Revisiting Fixation Toward Eye and Mouth Region in ASD Toddlers from the General Population: Cross Sectional and Longitudinal Analyses

Background:  Atypical eye contact is a well-known characteristic of children with Autism Spectrum Disorder (ASD), (APA, DSM-5, 2013), and it is thus not surprising that eye tracking studies have reported reduced fixation towards the eye region in ASD (Jones, Carr, & Klin, 2008; Jones & Klin 2013) .  However, several studies have not replicated this effect (e.g., Chawarska et al., 2013; Young et al., 2009).  One possible explanation for these inconsistent findings is different ages of participants.  In Jones and Klin’s (2013) study, ASD children showed similar rates of fixation as TD children on eye regions at 2 months and ASD children’s rates of fixation on eyes declined to half the rate of TD children’s at 24 months.  Therefore, comparing fixation times across multiple time points may influence differences detected between groups (Klin, Shultz, & Jones, 2015).

Objectives:  The present study examined the developmental changes in fixation time toward the eye, mouth and body region in ASD and TD children between 1 to 3 years of age.  

Methods:  Participants were 125 ASD and 110 TD toddlers ranging in age from 1 and 3 years. All toddlers participated in standard psychometric testing and were followed longitudinally until a diagnosis was confirmed at age three.  Toddlers watched a 44 second movie showing a close-up image of a female speaking short common phrases coupled with familiar hand gestures (e.g., peekaboo). Fixation duration within 3 AOIs (eyes, mouth, and body) was measured using a Tobii T120 eye-tracker and was subsequently compared between three age cohorts (ages 1, 2 & 3 years). Ninety seven children (47 ASD, 50 TD) also had eye-tracking data available for a subsequent evaluation, approximately one year later, and changes in looking times were examined (T1 vs T2).

Results:  Three two-way ANOVAs with Age (3) and Group (2) as between-subjects factors and proportion of fixation time of each AOI as a dependent variable revealed that only fixation time on body differed between ASD and TD children (F(1,229)= 5.342, p=.022, η²=.023), and the amount of this group difference did not differ across ages (p=.445, η² = .007). Change in fixation times across two visits also revealed that ASD children looked at body regions longer than TD children (F(1, 95) = 10.228, p=.002, η² = .097), and no differences were found in looking times at eye or mouth regions, p’s >. 465. The amount of group differences in fixation times on each of the 3 AOIs did not differ across time, p’s>. 129.

Conclusions:  Neither fixation times nor change in fixation times on eyes were different between ASD and TD groups. The ASD group did show slightly longer fixation to the body region (3-4 % difference at Ages 1 and 2) when compared to TD children. This result was consistent across one and two year old samples, but was not evident in three year olds.   Overall the fixation patterns between ASD and TD toddlers were strikingly similar.