Black box

Wartime electronics; developed as a method by W. Ross Ashby, 1956

A system studied only through its inputs and outputs, without access to its inner workings. Cybernetics turned this from a limitation into a method.

A black box is any system whose internal mechanism is hidden or unknown, so that it can be understood only by what goes in and what comes out.

As a method

The term came from wartime electronics, where engineers had to work out the function of captured or sealed equipment by testing it. W. Ross Ashby’s An Introduction to Cybernetics (1956) gave a whole chapter to the “problem of the Black Box”, and showed how an observer can build up a model of a box’s behaviour by systematically varying inputs and recording outputs, without ever opening it.

Ashby pointed out that this is the normal situation: a child learning to use a door handle, a doctor examining a patient, or a scientist studying the brain is in the same position. Every real object is, to some degree, a black box. Cybernetics therefore focuses on behaviour, what a system does, rather than on what it is made of.

Later developments

Stafford Beer used the idea in management: one does not need to understand every detail of a department to regulate it, only how it responds. Ranulph Glanville argued that black boxes are a relationship between an observer and a system, built through interaction, and a basis for respecting other systems’ autonomy rather than a failure of knowledge.

The term now has a critical edge in debates on algorithms: complex machine learning models and proprietary systems are described as black boxes because their decisions cannot easily be explained or audited.

Further reading

  • W. Ross Ashby, An Introduction to Cybernetics (1956), chapter 6
  • Ranulph Glanville, “Inside Every White Box There Are Two Black Boxes Trying to Get Out”, Behavioral Science (1982)
  • Frank Pasquale, The Black Box Society (2015)

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