Positive Affect Processing and Joint Attention in Infants at High Risk for Autism: An Exploratory Study.

The team measured brain waves in babies who have an older sibling with autism. These high-risk infants watched happy faces while wearing a soft EEG cap at nine months old. The researchers also tracked how well each baby later shared attention with an adult at 12 months.

Babies who later showed poor joint attention had weaker brain responses to subtle smiles. The difference appeared only for quiet, not broad, happy faces. The result is exploratory but points to early emotion processing as a red flag.

Lifshitz et al. (2014) saw the same risk group smile less during shared play. Their study used live toys, while P et al. used faces on a screen. The two papers agree: less positive affect in infancy links to later social trouble.

Lin et al. (2026) went further. They watched real-time parent-baby games and found low affective synchrony beat gaze alone at predicting autism. Their work widens the lens from single faces to whole social dances.

van Noordt et al. (2022) also recorded infant EEG, but they tracked theta rhythm consistency. Both labs show atypical brain reactions to faces forecast diagnosis, strengthening the neural marker idea.

You can’t give a nine-month-old an autism test, but you can watch how they react to a smile. If the baby seems uninterested, flag the file and schedule extra social games. Pair this check with parent coaching on joyful turn-taking. Early joy builds joint attention, and joint attention builds language.