Hello and goodbye: a study of social engagement in autism.

The team watched autistic and non-autistic people meet a stranger. They counted who said hello or goodbye on their own. They also timed eye contact and noted smiles or waves.

Everyone had similar verbal skills, so language level could not explain any differences.

Autistic participants rarely offered greetings or farewells without prompting. They looked at the stranger’s eyes less often and smiled or waved less.

The authors linked these gaps to weaker shared-moment connection, called intersubjective engagement.

Plant et al. (2007) ran the same lab setup nine years later and added engagement ratings. They again saw less eye contact and lower warmth, showing the pattern holds.

Matson et al. (2008) extended the finding to adults. They proved that less eye contact makes it harder to spot real smiles, chaining the early deficit to later social trouble.

Rutherford et al. (2007) pushed the timeline backward. Infant siblings of autistic children already smiled less and shared attention less between six and eighteen months, hinting these signs appear before diagnosis.

You can spot reduced greetings and eye contact early. Use these signs to flag toddlers for screening and to shape early goals such as “orient to partner” or “emit unprompted hello.” During sessions, prompt and reinforce brief eye contact and clear greetings. Track them as simple frequency data to show families quick wins.