MONTREAL — By the tender age of 18 months, most toddlers point at things, follow the gaze of someone else, or engage in pretend play.

Children who fail these three key indicators are the ones likely to be diagnosed with autism or its relative, Aspergers Syndrome, the high-functioning end of autism — and the spectrum is far more common in boys than in girls.

Simon Baron-Cohen’s voice is muddied by a hum from a bad telephone connection, but the British psychologist registers clearly when he says that gender might have everything to do with autism.

New research, says the director of the Autism Research Centre in Cambridge who has spent more than two decades studying autism spectrum disorders, might also link prenatal sex hormone differences in the brain to autistic traits.

For Baron-Cohen, autism is the case of the “extreme male brain.” It’s not a disease but a different mental style, a variation “and we have to make space for diversity.”

According to his theory, the female brain is predominantly hardwired for empathy while the male brain is hardwired for understanding and building systems. He calls it the empathizing-systemizing theory or E-S brain theory.

“The fact that there are these typical sex differences in empathy and systemizing is why I’ve made this connection that we can think of autism as an extreme of the male brain where empathy is below average but systemizing is either intact or even above average,” says Baron-Cohen.

He will be in Montreal Tuesday to give the keynote lecture at a conference on autism McGill University.

To bolster the “extreme male brain” theory, suggesting that natural sex differences are rooted in biology, the Baron-Cohen’s Cambridge group is studying hormones and behaviour in a sample of 500 children — which is too small to draw any conclusions about autism, he says.

The team is looking at testosterone levels in amniotic fluid to see how much of the male hormone babies had been exposed to in-utero, and then following the children after birth to note variations in speech development and eye contact. These children are now eight.

“We found that the higher the baby’s fetal testosterone, the less eye contact they make at their first birthday and the slower they are to develop language at their second birthday,” Baron-Cohen said.

Hormones are not the only big piece of the puzzle, genetics play a huge role too.

“Almost every month there is a new research paper showing some new genes have been found that are linked to autism,” Baron-Cohen said. “What we know is that genes are not the whole story.”

In identical twins, one might have autism but the other has a 60-per-cent chance of getting it. That leaves room for environmental factors, he added.

While autism spectrum disorder can be seen as a variation on the population, and people that are affected might simply be showing an atypical pattern of development, the disabilities should not be ignored, Baron-Cohen said.

cfidelman@thegazette.canwest.com