Tuesday, May 24, 2011

Mirror Symmetry

I'm afraid I have very little time for autism discussions these days, but I do want to make a few quick and unstructured remarks about the Mottron team's recent paper on mirror symmetry (Perreault et al. 2011). [And please note, I am using the term “Mottron team” simply as a rhetorical shortcut to reference the various people associated with Laurent Mottron and his research labs; as far as I know, there is no such thing as a formal Mottron team.]

First off, (Perreault et al. 2011) is one of the more well-crafted papers I have seen in recent history. Concise, well-written, with an extremely instructive and informative Discussion section. Although I still object to multiple-author papers on principle, the inclusion of a forthright Author Contributions section helps ameliorate some of the concerns. (I sure would like to see some of the hundred-author goliaths make a similar attempt at explaining who contributed what—that might be eye-opening.) More wonderful yet is that the paper has been published in an open access journal, so that everyone can read it without having to beg, borrow or steal a copy. Thoughtful science that can be reviewed by the public at large—now there's a radical idea!

This study is fairly straightforward and simple. It uses a series of pixel-based images to measure recognition of symmetry around various axis orientations. In short, the study reports two major findings: 1. both autistics and non-autistics are more capable of recognizing vertical symmetry than symmetry around other axis orientations; and 2. as a group, autistics are more capable of recognizing symmetry (around all axis orientations) than non-autistics are.

This is yet another result indicating that autistic perception seems to be geared towards recognizing various forms of structure and pattern to be found in the surrounding sensory environment. Similar results have been reported in for instance (Klin et al. 2009) and (Annaz et al. 2011), and of course the most eloquent discussion of this idea can be found in (Mottron, Dawson, Soulières 2009). What makes the members of the Mottron team unique in this regard is that apparently only they recognize that this characteristic of autistic perception is not a defect to be treated, but is instead a trait that can be valuable and profound. It would be difficult to overstate the importance of that recognition, or to overstate the blindness of researchers who fail to make a similar recognition.

As much as I like (Perreault et al. 2011), I do have a couple criticisms to make. The first is a criticism I have made in the past regarding the Mottron team and its efforts. For a team that does such an exceptional job of providing detailed, thoughtful, inventive, evidence-based descriptions of autistic perception, I am utterly astounded at how little effort is made towards providing a corresponding description of non-autistic perception. In this paper for instance, the complete discussion of non-autistic perception can be found in the statement “such parallel access would be less likely in non-autistic individuals, whose ability to use local information from early visual areas would be diminished due to typical globally-biased processing hierarchies.” Come to think of it, that is about thirty words more devoted to the subject than in past Mottron team papers. Indeed, if you were to fill in the persistent blanks from (Perreault et al. 2011) and most other Mottron-team articles, you would have to arrive at the following conclusion: non-autistic perception is simply a deficient form of autistic perception, completely lacking in local processing strength, utterly bereft of adequate perceptual processing and clearly defective at recognizing environmental structure and pattern. Heck, the Mottron team has even managed to perform some comparative brain imaging studies so that we can see in full glorious detail which sections of the non-autistic brain must be tragically miswired!

Of course, having had experience with this type of argument before, I feel fairly confident in saying that there is nothing deficient or defective about non-autistic perception at all—non-autistic perception is simply a different form of perception, with its own set of strengths and weaknesses, and should be valued as such. If it turns out that autistics do indeed possess enhanced perceptual functioning—as the Mottron team likes to suggest—then I assert that non-autistics must also possess an enhanced something. But ask the Mottron team what that enhanced something is and you will apparently get nothing in return but silence. That annoys me. All the excellent work the Mottron team has put into accurately and thoroughly describing autistic perception is going to go to waste if not accompanied by a similarly accurate and thorough description of non-autistic perception. The two shed light and contrast on each other.

I have many times suggested that the enhanced something of non-autistic perception is the keen ability to be species-aware or species-focused, to be perceptually sensitive to the species-related features to be found in the surrounding sensory environment. The Mottron team is perfectly free to disagree with that point of view, to provide alternatives, to weigh in with evidence, etc. But to remain silent on the subject—that I find hard to comprehend.

