by DCH Park
At one point during my undergraduate studies at MIT, I took a systems control class. I bring it up here because I find that some insights from that class are helpful in illuminating personal experience.
In the control class, we studied various ways to design and analyze dynamic control systems of various types, ranging from purely mechanical ones to electrical ones (which had no transistors) to electronic ones (which did). Analytically, all of these systems could be modeled and understood using the same principles. Mathematically they were identical in spite of the fact that completely different physical components and forces were in operation in different systems.
There are primarily two different philosophies or approaches to designing control circuits. One is called feedback and the other is called feed-forward. Most of the control systems in use in the world today are feedback systems.
In a feedback control circuit, a portion of the output of the system is fed back into the control circuit inputs. The control circuit combines this feedback with the operator (or other external) control inputs to automatically adjust the system.
For example, if you adjust the speaker volume in your car radio to a certain level, the volume setting is the “operator” or external control setting. As the volume setting is increased, the control circuit sends a signal to the speaker drivers telling them to work harder.
Since it’s a feedback control circuit, a portion of this speaker driver signal is also sent back to the control circuit and mixed with the manual volume setting. Typically, the feedback signal is inverted so that as the volume goes up, the feedback causes the control signal to decrease and if the volume goes down, the control signal increases.
This type of negative feedback control tends to be very stable because it tends to push the output toward a stable center – down if the output gets too high and up if it gets too low. This is why it is used so widely.
In positive feedback control, the feedback is not inverted. Thus, it tends to further amplify the system’s outputs. If the output goes up, positive feedback makes it go higher faster. This is what happens when a microphone is placed too closely to the speaker it drives. The speaker output is picked up by the mic and amplified through the speaker, leading to an unstable feedback loop that mounts continuously, destroying the signal and resulting in screeching.
In a feed-forward control circuit, there is no input that takes the system output to the external world back into the system. Certain assumptions are made about the way in which the system will behave and the ways in which the external world will respond, The (external) control inputs take these assumptions into account and are simply fed in.
As long as the assumptions are accurate, the system behaves as expected, but if the assumptions are off, even just by a small amount, the system can become disastrously unstable. Outputs may become unpredictable or even destroy the system altogether.
This is what happens when a car suddenly loses traction on a patch of ice. The car’s behavior suddenly changes so that the driver’s assumptions about how the car will react are suddenly wrong. Control inputs that are normally safe – holding the wheel straight and pressing on the brakes – are no longer safe. Instead of producing normal results – straightening out the car’s trajectory and slowing down – they do something else – promoting a spin with locked wheels (unless the car is equipped with anti-lock brake control, which all modern commercially produced cars are).
The solution to this problem is to “close the loop,” and make the external outputs of the system a portion of the inputs. In other words, make the feed-forward system into a feedback system by adding a sensor that loops back to the inputs. This is what anti-lock braking systems do.
In exactly the same way, enhancing the feedback control in your body and life can enhance your stability and equanimity. In this case, the key is to develop your facility with awareness. Jon Kabat-Zinn, one of the seminal influences in bringing mindfulness and meditation into the medical establishment mainstream, points out that awareness, like thinking, is an inherent ability that humans possess. However, in this culture, unlike thinking, it is an ability that is not widely prized or even recognized, much less one that many people are trained in using.
Control via thinking alone is a form of feed-forward control In the body, feed-forward control is essentially experienced as a kind of numbness that cuts you off from the external world. Without feedback, there is a tendency to easily slip into a perception that the external world is on the other side of an invisible and inviolable barrier – an impossibly fine and absolutely impregnable curtain that separates you from the external world.
In the body, Hansen’s disease, commonly known as leprosy, is an extreme example of what can happen when feedback is lost and only feed-forward control remains. Hansen’s disease victims lose sensation. Loss of sensation starts in the fingertips and toes and progresses inward. Motor function control is unimpaired.
However, because all sensation is lost, including pain, victims lose the ability to sense when they have damaged themselves. As a result, they inflict repeated trauma to affected tissues and the body begins to erode. Eventually fingers, toes, noses, and more can be lost to physical trauma caused not by the disease, but by the victim upon his or her self because the disease prevents feedback about his or her physical condition.
Hansen’s disease is an extreme example, but the same mechanism is at work in less extreme situations every day. When you feel a headache due to stress or over-work and take an analgesic instead of a break, you are choosing to numb the pain and dampen your natural feedback in favor of a feed-forward control signal to keep working or work harder.
Since feed-forward control is experienced as numbness in the body, it is expressed as discipline. In the absence of sensory connection and emotional immediacy, exertion of will remains as the only means to gain control. It is like being on one side of a wall and trying to control what happens on the other side of the wall by pulling and pushing rods that go through the wall without being able to directly see, hear, or feel what is happening, relying instead on graphical progress reports that are projected on a screen.
Cultivating your awareness is a key to addressing this shortcoming. By becoming more fully aware of the many cues that your body sends you and the depth and richness of your sensory experience of your environment, you strengthen your feedback loop. Your experience of your surroundings and even of yourself shifts. You pierce the barrier that separates you from your external world and feel the world more richly and subtly.
For example, when I wanted to lose weight many years ago, I noticed that it was a struggle as long as I approached it as a discipline. To make matters worse, I was keenly aware of flavor and the sensations of eating, swallowing, and feeling full, which became positive feedback signals that tended to amplify the unhealthy behavior and desire for unhealthy foods.
Once I began to notice other sensations, like the listlessness I felt after a food binge or unhealthy meal and the feeling of tightness and deflation I felt after just one bite of unhealthy food, my relationship with food and weight control began to change significantly. I no longer had to struggle to control something that I could grasp intellectually but not feel. I could cultivate awareness of what was going on in my body and how I felt and healthy choices dropped out of that awareness effortlessly.
Losing weight and eating more healthily were no longer hard. Given greater awareness of my body and how different foods affected my body, making healthy choices became the easiest things to do. Making unhealthy choices became hard because in order to make those choices I would have to ignore what I now so clearly felt.
If you don’t have sensation, you might hit your thumb with a hammer and not even know it. Without strict discipline and rigid attention to specific details, you might keep hammering and actually break your thumb or worse. On the other hand, with your awareness and sensation intact, if hit your thumb with a hammer, you stop pounding the nail because your thumb hurts. Taking care of your thumb becomes the easiest thing to do.
“Feedback Over Feedforward – Awareness Over Discipline” by DCH Park is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.