Originally posted on Cracking the Enigma, 2nd May 2012
Back in February, we spent a relaxing two weeks cruising around the North Island of New Zealand in a campervan, quickly christened Campo by my four-year-old. We saw the giant Kauri trees of Waipoua and the giant sand dunes on 90 mile beach; we went sailing on the Bay of Islands and bathing in the volcanic springs of Hotwater Beach. And, while I was under strict instructions not to do any work, the winding roads of Northland and Coromandel gave plenty of opportunity for idle philosophising.
For holiday reading, I picked up a copy of Richard Dawkins’ The Greatest Show on Earth, in a lovely little second hand bookshop in Devonport on the outskirts of Auckland. Dawkins, it must be said, is on top form, laying out the evidence for evolution and laying into creationists and flat-earthers at every turn. The highlight for me was his joyful description of Richard Lenski’s experiments in bacterial evolution. Even for someone far removed from this line of research, it’s inspirational stuff, demonstrating the elegance and power of science done well.
In Chapter 2, Dawkins ventures on an interesting tangent, asking why it took scientists so long to figure out evolution. After considering some of the more obvious explanations (religious objections, the unimaginable timespan of evolution), he ultimately concludes by laying the blame at the feet of the ancient Greek philosopher, Plato.
Plato’s idea was that all classes of things have an essence – a set of defining properties. Members of that category may vary in other respects, but they all share that essential nature. Chairs, for example, can vary in size, shape, colour, comfort, and so on, but they are still all essentially chairs; they all have the essence of chairness; they are variations on an ideal chair.
As the evolutionary biologist Ernst Mayr pointed out, this essentialist way of thinking about things becomes problematic when trying to understand evolution. Plato would consider any natural variation amongst rabbits as flawed deviation from the ideal essence of rabbit. In Mayr’s view, Darwin succeeded by breaking away from this Platonic mindset and realising that it is this variation, coupled with non-random selection, that is the driving force behind evolution. For Darwin, there was no essential quality of rabbitness; no ideal rabbit; and, crucially, no guiding hand directing historical proto-rabbits to become more rabbit-like.
Dawkins concurs with Mayr, and spends the rest of The Greatest Show on Earth piling on the evidence for evolution from every conceivable angle. The relevant point here, however, is that natural selection is counterintuitive. Our default mode of thinking in terms of essential, idealised qualities of different species proved an obstacle to scientific progress. This probably explains why Darwin was so late on the scientific scene; why he wasn’t beaten to the punch by a scientist centuries earlier. It probably also goes some way to explaining why so many people today still deny the possibility of evolution, in spite of the overwhelming evidence. It’s an illustration that our intuitions are often wrong or misleading and that the whole point of science is that it can and frequently does defy those intuitions.
I was trying hard not to think about work. But as I read about Plato, Mayr, and the essence of bunny rabbits, it struck me that there might be important lessons for autism research. Like Darwin’s contemporaries, I wonder whether we, as people interested in autism, may be stuck in an essentialist rut.
The following, from a recent post on the SFARI blog, expresses a familiar sentiment:
“Autism is a complex, heterogeneous disorder. But the core phenotype, which can be recognized to some degree in any individual on the autism spectrum, nonetheless suggests that there must be some common underpinnings.”
We acknowledge the heterogeneity within autism, but our intuitions still drive us to seek a common essence of autism.
It’s easy to see where this intuition comes from. Essentialism underlies our definitions of autism. Diagnostic criteria are aimed squarely at defining the “core” (essential) characteristics of the disorder. We can even think of an “ideal” autistic person as someone whom Kanner would have identified as autistic – someone with “classic autism”. Diagnostic boundaries indicate how much variation away from this ideal can be tolerated before the individual is deemed to be not autistic. Common symptoms that are not part of the diagnostic criteria, such as language delay, intellectual disability, attention deficit, and so on are considered to be non-essential “co-morbidities”, separate and on top of the autism.
The essentialist view of autism goes hand in hand with the way autism research is conducted and reported. Most studies involve taking a group of individuals with autism and comparing them to a control group. The assumption is that the group average is what matters. Individual differences within the autism group are considered to be non-essential variation.
Studies are then reported as showing, for example, that people with autism are good or bad at a particular test, that their brains are over- or under-activated in response to a particular stimulus, or that they do or do not respond to a particular intervention. This kind of generalization, from the handful of individuals taking part in the study to “people with autism”, is only licensed if people with an autism diagnosis are interchangeable – if they are essentially the same. Yet one only has to meet a few individuals to realise that this is not the case.
The Platonic mindset is revealed most explicitly by the widespread view that theories of autism should be evaluated according to their universality and specificity; the theory should apply to everyone with an autism diagnosis but nobody without autism and failure on either criterion is grounds for rejecting a theory.
A recent exposition of this view comes from a paper by Kevin Pelphrey and colleagues in a paper criticising the theory that autism stems from reduced connectivity in the brain:
“it is not yet clear how the underconnectivity perspective accounts for the specific patterns of dysfunction in individuals with ASD. That is, how might this perspective explain what is common among individuals with ASD and what separates ASD from other neurodevelopmental disorders that also feature underconnectivity?”
This is certainly a valid criticism insofar as proponents of “underconnectivity” sometimes portray it as a theory-of-autism, conveniently ignoring the evidence for atypical connectivity in other disorders. But Pelphrey et al.’s alternative is to look for the essence of autism elsewhere – in the brain mechanisms underlying the “core disruptions in social information processing”. Notably, none of the evidence from their own research comes close to universality or specificity either.
The problem doesn’t just apply to brain imaging studies. At every level of analysis, from genetics and neurobiology through to cognition and behaviour, there is variation within autism and overlap with other disorders. This all tends to undermine the fundamental underlying assumption that there is this discrete thing called autism that people either do or don’t have. This isn’t the same thing as saying that autism doesn’t exist – any more than Darwin was proposing the nonexistence of rabbits. But it does suggest that we need to change the way we think about and research autism.
There are certainly moves in this direction, with increasing interest in autism subgroups, individual variation, and cross-diagnostic comparison. Perhaps the most radical new approach was recently announced by the Simons Foundation. Their Variation in Individuals Project is looking at deletions and duplications in region 16p11.2 of chromosome 16, which has been linked to autism, developmental delay, schizophrenia, and bipolar disorder. But rather than looking only at people who meet criteria for a particular condition, participants are being recruited and studied regardless of their diagnosis.
This I think is beginning to approach the crux of the problem. Ultimately, “autism” is a label for a set of behaviours. By always beginning with autism and working backwards, we have invested too much significance in the label itself.
Another bookshop, this time back in sleepy old Brooklyn, New South Wales. Hiding behind the anniversary edition of The Selfish Gene is a small battered copy of The Common Sense of Science by Jacob Bronowski. Flicking through, I stop on page 62.
“In many scientific problems, the difficulty is to state the question rightly; once that is done it may almost answer itself.”