One thing I like to do to make the time I spend reading more valuable is to write up “book reports” distilling insights that might be valuable for the rest of my team.
This week I wrapped up “The Design of Everyday Things” by Don Norman — here are my takeaways. Note that this isn’t a complete summary; if you find this interesting, I recommend picking up the book for yourself.
The seven fundamental principles of design:
Discoverability: It is possible to determine what actions are possible and the current state of the device
Feedback: There is full and continuous information about the results of actions and the current state of the product or service. After an action has been executed, it is easy to determine the new state.
Conceptual model: The design projects all the information needed to create a good conceptual model of the system, leading to understanding and a feeling of control. The conceptual model enhances both discoverability and evaluation of results.
Affordances: The proper affordances exist to make the desired actions possible.
Signifiers: Effective user of signifiers ensures discoverability and that the feedback is well communicated and intelligible.
Mappings: The relationship between controls and their actions follows the principles of good mapping, enhanced as much as possible through spatial layout and temporal contiguity.
Constraints: Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.
Definitions and considerations:
Discoverability: Is it possible to even figure out what actions are possible and where and how to perform them?
Understanding: What does it all mean? How is the product supposed to be used? What do all the controls and settings mean?
Affordance: A relationship between the properties of the object and the capabilities of the agent that determine just how the object could be used. Jointly determined by the qualities of the object and the abilities of the interacting agent. Determines what actions are possible.
Signifier: Any mark or sound, any perceivable indicator that communicates appropriate behavior to a person. Communicates where actions should take place.
Feedback: Some way of letting you know that the system is working on your request.
Feedback must be immediate: even a delay of a tenth of a second can be disconcerting.
Feedback must also be informative.
Every action is associated with an expectation.
Information in the feedback loop of evaluation confirms or disconfirm expectations, resulting in satisfaction or relief, disappointment or frustration.
Feedback provides reassurance, even when it indicates a negative result.
A lack of feedback creates a feeling of lack of control, which can be unsettling.
Feedback is critical to managing expectations.
When a delay can be predicted, provide time estimates as well as progress bars to indicate how far along the task has gone.
It is wise to underpredict, to say that an operation will take longer than it actually will, so that expectations are likely to be exceeded, leading to a happy result.
Conceptual model: An explanation, usually highly simplified, of how something works.
Simplified models are valuable only as long as the assumptions that support them hold true.
A good conceptual model allows us to predict the effects of our actions.
Conceptual models do not have to be accurate as long as they lead to the correct behavior in the desired situation.
People invariably object and complain whenever a new approach is introduced into an existing array of products and systems.
Consistency in design is a virtue. It means that lessons learned with one system transfer readily to others.
If a new way of doing things is only slightly better than the old, it is generally better to be consistent.
It is psychological perceptions that matter — the conceptual model — not physical consistency.
Standards simplify life for everyone. At the same time, they tend to hinder future development.
Skeuomorphic designs are often comforting for traditionalists. One way of overcoming the fear of the new is to make it look like the old.
The Gulf of Evaluation: the amount of effort that a person must make to interpret the physical state of the device and to determine how well expectations and intentions have been met.
Feedback and a good conceptual help bridge the Gulf of Evaluation.
Flow state: when the challenge of an activity just slightly exceeds our skill level, so full attention is continually required, but is not so difficult that it invokes frustration and anxiety.
The constant tension of a flow state, paired with continual progress, can result in an engaging, immersive experience.
Failure: a learning experience.
To fail is to learn: we learn more from our failures than our successes. With failure, it is often possible to figure out why, to ensure that it will never (or rarely) happen again.
Failures are an essential part of exploration and creativity. If designers do not sometimes fail, it is a sign that they are not trying hard enough.
It is possible to avoid failure, to always be safe. But that is also the route to a dull, uninteresting life.
Eliminate all error messages. Instead, provide help and guidance.
Make it possible to correct problems directly from help and guidance messages.
Never make people start over.
Assume that what people have done is partially correct, so if it is inappropriate, provide the guidance that allows them to correct the problem and be on their way.
What we call an error is usually bad communication or interaction.
We can’t fix problems unless we admit they exist.
Make it possible to reverse actions — to “Undo” them — or make it harder to do what cannot be reversed. The best systems have multiple levels of undoing, so it is possible to undo an entire sequence of actions.
When people err, change the system so that type of error will be reduced or eliminated. If a system lets you make the error, it is badly designed.
Present information about the state of the system in a way that is easy to assimilate and interpret, and provide alternative explanations and interpretations.
Procedural knowledge: Knowledge of how to complete a task or activity.
Procedural knowledge is usually difficult or impossible to write down and difficult to teach. It is best taught by demonstration and best learned through practice.
