Preference for geometric patterns early in life as a risk factor for autism

Abstract

Context: Early identification efforts are essential for the early treatment of the symptoms of autism but can only occur if robust risk factors are found. Children with autism often engage in repetitive behaviors and anecdotally prefer to visually examine geometric repetition, such as the moving blade of a fan or the spinning of a car wheel. The extent to which a preference for looking at geometric repetition is an early risk factor for autism has yet to be examined.

Objectives: To determine if toddlers with an autism spectrum disorder (ASD) aged 14 to 42 months prefer to visually examine dynamic geometric images more than social images and to determine if visual fixation patterns can correctly classify a toddler as having an ASD.

Design: Toddlers were presented with a 1-minute movie depicting moving geometric patterns on 1 side of a video monitor and children in high action, such as dancing or doing yoga, on the other. Using this preferential looking paradigm, total fixation duration and the number of saccades within each movie type were examined using eye tracking technology.

Setting: University of California, San Diego Autism Center of Excellence.

Participants: One hundred ten toddlers participated in final analyses (37 with an ASD, 22 with developmental delay, and 51 typical developing toddlers).

Main outcome measure: Total fixation time within the geometric patterns or social images and the number of saccades were compared between diagnostic groups.

Results: Overall, toddlers with an ASD as young as 14 months spent significantly more time fixating on dynamic geometric images than other diagnostic groups. If a toddler spent more than 69% of his or her time fixating on geometric patterns, then the positive predictive value for accurately classifying that toddler as having an ASD was 100%.

Conclusion: A preference for geometric patterns early in life may be a novel and easily detectable early signature of infants and toddlers at risk for autism.

Figure 1

Sample stimuli illustrating 5 movie frames (Yoga Kids 3; Gaiam, Boulder, Colorado, http://www.gaiam.com, created by Marsha Wenig, http://yogakids.com/) contained within the larger movie with dynamic geometric images on the right and dynamic social images on the left. Half of the subjects viewed the movie with this orientation and the other half, with the side of dynamic geometric images and dynamic social images reversed. The areas of interest are depicted by the white box highlighted on the first frame. Eye tracking data were recorded at 120 Hz for a total of 7200 data collections across the 1-minute movie.

Figure 2

Scatterplot illustrating the percentage of fixation time on both dynamic geometric images (DGI) and dynamic social images (DSI) for each toddler with an autism spectrum disorder (ASD), typically developing (TD) toddler, and toddler with developmental delay (DD). Total percentage of time viewing DGI and DSI sums to 100% for each toddler. For example, a toddler who spends 80% of viewing time on DGI (as noted on the y-axis on the left) thus spends 20% of viewing time on DSI (as noted on the y-axis on the right). A toddler who spends more than 50% of viewing time on DGI is considered a “geometric responder” and a toddler who spends more than 50% of viewing time on DSI is considered a “social responder.”

Figure 3

Example scan paths for a typically developing (TD) toddler, toddler with developmental delay (DD), geometric responder with an autism spectrum disorder (ASD), and social responder with an ASD across a 3-second scene overlaid on a single movie scene (Yoga Kids 3 ; Gaiam, Boulder, Colorado, http://www.gaiam.com, created by Marsha Wenig, http://yogakids.com/). The numbers inside the circles represent the order of saccades, with larger circles representing longer fixation times.

Figure 4

Line graph depicting the time course of percentage of fixation on dynamic geometric images (DGI) across the 1-minute movie divided into 3 periods for geometric responders with an autism spectrum disorder (ASD), social responders with an ASD, typically developing (TD) toddlers, and toddlers with developmental delay (DD). Period 1 represents the mean percentage of fixation from 0 to 19.99 seconds, period 2 represents the mean percentage of fixation from 20 to 39.99 seconds, and period 3 represents the mean percentage of fixation from 40 to 60 seconds. Percentage of fixation on DGI was significantly different between periods 1 and 2. Error bars represent standard error of the mean.

Figure 5

Bar graphs illustrating the mean number of saccades during the viewing of dynamic social images (DSI) (left) or dynamic geometric images (DGI) (right). The toddlers with an autism spectrum disorder (ASD) were grouped according to movie preference (ie, geometric or social responder). When viewing social images, geometric responders with an ASD had significantly more saccades than all other groups. When viewing geometric images, geometric responders with an ASD had significantly fewer saccades. *P<.01. †P<.001. ‡P=.02. DD indicates developmental delay; TD, typically developing.