“For healthcare providers, we have a message that’s pretty direct about ASD. And the message is: The 4-year-old with autism was once a 3-year-old with autism, which was once a 2-year-old with autism.”

Many researchers are now on the hunt for atypical behaviors cropping up in infancy that could be telltale signs of ASD. For instance, a team of experts led by Dr. Karen Pierce at the Autism Center of Excellence at the University of California, San Diego, has used eye-tracking technology to determine that infants as young as 14 months who later were diagnosed as autistic showed a preference for looking at movies of geometric shapes over movies of children dancing and doing yoga. This predilection for being engaged by objects rather than “social” images is thought to be a marker for autism.

Even the quality of infants’ crying has come under scientific scrutiny as a possible sign of the disorder. Dr. Stephen Sheinkopf and some colleagues at Brown University compared the cries of a group of babies at risk for autism (due to having an autistic sibling) to typically developing babies using cutting-edge acoustic technology. They discovered that the at-risk babies emit higher-pitched cries that are “low in voicing,” which is a term for cries that are sharper and reflect tense vocal chords. Dr. Sheinkopf, however, cautioned parents against over-scrutinizing their babies’ cries since the distinctions were picked up by sophisticated acoustic technology, not by careful human listening.