Key Lessons from The Design of Everyday Things
I just finished reading the design of everyday things and there were so many important lessons from the book that I had to write a summary and record what I learned.
This post contains what I felt are the most important takeaways from the book.
Chapter 1: The Psychopathology of Everyday Things
There are several areas of design specialty:
- Industrial design emphasizes form and material
- Interaction design emphasizes understandability and usability
- Experience design emphasizes emotional impact
“Great designers product pleasurable experiences.”
“Experience is critical, for it determines how fondly people remember their interactions. Was the overall experience positive, or was it frustrating and confusing?”
There are several fundamental psychological principles of interaction:
- Affordance - a relationship between the properties of an object and the capabilities of a person that determines just how the object could possibly be used (e.g. chairs afford sitting, glass affords transparency)
- Signifier - any perceivable indicator that communicates appropriate behavior to a person
- Mapping - a relationship between the controls of a object and the resulting changes
- Feedback - the communication of the results of an action
- Conceptual model - a simple explanation of how an object works, often inferred from the object itself
- System image - the combined information available to us about a particular object, including what it looks like, what we know about it from using similar things, etc.
Design requires the cooperative efforts of multiple disciplines and each discipline thinks its contribution is most important:
- Marketing says price plus features is most important
- Engineering says reliability is most important
- Support says the design needs to solve the customer support problems
Everyone must understand the viewpoints of others in the organization and work together to build the product with all constraints considered.
FIGURE 1.2. Problem Doors: Signifiers Are Needed. Door hardware can signal whether to push or pull without signs, but the hardware of the two doors in the upper photo, A, are identical even though one should be pushed, the other pulled. The flat, ribbed horizontal bar has the obvious perceived affordance of pushing, but as the signs indicate, the door on the left is to be pulled, the one on the right is to be pushed. In the bottom pair of photos, B and C, there are no visible signifiers or affordances. How does one know which side to push? Trial and error. When external signifiers (signs) have to be added to something as simple as a door, it indicates bad design.
FIGURE 1.3. Sliding Doors: Seldom Done Well. Sliding doors are seldom signified properly. The top two photographs show the sliding door to the toilet on an Amtrak train in the United States. The handle clearly signifies “pull,” but in fact, it needs to be rotated and the door slid to the right. The owner of the store in Shanghai, China, Photo C, solved the problem with a sign. “don’t push!” it says, in both English and Chinese. Amtrak’s toilet door could have used a similar kind of sign.
FIGURE 1.7. Good Mapping: Automobile Seat Adjustment Control. This is an excellent example of natural mapping. The control is in the shape of the seat itself: the mapping is straightforward. To move the front edge of the seat higher, lift up on the front part of the button. To make the seat back recline, move the button back. The same principle could be applied to much more common objects. This particular control is from Mercedes-Benz, but this form of mapping is now used by many automobile companies.
FIGURE 1.8. Junghans Mega 1000 Digital Radio Controlled Watch. There is no good conceptual model for understanding the operation of my watch. It has five buttons with no hints as to what each one does. And yes, the buttons do different things in their different modes. But it is a very nice-looking watch, and always has the exact time because it checks official radio time stations.
Chapter 2: The Psychology of Everyday Actions
When people use something, they face two gulfs:
- The gulf of execution, where they try to figure out how it operates
- The gulf of evaluation, where they try to figure out what happened
There are two parts to an action: executing the action and evaluating the results. This can be expanded to seven stages of action:
|Goal||Form the goal||What do I want to accomplish?|
|Plan||Plan the action||What are the alternative action sequences?|
|Specify||Specify an action sequence||What action can I do now?|
|Perform||Perform the action sequence||How do I do it?|
|Perceive||Perceive the state of the world||What happened?|
|Interpret||Interpret the perception||What does it mean?|
|Compare||Compare the outcome with the goal||Is this okay? Have I accomplished my goal?|
Conscious attention is necessary to learn most things, but after the initial learning with continued practice and study, overlearning has occured and performance appears to be effortless, with little or no awareness.
Cognition and emotion cannot be separated. Cognitive thought leads to emotions and emotions drive cognitive thoughts. The brain is structured to act upon the world, and every action carries with it expectations, and these expectations drive emotions.
Cognition attempts to make sense of the world while emotion assigns it value. Cognition provides understanding while emotion provides value judgments. A human without a working emotional system has difficulty making choices while a human without a cognitive system is dysfunctional.
Our two systems of cognition are our conscious and subconscious systems:
|Multiple resources||Limited resources|
|Controls skilled behavior||Invoked for novel situations like learning & danger|
A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done. Too much, and we call the person scatterbrained, flitting from one topic to another, unable to finish one thought before another comes to mind.
A brain in a negative emotional state provides focus, precisely what is needed to maintain attention to a task and finish it. Too much, however, and we get tunnel vision, where people are unable to look beyond their narrow point of view.
Both the positive, relaxed state and the anxious, negative, and tense state are valuable and powerful tools for human creativity and action. The extremes of both states, however, can be dangerous.
The brain has three levels of processing:
- The visceral level - part of the basic protective mechanisms of the human affective system, making judgments about the environment and responding quickly and subconsciously
- The behavioral level - the home of learned skills, triggered by situations that match the appropriate patterns, operating largely within the subconscious
- The reflective level - the home of conscious cognition, where deep understanding develops and where reasoning and conscious decision-making take place
Design must take place at all levels: visceral, behavioral, and reflective.
