On posting comments

It seems that some people are unable to post comments on this blog. If you are in that situation, please feel free to email your comments to me (davidwhitehorn@eastlink.ca) and I will post them for you.

Below are two interesting comments sent to me from Dennis P. I will respond to them in a day or so. Thanks Dennis.

Re: An Optical Illusion and Psychosis (April 21, 2009)
Hello David:

This is a fascinating observation, but I think that we have to be a bit careful in how we interpret it. Saying that we "impose our preconceptions" on the sensory data is cognitively loaded and carries a connotation of intentionality, while the processes at work may not be particularly cognitive at all. Our brains have encountered thousands (millions?) of examples of faces in our experience, including under conditions of degraded sensory input, prior to exposure to the stimulus evoking the illusion. The hollow mask stimulus confronts us with sensory data that are somewhat ambiguous, and most intelligent perceivers (man or machine) would probably default to the interpretation that has been helpful so many times before. I'm reminded of the case of relative motion. When a small object and a large object move relative to each other in the absence of other disambiguating information, the default interpretation is that it is the smaller object which is moving because the perceptual system has encountered that scenario far more often than the alternative. In both the "hollow mask" illusion and relative motion cases, we don't need to postulate that the perceptual system is attempting to "match our past experiences"; rather, the perceptual system uses past experience to provide the most likely interpretation of incoming, impoverished sensory data.

It remains fascinating that schizophrenics may not generally behave this way (at least with regard to the hollow mask illusion), and your point that our past experience influences our present perceptions is well taken. The point I'm trying to make here is that the mechanism through which experience expresses its effect may be much more low-level than the cognitive one that the expression "impose our preconceptions" implies. As I type this, it occurs to me that a low-level account of the hollow mask illusion might speak to the "salience" issue raised in your earlier posts: is the finding with the hollow mask illusion evidence that schizophrenics have an impaired ability to weight the data from the various sources of information (bottom-up, top-down) normally used in perceptual judgements? I hope that this helps. Kind wishes,

DPP


Re: Separating 'this' from 'that' (February 26, 2009)

Hello David:
I wonder how much of this "duality" is a natural consequence of the human gift of language? As soon as we apply the (linguistic) label "chair," everything else becomes "not chair." On the one hand, as you imply, this skill is what makes our interactions with others, and with the world, so workable. On the other hand, the labels create a duality that runs counter to the reality of the interdependence of all things, or "interbeing," to borrow the term from Thich Nhat Hanh. A quite striking case supporting this view is the work of Jill Bolte Taylor (see "My Stroke of Insight"; see also her talk at ted.com), the neuroscientist who suffered a left hemisphere stroke which, among other things, left her temporarily with a severe language impairment. In her book, Taylor describes her perceptions at the time of the accident, which I might in turn describe as "perception stripped of language." In this state, Taylor experienced a loss of boundary between self and other, and something of a dissolution of ego as hard, separate, and permanent; instead, everything, including perceptions, became fluid, with a distinct sense of "flow." This afforded Taylor a quite profound insight. It also rendered her interaction with her world almost unworkable.

Jill Bolte Taylor's retrospective descriptions of her stroke experience use a language (so to speak) that is a little different to that offered by meditation masters trying to teach us about absolute and relative truth. It seemed to me, however, that the descriptions have common themes, and this made me wonder if one of the insights provided by the disciplined meditative practice is to "see" past the language layer that we automatically impose on what would otherwise be more direct perceptions. Perhaps the real gift of being human is the ability to have a heartfelt appreciation of interdependence and impermanence, balanced with a language facility that enables us to communicate effectively with our world.
Thanks for your blog. Kind wishes,
Dennis PP