Parental perception of behavioral symptoms in Japanese autistic children.

The team asked Japanese parents to look back and note when they first saw autism traits.

They mailed a simple survey. Parents ticked boxes for social, language, and repetitive behaviors.

Most kids in the sample had autism. The goal was to map the timing of early signs.

Seven in ten parents spotted clear symptoms before age two and a half.

Social quirks kept climbing even up to age nine, longer than U.S. reports usually show.

Language and repetitive issues showed up sooner and then leveled off.

Katz et al. (2003) ran a near-copy survey and also found parents recall four key areas: motor, social, language, and odd interests. Their data line up with M et al., giving cross-check evidence that parent memory is reliable.

Joyce et al. (1988) asked U.S. parents the same timing question. They saw most kids flagged before 24 months and linked earlier onset to higher severity. The Japanese curve stretches longer, but both studies agree parents are the first screen.

Warnes et al. (2005) add a twist: they tracked kids to preschool and found onset timing did NOT predict later IQ or severity. So M et al.’s longer social peak may not spell worse outcome — it just shows a wider window for spotting signs.

You can trust parents’ timeline reports across cultures. If a Japanese family says social oddities keep growing till age nine, still assess now rather than wait. Use their rich detail to pick targets for social-skills teaching, peer modeling, and parent coaching. The wider peak simply gives you more runway to intervene.