Based on the new findings, perhaps using EEGs to measure this type of brain activity could be a biomarker for autism, he says. A biomarker is a distinct characteristic that indicates a particular condition.

Measuring a baby's brain activity as early as 3 and 6 months could identify changes in the brain before changes in behavior are noticed, he says, and therapy could begin even earlier.

The ESDM model could be applied as early as 12 months, say Dawson and Rogers.

More research will probably have to be done to confirm the biomarker. So until there is a definitive test for diagnosing autism, Dawson says this it's even more important that pediatricians screen children for autism as early as possible.

"The average age of diagnosis is still 4 and 5 and even older in minority groups," she says. "We really need to close the gap."

Autism Speaks has many tools on its website to help parents see what a child with autism looks like compared to a typically developing child. There are also many tool kits to help families of children with autism.