated a continuous, unimodal score distribution, good internal consistency (Cronbach’s α=0.75-0.89) at all three ages (Fig. 1), and significant cross-age correlations (6-12 months: r=.58, p<.001, n=171; 12-24 months: r=.45, p<.001, n=183; 6-24 months r=.27, p<.001, n=210), suggesting trait-like stability (Fig. 2). Lower SMI scores were observed by age 6 months for infants later diagnosed with ASD (6 months: t(298)=-3.15, p=.002) and 6-month SMI scores significantly correlated with ADOS calibrated severity scores at 24 months (r=-.21, p<.001). A binary logistic regression model testing the effect of sex and 6-month SMI on categorical ASD diagnosis at 24 months was significant (χ2(2)=18.52, p<.001), with sex and SMI each accounting for 5% of the variance. The effect of SMI remained significant when the 6-month Mullen Early Learning Composite, a measure of general cognitive development, was added to the model. The 6-month Vineland Socialization subscale, a parent-report metric of social function, did not significantly predict ASD diagnosis when substituted for SMI in the model.

Conclusions: These findings provide initial evidence for a measurable social motivation construct in infancy which shows predictive validity for ASD by 6 months of age. ASD-related SMI score differences suggest that further characterization of social motivation in infancy could promote earlier identification of children with ASD who would benefit from intervention.