If you are autistic and ever venture or are pushed into public, a near-certainty is that you will publicly be ranked and classified by total strangers.
For example, you will be assigned to the "high end" or the "low end" of the autistic spectrum, according to whether you are claimed to have a good or bad outcome (I've been claimed to have both). Non-political observers may notice how ethically and scientifically problematic this is, but there are few discussions, formal or informal, in which autistics aren't automatically assigned "high-functioning" and "low-functioning" rankings as definitive and permanent aspects of ourselves: there are LFAs and then there are HFAs.
If the whole area of autism were not so politicized, it might have long been seen as important to check the scientific basis for these ubiquitous rankings. It might even be seen as an ethical obligation. It might be noticed that there is something wrong with discarding and therefore dishonouring the contributions to research made by the countless autistic children and adults who have been recruited as participants in autism research, and without whom there would be no autism research at all.
I've never been impressed by autism politics, on whatever "side," so I'll start with some basic information about levels of functioning as reported in autism research, then provide several examples pulled from some of the numerous papers I've recently looked at.
What does level of functioning mean in autism research?
In autism research, autistics' level of functioning is most often judged according to scores on specific tests of IQ (e.g., Wechsler) or developmental level (Mullen, Bayley, sometimes the Vineland) at a specific time.
The reported threshold dividing "high" from "low" functioning ranges from 50 to 90--at least in papers I've read so far; the actual range might be even greater. Those are IQ or IQ-type scores with a mean of 100 and a standard deviation of 15. So the threshold, the line dividing "high" from "low" functioning in autism research, is almost three SDs wide. Fall into that impressive span, and you may be high or you may be low functioning, depending on who you ask.
If 90 is the threshold, then about 25% of the entire population (autistic, nonautistic, everyone) is low-functioning. If the more common threshold of 85 is chosen, then about 16% of everyone is low-functioning.
70 is the threshold often considered to be standard even if in reality, if you read the literature, the threshold varies dramatically. But there are different tests and within commonly-used tests there are different ways to set a threshold, even when the threshold is numerically set at 70.
With this in mind, here are some examples.
Example 1
In Farley et al. (2010) the threshold is indeed 70 and autistics with lower baseline (circa age 8yrs) IQs were excluded. As the authors write, "all participants had baseline IQs in the nonimpaired range."
In fact the full-scale baseline IQs of autistics deemed to meet the 70 threshold, and included as participants, range down to 36. An IQ of 36 is near the current threshold for severe intellectual disability. An IQ of 36 (if you were under age ~4yrs) would exclude you from Ivar Lovaas' famous ABA study--you are too low-functioning.
But in different circumstances, which are specified by Farley et al., a full-scale IQ of 36 can also be considered to grossly underestimate your abilities and to put you in a study of participants who would widely be ranked as high-functioning.
Example 2
Klin et al. (2007) is another study where the autistic participants (ages 7-18yrs) are all considered high-functioning and the threshold is 70. In one of two samples, verbal, performance, and full-scale IQs run from 52 to 150. Then there are Vineland scores. While Vineland is a test of adaptive behavior, in autism research Vineland scores can also be used as measures of intelligence ergo level of functioning.
Vineland composite scores in this sample range down to 25. Two of the Vineland domain scores range down to 20. In a recent population-based study (ages 9-14yrs), an assigned Vineland score of 19 was used to represent profound intellectual disability. But in Klin et al., you can have a Vineland composite score of 25, or Vineland domain scores of 20, and you are high-functioning. You are in the same category as someone with a verbal IQ of 150.
Example 3
In Akshoomoff et al. (2004), there is also a threshold of 70, but autistics falling on either side of this threshold are included then divided into lower and higher functioning groups. Performance IQ scores in the lower-functioning group range up to 128. That is not only higher than the individual scores of the entire higher-functioning group, it is higher than all but ~3% of the entire population. If a PIQ of 128 ranks you as low-functioning, as it does in Akshoomoff et al., then almost everyone is low-functioning.
