computer science

Law of conservation of complexity

Law of conservation of complexity is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Law of conservation of complexity rather than just read about it. In short: The law of conservation of complexity, also known as Tesler's Law, or Waterbed Theory, is an adage in human–computer interaction stating that every application has an inherent amount of complexity that cannot be removed or hidden. Instead, it must be dealt with, either in product development or in user interaction.

Key takeaways

Law of conservation of complexity belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Law of conservation of complexity to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Law of conservation of complexity from memory before moving on to harder problems.

Reference excerpt

The law of conservation of complexity, also known as Tesler's Law, or Waterbed Theory, is an adage in human–computer interaction stating that every application has an inherent amount of complexity that cannot be removed or hidden. Instead, it must be dealt with, either in product development or in user interaction. This poses the question of who should be exposed to the complexity. For example, should a software developer add complexity to the software code to make the interaction simpler for the user or should the user deal with a complex interface so that the software code can be simple?

Background While working for Xerox PARC in the mid-1980s, Larry Tesler realized that the way users interact with applications was just as important as the application itself. The book Designing for Interaction by Dan Saffer includes an interview with Larry Tesler that describes the law of conservation of complexity. The interview is popular among user experience and interaction designers. Larry Tesler argues that onus for handling complexity should be on the programmer, not the user:

If a million users each waste a minute a day dealing with complexity that an engineer could have eliminated in a week by making the software a little more complex, you are penalizing the user to make the engineer's job easier. However, Bruce Tognazzini proposes that people resist reductions to the amount of complexity in their lives. Thus, when an application is simplified, users begin attempting more complex tasks.

Applications Possible applications of Tesler's Law:

Programming Vehicles Home appliances Workplace equipment

References

External links http://www.nomodes.com

Worked examples

Example 1 — a first encounter with Law of conservation of complexity

Start with the simplest possible case. Write down what Law of conservation of complexity claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Law of conservation of complexity before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Law of conservation of complexity ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Law of conservation of complexity

In research: Law of conservation of complexity appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Law of conservation of complexity in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Law of conservation of complexity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Human–computer interaction, Software development philosophies, Software engineering folklore, so understanding it makes those chapters shorter.
In everyday life: Look for Law of conservation of complexity outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Law of conservation of complexity in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Law of conservation of complexity means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Law of conservation of complexity out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Law of conservation of complexity in simple terms?

Why does Law of conservation of complexity matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Law of conservation of complexity?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Law of conservation of complexity.