When is it typical to noctice Autism?

So while reading through this and hearing the parent talk about when they realized their son had autism. I have kind of wondered when the typical age for autism diagnosis is. Is there a specific age that most people find out at? I searched the New York Times and found an article all about autism.

According to the New York Times parents begin to notice at arounf 18 months and usually no later than 2 years old. They begin to notice things such as the child will have trouble with pretend play, social interactions, and verbal/nonverbal communications. The article stated that most children will seem perfectly normal before the age of one then everything will start to change after about the one year mark. I was also very interested to see that autism will affect more boys than girls (just an interesting little fact I didnt know)

Within the story I am reading they did find out before the child was a year old, so they are a little different than most families. Their child was very motionless and didnt respond to verbal cues at all. I guess its different for every child when autism will appear. 


Here's the link to the article in the New York Times:
http://health.nytimes.com/health/guides/disease/autism/overview.html