Physical Properties of Social Scenes Modulate Visual Engagement in School-Age Children with Autism Spectrum Disorder

Background: While reduced engagement with the social world is a defining feature of Autism Spectrum Disorder (ASD), less is known about what is perceived as important to individuals with ASD. Building on previous research demonstrating that individuals with ASD show increased attention to physical cues, including inanimate objects (Rice et al., 2012), objects in motion (Shultz et al. 2011), and audiovisual synchrony (Klin et al. 2009), the present study examines the extent to which viewers with ASD are engaged by physical cues within naturalistic social scenes. Viewer engagement is quantified by measuring patterns of eye-blink inhibition, a method that capitalizes on the fact that blinking temporarily interrupts visual information (Shultz et al., 2011). To accommodate this interruption, viewers unconsciously adjust the timing of their eye-blinks to minimize the likelihood of missing critical information. Probabilistically, people are least likely to blink when looking at what they perceive to be most important. Thus, by measuring change in rate of eye-blinking relative to ongoing scene content we can index engagement in viewers with ASD.

Objectives: Determine whether physical properties within social scenes, such as motion, luminance, and loudness, are engaging to children with ASD.

Methods: Eye-tracking data were collected from 92 children with ASD (mean age=10.3(3.2) years; 28 female) and 44 age- and IQ-matched typically-developing (TD) children (mean age=10.0(2.9) years; 15 female) during viewing of movies depicting age-appropriate social scenes. Motion, luminance, and loudness were quantified at each movie frame. Peristimulus time histograms were created to quantify percent change in blink rate relative to movie frames with physical property values exceeding a percentile threshold. A range of percentile thresholds were used to examine how engagement varies as a function of onscreen physical properties (Figure 1). 

Results: Preliminary analyses revealed that both TD and ASD viewers are highly engaged when viewing motion, with engagement increasing as onscreen motion increases (Figure 2A). However, level of engagement was highest amongst ASD viewers, even at lower motion thresholds, with absolute change in blink rate peaking at 21.4% relative to movie frames with motion values above the 70^th percentile. By contrast, absolute change in TD blink rate peaked at 15.1% relative to frames with motion values above the 80^th percentile (Figure 2B). Both groups showed greater engagement immediately before and after motion events, with ASD engagement peaking approximately 350ms before and 330ms after motion events and TD engagement peaking approximately 650ms before and 950ms after motion events (Figure 2C).

Conclusions: While motion modulates engagement for both groups, viewers with ASD showed a more pronounced increase in engagement that was also more closely time-locked with motion events compared to TD viewers. These findings suggest that viewers with ASD show greater sensitivity towards motion and perceive motion to be more salient compared to TD viewers. Future analyses will ascertain the influence of luminance and loudness on visual engagement in viewers with ASD. These efforts will shed light on cues that engage individuals with ASD and may identify alternate viewing strategies used by these individuals to make sense of complex scenes.