Reduced Attention to Social Content In Preverbal Infants at Risk for Autism

Background:  Does reduced attention to biological motion and faces by 9 months distinguish between the infant siblings of children with autism and low-risk infants? Preferential attention to biological motion and faces is typically observed soon after birth (Johnson et al., 1991; Simion et al., 2008). The absence of this preference in toddlers and older individuals with autism may limit opportunities for social learning (Klin et al., 2009; Osterling & Dawson, 1994). Neural evidence suggests that infant siblings process faces relative to objects differently than low-risk infants by 10 months (McCleery et al., 2009). Orienting towards faces may support cortical specialization for social stimuli (Morton & Johnson, 1991). 

Objectives:  The current study examines whether infant siblings orient to faces and low-level biological motion less than low-risk infants. Reduced orienting to social stimuli in infancy would restrict opportunities to learn about social interaction very early in the development of infant siblings.  

Methods:  In the Animacy task, infants viewed eight side-by-side presentations of video displays consisting of two dots moving within a pair of 10 x 10 cm regions.  The dots moved either in a contingent fashion, judged by naive adult observers to be "chasing" (Animate displays) or in random fashion (Inanimate displays).  Eye movements were recorded with a Tobii T60 eye tracker.  In the Face Detection task, infants viewed two 4-min video segments taken from a cartoon (A Charlie Brown Christmas) or from a children's television program (Sesame Street).  Videos were matched for duration, action sequences, motion, social interactions, and musical and linguistic content.  Eye movements were recorded with a Tobii T60 eye tracker.

The at-risk group consisted of infants between 6 and 9 months of age who were younger siblings of children previously diagnosed with autism (Animacy task N = 7, Face Detection task N = 8).  The control groups (N = 21 and 24, respectively) were in a similar age bracket and came from families who did not report autism in first-, second-, or third-degree relatives.

Results:  Infants in the control group showed a strong preference for Animate displays, t(20) = 7.38, p < .0001.  In contrast, at-risk infants showed no consistent preference, t(6) = 1.48, ns.  Similarly, infants in the control group looked overall more at the faces in the cartoon relative to at-risk infants, t(30) = 4.85, p < .0001, and at the faces in the children's television program, t(30) = 3.74, p < .001.

Conclusions:  Infant siblings of children with autism showed less interest in social content available in video stimuli.  The effect generalized to real faces, cartoon faces, and abstract motion displays in which adults detected contingent interaction between two dots.  These results imply that behavior in preverbal infants, younger than the conventional age of diagnosis of autism, may reveal subtle signs of risk status in vulnerable populations.