THIRD kind of feedback discovered!

This just in! They found a third kind of feedback! The third kind is really, really, really important to understand if you want to understand what's going on in society today.




You know about the first kind of feedback, where the technician puts the speaker blasting into the microphone, and the result is a terrible sound, a rising squeal: e-e-e-e-e-EEEEE.

It's called "feedback" because the sound coming out of the speakers is fed back into the microphone, where it goes around again and the even louder sound comes out of the speakers and is fed back into the microphone where it is amplified and gets even LOUDER, etc.

Even though the result is unpleasant, this is called "positive feedback" because the signal is being reinforced and encouraged to grow stronger and stronger. Mathematically, with each loop more volume is being added in, so the equation, if we wrote it out, would need a PLUS SIGN.

Unfortunately, we are all familiar with the second kind of feedback, "negative feedback", which is what out best ideas or songs usually receive from friends and teachers.


You can see the "minus sign" on my second clever picture where a music student has just gotten his music test back with 0% correct, and is thinking of throwing his guitar, and his musical career, in the trash can.

This is "discouraging" feedback.

So, with positive feedback being "encouraging" and negative feedback being "discouraging", it's hard to see where there's room for a third kind.

I mean, what would it be? "Neutral" feedback, neither positive or negative?

The third kind of feedback can be called "goal-seeking" feedback, or "intelligent feedback" or "smart feedback" or "cybernetic feedback" or "regulatory feedback" or "feedback control."

Rather than blindly being always POSITIVE or always NEGATIVE, this kind of feedback varies depending on whether the news coming in that second should be encouraging or discouraging.



That concept implies that this is both "feedback with eyes" to see what the news is, and "feedback with brains" to decide how to interpret the news.

 

 

 

 

If we start at the glass being filled with water, the information flows from the glass into the person's eyes, then to their brain, where it is compared to a desired goal - a glass filled up to some mark or point. Since the water is not up to that level yet, the brain decides that the spigot could be opened wider to let more water flow, so this message is sent down to the hand, which carries out the message. That action causes more of the water in the 55-gallon drum to flow out of the spigot into the glass, raising the level of water in the glass. That information flows into the eyes, which ... goes around the loop again and again.

But, each time the information goes around the loop, the result may vary, depending on how full the glass is. The same kind of loop happens in a car, where the driver has some speed they want to go, looks at the speedometer, reads how fast they are going now, and decides whether more gas or more brake pedal is the right thing to do next, does that, and the control information goes around the loop again.

Now, this is a different kind of animal, this feedback control loop. But it is a very very popular design pattern. You'll find it everywhere, once you look, because it is a key building block for anything that's alive, and even for many things that are not alive, but act sort of alive, - like robots or automatic-speed-controls on your car.

Notice that I drew a closed path, a loop, but

what is flowing around the loop is actually control INFORMATION.

The information doesn't really care what carries it - whether it is an electrical wire or knots in a piece of string like the Inca's used, or a handful of pebbles or a piece of paper or flow of water or movement of a muscle. Information is cool - it will hitch a ride on anything it can get.

In our loop, the information starts as level of water in a glass, then it changes to light rays, then it goes in the eyeball and changes to nerve impulses, and goes around the brain comparing itself to some mental goal or image then gets goes through some kind of "decider" mechanism to decide whether the glass is full yet or not, then gets resolved to nerve impulses down a motor nerve, then gets resolved to muscle movement in the hand, then changes to spigot movement, then changes back into the water in the drum moving down to the glass.

The loop is a picture of "control information flow", and the math doesn't care what physical thing is used to implement different parts of the flow. The concept is both very real, and at the same time very abstract.

But, this is the tremendous power of this concept. Nothing depends on whether the process being described is physical, or solid, or liquid, or light or electrical impulses, or thoughts, or images, or muscle tissue.

The only thing that matters is whether the CONTROL loop exists, and has some kind of SENSOR (the eyeball), some kind of GOAL (how full I want the glass), Some kind of COMPARER (is the glass that full yet or not?), Some kind of mental model of what changes what ("To get MORE water, PULL the spigot lever forward towards me"), and some kind of ACTION-TAKER (to make that happen, move my hand towards me, and to make that happen, send a pulse down, let's see. ... oh yeah, down THIS nerve. )

The PATTERN is like a song, and the song doesn't care whether it is sung, or played on a piano, or played on a guitar, or played on bottles filled with different amounts of beer being hit by a stick -- it's still the "same song."

