Autism reaches out in many different directions. It can be associated with language delays. It can be associated with epilepsy. It can be associated with some degree of intellectual disability, but the two core features of autism, I see, is impairments and social cognition, understanding and in restricted interests and repetitive behaviors.

It is not all that common, but there is a phenomenon where autism could get worse at about age two. There are some controversies whether regression is a prominent part of autism, but many people feel that it's very hard to diagnose autism before you can begin really talking in detail with a child.

There is no question there are differences between male and female brains. They are called sexual dimorphisms and you can point to different anatomical structures.

I think the gold standard is a clinical diagnosis, that an astute clinician interacting with a child, interviewing the parents, talking with teachers makes the diagnosis based on some standard tests and also on clinical impression and skill.

I think my own bias is that there may be something wrong with the timing and the connectivity between regions rather than pointing to one particular spot in the brain.

The brain immediately confronts us with its great complexity. The human brain weighs only three to four pounds but contains about 100 billion neurons. Although that extraordinary number is of the same order of magnitude as the number of stars in the Milky Way, it cannot account for the complexity of the brain. The liver probably contains 100 million cells, but 1,000 livers do not add up to a rich inner life.

In autism there is just genes in part more or less of a probability that you will have the disorder, and that is where interactions with the environment are key.