Thursday, February 17, 2011
Psychometrics Here I Come
Because the regional autism programs in Ontario rely so much on standardized testing to determine how well intensive ABA (known as IBI in Ontario) is working, I have (probably not surprisingly to some readers) taken an active interest in psychometrics - instruments, theory and interpretation. It's really quite fascinating, but at the same time - potentially unfair - to children with autism and their parents.
There are two measures of importance that regional autism providers use to determine if IBI is effective. The first is called adaptive behaviour. A measure of adaptive behaviour is basically a test that determines how well - compared to children of the same age - a child is able to function "in the real world". Examples include understanding when people give instructions, being able to ask for something, using the toilet, making phone calls, understanding that cars are dangerous, how to make friends, following rules, and how to play on a playground or cut with scissors. It essentially covers everything we need to do in order to live independently "normal" lives. Some psychologists use it as a measure of development because if someone has the adaptive behaviour of a two year old, they will mostly act and behave like a two year old does, even if they are say, four. This is vastly different from intelligence (discussed next) because it is a very practical measure. Someone with high IQ could potentially solve differential equations but yet be unable to make change. Making change is much more practical (i.e. useful in everyday life) than solving equations (and more of the population can do it), so it's an adaptive behaviour but solving equations is not.
Most people with autism have severe deficits in adaptive behaviour. If they didn't, they wouldn't have autism. Usually as children with autism age, they continue to develop, but still slower than their peers, so their overall level of functioning continues to become more delayed. If intervention can slow the delay by increasing rate of development, the Ontario regional autism providers deem IBI to be successful.
Intelligence is a completely different matter. Although many estimate 75% of children with autistic disorder (not Asperger's or the generic PDD-NOS) to have a cognitive disability (IQ < 70), some do not have a cognitive delay or intellectual disability. This is another important measure guiding discharge for IBI because if a child has an IQ equivalent of 24 month old and has adaptive behaviour around 24 months (or lower) and little change is observed, they typically will discharge from IBI with the explanation that the child has "maximized their potential given their cognitive functioning."
There are two types of intelligence. Crystallized intelligence (often abbreviated Gc) is intellectual ability for a particular task. Generally tests that look for Gc are verbal tests and involve vocabulary and knowledge of the world. Children with autism usually do poorly with Gc. It is very difficult to do a verbal test if you can't speak. For this reason, good psychologists will measure non-verbally, using the non-verbal part of a test, or a non-verbal test that provides a full scale IQ.
Fluid intelligence (often abbreviated Gf) is general intellectual ability that can be applied in all situations. It is usually tested with non-verbal tasks, such as doing puzzles, mazes, replicating block designs, remembering things, visualizing 3-D shapes in your head, etc. Children with autism do much better at these tasks because they don't require language.
If you are interested, here are some common tasks that measure Gf that have been adapted for use on most modern IQ tests, such as Weschler tests: