Facial movements of others during verbal and social interaction are often too rapid to be faced and/or processed in time by numerous children and adults with autism spectrum disorder (ASD), which could contribute to their face-to-face interaction peculiarities. We wish here to measure the effect of reducing the speed of one's facial dynamics on the visual exploration of the face by children with ASD. Twenty-three children with ASD and 29 typically-developing control children matched for chronological age passively viewed a video of a speaker telling a story at various velocities, i.e., a real-time speed and two slowed-down speeds. The visual scene was divided into four areas of interest (AOI): face, mouth, eyes, and outside the face. With an eye-tracking system, we measured the percentage of total fixation duration per AOI and the number and mean duration of the visual fixations made on each AOI. In children with ASD, the mean duration of visual fixations on the mouth region, which correlated with their verbal level, increased at slowed-down velocity compared with the real-time one, a finding which parallels a result also found in the control children. These findings strengthen the therapeutic potential of slowness for enhancing verbal and language abilities in children with ASD.
Keywords: attention to mouth; autism spectrum disorder; eye-tracking; mean duration of fixation; slowness.