Monday, September 13, 2010

Meaningless Aperture Vision?

In an earliest post, I wrote " something is going on during episodes of so-called "aperture vision" and a scientist might well want to know what.  So, why not have a scientific study of aperture vision along with a scientific study of "the actual binocular vision system"?

In the comments, Gary wrote the following

What he meant was that mere sensory stimulation falls shorts of *meaningful* perceptual awareness i.e. an awareness of an affordance. It isn't like when you look through an aperture your vision fades to black or anything, *it just doesn't mean anything*. Gibson liked to talk about the Ganzfeld experiments wherein subjects looked at an undifferentiated visual field (you can try this with cut-open pingpong balls; it's fun). When you perceive an undifferentiated visual field (such as when looking at the pure sky), there is *sensory stimulation* but no available *stimulus information* and thus no perception an affordance, which is defined in terms of stimulus information (the information discrimination of which can help effectively regulate your changing relationship with the environment).

So Gibson would respond to Ken by saying that in the aperture experiment, there is mere sensation going on, but no perception, because perception is defined as the discrimination of meaningful ecological information and there is none available in the ambiguity of the aperture experiment.
I hope that clarifies things. 
So, here's a claim: in aperture vision there is no discrimination of meaningful ecological information.

I don't understand why that is true.   Don't the windows, or children, or balloons give me meaningful ecological information? Don't the windows afford something like "see-out-ability"?

And don't the doors in the version of the Ames room belong afford "walk-through-ability?"


  1. Gary's not quite precise enough, I don't think. A quick Google found me this by Sverker Runeson, and it's much more detailed:

    Runeson, S (1988). The distorted room illusion, equivalent configurations, and the specificity of static optic arrays. JEP:HPP 14(2), 295-304.

    Runeson goes over an ecological analysis of the DRI with reference to an earlier JEP paper that had tested the magnitude of the illusion with the head restrained so the eyes were in the right place vs. free head movements and binocular vision. They found the illusion effect decreased from ~70% to ~9% with this simple change (although they interpret this residual effect as still refuting Gibson - see what we have to put up with!! :) Given the tiny scale of the allowed free viewing movements, this is an astounding effect; hell, you can't visually perceive metric object shape without perspective shifts of up to 45°!

    Anyway, Runeson does the business on the Ames Room in his usual style; this I think should answer any questions :)

  2. The Runeson piece was in the queue for tomorrow, but I'll post it in a minute.

    So, I like the paper because it shows a way to provide a Gibsonian analysis to the case.

  3. I wouldn't say that the paper answers all questions. In truth, it seems to me to get the discussion back on empirical track. Now, we are not dumping on the study of the Ames room as boring or irrelevant. We are back to seeing how Gibsonian theory can be applied, or not, to the Ames room.

    I was reading this paper this summer, when I was very disappointed to find that p. 299 of the copy available through Google scholar is cut off half-way through. I got sidetracked before I got a complete copy (which I have now).

  4. Ken,

    Andrew was right. My initial formulation was not precise enough to apply to the Ames room. I would say that, in the particular case of the Ames room, there is ambiguity in regards to the stimulus information for the spatial-depth of the room but there is also meaningful stimulus information in regards to some things such as that there are windows, people, doors, floors, etc. I don't think perceptual failure is an all-or-nothing affair.

    But I was not precise in that formulation because I wanted to capture a problem with contemporary psychology from the ecological perspective. The artificial nature of these experiments on illusions is such that natural mobility is restricted (for methodological purposes). When you introduce mobility into vision science the *information available* for the organism becomes radically different. If we are going to build a science of psychology, then we need to study perception under natural conditions where the organism is in full contact with all the affordances that were available to its evolutionary ancestors. Darwin's study on the functional specificity of earthworm perception is a good examples (See Reed 1996).

