004 Atypicality, IQ, and Diagnostic Categories

Any degree of atypicality from mild to severe can coexist with any level of intelligence, from genius IQ to profound mental retardation. (If you're new to this blog, go back and read the last couple of posts). Here is our graph again, depicting Atypicality on the horizontal (X) axis, and Intelligence on the vertical (Y) axis. Atypicality runs from severe to mild on the X axis, with severe atypicality on the left and mild atypicality on the right. Intelligence runs from Genius IQ at the top of the Y axis, down to profound mental retardation at the bottom of the Y axis. The Origin (where the two axes cross) corresponds to moderate atypicality and an IQ of 70 (IQ below 70 is in the range of mental retardation).

This time, we've added some of the commonly used labels that are in circulation at the moment.

Source: James Coplan MD

First, notice the large circle occupying the entire left side of the graph, labeled AUTISM. This circle encompasses anyone whose atypicality on the X axis is Moderate to Severe (the entire left side of the graph, spilling over a bit to the right side of the graph): poor eye contact, delayed and odd language (echolalia, odd inflection, etc.), intense stereotypes such as flapping or spinning, rigid behaviors and sensory reactions, etc. The circle is composed of two equal halves: The upper half of the circle is designated "High Functioning Autism," and the lower half is designated "Low Functioning Autism." The difference between High- and Low-functioning autism is not the degree of atypicality (moderate to severe in all cases), but the coexisting level of general intelligence.

Next, notice the dashed circle (actually, an ellipse) in the upper right hand quadrant of the graph, labeled Asperger Syndrome (AS). Persons with AS, by definition, have general intelligence in the normal range; that's why the AS circle is strictly above the X axis; there is no such thing as "low functioning AS." Second, and not actually depicted on the graph, is the fact that persons with AS are hyperverbal. (The DSM gets this wrong, simply stating that there is no gross delay in language, but failing to emphasize the signature feature of AS that figures so prominently in Dr. Asperger's original description).

At their extremes, Autism and Asperger Syndrome are easily distinguishable by the presence or absence of relentlessly hyperverbal, pedantic speech. However, Mother Nature does not put everyone into neat little cubbies. This brings us to the stippled area in between Autism and Asperger Syndrome, labeled PDD-NOS (Pervasive Developmental Disorder, Not Otherwise Specified). The Term PDD-NOS indicates moderate to mild atypicality, without falling cleanly into either the category of Autism, or the category of Asperger Syndrome. If we wished, we could break PDD-NOS into two portions: "High Functioning PDD-NOS" (IQ 70 or above) and "Low Functioning PDD-NOS" (IQ below 70), exactly as we have done for Autism, to emphasize the importance of IQ as a factor driving prognosis. Unfortunately, this is not generally done. But two children with the same degree of atypicality will have vastly different outcomes, depending on the coexisting IQ.