On simplicity

When we talk about design – whether to critique it or perform it – we use terms for which people often have vague or conflicting definitions. One particular favourite stands out: simplicity.

“Simplicity” is a common term and a commonly misused one. Attempts are made to define simplicity by example, by the methods used to achieve it, or in terms of vague words like elegant or beautiful. It turns out that the good old Oxford Dictionary of English will do just fine:

simplicity (noun): the quality or condition of being easy to understand or do.

That is, a simple object is one that is easy for humans to use or understand. This means that simplicity is relative to people and their experiences, their culture, their context, their education, and their mental models.

Without a clear understanding of how to evaluate the simplicity of a design, simplicity will be unnecessarily hard to realise. What the designer should ask themself is: is it easy for a particular subset of people to understand or use this in a particular context?

Even when they do that, achieving simplicity is still hard: it is hard because what can, or should, be assumed about the context is not obvious; it is hard because the appropriate mental model for usage is not clear even to the designer; it is hard because the space of possible solutions is large and expensive to explore; it is hard because there are several things to trade off – versatility, cost of usage, cost of familiarisation, size, potential for damage, and aesthetics. This is where experience, heuristics, and processes can help, but that’s for another essay.

The London Tube map is a striking example of a simple design:

London Tube map

London Tube map

The map makes few assumptions: that users can handle a modicum of abstraction (mapping of symbols and locations to the real world in a non-linear manner), that the context (subway lines and stations) is understood, and that users are intelligent enough to draw simple conclusions about the meaning of colours and symbols.

Because simplicity is relative to people’s mental models, it is affected by learning. That gives designers an option to consider a large number of additional solutions that without training would be too complicated for the target group to use. Some of these additional solutions are likely to be considerably more powerful than the original ones. Whether or not it is practical and justifiable to ask a target group to invest time and effort in learning depends on context and the potential long-term value of the design.

Consider the bicycle; it requires a notable investment of time and effort to learn how to ride the bicycle, but it then becomes both easy to use and remarkably valuable.

Now that we have a better understanding of what simplicity is, does it deserve all the hype it receives? Yes, I think so, with one caveat.

We all have a limit on the mental load we can bear and overloading it is costly, causing accidents, stress, and inefficiency. Making things simpler decreases mental load and that is distinctly valuable.

The caveat is that simplicity is too often achieved at the cost of functionality and power, because removing functionality is an easy way to make something simple. This is sometimes justified, but often not. The risk with this is that people grow unwilling to use tools or theories that require learning; and that aversion is both costly and dangerous.