Physical, cultural, and other constraints reduce the amount that must be learned to a reasonable quantity.
Skeuomorphism: incorporating old, familiar ideas into new technologies, even though they no longer play a functional role.
Slip: when a person intends to do one action and ends up doing something else.
Slips are the result of subconscious actions getting waylaid en route.
Slips, paradoxically, tend to occur more frequently to skilled people than to novices, because experts tend to perform tasks automatically, under subconscious control.
Memory-lapse slips are difficult to detect precisely because there is nothing to see: when no action is done, there is nothing to detect.
The best way to mitigate slips is to provide perceptible feedback about the nature of the action being performed, then very perceptible feedback describing the new resulting state, coupled with a mechanism that allows the errors to be undone.
Checklists are powerful tools, proven to increase accuracy of behavior and reduce error. They are especially important in situations with multiple, complex requirements, and even more so when there are interruptions.
It is always better to have two people do checklists together as a team: one to read the instructions and verify execution, and the other to execute each step.
In many complex tasks, the order in which many operations are performed may not matter, as long as they are all completed. In general, it is bad design to impose a sequential structure to task execution unless the task itself requires it.
Make it easier for people to discover the errors that do occur, and make them easier to correct.
Do sensibility checks. Does an action pass the “common sense” test?
Mistake: when the wrong goal is establish or the wrong plan is formed.
Mistakes result from conscious deliberations.
Make the item being acted upon more prominent. That is, change the appearance of the actual object being acted upon to be more visible: enlarge it, or change its color.
Mistakes are hard to detect because there is seldom anything that can signal an inappropriate goal.
If every decision had to be questioned, nothing would ever get done. But if decisions are not questioned, there will be major mistakes — rarely, but often of substantial penalty.
Activity: a collected set of tasks, all performed together toward a common high-level goal.
Let the activity define the product and its structure. Let the conceptual model of the product be built around the conceptual model of the activity.
Although people are unwilling to learn systems that appear to have arbitrary, incomprehensible requirements, they are quite willing to learn things that appear to be essential to an activity.
Well designed devices package together the various tasks that are required to support an activity, making them work seamlessly with one another.
Apple’s success with the iPod came from supporting the entire activity involved in listening to music: discovering it, purchasing it, getting it into a music player, developing playlists (that could be shared), and listening to the music.
Design for activities and the results will be useable by everyone.
Task: an organized, cohesive set of operations directed toward a single, low-level goal.
Other lessons:
Mappings:
A device is easy to use when the set of possible actions is visible, when the controls and displays exploit natural mappings.
Natural mappings are those where the relationship between the controls and the object to be controlled is obvious.
When mappings use spatial correspondence between the layout of the controls and the devices being controlled, it is easy to determine how to use them.
Designers have a special obligation to ensure that the behavior of machines is understandable to the people who interact with them.
Memory:
How much can be retained in memory depends on the familiarity of the material.
From a practical point of view, it is best to think of short-term memory as only holding three to five items. Don’t count on much being retained.
Visual information does not much interfere with auditory, actions do not interfere much with either auditory or written material. To maximize efficiency of working memory, it is best to present different information over different modalities.
Memory lapses are common causes of error. The immediate cause of memory lapses is interruption.
The most effective way of helping people remember is to make it unnecessary: provide constraints and forcing functions, natural good mapping, and feedback. If all else fails, put the information they need to remember into the world where they will perform the activity requiring that information.
To combat memory-lapse errors, minimize the number of steps or provide vivid reminders of steps that need to be completed.
Don’t require that all knowledge to operate technology be in the head. Allow for efficient operation when people have learned all the requirements, but make it possible for non-experts to use knowledge in the world. This will also help experts when they need to perform a rare, infrequently performed operation or return to the technology after prolonged absence.
Make something too secure, and it becomes less secure.
The lack of clear communication among the people and organizations constructing parts of a system is perhaps the most common cause of complicated, confusing designs.
Requirements made in the abstract are invariably wrong. Requirements made by asking people what they need are invariably wrong.
It turns out that most cases are “special.” Any system that does not allow for special cases will fail.
No matter how much time the design team has been allocated, the final results only seem to appear in the last twenty-four hours before the deadline.
In the history of all technological fields, some improvements in usability come naturally through the technology itself, others come through standardization.
Concentrate on areas where your product is strong and strengthen it there even more. Then focus all marketing and advertisements to point out the strong points. This causes the product to stand out from the mindless herd. If the product has real strengths, it can afford to just be “good enough” in other areas.
Quality only comes about by continual focus on, and attention to, the people who matter: customers.
With technology, the brain gets neither better nor worse. Instead, it is the task that changes.
Over time, the mix of technologies and tools makes quick and rough creation easier, but polished and professional level material much more difficult and expensive.