Altered face scanning and impaired recognition of biological motion in 2-year-olds with autism

Background: Preferential attention to the eyes of others and the ability to perceive motion tied to a biological context are early emerging and highly conserved social behaviors. Here we build on findings on two older cohorts to study these basic mechanisms of socialization in toddlers with ASD.

Objectives: To quantify preferential attention to the eyes of others (first study) and processing of biological motion (second study) at what is presently the earliest point of diagnosis.

Methods: Participants were toddlers with ASD well matched on nonverbal mental age to typically developing toddlers, and on verbal mental age to non-autistic developmentally delayed toddlers. We presented them with 10 videos showing a female actor playing the role of caregiver (first study), and with 5 sets of point-light social animations each presented in right-side up and inverted forms side by side in a half-screen format (second study). Visual fixation patterns and preferential viewing were measured by eye-tracking.

Results: First study: Looking at the eyes of others was significantly decreased (p<.001) while looking at mouths was increased (p<.01) in toddlers with ASD relative to controls. Less fixation on eyes predicted greater social disability (r= -.669, p<.01). Second study: Toddlers with ASD lacked preferential sensitivity to upright point-light animations relative to both control groups (p<.0001). Further, 90% of the viewing behavior of toddlers with ASD could be accounted for in terms of their acute sensitivity to normally unprocessed audiovisual synchronies between point-light movements and the speech sounds of the accompanying audio.

Conclusions:

The combined results suggest that toddlers with ASD view social action as a composite of physical (not social) contingencies since the mouth region of the face contains maximal episodes of purely physical contingencies: the synchronous occurrences of mouth movements and speech sounds. Implications for subsequent neuroplastic specialization of the social brain are discussed.