Social engagement with parents in 11-month-old siblings at high and low genetic risk for autism spectrum disorder.

Researchers watched 11-month-old babies play with a parent. Half the babies had an older sibling with autism. The other half had no family history of autism.

Each pair played for ten minutes. Trained coders counted how often the baby looked at, smiled at, or talked to the parent. They also noted how the parent acted toward the baby.

Babies who later got an autism diagnosis looked at their parents less. They smiled less and babbled less during play.

Parents in both groups acted the same. They talked, smiled, and touched their babies just as much. The difference was in the babies, not the parents.

This study builds on Toth et al. (2007). That team saw social lags by 18 months. We now know the gap shows up even earlier, at 11 months.

Geurts et al. (2008) used old home videos and found gaze problems from 6 months. Our study proves those early signs can be spotted in real time during a short play session.

Kaddouri et al. (2025) found no difference in how moms talk to 9-month-old high-risk babies. That matches our finding: parents behave normally, but babies respond less.

Shire et al. (2019) showed a parent checklist can flag risk at 12 months. Our live observation gives another way to catch the same early warning signs.

If you work with families who already have one child with autism, watch the baby during simple play at 11 months. Less eye contact, smiling, or babbling is a red flag. You can reassure parents it is not their fault—their parenting style looks fine. Early spotting means earlier support, and programs like Baby JASPER or PRT can start sooner.