Feedback loops

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Feedback Loops

feedbackloop.pngThis is an appropriate place to discuss feedback loops.  Being educated in the field of electronics and control systems, the second order equation for feedback loops is very familiar to me.  It applies all around us in nature and seems to be very much part of the natural environment.  I won’t go into the mathematics too much, but the equation takes the general form:


The graph below shows what happens to the system in response to a step change (ie from previous state 0 to new state 1).  Depending on the damping (the zeta symbol in the equation), there can be a slow but steady change in the output until it reaches the input, or there can be a rapid response and overshoot, with a settling down oscillation as the output aligns itself to the input.  The frequency of oscillation is the undamped natural frequency (wn in the equation, where omega w = 2 x pi x frequency).


Don’t worry about this too much if you didn’t do this at school (or see damping ratio on wikipedia).  The point here is that we are surrounded by feedback systems.  These are commonly negative feedback systems, but positive feedback systems also occur and these can be useful too.  The parameters that determine the damping factor and undamped natural frequency vary depending on whether we are dealing with electrical systems or mechanical systems (pendulums, springs) or chemical systems like the human body.  For example, tuned circuits are used in radios to select the radio station – using an inductor and a capacitor, with minimal damping so the circuit resonates at the frequency we want to tune in.  At work, the office air-conditioning systems use temperature control in a negative feedback loop which should ideally be critically damped, so that air conditioners and/or heaters are switched on and off to quickly regulate the temperature (oscillations here are highly undesirable).

We have negative feedback systems in the human body.  Lots of them.  Our body homoeostasis (see Hypothalamus in the limbic brain, and the Thyroid) is constantly adjusting our operating parameters to regulate items such as:

  • body temperature (eg sweating to cope with heat)
  • blood pressure
  • blood sugar (diabetes occurs when this regulation mechanism fails)
  • oxygen and carbon dioxide levels

These are all important unconscious mechanisms that keep our physical bodies healthy and in good condition.  We don’t normally have to think about them.

Feedback loops in our conscious experience

timeout.pngThere are also negative and positive feedback mechanisms that go on in our conscious emotional and mental worlds.  This is part of our learning and experience as we grow up.  Our thinking processes, in conjunction with memory and our set of moral values, is very valuable in establishing these negative feedback mechanisms.  For example, we soon learn that throwing a tantrum and hurting other people has serious repercussions.  If the feedback loop is working well, we stop doing behaving that way when we are at a young age.  A child throws a tantrum and hits one of their siblings; so the parents sends the child to their room and deprives them of ice cream or some other treat.  So the child reflects and sees the result of their action, and if they wish to be included and accepted by the group they modify their behaviour accordingly.  Negative feedback loops are at work all the time and are extremely important for establishing resilient human relationships.  It works better for some people than others.  There are often competing feedback loops at work, and the reward feedback loop (with the dopamine pathway into the limbic brain) is often powerful enough to override reasoning and moral values.

Positive feedback loops

ocdPositive feedback loops also occur in human beings, and they can be both useful and destructive.  Falling in love is an example of a positive feedback loop.  It is a special case of OCD (obsessive compulsive disorder).  The more general case of OCD is a also positive feedback loop and is usually unhelpful – people can become obsessed with cleanliness or checking that everything is switched off before leaving the house.

Some positive feedback loops are in place to respond to a temporary stimulus.  Childbirth is an example of a positive feedback loop, where hormonal changes take place in a female body to expel the foreign object (the baby!) after which the female body returns to normal.  Positive feedback loops operate unconsciously to help us learn – walking, talking, learning motor skills.  It appears that attention deficit hyperactivity disorder (ADHD) may result from this positive feedback mechanism going wrong.  Some people get addicted to learning and exploring and develop an over-curious positive feedback loop.  This can sometimes lead to something positive like new discoveries and inventions; but it can also be detrimental to relationships and personal health and hygiene.

Feedback loops and enlightenment

The impetus, stimulation or motivation to change oneself and grow spiritually requires us to create our own positive feedback loop.  It is a departure from the normal body mode of homoeostasis.  It is not a naturally occurring state.  Left on our own without external stimulus, our inbuilt negative feedback mechanisms will return us to a docile state of in-action.

self-motivation.pngIn mechanical and electrical systems, a useful form of positive feedback is resonance.  When resonance occurs, a small input gives rise to a powerful sustained vibration at a particular frequency (in electronics this is used to set the frequency of oscillators and tune in radio stations).  Resonance can also be destructive (like when opera singers use a pure high-pitched sound to destroy a piece of glass), but in this context I am promoting the practice for us to develop a deliberate way of living by way of a set of spiritual practices that become a sustainable way of life.  When the effort and changes that you have adopted in your life “ring true” (resonate), these activities become sustainable and these life-long practices becomes easy and sustainable.  Without the resonant energy to amplify and sustain the initial effort, the initial enthusiasm will soon die.  That is exactly what happens to most people; not just with efforts towards enlightenment, but in many other activities and endeavours they undertake in life.  The natural human state is mainly governed by negative feedback homeostasis, which ultimately leads to a state of comfortable lethargy (nodding off quietly in a rocking chair).