Decreased Social Attention in 6-Month-Old Infants Later Diagnosed with ASD

Background: The ability to spontaneously attend to the social overtures and activities of others is essential for the development of social cognition and communication.  This ability is critically impaired in toddlers with autism spectrum disorders (ASD); however, it is not clear if prodromal symptoms in this area are already present in the first year of life of those affected by the disorder. 

Objectives: To examine whether 6-month-old infants later diagnosed with ASD exhibit atypical spontaneous social monitoring skills.

Methods: Visual responses of 67 infants at high-risk (HR) and 50 at low-risk (LR) for ASD were studied using a free-viewing eye-tracking task (Chawarska, Macari & Shic, under review).  The stimulus consisted of a 3-minute video of an actress filmed in a setting containing four toys and a table with ingredients for making sandwiches (see Chawarska et al., 2012). The video contained four types of activity (conditions) interspersed with one another, depicting a woman making a sandwich, occasionally looking at the camera and trying to engage the viewer using eye contact and child-directed speech, then going back to the sandwich, or looking at the toys, with toys sometimes remaining still and sometimes moving.  Dwell time on the entire scene, the actress, her face, and objects in the background were recorded. Based on their clinical presentation in the 3^rdyear, infants were divided into those with ASD, those exhibiting atypical development (HR-ATYP), and those developing typically (HR-TYP, LR-TYP). 

Results: Primary hypotheses were tested using linear mixed effects models with group (4) as a between-group factor and condition (4) as a within-group factor.  Considering that the task relied heavily on visual discrimination skills and attention to language, individual age equivalents on the Mullen Visual Reception and Receptive Language scales at 6 months were included into the model as covariates. All post-hoc contrasts are reported with a Tukey-Kramer correction for multiple comparisons. Compared to the control groups, 6-month-old infants later diagnosed with ASD attended less to the social scene, and, when they did look at the scene, they spent less time monitoring the actress in general and her face in particular. Limited attention to the actress and her activities was not accompanied by enhanced attention to objects.

Conclusions: Prodromal symptoms of ASD at six months include a diminished ability to attend spontaneously to people and their activities. A limited attentional bias towards people early in development is likely to have a detrimental impact on the specialization of social brain networks and the emergence of social interaction patterns. Further investigation into its underlying mechanisms and role in the psychopathology of ASD in the first year is warranted.