Design of Everyday Things
Just finished reading the marvelous "Design of Everyday Things" by Donald A. Norman.
According to Norman, fundamental ingredients of designing for people are:
- Affordances
- Constraints,
- Mapping,
- Feedback,
- Making things visible.
Affordances. Affordance refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used. A chair affords ("is for") support and, therefore, affords sitting. A flat plate on the door affords pushing - meaning, the door is meant to be pushed. An empty container affords filling and so on.
A good designer makes sure that appropriate actions are perceptible and inappropriate ones are invisible. Rule of thumb - if instructions have to be pasted on something (push here, enter this way, turn off before doing this), it's badly designed.
Constraints. The surest way to make something easy to use, with few errors, is to make it impossible to do otherwise - to constrain the choices. Want to prevent people to enter memory cards into cameras the wrong way, design them so that they only fit one way.
The thoughtful use of affordances and constraints together in a design lets a user determine readily the proper course of action even in a novel situation.
There's an interesting relationship between affordances and constraints. They're in opposition to each other. Affordances suggest the range of possibilities, constraints limit the number of alternatives.
Mapping is a technical term describing the relationship between two things, in this case, between the controls and their movement and the results in the world.
For example, if you steer a car, mapping is following: to turn a car to the right, turn a steering wheel to the right, to turn to the left, turn a steering wheel to the left. Steering a car is a great example of intuitive and simple mapping. On the contrary, compare with bad mapping like unintuitive placement of knobs operating your stove hot plates. If they were done right, you didn't need to double-check each time which particular knob operates the bottom right burner.
Feedback. It's important to immediately see effect of our action. Without feedback one is always wondering whether anything has happened. Maybe the button wasn't pushed hard enough, maybe machine stopped working, Feedback is critical.
To sum it all up. Great design is where all relevant things are visible, primary actions are clearly affordable, unintended actions are constrained, the design uses intuitive mapping, and finally, users get prompt feedback of their actions.
Norman makes some very interesting observations:
- On accidents: Apparently, in most cases, major airline accidents or nuclear plant malfunctions, are not due to human error (which is a common belief), but to inappropriate design of the controls! If it wasn't for bad design of equipment, we could have saved thousands of lives.
- On errors: Assume that every possible mishap will happen, so protect against it and plan for it. Make actions reversible. Try to make them less costly.
- On users: There is no such thing as the average person.
- On functionality: The system should provide actions that match intentions.
- On ease of use: Most things are intended to be easy to use, but aren't. But some things are deliberately difficult to use and ought to be. The number of things that should be difficult to use is surprisingly large ie: security systems, dangerous equipment, bottles of medications or games.
At the end of the book Norman summarizes:
1. Use both knowledge in the world and in the head
2. Simplify the structure of tasks
3. Make things visible
4. Get the mappings right
5. Exploit the powers of constraints-Natural & Artificial
6. Design for Error
7. When all else fails, standardize
- Not intending to overuse inverted comas in this post I purposefully omitted them, but most of the above was authored by Donald A. Norman, author of the book -
1 comment
Feb 28, 2010
webcentric_sa said...
well done.. I like the part about the "car turning" we take things for granted. But dont worry.. some genius will come up with the opposite, and it will be fenomenally genius! LOL