Learned helplessness occurs when people experience repeated failure at a task. As a result they decide the task cannot be done and they stop trying.
Advice to designers:
- Do not blame people when they fail to use your products properly.
- Take people’s difficulties as signifiers of where the product can be improved.
- Eliminate all error messages from electronic or computer systems. Instead, provide help and guidance.
- Make it possible to correct problems directly from help and guidance messages. Allow people to continue with their task. Don’t impede progress. Help make it smooth and continuous. 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.
- Think positively, for yourself and the people you interact with.
There are 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 use 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.
FIGURE 2.5. Panic Bars on Doors. People fleeing a fire would die if they en- countered exit doors that opened inward, because they would keep trying to push them outward, and when that failed, they would push harder. The proper design, now required by law in many places, is to change the design of doors so that they open when pushed. Here is one example: an excellent design strategy for dealing with real behavior by the use of the proper affordances coupled with a graceful signifier, the black bar, which indicates where to push.
Chapter 3: Knowledge in the Head and in the World
Precise behavior can emerge from imprecise knowledge for four reasons:
- Knowledge is both in the head and in the world
- Great precision is not required
- Natural constraints exist in the world
- Knowledge of cultural constraints and conventions exists in the head
“Because behavior can be guided by the combination of internal and external knowledge and constraints, people can minimize the amount of material they must learn, as well as the completeness, precision, accuracy, or depth of the learning.”
There are two types of memory:
- Short term memory
- Long term memory
Long term memory can be divided into two categories:
- Memory for arbitrary things
- Memory for meaningful things
“Well-learned skills bypass the need for conscious oversight and control: con- scious control is only required for initial learning and for dealing with unexpected situations. Continual practice automates the action cycle, minimizing the amount of conscious thinking and problem-solving required to act.”
How pilots remember what air-traffic control tells them:
- They write down the critical information.
- They enter it into their equipment as it is told to them, so minimal memory is required.
- They remember some of it as meaningful phrases.
“There are two different aspects to a reminder: the signal and the message. Just as in doing an action we can distinguish between knowing what can be done and knowing how to do it, in reminding we must distinguish between the signal—knowing that something is to be remembered, and the message—remembering the infor-mation itself.”
“Knowledge in the world and knowledge in the head are both es- sential in our daily functioning. But to some extent we can choose to lean more heavily on one or the other. That choice requires a tradeoff—gaining the advantages of knowledge in the world means losing the advantages of knowledge in the head.”
Tradeoffs Between Knowledge in the World and in the Head:
|Knowledge in the World||Knowledge in the Head|
|Information is readily and easily available whenever perceivable.||Material in working memory is readily available. Otherwise considerable search and effort may be required.|
|Interpretation substitutes for learning. How easy it is to interpret knowledge in the world depends upon the skill of the designer.||Requires learning, which can be considerable. Learning is made easier if there is meaning or structure to the material or if there is a good conceptual model.|
|Slowed by the need to find and interpret the knowledge.||Can be efficient, especially if so well-learned that it is automated.|
|Ease of use at first encounter is high.||Ease of use at first encounter is low.|
|Can be ugly and inelegant, especially if there is a need to maintain a lot of knowledge. This can lead to clutter. Here is where the skills of the graphics and industrial designer play major roles.||Nothing needs to be visible, which gives more freedom to the designer. This leads to cleaner, more pleasing appearance — at the cost of ease of use at first encounter, learning, and remembering.|
“It is this combination of technology and people that creates super-powerful beings. Technology does not make us smarter. People do not make technology smart. It is the combination of the two, the person plus the artifact, that is smart. Together, with our tools, we are a powerful combination.”
Natural mappings are those where the relationship between the controls and the object to be controlled is obvious. Depending upon circumstances, natural mappings will employ spatial cues.
Three levels of mapping, arranged in decreasing effectiveness as memory aids:
- Best mapping: Controls are mounted directly on the item to be controlled.
- Second-best mapping: Controls are as close as possible to the object to be controlled.
- Third-best mapping: Controls are arranged in the same spatial configuration as the objects to be controlled.
“What is natural depends upon point of view, the choice of metaphor, and therefore, the culture. The design difficulties occur when there is a switch in metaphors.”
Figure 3.2 Mappings of Stove Controls with Burners. With the Traditional arrangement of stove burners shown in Figures A and B, the burners are arranged in a rectangle and the controls in a linear line. Usually there is a partial natural mapping, with the left two controls operating the left burners and the right two controls operating the right burners. Even so, there are four possible mappings of control to burners, all four of which are used in commercial stoves. The only way to know which control works which burner is to read the labels. But if the controls were also in a rectangle (Figure C) or the burners staggered (Figure D), no labels would be needed. Learning would be easy; errors would be reduced.
Chapter 4: Knowing What to Do: Constraints, Discoverability, and Feedback
There are four kinds of constraints:
Chapter 5: Human Error? No, Bad Design
Ensure simple errors cannot cause widespread damage by:
- Understand the causes of error and design to minimize those causes
- Do sensibility checks. Does the action pass the “common sense” test?
- Make it harder to reverse actions–to “undo” them–or make it harder to do what cannot be reversed.
- Make it easier for people to discover the errors that do occur, and make them easier to correct.
- Don’t treat the action as an error; rather, try to help the person complete the action properly. Think of the action as an approximation to what is desired.