My other criticism has to do with the argument that sensitivity to vertical symmetry can serve as a proxy for global processing. It may be that I'm misunderstanding the argument, but if I'm reading it correctly it seems to run something like this:

  • Non-autistics, who tend to be good at global processing, are more sensitivity to vertical symmetry.
  • Perhaps non-autistic sensitivity to vertical symmetry is driven by biological experience, such as the awareness of human faces (which evince vertical symmetry).
  • Since autistics are more sensitivity to vertical symmetry than symmetry around other axis orientations, autistics must also possess some of the same global processing abilities and biological awareness as non-autistics do.
  • But in addition, since autistics are more sensitive than non-autistics to symmetry in all orientations, autistics must also possess local processing and other perceptual strengths. (Thus, autistics can see both the forest and the trees, as the authors would have it.)

To be honest, I'm not sure any of that argument scans logically, but even putting that concern aside, I have a much bigger objection to the use of vertical symmetry as a proxy for global processing, and I can sum that objection up in one word: gravity.

On the surface of this planet, the main line of force runs straight up and down. Indeed, that's what vertical means—it's the axis of orientation in line with gravity's effect. In an environment in which there were no primary line of force, the assignment of vertical would be an arbitrary choice. But it's not arbitrary around here.

For various biological and physical reasons all relating to gravity, the primary form of symmetry to be found on the Earth's surface is vertical symmetry. Many plants and animals have evolved in concert with vertical symmetry, because fighting the effects of gravity is not biologically economical. This preference for vertical symmetry has also carried over to man's many constructions—the Parthenon for instance is an orgy of vertical symmetry, because otherwise it would fall down. And not only are most of the objects being perceived oriented around vertical symmetry, the entities doing the perceiving are also oriented in the same way. Look at the position of the eyes, ears and hands and tell me that we (and most other animals) are not naturally geared towards the perception of vertical symmetry. Vertical symmetry is the rule on this planet; everything else is the exception.

Thus as a surmise, I could take autistics and make the assumption that they have no global processing abilities whatsoever and no biological recognition at all, including the recognition of human faces, and yet I would still expect them to have more sensitivity to vertical symmetry than to any other orientation. Whatever autistics are perceiving in their environment the chances are still extremely high that it is mostly oriented around vertical symmetry. That is just a natural consequence of being an inhabitant of the Earth's surface.

To be honest, I'm not sure I even understand what global processing is supposed to mean. But when it comes to explaining perceptual sensitivity to vertical symmetry, I don't need to understand global processing. Gravity makes for a far simpler explanation.

Criticisms aside, (Perreault et al. 2011) is yet another instructive work from the Mottron team. That team's continuing emphasis on autistic perception and the team's recognition of the importance of symmetry and pattern to autistic perception have provided a consistent, positive way forward to understanding autistic individuals, valuing their contributions, and helping them to succeed. As usual, I find myself both rewarded and inspired by these thoughtful efforts.

(Perreault et al. 2011): Perreault A, Gurnsey R, Dawson M, Mottron L, Bertone A. 2011. “Increased Sensitivity to Mirror Symmetry in Autism.” PLoS ONE 6(4): e19519.

(Klin et al. 2009): Klin, Ami; Lin, David J.; Gorrindo, Phillip; Ramsay, Gordon; Jones, Warren. 2009. “Two-year-olds with Autism Orient to Non-Social Contingencies Rather than Biological Motion.” Nature 459: 257–61.

(Annaz et al. 2011): Annaz, D.; Campbell, R.; Coleman, M.; Milne, E.; Swettenham, J. 2011. “Young Children with Autism Spectrum Disorder Do Not Preferentially Attend to Biological Motion.” Journal of Autism and Developmental Disorders (ePub ahead of print).

(Mottron, Dawson, Soulières 2009): Mottron L, Dawson M, Soulières I. 2009. “Enhanced perception in savant syndrome: patterns, structure and creativity.” Philosophical Transactions of the Royal Society 364: 1385–1391.


autismnorthernireland said...

What an incredible piece of writing, well thought out and easily understandable critique.
Thank you for that!
Please let us have more of your thoughts on 'core deficits' as well. This bugbear continues to thwart the independence and success of so many individuals with autism because it is used as an excuse by 'professionals' to deny those individuals help because they 'have core untreateable deficits' - yeah right.

love your blog, really do!! Can you make your text a bit bigger?

autismnorthernireland said...

my bad, your text is fine - it was my view settings!!