The Law Of Requisite Variety

You will no doubt have heard the following before, spuriosuly linked  to Henry Ford:

If you always do what you have always done, you’ll always get what you’ve always got.

It’s been said a lot on edu-Twitter and in plenty of educational conferences and CPD sessions.

It’s pretty self-explanatory but I’m always surprised that it isn’t referenced to W. Ross Ashby as this is sometimes referred to as Ashby’s Law of Requisite Variety.

Ashby proposed the idea in his 1956 book An Introduction to Cybernetics and later expanded on it in his paper Requisite variety and its implications for the control of complex systems. The idea became one of the foundational concepts of the field of Cybernetics. It is also known as the First Law of Cybernetics.

In everyday terms Ashby’s Law has come to be understood as follows: if a system is to be able to deal successfully with the diversity of challenges that its environment produces, then it needs to have a repertoire of responses which is (at least) as nuanced as the problems thrown up by the environment. Ashby put it as , “only variety can absorb variety.”

So a viable system is one that can handle the variability of its environment. If we think about this another way then the only way you can control your destiny is to be more flexible than your environment.

The system/person with the most flexibility of behaviour will control the system. The more flexible you are when you hit a challenge the more likely you will control your life and get what you want. In other words, it’s considered a good strategy to generate more choices in a given situation.

A system without requisite variety will fail whenever it encounters the unexpected and as such is not a “viable system”. We see this in school systems all the time. For example, if your environment is more sophisticated in terms of complexity than your teams available responses then the moves will be simplistic and ineffective. If a team has too much structure then it won’t be agile or fast enough to react to changes in its environment.

Variety and interconnectedness are among the necessary ingredients that allow a system to survive and thrive in a variety of environments.

In practice, the Law of Requisite Variety says that, in order to fulfil its purposes and survive, the system must be capable of a greater variety of responses than the variety of agitations in the environment.

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