Experiential Blindness

Imagine a huge field strewn with rocks, perhaps like the fields around West Kennet Long Barrow, littered with hunks of flint. Now picture the field is full of academics hurling the rocks at each other, occasionally with epithets. So there you are, walking alongside the field, picking up bits of rocks and showing them to your fellow walkers saying “Look at this one. Isn’t it interesting? Isn’t it pretty!”, whilst trying not to get caught up in the flinty free for all beside you. Reading about cognition and perception is a bit like that. So… here’s a chipping from the flint that is currently holding my attention

I’m currently reading “Action in Perception” by Alva Noë. I can’t pretend that I’ve fully wrapped my head around the depths of his argument but some of the opening material is giving me pause for thought. In the introductory chapter, he relates case studies that describe the experience of people receiving their sight, usually after some form of restorative surgery. The descriptions of these people’s experiences (both on p5 of the book) are striking…

Drawing from the work of Gregory & Wallace, he recounts on patient’s experiences when the patient’s bandages were removed after cataract surgery: “[The patient] heard a voice coming from in front of him and to one side: he turned to the source of the sound and saw a ‘blur’. He realised that this must be a face. Upon careful questioning, he seemed to think that he would not have known that this was a face if he had not previously heard the voice and known that voices come from faces.”

He also cites one of Oliver Sacks’ observations of his patient, Virgil, in similar circumstances: “[In] this first moment, he had no idea what he was seeing. There was light, there was movement, there was colour, all missed up, all meaningless,  all a blur. Then out of the blur came a voice that said ‘Well?’ Then, and only then, he said, did he realise that this chaos of light and shadow was a face and, indeed, the face of his surgeon.”

(It seems to me that there is also a passing similarity with the account in the Gospel of Mark when after Jesus restores a man’s sight he asks the man if he can see anything and he says “I see people; they look like trees walking around.” (Mark 8:24, NIV) which intrigues me.)

Noë proposes that these people’s experiences can be accounted for with the concept of experiential blindness. That is, although these people were receiving some form of visual input (visual sensation) they were not able “to integrate [that] sensory stimulation with patterns of movement and thought”. (p4) “Their visual sensitivity is restored, to be sure. Each of them undergoes dramatic and robust visual impressions or sensations in the immediate aftermath of the surgery. But none of them, in having these sensations, bas acquired the ability to see, at least not in anything like the normal sense. The visual impressions they now receive remain confusing and uninformative to them, like utterances in a foreign language. They have sensations, but the sensations don’t add up to experiences with representational content.” (p5) It is worth recalling that in Sacks’ account (above), Virgil describes his sensations as meaningless.

There are 2 ideas in there that are central to the argument that Noë goes on to develop: (1) that sensory stimulation needs to be integrated with patterns of movement and thought; and (2) that there is a distinction between sensory stimulation and perception. The role of movement and action in perception is critical to his model of enactive perception and I’ll save that one for another blog entry, once I’ve thought on it some more. The second point, regarding the role of cognition in perception is something that has created the more immediate challenge for me.

At one point, Noë characterises perceptual experience as that which has “genuine world-presenting content” and is distinct from mere sensory stimulation. This applies to all forms of sensation, not merely visual. Furthermore Noë argues that for the stimulation to constitute perceptual experience “the perceiver must possess and make use of sensorimotor knowledge” (p10). (To follow this thread further would be to drift into point (1), so I’ll stick with this distinction for the moment.) So, to clarify (hopefully!), raw sensory stimulation is insufficient for meaningful perceptual experience. We, the perceivers, do something with that stimulation to make it meaningful. This is the idea that has thrown me.

I’ve written in previous blogs about Daniel Heller-Roazen’s book. Through the chapters of that book, Heller-Roazen develops the arguments that perception is fundamental to identity and (following Liebniz) that perception precedes cognition. How to resolve the tension?

Part of the answer may lie with what is meant by cognition. Later in his book (p117-122), Noë begins to explore the possible form of sensorimotor knowledge. Here he argues that it may take the form of ‘non-propositional know-how’ (p122) or ‘expectations’ (p119) that the perceiver acquires over the course of their life but may not be able to explicitly voice. (That said, Noë is keen to avoid the idea of tacit knowledge.) So here is the idea that the cognition needed to render sensory stimuli meaningful is not necessary on the level of conscious, deliberative thought but something experiential and below the level of conscious awareness. It could also be said (perhaps) that sensorimotor knowledge must be a form of memory..

This separation of sensation and perception accommodates (I think) examples such as when my wife would leap out of bed at the sound of a crying baby before she was actually awake: the auditory stimulus had been given meaning while she was sleeping and she responded automatically (rather like those sub-cortical threat-avoidance mechanisms / pathways that are utilised when a large object comes bearing down on us). The more I think about this bit the less sure I am.

It may also shed light on another conundrum seen in the experience of people with dementia…

It has been noted that people with dementia sometimes live in the past to the extent that they do not recognise themselves in the mirror nor their partners of many years. If we take the visual stimuli to be that which the person with dementia gains by looking at someone’s face then, initially, it has no meaning. The meaning-laden perceptual content is given by the person with dementia based on their knowledge. But their knowledge has been damaged by the dementia, so that there is a mis-match between the objective world around them and the meaning that they can give to it.

Perhaps something similar was at play when I delivered handling sessions for small children using contemporary craft objects. But to think my way through that one I need to deal with Noë’s idea of sensorimotor knowledge more thoroughly…

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About Bruce Davenport

Museum educator and researcher.
This entry was posted in Cognition, dementia, Perception. Bookmark the permalink.

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