In our case, here's the song that Nature sings over and over again, everywhere inside our bodies and outside our bodies. When I write it out, it looks boring, like sheet music compared to actually playing the music. So, don't expect it to LOOK exciting. What matters is what happens when the music is PLAYED.

The other truly good news is that, once you understand how this kind of loop operates, and what you can do with it, and what you cannot do with it, that insight will carry over to thousands of different parts of life where the same loop operates - a different musician singing the same song.

So, here's the loop, that looks, as I promised, boring on paper.



Well, you wouldn't ask but I will, what about the first two kinds of feedback? Do we need a different picture of what "song" those are singing?

No, more good news is that one picture will do. Those loops are really boring songs, that essentially involve going up one key on the piano at a time, or going down one key on the piano at a time. Yawn.

Positive feedback is the same loop with stunted growth. It has no comparer, no goal, no mental model, and a single decider which is "ADD MORE".

Negative feedback is the same stunted loop with a simple decider rule "WHATEVER
you give me, I'll give you back less."

But, oh boy, control feedback can play a symphony with 8 voices and harmony. To think of "positive" feedback and "control feedback" being in the same family is like comparing a clock to a fancy BMW sports-car -- yes, they are both machines. Yes, one has a really boring song ("whatever time you showed last, add one second and show that next.") and the other has an "open-ended" song: "Wherever the driver wants to go and however fast she wants to go ... make it so!"

So, this is the background I wish my audience had when I did my Capstone presentation on how small teams of regular people (not doctors) could help each other get diabetes under control. There's that word again - "control", and, yes, there's a "regulatory feedback loop" involved with actions, looking to see if the actions worked, deciding what to to next, trying to do that, and around the loop again.

In any case, I will end with the same thought I put into that Capstone -- If we want to get things "Under control" and we want to use "regulations" in a loop and "monitor" how successful they are, and "modify" them based on that information, then we are playing in the "control loop" ballpark and it seems a minimum of due diligence to read the literature in that field and not reinvent the wheel, let alone get it wrong.

Feedback control theory is over 100 years old, and is very well developed, and has really neat toys and calculators to do all the hard stuff and make it easy to use. Probably any engineering college in the US has at least a course in "Control System Engineering". There are textbooks and journals and conferences, etc.

I found "Feedback Control of Dynamic Systems" to be the most readable, for the first two chapters, coming into the area from the outside.

There's a lot of interest lately in another 50 year old field - System Dynamics, where one of the goals is to try to capture, even qualitatively, the LOOPS in whatever system or organization or process you're trying to change, and then, if you can, the DIRECTION of push , be it "positive" or "negative". The Systems Dynamics Society has a whole literature and set of publications on how to do that and there's a graduate program at Worcester Polytechnic Institute in that field.

But, I have to note with some dismay, those analyses do not tease apart CONTROL loops from "positive feedback" and "negative feedback" loops. As I argue above, these are very different animals. Getting the connectivity and loops mapped out is a big part of the task. But I think the modeling of what happens next when you simulate this would be greatly improved if "control loops" were then distinguished from "dumb loops".

Just a suggestion for any SDS members who happen to be reading this. :)

(For more on Systems Dynamics and links, see my post "The Law of Unintended Consequences")

Oh, yes, I kind of lied a little bit when I titled this "Third kind of feedback discovered!" because it's only been discovered in the engineering literature, and has not been officially noted yet in the Public Health literature, and therefore, lacking "judicial notice" it currently does not exist so far as Public Health practice is concerned.

Again, my suggestion for due diligence applies.

And, no, it doesn't matter that human beings and possibly corporations and cultures and even lawyers are part of the system being studied in public health -- the theory and operation of control systems is identical. It doesn't matter whether it's animal, vegetable, mineral, light, people, chemicals, water -- the same control system laws control what can happen, can predict what might happen if you changed something, and can guide your intervention along pathways that are even conceptually feasible.