If you've been following along from the beginning, by now you should be pretty comfortable with the 2-dimensional graph depicting degree of atypicality on the X axis, and level of intelligence on the Y axis. This is our way of illustrating the fact that any degree of atypicality can coexist with any degree of intelligence. We've used the comparison of a train, where the number of wheels off the track corresponds to the degree of atypicality, and the speed of the train corresponds to the level of intelligence. Another way to think about it is height and weight: you can have any combination of these two properties: Tall and skinny like a basketball player, tall and broad like a football player, short and skinny like a jockey, short and broad, like a snowman - or any combination in between. Likewise, you can be anywhere on the XY graph, with any combination of atypicality and IQ.
As useful as this 2-dimensional model is, however, it's just a static picture: a snapshot at one moment in time. Now, we're about to change all that. Put your math anxiety aside, hang on to your hat, and take a look at figure 5:
Get the idea? What we've done is to take Figure 4, and add a third dimension, Time (or, age), to the picture. Every child starts out somewhere in the XY plane, with his or her unique combination of atypicality and IQ, and then that child moves to the right, as time passes. (I haven't shown tic marks on the Time axis, but you can think of it as calibrated in months or years). Let's see how this plays out in real life.
Figure 6 displays two hypothetical children. These two children have the same degree of atypicality (moderate), but different IQ's. Child A has an average IQ (100); Child B has an IQ in the range of Moderate Mental Retardation (40 to 55). The little cubes represent the autistic symptoms. They start out identical in size. But as Child A gets older, his or her symptoms shrink, and break up into smaller pieces, while for Child B they remain unchanged over time. Instead of thinking about atypicality as a train with derailed wheels, now I want you to think about atypicality as a chunk of ice floating in the water: it can be a big piece (severe atypicality) or a small piece (mild atypicality). The child's IQ is like the water temperature: the warmer the "water" - the higher the IQ - the faster the ice melts.
There have been at least ten long-term follow-up studies of persons with ASD, going back nearly 40 years and totalling over 1000 subjects, that bear out this fact. In 1976, one researcher correctly concluded "In terms of scholastic progress, social competence, and work opportunities, the child's IQ level is as influential as the presence of autism." For details, see Chapter 5 and Appendix II of my book. What's new is the 3D graph, which gives us a way to display this phenomenon visually, and provides a map on which to track a child's progress over time, as this process unfolds.
One word of caution: Figure 6 is a map, but it is not a crystal ball. Often, at the end of the first office visit, I have tell parents "This is the map, but I can't tell you at the moment exactly where your child is on the map." The usual reason for this is the difficulty in measuring intelligence in a young child who is not engageable for testing.
I have had some pleasant surprises over the years, as the child's intelligence becomes measurable and the atypicality begins to "melt." Likewise, when you hear of children who have been "cured" or "rescued" from ASD, the odds are they started out like Child A, with normal IQ. Whether the "rescuers" really altered the outcome is a discussion for another post.