In the years to come, I began to work with babies. Why? Because the only way we could trace the early development of individuals with autism was if we were to follow the younger siblings of children already diagnosed with autism. We weren’t sure of the recurrence rate in families, and in fact we greatly underestimated it. It became clear that about one in five of the younger siblings of children with autism also develop autism, and that an additional one in five developed something that either was a transient form of autism, or a sub-threshold form. We felt that we were looking at a broad spectrum, one that crossed thresholds of clinical diagnosis. We now know that this is true.
Once we began to follow babies from birth, it was possible to start tracing their developmental trajectories—those who developed normally as well as those who eventually developed autism. And what we and others in the field discovered is that there is much, much greater malleability in ASD than we once thought. We started looking into ways in which we could promote better outcomes by trying to intervene between birth and the age of 3 years. If we could increase their abilities by the age of 3, we would be changing their lifetime trajectory.