- No big smiles or other warm, joyful expressions by 6 months or thereafter
- No back-and-forth sharing of sounds, smiles or other facial expressions by 9 months or thereafter
- No babbling by 12 months
- No back-and-forth gestures, such as pointing, showing, reaching or waving, by 12 months
- No words by 16 months
- No two-word meaningful phrases (without imitating or repeating) by 24 months
- Any loss of speech or babbling or social skills at any age
From First Signs, a group that is publicizing the first signs of autism to help parents get early identification and treatment
