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If you've just loaded up a movie to watch and the actor's speaking is lagging behind their lips moving, you know the movie's audio and visual aren't synced properly. It’s distracting.

This is what it's like for some children with autism, says a study by University of Toronto psychology postdoctoral researcher Ryan Stevenson.

"Our study shows that individuals with autism have difficulties processing the timing of what they hear and what they see, often reporting two events as synchronous when they are quite far out of sync," said Stevenson, who started the research while working at Vanderbilt University.

Stevenson and his team also directly linked the ability of people with autism to process the timing between sight and sound with their abilities to perceive audiovisual speech. The people with autism who showed less precise timing between sight and sound were less likely to correctly perceive audiovisual speech, which drastically impacts their ability to communicate and have good social interactions.

The team tested 64 children with and without autism between the ages of 6 and 18. Each child completed various tasks. In one, they were presented with a simple flash of light and a beep at varying levels of asynchrony (i.e., the flash either came before, after or at the same time as the beep). The children pressed a button indicating if what they heard and saw were synchronized. They also used an illusion called the McGurk Effect, which measured whether or not the child could perceive what they heard a speaker say and what they saw a speaker say as a single event, which indicates a high ability to perceive audiovisual speech, or as two separate events.

"One of the primary issues that individuals with autism face is difficulty with social communication," says Stevenson. "One of the fundamental building blocks needed to have success in social communication is the ability to accurately perceive what is going on around you. If you have difficulties perceiving the world around you, it’s intuitive that you may also have difficulties interacting with that world, and the other people in it."

Stevenson says these new insights may prove useful in designing treatments for children with autism. He notes that sensory systems are extremely adaptable, and he and his team are currently testing a new computer-based treatment for individuals with autism. The goal is to improve the sensory abilities of individuals with autism, which may lead to improved social communication abilities.

Stevenson worked with Mark Wallace at the Vanderbilt Brain Institute in Nashville, Tennessee. Their study entitled "Multisensory Temporal Integration in Autism Spectrum" was published in on January 15. The research was funded by the United States National Institute of Deafness and Communicative Disorders.

Jessica Lewis is a writer with the Faculty of Arts & Science at the University of Toronto.