People with autism have difficulties with behaviour, communication, social interaction and dealing with sensory input. However, not everyone on the "autism spectrum" displays all these characteristics and to the same degree.
Parents of autistic children have problems with the fact that their kids rarely look people in the eye. Now, new research is suggesting reasons for this phenomenon.
"Contrary to what has been thought, the apparent lack of interpersonal interest among people with autism is not due to a lack of concern," said study co-author Dr Nouchine Hadjikhani.
"Rather, our results show that this behaviour is a way to decrease an unpleasant excessive arousal stemming from overactivation in a particular part of the brain," she said.
Hadjikhani is director of neurolimbic research at Massachusetts General Hospital's Center for Biomedical Imaging.
According to the South African Medical Journal (SAMJ)The United States Department of Health estimates that cases of autism have increased 500% over the past five years.
Toxic environmental "trigger"
While avoiding eye contact is often regarded as a sign of social or personal indifference, many people with autism say eye contact causes them discomfort or stress, the study authors noted.
Autism is a behaviourally defined developmental disorder which appears to be caused in early development by the impact of the environment on a genetic predisposition.
Usually diagnosed before the age of three, a pattern of initial seemingly normal development, followed by a regression or loss of skills around 18 months, is common.
This is bolstering a growing body of opinion that genetically predisposed children are encountering a neurologically toxic environmental "trigger" that disables them and disconnects them from the world.
Brain activity monitored
The new research traces the problem to part of the brain that triggers babies' natural attraction to faces and helps people perceive emotions in others. It's called the subcortical system, and it's activated by eye contact.
To learn more, the study authors monitored brain activity while people with and without autism looked at images of faces either freely or when restricted to seeing only the eye area.
Both groups showed similar levels of brain activity when viewing pictures of the entire face.
But when participants with autism were shown only the eye area, their subcortical brain system was overactivated, the findings showed. This was especially true when they saw fearful faces, but also with happy, angry and neutral ones.
The study was published online in the journal Scientific Reports.
The findings could lead to more effective ways to engage people with autism, according to Hadjikhani.
"Forcing children with autism to look into someone's eyes in behavioural therapy may create a lot of anxiety for them," she said in a hospital news release.
"An approach involving slow habituation to eye contact may help them overcome this overreaction and be able to handle eye contact in the long run, thereby avoiding the cascading effects that this eye-avoidance has on the development of the social brain," Hadjikhani suggested.