The Brain's Model

[From Bruce Abbott (2018.06.21.1010 EDT)]

Open your eyes and look around you. If you have reasonably normal vision, you see a world of objects, objects located at various positions in three dimensional space and imbued with numerous properties, among which are shape, texture, and color. Having become familiar with these objects, you almost instantly recognize them: I’m in the kitchen, that’s the counter top and sink, and here is my coffee cup. I walk toward the counter and as I do so, my viewpoint changes. The cup appears closer to me, and I can now see the handle that a moment ago was obscured by the body of the cup. I reach for the cup. As I do so, I can feel the muscles in my arm and shoulder tense up and see (and feel) my arm rising and extending, my hand moving smoothly toward the cup. As my hand reaches the cup, I close my fingers around the handle and begin to lift the cup. I see my fingers tighten around the handle, feel the pressure and hardness of the handle against the skin of my fingers, and feel the handle’s coldness. As I lift, I experience an increase in downward pressure on my arm as the cup rises off the counter.

I move the cup toward my lips. I see the cup approaching, notice the steam rising from the coffee it contains, and smell the aroma. As the cup reaches my lips, I feel its rim against my lower lip. I tip the cup and some of the coffee enters my mouth, giving rise to sensations of wetness, a slightly bitter taste, and heat (among others).

In a sense, none of this is real.

I am not experiencing the real world, but only my perceptions. For all I know, I could be hallucinating all of it.

Yet most of us behave as if the reality of our perceptions is reality. Why? Because by doing so, we seem to get along well in that world of our perceptions.

My visual perceptions tell me that I am walking toward a closed door. If I assume that the door is “only a perception” and try to walk right through it, I will soon experience a sudden arrest of my forward motion and pain in various body parts as my toes, knees, chest, and face forcefully contact what I perceive to be the surface of the door. Unless I am hallucinating the door, I won’t experience myself moving right through the door like a ghost. If I still want to exit the room, I am going to have to open the door first before stepping through.

It is possible that nature has arranged things such that we experience certain perceptions in consistent ways (e.g., that trying to walk through an apparently solid door will result in pain and bruises) without there being any “real reality” behind them, but then, what is arranging our perceptions so consistently that our various senses generally agree on what is happening? Why is the visual perception of a cup full of coffee so consistently associated with particular attributes, such as the feel of the cup – its tactile shape, hardness, and heft – and the smell and warmth of hot coffee as the cup is brought to the mouth? Is there a kind of Maxwell’s Demon out there, making sure that our perceptions almost always produce a self-consistent picture? A far simpler explanation is that there is a physical reality outside our perceptions that enforces these correlations.

This view also explains why I can’t perceive the world in my imagination with nearly the detail that is present when I seem actually to be experiencing reality. Reality seems far better at “remembering” those details than I am. I put a new K-cup in the coffee maker and start the process of rendering a fresh cup of coffee. I get distracted and forget that I have done so, but Reality doesn’t forget – the cup is still there in the coffee maker, holding a now cool cup of coffee that I discover the next time I’m in the kitchen.

In general, we don’t experience our perceptions passively. From the time we are infants, we learn how our perceptions change as we move about and do various things. Such experiences help us build a perceptual model of that underlying reality. We learn how appearances change under different lighting conditions, distances, and angles of regard. We learn how different sensory experiences will change together as we do things like lift a cup or take a sip of coffee. We learn that once put in motion, heavy objects are harder to stop than lighter ones, that objects thrown into the air will soon slow in the vertical dimension and then accelerate as then fall back toward earth. What we learn, together with what we come into the world already “knowing,” becomes our model of the world and our interactions with it.

Perception, however, is not reality. Our biological inheritance has equipped us with the sensory and analytic machinery to render those perceptions, but our equipment has limitations. We are unable to sense every property of “real reality,” but must make do with sensory systems that sample only a portion of that reality and use analytic methods that may include heuristic “tricks” – methods that yield generally “good enough” approximations with a minimum of processing, thus saving both brain power and time. These usually work well but under certain circumstances yield an incorrect or misleading perception. The various perceptual illusions to which we are subject are the result. Bees can see colors in the ultraviolet range and the polarization of light; sharks can perceive electrical disturbances produced by other fish and pressure waves along their body surfaces that signal the presence of prey. Bats and dolphins can generate perceptions of objects through echolocation. We humans are blind to such experiences – our experience of “reality” and those of other species are different (Von Uexkull coined the term “umwelt” to refer to the sensory world that a particular species or individual inhabits.)

