In the first year of life, children’s social and communication development is an important area to watch for early signs of autism. Social and communication development includes things like learning to smile, make eye contact, and use gestures.
The key behaviors to look for in a two-year-old that is most predictive of autism are:
Lack of “Protodeclarative pointing”. If you watch a typical two-year-old, they are constantly pointing to show you things. They want to show you what they see. Watch a typical two-year-old for an hour, and you will see dozens of these points. Kids on the autism spectrum rarely if ever do Protodeclarative pointing. Studies have shown this is one of the most consistent indicators.
Lack of shared attention: When you play with a typical kid, they constantly look to you for approval or to share what they are doing. Kids on the autism spectrum rarely do.
Lack of response to their name. Call your child’s name from behind, and they are less likely to respond. Often parents think kids on the spectrum might have a hearing disorder.
Lack of imaginative play: Typical kids play pretending to do activities; pretending to drink from a toy cup, racing cars (rather than just rolling them back and forth), pretending to cook, etc.
A lot of the other stereotypical behaviors of autism may not be blatantly noticeable in a two-year-old. If your kid has some of the behaviors above, he/she might have autism and should be evaluated, but it is by no means certain. Find good, experienced professionals (developmental pediatricians, experienced child psychologists, development pediatricians) who use standardized tests (ADOS, ADI-R) to do a complete evaluation. Unfortunately, general pediatricians are terrible at diagnosing autism at a young age.
The suggestion that autism can’t be diagnosed until age 4 or 5 is categorically wrong.