Sensory input is essential to the development of humans - from birth to life's last breath. Infants particularly rely on the sights and sounds they take in as they explore their world, well before they actually are mobile enough to do so. Research has shown that infants tend to pay more attention to social stimulus, especially faces or face-like stimuli as well as motion.
Scientists call this social visual engagement, and it shapes typical development in people from birth.
New research has found that this social visual engagement is atypical and presents differently in children who are diagnosed as having autism. This difference is believed to be caused by genetic information that makes one who she or he is.
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Researchers used a series of eye-tracking experiments with 338 toddlers - this group included 166 twins, 88 non-twins with autism and 84 non-twins without autism. They found that in the monozygotic twins, there was a high correlation between social tracking cues and input functioning, not found in the others of they study. In essence, it would seem that genetic information we all possess leads us to different brain development patterning, and this genetic information may lead to children developing autism.
The study asserts that our genetic coding cues us as to how we seek out social interaction like making eye contact or 'reading' someone's face, but also leads some to theorize that while nature plays an obvious part, nurture can make a difference simply by knowing the possibility.
Dr. Charles A Nelson, III is a professor of pediatrics and neuroscience at Harvard Medical School and Boston Children's Hospital. He believes this new research does seem to show that autism may have a genetic basic component, yet nothing specific regarding which genes may influence autism has been found. It is believed however, that since this study shows social behavior being measurably different in children with autism (based on genetics), scientists may be able to research further to find those specific genes, and to gain a better understanding of autism characteristics.
As the study gave detailed data on how children viewed faces, including what they focused on and when and where their eyes moved from one place to another, it's possible this research may lead to looking at specific genetic circuitry that could lead to big advances in understanding autism, Dr. Nelson believes.
Scientists study identical twins because the genetic makeup is 100% the same, thus when their findings differ from other children in measurable ways, a correlation with genetic makeup is made, and it's believed that at the traits under study are partially inherited. Big differences between identical and nonidentical twins can also suggest that the traits are genetically influenced.
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The study looked at how much the children looked at the eyes of people on a screen, as well as their mouth patterns, and found that identical twins often moved their eyes at nearly the same rate and points of movement, even though each child in the study watched the videos separately and had no other cues given to them.
Dr. Warren Jones is the study's senior author and also an assistant professor of pediatrics at Emory University School of Medicine. He said that when unrelated children were randomly paired, the time they spent looking at eyes had absolutely no matching at all, while the identical twins' eye movements were as close as 16.7 milliseconds apart, and always in the same direction.
Dr. Jones could not believe the match between the identical twins was as close as it was, wondering if he'd accidentally matched data from the same twin twice. In fact, the difference was so consistent in the identical twins, the researchers of the study could often identify most of the children with autism simply by looking at the data from the eye-tracking results. Even when identical twins watched different videos, their eye patterns matched.
What this means is that seeking out social information found in eyes is genetically driven, and believed to be disrupted in children with autism as they develop. Dr. Nelson cautions about overemphasizing that role, however, as though twins may have identical DNA, their experiences and brains are different, therefore meaning there is room to look at how different experiences and promoted vs. sought social interactions may play a role in the development of autism as well.