Social Interactions Between 24-Month-Old Children and Their Older Sibling with Autism Spectrum Disorder: Characteristics and Association with Social-Communicative Development.

Bontinck et al. (2018) watched 24-month-old toddlers play with their older autistic siblings.

They counted smiles, imitation, and total turns to see how the pairs got along.

The team also tracked which toddlers later showed more autism traits.

Pairs with an autistic older brother or sister had fewer happy exchanges and less copying.

Surprise: toddlers who played more often with the sibling later showed more autism markers.

The data signal that high interaction plus low imitation may flag risk.

Watkins et al. (2021) extends the same picture. After seeing the low interaction, they taught families simple play games. Sibling contact rose for both kids, showing the gap can be closed.

Yoder et al. (2020) also extends the line. They gave parents ImPACT coaching but gains showed up only for low-risk girls. Together the three papers say: watch the toddler, pick the right helper, and don’t expect one-size-fits-all results.

Levinson et al. (2020) conceptually replicates the risk signal. Parent questionnaires at 18 months also predicted later traits, so both live play and survey scores can alert you.

If you work with families who have an autistic child plus a toddler, run a quick five-minute sibling play probe. Note how often the little one copies or smiles. Few copies plus lots of contact? Share the clip with the pediatrician and start early-intervention referral. You can also teach the older child simple model-and-wait steps; Watkins et al. (2021) shows it boosts both kids’ engagement without extra hours in clinic.