Monday, January 07, 2013

Negative Feedback a Positive Thing

I've long been fascinated with the concept of negative feedback since my my technician training days. Wikipedia tells us:
"Negative feedback occurs when the result of a process influences the operation of the process itself in such a way as to reduce changes. Negative feedback tends to make a system self-regulating it can produce stability and reduce the effect of fluctuations."
 In short, by applying a percentage of the output of some system or process in a negative or subtractive way to the input, you get a smaller but more useful result. In electronics (bear with me) for example, it is possible to achieve amplification levels of many thousand times the input signal, but at a single, limited and unstable frequency, making it unsuitable for, say, audio. Take some of the output and apply it out-of-phase (cancelling out) to the input and you have a modest amplification level of say, ten times the input and a useful frequency range.

Negative feedback is used routinely in mechanical systems around your house: thermostats, ballcocks, daylight switches and more. It occurs everywhere in nature too. Diabetes, for example, is the failure of the body's negative feedback loop to control glucose levels.

Another Whare Flat Folk Festival is behind us and by many measures, a most successful one. Weather near perfect, good turnout and above all, great artists and music. If we think of the people coming in to the festival as the system input and the smooth, satisfactory consumption of music and dance as the output, one area in which we have developed a massive, potentially unstable peak is in teenage attendance which this year was the largest ever, close to that of all other ages combined. The vast majority of these teens are delightful contributors to the life of the event but, of course, there are always one or two spoilers that have a disproportional effect on the output, especially from the point-of-view of the organisers. So, what of the output can be looped back into the input to good effect?

The burgeoning teen attendance is largely due to the positive feedback elements of word-of-mouth and social networking. It has been through monitoring social networking that we have learned of security loopholes that some have been taking advantage of. Negative feedback applied. Various vagaries in our our publicity material has lead to creative interpretations of the rules for attendance. Review and clarify. Negative feedback applied. The trick is to suppress the peaks that cause instability while reinforcing the mainstream flow. In an ideal system the fluctuations in the input are regulated in real time by the application of the feedback elements - a bit tricky in a three day festival event without disruption to all involved.

Filtering at the input (say, rejecting teens with alcohol) is one way of suppressing an undesirable element but it needs to be acknowledged that while the output elements of audience satisfaction and operational smoothness are improved, it is at the expense of festival profit.

Like any system or process, elements constantly need fine tuning for smooth running. This is why the best organisations have robust complaints procedures. Complaint resolution is not just for the satisfaction of the complainant, if used correctly it is the negative feedback loop that suppresses further complaints and enhances the organisation's effectiveness. The corollary to this is the Roadrunner/Wyle E Coyote approach where each failed attempt at snaring the bird is abandoned in favour of the next fraught methodology. I've seen a lot of well-meaning organisations abandon perfectly good initiatives instead of adjusting the process for a more refined result. Negative feedback is a truly positive thing.

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