Interesting article from Time. Definitely something any new parents should know to watch for.
Show the average 14-month-old baby a sealed jar of cookies, and you get some pretty predictable behavior. The child will reach for the treats and, when thwarted, look beseechingly at the nearest adult. The request for help — delivered with eye contact, gestures and often with pleading sounds — is unmistakable. But some babies don’t do it. One little boy, captured on video by psychologist Wendy Stone at Vanderbilt University, repeatedly places a researcher’s hand on the cookie jar but never once looks at her face to see why she isn’t responding. Eventually, tragically, he gives up.
Show the average 18-month-old a video of toddlers at play, and you can bet that the tot will be mesmerized by scenes with strong emotion: a fight or kiss. But some babies have other interests. At the Yale Child Study Center, psychologists Warren Jones, Ami Klin and Sarah Shultz measure when toddlers stop blinking — a reliable indicator of rapt attention. The typical child will stare at the scene of a kiss, but a child with autism will be transfixed by the opening and closing of a door.