Early social, imitation, play, and language abilities of young non-autistic siblings of children with autism.

Toth et al. (2007) watched 18- to 27-month-old brothers and sisters of kids with autism. None of the toddlers had an autism diagnosis themselves.

The team gave each child six short tests. They checked talking, listening, IQ, copying others, play, and everyday self-help skills. They also asked parents to fill out a social form when the babies were 13 months old.

The toddler siblings scored lower than same-age peers with no family history of autism. The gaps showed up in talking, understanding words, IQ, daily living skills, and social games.

Parents had already noticed social slips at 13 months. By 18 months the lag was big enough to measure with standard tests.

Maddox et al. (2015) saw the same social dip even earlier. High-risk babies looked at their parents less during play at just 11 months. Karen’s team picks up the story a few months later and shows the lag lasts into the second year.

Titlestad et al. (2019) seems to say the opposite. They found that less brain “gamma” activity at 24 months went hand-in-hand with better talking in high-risk toddlers. Karen found worse talking. The gap is only skin-deep: L’s EEG marker may point to a brain workaround, not a delay. Behavior still lags, so both papers can be true.

Kaddouri et al. (2025) adds another twist. Moms of 9-month-old high-risk babies talked to them just as often and as clearly as moms of low-risk babies. If the input is equal, the later language gap Karen caught is more likely rooted in the child’s own processing, not in how parents speak.

Screen brothers and sisters before their second birthday. Use a quick language checklist at 12 months and a fuller test at 18. Start small routines—turn-taking games, joint attention bubbles, or sign language—while you wait for the full eval. Early play sessions can shave months off later therapy time.