Autism Diagnostics Special interests

Autistic Spectroscopy: Exploring what the “spectrum” means5 min read

What it means to be autistic and how the spectrum is often misunderstood-- an analogy from a science teacher.

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Autistic Spectroscopy

When Lorna Wing started talking about autism as a ‘spectrum disorder,‘ it was a major step forward in understanding what autism is.  Integrating Hans Asperger’s important work from the 1940s, she showed that many more people than had been realised have minds that have much in common with the autistic population previously identified by Kanner.

She apparently always thought of it as multidimensional, not like a linear scale; it’s been suggested that a constellation is a better way to think of this than a spectrum, which has lent itself so badly to confused ideas like “further along the spectrum.”  The spectrum analogy is strong if you break it down a bit though, and CL Lynch has recently made a great case that, “‘It’s a spectrum’ doesn’t mean what you think it means.”

As an autistic science teacher, I endorse her explanation, but I wanted to go into a little more of the physics of spectra.  If you understand what a spectroscope does, the metaphor really falls into place.

The idea of a spectrum was first introduced by Isaac Newton when he was working on optics to describe the smoothly-varying colours you get when you split white light up using a prism.  More broadly, a spectrum is anything that varies smoothly so that things can be at any point along it.

Around 1800, it became clear that not all ‘light’ is on the visible spectrum — just past one end there’s infrared radiation, and just past the other, there’s ultraviolet.  Every kind of electromagnetic radiation is on electromagnetic spectrum, but it turns out that only a tiny proportion of it is on the visible spectrum.

The electromagnetic spectrum 
runs from radio waves at frequencies below about 10 million Hertz, through radio and microwave to IR, visible light, UV, x-rays and gamma.
Illustration of the electromagnetic spectrum by Sonny Hallett.  Only light between about 10¹⁴ and 10¹⁵ Hz is visible.

 So the idea that autism is a spectrum obviously doesn’t imply that everyone is ‘on the autistic spectrum.’ Most electromagnetic radiation is nowhere near the visible spectrum!  Not only that, but most light is made up of light of various frequencies.  With the exception of some laser light, every light source has its own spectrum.

That’s what you see when light passes through a prism, or reflects off raindrops.  It’s a mistake to think of a person (or a light source) as being at a point along a spectrum; if you can, it’s much more fruitful to break it down and understand various things contributing to their nature. 

The solar spectrum

If you look at the spectrum from refracted sunlight, it is a pretty smooth continuum: it runs from blue through green to yellow to red, with no obvious gaps or stripes.  If you look really carefully, though —  and here it helps if you use a dedicated spectroscope, rather than relying on rainstorms —  it’s not as smooth as all that.

There are gaps where something has absorbed a particular frequency as the light passed through upper layers of the sun, or our own atmosphere.  There are also bright stripes corresponding to superheated elements in the sun.  Helium is named after the sun, Helios, because the first we knew of it was a mysterious line in the sun’s spectral signature a quarter of a century before it was found on Earth.

A continuous spectrum is contrasted with the bands of colour shown in the spectrum of an LED light.
The spectrum from an incandescent bulb is smooth, approximating black-body radiation.  An 11W energy-saving LED might light look the same at first glance, but it is a different kind of light.

Other kinds of light source show spectra which are much more obviously spiky.  Fireworks show the colours of the metal ions they release.  Florescents and LED lights can look white, but if you break them down, they consist of a few bright peaks —  nothing like the smooth-seeming spectrum of sunlight and incandescent lights.

If you want to see this for yourself, you can use a phone screen or a DVD as a diffraction grating, and look at the reflection of a point of light in a dark room.

A phone screen can act as a diffraction grating, splitting incoming light into a series of spectra.
My phone screen is not the best spectroscope, but I think this light is incandescent.

One thing it’s important to realise is that the same things that can cause a bright stripe in a spectrum can also cause a dark gap.  Those dark lines in the solar spectrum are at the same frequencies as the emission lines from certain elements, but in the upper layers of the sun they’re cool enough to absorb more than they emit.

There’s an analogy there with the way autistic people tend towards extremes in certain traits: we might be obsessively neat or incapable of maintaining a tidy environment.  We might develop precocious language abilities at an early age, or we might find language a struggle for much of our lives.

Often, these complementary differences come from the same place, and they can be found in the same person at different times, or in different ways.

Emission lines are absorption lines, only backwards.

CL suggests the following as components of the autistic spectrum; I’d be tempted to suggest each of these is best thought of as an emission line (or perhaps an absorption line) within the broader spectrum of human cognitive diversity, with the full autistic spectrum being characterised by the presence of most or all of these.

CL Lynch's autistic spectrum divides into pragmatic language; social awareness; monotropic mindset; information processing; sensory processing; repetitive behaviours; and neuro-motor differences. 

As with an actual emission spectrum, there may be an underlying cause for all of these, or perhaps more than one; we don’t know if autism is really one thing that manifests differently in different people, or multiple things that manifest similarly!

Unfortunately we can’t take an actual spectroscope to the human mind, so we have to study it by observing carefully, and trying to work out how people think.

CL picks out ‘monotropic mindset’ as one of the dimensions on which autism varies:

[ …  ] narrow but intense ability to focus, resulting in “obsessive” interests and difficulty task-switching.

This is accurate as far as it goes, but I do see monotropism as more like an ion than a single emission line in this story: it’s not just one feature, but a common explanation for a whole range of things.

Sodium vapour lights have two very strong emission bands in the yellow, but they also have several other emission lines at different frequencies:
There’s more to the orange-yellow glow of sodium ions than meets the eye.

If the Monotropism hypothesis is correct, the tendency to concentrate our processing resources explains our intense interests and resistance to task-switching; furthermore, it also provides insight into autistic social, processing, and motor differences.

It directly leads to the uneven skill sets that are such a central feature of autistic experience and helps explain why no two ‘spiky profiles’ quite match.  It all depends where our resources ended up getting clumped.  Developing skills in one area tends to leave other areas under-developed.

So autism is multidimensional: a constellation in hyperspace, not just a setting that can be dialed up and down.  Understanding what it means for any individual means taking on board the many ways it varies in practice.  Even so, if I’m right, a single dimension of variation — from monotropic to polytropic — indirectly explains the whole spectrum.

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