Tuesday, January 20, 2015

Perceptual Transparency and Sinha’s Observations
In 1976, when I delivered the John Locke Lectures at Oxford, I often spent time with Peter Strawson, and one day at lunch he made a remark I have never been able to forget. He said, "Surely half the pleasure of life is sardonic comment on the passing show".  This blog is devoted to comments, not all of them sardonic, on the passing philosophical show.
Hilary Putnam

Pawan Sinha, who with Richard Held carried out the observations on children in India who had been blind from birth and subsequently (at ages ranging from 8 to 17) had their vision restored with the aid of corneal implants - experiments that I described in the previous post (as well as in my post of August 27, 2014) has shared the following observations with Held and myself:

“     Regarding Prof. Putnam's question about the subjective reports of children prior to the establishment of cross-modal connections, I think the answer is rather unremarkable. The children do have a sense of 'objectness' in the visual domain. They have difficulties parsing an image into distinct objects, but they do seem to understand the notion of objecthood. For instance, after their surgery, one can wiggle fingers in front of their eyes and ask how many things they see. If they are familiar with counting, they can respond correctly. Similarly, one can ask them to enumerate the number of items scattered on a plain background. I think some of this sense of objectness has its genesis in the fact that the children have light perception prior to surgery. This also means that they can see vague shadows when they pass their hands over their eyes in bright sunlight. Even this very rudimentary stimulation may suffice to help them associate the notion of objectness derived from proprioception and touch with one in vision.”

This further information is fascinating, but in no way incompatible with my claim that the Held-Sinha observations show that “transparency” is not innate or intrinsic to visual experiences. To explain why it isn’t incompatible, let me describe the issue as it now arises in the philosophy of visual perception. First. a couple of words about what the debate isn’t about. The transparency thesis is a thesis about all visual experiences. That is why Molyneux patients (as I shall call them) and Held’s famous kittens are highly relevant. The key claim (of, e.g., “representationalists” like Tye) is that transparency (or “diaphanousness”) is not just a normal feature of (mature, human) visual perception, which is uncontroversial, but that it is an essential  feature of all visual experience, i.e. there couldn’t be a visual experience which lacked it. The defenders of  “perceptual transparency” are transparency essentialists. So it is enough to show that some visual experiences are not “transparent” to refute their position.
Secondly, the debate is not about whether one could have a visual experience without having “the notion of objectness” – if I understand that question, it would seem to be about whether perception is conceptualized, which is a different issue[1]. Moreover, even if the defenders of transparency were claiming that subjects conceive of what they see as objects, in the logical sense of object, in which anything one can count (including shadows) is an object”,  that sense of object is much too weak to capture the idea that perception is “transparent”.
So, not to keep you waiting, I want to come to what “transparency” is supposed to be, and finally to a related question, whether what Sinha reports is or is not in conflict with what Ostrovsky et al reported[2].

What “transparency” is supposed to be

The observation that visual experiences are normally experienced as transparent goes back to G.E. Moore (who was not a transparency-essentialist, however). The following paragraph from Moore’s Refutation of Idealism has been widely quoted:

“…when we refer to introspection and try to discover what the sensation of blue is, it is very easy to suppose that we have before us only a single term. The term blue is easy enough to distinguish, but the other element which I have called consciousness — that which sensation of blue has in common with the sensation of green — is extremely difficult to fix. That many people fail to distinguish it at all is sufficiently shown by the fact that there are materialists. And, in general, that which makes the sensation of blue a mental fact seems to escape us: it seems, if I may use a metaphor, to be transparent — we look through it and see nothing but the blue.”

Similarly, in  Seeing Things As They Are: A Theory of Perception (p.188), John Searle explains transparency thus:

“The veridical case of the perception reaches right up to the object itself. We see right through to the object, we do not see any intermediate entities, and the description of our perception is precisely a description of the object in the external world. If you try to describe the experience, you end up describing the objects and states of affairs that you perceive.

Speaking for myself, I think that what it is to see something as “an object in the external world” is to see it as possessing what Gibson called “affordances”, e.g., as something I can touch by stretching out my hand so, or, alternatively, as something “too far away to touch”. If that is what transparency means, then Held’s observations (both on kittens and on Molyneux patients) shows that transparency is learned and not innate or intrinsic to the visual sensations themselves. That is why I think that the fact that cross-modal connections are learned already refutes transparency. “Out-thereness” is cross-modal. But even if there is a sense in which a purely visual sensation, unassociated with any haptic elements, could look “external”), if even some subjects satisfy the description of Ostrovsky et al, even part of the time, viz. “they pointed to regions of different hues and luminances as distinct objects. This approach greatly oversegmented the images and partitioned them into meaningless regions, which would be unstable across different views and uninformative regarding object identity”, then in those situations even if they think of those regions as “objects”, they don't see them as external  objects in any meaningful sense of “external”. If even visual sensation of the sort these investigators describe count as experiences of “external objects”, what content does “external” have?

[1] See Hilla Jacobson and Hilary Putnam, “Against Perceptual Conceptualism”, International Journal of Philosophical Studies (accepted). 
[2] Here is a description of the subjects studied by Ostrovsky et al:
“subjects’ responses were driven by low-level image attributes; [when asked to point to objects] they pointed to regions of different hues and luminances as distinct objects. This approach greatly oversegmented the images and partitioned them into meaningless regions, which would be unstable across different views and uninformative regarding object identity. A robust object representation is difficult to construct on the basis of such fragments”  (Ostrovsky, Y., et al. 2009. “Visual parsing after recovery from blindness”. Psychological Science 20, 1484-1491. 


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  2. Hmmm...I tried to post a response to this but I;ll try again now. I think what Sinha showed is that there is a critical period for object-perception. He did not show that we have to learn cross-modal connections. There is a ton of data showing that human babies have built-in cross-modal connections at birth. Human babies will turn towards a sound at birth. And human babies prefer to look at a picture of the pacifier they have in their mouth. Also, babies imitate facial expressions. Here is a movie of a 10 minute old baby doing that.

  3. really nice article, and very clearly descriptive

  4. hi! really nice article, and very clearly descriptive. thanks



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