Sept. 11, 2010— -- A toddler's fixation on geometric patterns may be an early warning sign of autism, researchers found.
Children ages 14 to 42 months with autism spectrum disorder spent significantly more time watching repetitive moving geometric images when given the option to look at either those images or at kids dancing and doing other activities, reported Karen Pierce, of the University of California San Diego, and colleagues.
In fact, spending more than 69 percent of the time during the experiment looking at the geometric images held 100 percent positive predictive value for autism spectrum disorder, they wrote online in the Archives of General Psychiatry.
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These results, which should be easy and inexpensive to replicate in the clinic, provide strong evidence that some infants at risk for an autism spectrum disorder begin life with an unusual preference for geometric repetition, the investigators suggested.
Toddlers who show such a preference would be excellent candidates for further developmental evaluation and possible early treatment, since enriching their environment has been shown to effectively improve brain structure and function, Pierce's group noted.
Basing diagnosis solely on social deficits that may not become obvious until children are older may miss some opportunity for intervention, they suggested in the paper.
The investigators used eye-tracking technology while showing a one-minute video to 37 toddlers with autism spectrum disorder, 22 with developmental delay, and 51 that appeared to be developing normally.
The video showed moving geometric patterns recorded from a screen saver on one side and children doing yoga and dancing on the other side.
As part of a larger study in which children were screened for developmental issues at well-baby visits, these toddlers had been diagnosed as young as 12 months.
Those with autism spectrum disorder spent significantly more time fixated on the geometric patterns during the video than did normally developing children or those with developmental delay.
Within the group with autism spectrum disorder, 40 percent spent more than half of their viewing time looking at the geometric images, whereas only 1.9 percent of normal toddlers did.
Rapid eye movements indicating a shift in attention were significantly less common among autism spectrum disorder toddlers who were looking at their preferred geometric images and more common when they were looking at video of children than in all other groups.
The researchers urged caution in interpreting the results because about 20 percent of the patient sample had to be excluded due to poor compliance during testing, and because of the use of only a one-minute video watching session.
Age didn't appear to make a difference, "suggesting that the current paradigm is suitable for use across at least the first three or four years of development," the researchers wrote in the paper.
Preference for geometric versus "social" images didn't predict score on different aspects of autism spectrum disorder.
Although one minute is about all the attention span of the average one-year-old can handle, use of multiple testing sessions would have made the results more compelling, the researchers acknowledged.
Among the roughly one-third of kids who came back for retesting, movie type preferences remained relatively stable compared with their earlier testing session.
One reason that such a large proportion of toddlers with autism spectrum disorder behaved just like others in preferring "social" images may have been that these were highly compelling images -- not just adult strangers, but children doing attention-grabbing movement, the researchers suggested.