So what we have is a perceptual apparatus that renders a version of reality, one that in general has served the members of our species well enough that most of us are able to survive and even prosper, often living long enough to produce offspring and raise them to the age at which they can care for themselves. It is not “real reality” in all its detail, but a representation that usually works well enough for practical purposes. It is a kind of model of reality and like all models, it is selective and simplified relative to the thing modeled.

In PCT, we often refer to perceptions as scalar neural signals that encode the level of some variable such as the intensity of light or a person’s degree of honesty. Yet our perceptual world is far richer than a set of scalar variables. True, we can pick out some perceived characteristic and follow its changes over time, as when in a tracking study we attempt to keep a cursor aligned with a moving target. But let us not forget that our perceptual apparatus is far more capable. It produces not merely a large set of scalar perceptual signals but a complex, multidimensional array of interlocking perceptions whose status and dynamic changes provide us with a highly functional perceptual model of reality that includes ourselves and the effects of our actions on it.



p.s. Happy Summer Solstice!

[Rick Marken 2018-06-21_15:45:39]

[From Bruce Abbott (2018.06.21.1010 EDT)]


BA: Open your eyes and look around you...


BA: In a sense, none of this is real...


BA: I am not experiencing the real world, but only my perceptions. For all I know, I could be hallucinating all of it...


BA: A far simpler explanation is that there is a physical reality outside our perceptions that enforces these correlations...


BA: Perception, however, is not reality...


BA: So what we have is a perceptual apparatus that renders a version of reality, one that in general has served the members of our species well enough that most of us are able to survive and even prosper...Â


BA: Comments?Â

RM: I think this is excellent, perhaps because it is completely consistent with my way of looking at things (which, of course, I think is the PCT way). But this discussion of the relationship between perception and reality (the "environment" in PCT diagrams) has led me to ask myself: "so what"? Or, to put it another way: "What's epistemology got to do, got to do with it"! "It", of course, being PCT. And I think the answer is "not that much".Â
RM: Of course, we do have to assume that there is a real world out there on the "other side" of our perceptions because, as Bruce notes in his treatise, that is what puts constraints on what we can control and how we can control it, in both actual behavior and in our models of it. But in PCT there is less interest in determining the relationship between perception and reality than in characterizing the nature of the perceptions themselves, particularly the perceptions that are being controlled.Â
RM: So, for example, in the object interception research, the goal was to determine what perceptual variables are being controlled when an agent carries out this task. One of the perceptual variables that is controlled is vertical optical velocity, which is defined in terms of the optical angle of the pursued object relative to some fixed point in the optic array. What is being done here is that a perceptual variable (optical velocity) is being defined in terms of another perceptual variable (optical angle). Optical angle is itself defined in terms of perceptions -- of the distance between points in the optical array. And this distance is defined in terms of still other perceptions-- of the points between which the distance is measured.Â
RM: The points are perceptions that would be defined in terms of physical variables. But we didn't have to go all the way down to that level to get a good definition of the perception of optical velocity. The definition of optical velocity in terms of the perception of optical angle told us what type of perception was being controlled (a transition) and, more importantly, that it was a better definition of the perception being controlled that other definitions -- such as optical acceleration and optical trajectory -- what are also defined in terms of optical angle.Â
RM: So I would say that epistemology -- at least the aspect of it that deals with the question of the relationship between perception and reality -- is relevant mainly to the lowest level perceptions, which Powers called the "intensity" perceptions. These are perceptions that must be defined in terms of physical variables -- variables that represent the reality defined by the models of the physical sciences. But all other perceptual variables can presumably be defined in terms of other perceptual variables. And that, I think, is the goal of research on living control systems: to find the best definitions of the perceptual variables that organisms are controlling when they can be seen to be performing various behaviors. And these definitions will be in terms of other perceptual variables, except for the lowest level "intensity" perceptions.Â


Richard S. MarkenÂ
"Perfection is achieved not when you have nothing more to add, but when you
have nothing left to take away.�
                --Antoine de Saint-Exupery