I hate design principles. Sure, they can be memorable like an equation (“Less is more”¹) or incisive as an oracle’s words (“Form follows function”²), but sometimes they just sound like tautologies (“Good design is innovative”³) that won’t help gauge design decisions. The more obscure, the more they are misused as an alibi to hide behind, like big flags of a conquered territory we didn’t fight for.
To make things worse, they are often confused with rules and laws (like in this book), a lack of distinction that makes our job orphan of rigorous science. Laws, rules, and principles have in fact specific roles, and together they shape the foundation of the design discipline.
Providing better definitions and mapping their role will help us understand how to use principles better:
- A law is a statement that describes aspects of user behavior, based on repeated experimental observations. Under the same conditions, a law always applies and implies that its elements have a causal relationship. (See for example Fitts’s Law or Hick’s law)
- A rule is a prescription that we are ordered to follow strictly and rigorously. Rules are usually generated by convention as a consequence of an established pattern (which is a law as defined above)
- A principle, instead, is a powerful statement that describes a universal value or an intrinsic quality that a product should have
So, the relationship becomes more clear: principles are induced from laws, but laws cannot be deduced from principles. Rules are inferred from laws to support the obedience to the overarching principles. Clear? Well let’s use an example:
From observation we know that users can’t process too many elements of an interface simultaneously (Miller’s law), so we need a rule that tells us to keep the number of elements to 3 or less on a given page (rule), which help us adhere to the goal of keeping things simple (principle).
Essentially, principles are self-generated from a repeated application of a series of practices until some of those practices survive and some will die. Principles are almost like an explicit effect of a Darwinian fight for the “ruling” practice. And that’s when I appreciate principles: when they are the glue that holds many rules together.
Essential Three: Efficiency, Clarity, and Control.
How many design principles do we need to design a good product? If we restrict our question to interface design, Bruno Tognazzini’s list, alone, counts 76 of them, which is only an appetizer compared to the 1370 principles listed on this website.
As a designer, obsessed with improving the world, and as a human with inevitably degrading memory, I couldn’t keep myself from trying to find the most effective keywords that I can easily remember and evangelize.
After going through the most popular collections from Don Norman, Bruce Tognazzini, Jakob Nielsen, John Maeda, Massimo Vignelli, and the more recent Apple HI Guidelines, Google, and Facebook’s Design Principles, and not least, my personal experience, I came up with my short list as a starting point to design products that works:
- Efficiency. A good system should employ the smallest number of elements to produce the maximum outcome given the desired goal. The cognitive experience is not dissimilar in fact from the economics behavior where our currency is a token of cognitive energy that users have to spend when they read our interface. You don’t want them to be left penniless too soon.
- Clarity. A good system should always prevent ambiguity, whenever it is caused by labels, visual elements or the absence of both. Ambiguity is an obstacle that prevents users to move forward or move at all.
- Control. A good system should let the user have control of the experience unless the system is trying to prevent users from errors. Visual feedback should reassure about system status and navigation, along with the availability of recovery modes, undo actions and escape options anytime the user needs.
These principles are like a path defined to walk straight and prevent us from derailing, but they don’t teach how to walk —if we stick with the metaphor— nor they teach how to make a product beyond good. That’s why you need rules.
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Sources
[1] https://www.britannica.com/biography/Ludwig-Mies-van-der-Rohe
[2] https://www.britannica.com/biography/Louis-Sullivan
[3] https://www.vitsoe.com/us/about/good-design