    Gibson doesn't really repudiate the conclusions of these vision researchers, he just states them differently. Rather than saying that these experiments on immobile sensation support the idea that meaningful perception itself is about constructing mental models which are read out in order to determine what specific commands to produce, Gibsonians can simply say that such experiments emphasize the way in which meaningful perception is based on the detection of information and it is no surprise that when you restrict the natural means by which to detect information (locomotion), perception will falter and so-called "misrepresentations" will occur. However, the misrepresentations are interpreted as failures in process of information detection, not failures in the process of constructing mental models. The power of Gibsonian information processing is that it brings with it a normative structure of good perception vs bad perception without the possibility of radical skepticism as with computational neuroscience (brain-in-a-bat, inverted spectrums, etc.).

  5. Gary,

    Re: your paragraph #1. Let's make claim 1)more precise along the lines of 1*):

    1) in aperture vision there is no discrimination of meaningful ecological information.

    1*) in aperture vision there is no discrimination of meaningful ecological information regarding the spatial-depth of the room.

    If the Gibsonian says that there is no meaningful ecological information regarding the spatial-depth of the room, then how is it that one gets the impression that the room is rectangular? It still sounds like the view is that ecological psychology does not apply to this case.

  6. Gary,

    Re: your paragraph 2. My question about aperture vision began with the idea of focusing on it alone, setting aside the larger question of how the results from such a narrow kind of study would, or would not, bear on the whole of contemporary psychology.

  7. Gary,

    Re: your claim "Gibson doesn't really repudiate the conclusions of these vision researchers, he just states them differently."

    Gibson writes, "The demonstrations do not prove, therefore, that the perception of layout cannot be direct and must be mediated by preconceptions, as Adelbert Ames and his followers wanted to believe" (Gibson, 1979, p. 168). That seems, to me at least, to be a repudiation of the conclusions of Ames (and Ittelson).

  8. The Ames room isn't complicated. At one (and I mean one) very particular point (and I do mean point) in space, the static perspective structure specifies a rectangular room. The paper Runeson reviewed showed that a) even with the head restrained the illusion is only of a certain magnitude and b) the instant you allowed people to move away from the approximation of the single point in (a) the illusion effectively broke.

    If at time-1 you are that single point, then for the duration of your stay you will perceive the room as rectangular. The reason this isn't really all that interesting is that this can never happen because of all the mechanisms in human perception-action designed to generate flow, etc; the real stuff that's of actual use. As soon as you have access to that information, the illusion breaks and you begin to discover more about the room.

    Ecological psychology can be used to talk about this case, but it's not interesting because it isn't evidence that the information for vision is intrinsically ambiguous, the specific context for that Gibson quote just above me.

    All the Ames Room is evidence for is that if you break the conditions for perception, then perception will give you broken and weird answers. The only thing of interest about this is how incredibly hard it actually is to break perception.

    Ken, I'm not sure what your goal here is. Maybe that would help.

  9. Andrew,
    My goal is simple. There should be a scientific analysis of what is going on when a normal human looks into the Ames room without moving around. What is this account?

    Your answer often has the tone: who cares?

    Gary's answer often has the tone: Gibsonian theory doesn't apply to that case.

    Runeson's answer is: Here is the unique "Gibsonian" information you get from a single point.

    Now, I happen to like Runeson's approach. Your answer sounds like special pleading for Eco Psych. Gary's answer sounds like a defeat for Eco Psych. Runeson's account sounds like a possible step forward.

  10. Runeson's account sounds like a possible step forward.
    I think the reason I'm in the 'I don't care' camp is that a) it's been done, b) by doing it Runeson showed it's really not all that interesting, and c) the ecological field has moved on from trying to cope with the flawed examples of the cognitive approach.

    But ok, you're right that Runeson was right to address it. I'm just more interested in the real thing :)

  11. Andrew,
    I'm glad we have at least arrived at some understanding.

    Winning you over to the side of light and truth will have to wait until next month, when I'll have more time!