If you drive, you’ve had the experience of having to learn what the warning sign on the bottom of your passenger ‘s side car mirror means. A current discussion on a list-serve frequented by optometrists engaged in vision therapy brought this to mind.
Q: I do not understand the concept that there can be “a mismatch between where it looks like it is in space and where he directs action to find it.” I can understand there being a mismatch between where it looks like it is in space and where it is in space or a mismatch between where he directs action and where it is in space. But why would there ever be a mismatch between where it looks like it is and where he directs action?A: The discrepancy lies in the fact that where he/they think it is is not where it is. So he / they direct action action to where the object is not.
Hmmm … sounds like a variant of Heisenberg’s Uncertainty Principle, doesn’t it?
So perhaps another way to look at this conundrum of how objects can appear to be in a location different from where they actually are can be explained in a quote cited by Linda Sanet, COVT:
“The location of an object in physical or objective space must be matched with our localization of the object in visual or subjective space.”
I like that quote, so let’s explore it a little more. What is the location of an object in physical space? In the macro world, two different objects can’t occupy the same space at the same. Borrowing again from an automobile analogy, if there is a curb or a parking log toward which the front end of a car is approaching, the visual judgement of the driver doesn’t change the physical facts of the space between the lower edge of the bumper and upper edge of the curb. There is a physical measurement that can be made showing whether the bumper will scrape the log or clear it. In the design challenge of self-driven cars, this could be something easily gauged and guided by sensors on bumper
In the absence of a physical sensor, you must match your localization of where the log or curb is in relation to the physical location of your bumper. Make a good match and your bumper will remain intact; make a poor match and you’ll wind up with a scratch or worse. That’s what we call feedback, and it always involves motor movement (is that redundant?).
I recall discovering this challenge matching an object in physical or objective space with localization of the object in visual or subjective space at a young age. As a young child, well before I understood anything about lenses, prisms, or optics I noticed that when I got my new pair of glasses my feet appeared further away than usual. At some level I wondered why my new glasses didn’t come with a warning that objects through them were closer than they appeared, though it was nice to think that perhaps I really was getting taller.
One day, very much in passing, I noticed that when I looked at a light bulb through my glasses it appeared to be in one location, but when I moved the lens down a little bit a second version of the image appeared simultaneously in a different location. Although my 12 year-old brain couldn’t label it at the time, I was doing my own version of split pupil rock – and exploring the metaphysical question of where the “real” location of that object was: Was it in the location through my glasses, or in the second location outside of my glasses?
The short answer answer to that question is that the “real” location of the object is wherever it is physically located in reference to my observer’s frame. If I reached out and touched the light bulb my brain could either register a larger blurrier finger touching the bulb in the location I saw it outside of the lens, or the in focus images of my hand and light bulb through the lens. In a deeper sense it was a reconciliation of opposites, as explored by our colleague Dr. Steve Gallop in this essay.
So let’s consider the quote again: “The location of an object in physical or objective space must be matched with our localization of the object in visual or subjective space.” In other words, objects are located where they appear to be when I am localizing them through eye/body coordinates that provide accurate reference.
Take the simple example of putting a pointer into a straw. If I localize the pointer and the straw in the same plane I will see and feel the pointer sliding into the straw. Assuming my hand control is good, if I past-point so that the pointer misses the straw’s hole, I receive feedback that my visual or subjective space isn’t aligned with the physical location of the straw. In other words, my visual system is misguiding me. I might even have to hold the straw myself in order to create an accurate match, so that I can feel the location of the straw to gain additional feedback. As reviewed by one of my earliest mentors Dr. Ralph Garzia, this is part of the developmental process known in Kephart’s terms as a perceptual-motor match; or as elaborated by Getman the development of the visual-motor hierarchy. It’s worth taking a look at Ralph’s outline here.