Example 4
In view of the above it might seem wise to abandon the 70 threshold and try something completely different. Annaz et al. (2009) created high-functioning and low-functioning autism groups (ages 5-11yrs) by incorrectly using the CARS (Childhood Autism Rating Scale), which is supposed to be a measure of autism "severity." This study features two measures of intelligence, one verbal (British Picture Vocabulary Scale, a verbal IQ equivalent) and one non-verbal (a subtest from the British Ability Scales).
One result is that you can have a verbal IQ of 62 and be classified as high-functioning, and a verbal IQ of 111 and be classified as low-functioning.
The non-verbal measure is reported in age-equivalents only, but the two autistic groups are remarkably well-matched on age. And the mean non-verbal age equivalents are both (1) the same for the two autistic groups, and (2) very nearly the same as mean chronological age, again for the two autistic groups.
In other words, another result is that both high- and low-functioning autistics here represent groups whose mean measured non-verbal intelligence is the same as the general population mean, and of course vice-versa. Setting aside possible differences in distribution, now everyone is both high- and low-functioning.
Conditional examples 5 and 6
This is a bit of a digression, but if you adhere to the common political or ideological prejudice that "Kanner's autism" is "classical autism" is "low-functioning autism" you are then required to achieve an IQ of over 140 (from Kanner's original 11) or 150 (from Kanner's 1956 follow-up) to be ranked as high-functioning. That means you have to be better than the 99th percentile.
Now what?
The above doesn't nearly convey the arbitrariness in the existing autism literature. As I wrote, I've provided just a bunch of examples, among many others, you will find if you read a lot of papers. Also, I've left out entire major areas, like changes over time and results from deliberate comparisons between different tests of intelligence.
While this was not intentional, the examples above might be construed as exploiting the atypically high variability characterizing individual autistics and in addition characterizing autistics as a group. Then the question is whether it serves the interests of autistics, and whether it advances autism research, to diminish, misrepresent, trivialize, denigrate, obscure, or deny this characteristic variability.
And as usual, the above can be verified by reading the existing autism literature. If there are any factual errors, as is always possible, please let me know.
Futher reading
The late Ivar Lovaas expressed his views about levels of functioning in autism in one of the major ABA manuals; this is quoted here. From a different point of view, this article concisely applies ethical consideration to the issue of level of functioning, among others. In autism politics, the dimension of autism "severity" and the different dimension of "level of functioning" are often wrongly confused or conflated. You can find science-based information about autism "severity" here and here.
References:
Akshoomoff N, Lord C, Lincoln AJ, Courchesne RY, Carper RA, Townsend J, & Courchesne E (2004). Outcome classification of preschool children with autism spectrum disorders using MRI brain measures. Journal of the American Academy of Child and Adolescent Psychiatry, 43 (3), 349-57 PMID: 15076269
Annaz D, Karmiloff-Smith A, Johnson MH, & Thomas MS (2009). A cross-syndrome study of the development of holistic face recognition in children with autism, Down syndrome, and Williams syndrome. Journal of experimental child psychology, 102 (4), 456-86 PMID: 19193384
Farley MA, McMahon WM, Fombonne E, Jenson WR, Miller J, Gardner M, Block H, Pingree CB, Ritvo ER, Ritvo RA, & Coon H (2009). Twenty-year outcome for individuals with autism and average or near-average cognitive abilities. Autism research : official journal of the International Society for Autism Research, 2 (2), 109-18 PMID: 19455645
Klin A, Saulnier CA, Sparrow SS, Cicchetti DV, Volkmar FR, & Lord C (2007). Social and communication abilities and disabilities in higher functioning individuals with autism spectrum disorders: the Vineland and the ADOS. Journal of autism and developmental disorders, 37 (4), 748-59 PMID: 17146708
Postscript: This post has been included in the 40th edition of Scientia Pro Publica.