Emerging symptoms of autism including a lack of shared eye contact, grinning and communicative babbling emerges in infants after the first 6-months of their birth.

Scientists carried out the research over five years by thoroughly counting each case of smiling, babbling and eye contact in tests until the kids were 3 years old.

They discovered that by 12 months the two groups' growth had varied in a significant manner.

Intentional social and communicative behavior among kids growing normally heightened while among infants later diagnosed with autism it diminished in a dramatic manner.

Lead author Sally Ozonoff, professor of psychiatry and behavioural sciences at the University of California-Davis (UC-D), stated, "This study provides an answer to when the first behavioural signs of autism become evident."

"Contrary to what we used to think, the behavioural signs of autism appear later in the first year of life for most children with autism."

"Most babies are born looking relatively normal in terms of their social abilities but then, through a process of gradual decline in social responsiveness, the symptoms of autism begin to emerge between six and 12 months of age," Prof. Ozonoff added.

Abnormal brain growth, probably beginning prenatally, is known to be fundamental to the behaviours that characterise autism.

Abnormal brain growth, probably beginning prenatally, is known to be imperative to the behaviors, which portray autism.

Recent estimations put the condition's occurrence at between 1 in 100 and 1 in 110 kids in United States, a university release said.

The results of the research appeared online and will be published in the March issue of the Journal of the American Academy of Child and Adolescent Psychiatry. (With Input from Agencies)