The Design of Everyday Things

By

Don Norman

My Thoughts

A must-read for anyone who's involved in the process of making things. It will have you questioning the design of just about every man-made object you come across.

Highlights & Summary Notes

Good design is actually a lot harder to notice than poor design, in part because good designs fit our needs so well that the design is invisible, serving us without drawing attention to itself. Bad design, on the other hand, screams out its inadequacies, making itself very noticeable.

To understand products, it is not enough to understand design or technology: it is critical to understand business.

The design principles here, based on psychology, on the nature of human cognition, emotion, action, and interaction with the world, will remain unchanged.

The Psychopathology of Everyday Things

Discoverability and Understanding

The most important characteristics of good design.

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 different controls and settings mean?

Human-Centered Design

Design is concerned with how things work, how they are controlled, and the nature of the interaction between people and technology.

But most of the problems come from a complete lack of understanding of the design principles necessary for effective human-machine interaction.

We must design our machines on the assumption that people will make errors.

The solution is human-centered design (HCD), an approach that puts human needs, capabilities, and behavior first, then designs to accommodate those needs, capabilities, and ways of behaving.

Good design starts with an understanding of psychology and technology.

The HCD principle is to avoid specifying the problem as long as possible but instead to iterate upon repeated approximations. This is done through rapid tests of ideas, and after each test modifying the approach and the problem definition.

Fundamental Principles of Interaction

Affordances

The term affordance refers to the relationship between a physical object and a person (or for that matter, any interacting agent, whether animal or human, or even machines and robots).

To be effective, affordances and anti-affordances have to be discoverable—perceivable.

Affordances exist even if they are not visible. For designers, their visibility is critical: visible affordances provide strong clues to the operations of things.

Signifiers

Affordances determine what actions are possible. Signifiers communicate where the action should take place. We need both.

Signifiers are signals. Some signifiers are signs, labels, and drawings placed in the world, such as the signs labeled “push,” “pull,” or “exit” on doors, or arrows and diagrams indicating what is to be acted upon or in which direction to gesture, or other instructions.

Some signifiers are simply the perceived affordances, such as the handle of a door or the physical structure of a switch.

When external signifiers (signs) have to be added to something as simple as a door, it indicates bad design.

Contraints

Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

Mapping

Mapping — The relationship between the elements of two sets of things.

The relationship between a control and its results is easiest to learn wherever there is an understandable mapping between the controls, the actions, and the intended result.

Feedback

Feedback — Communicating the results of an action

Feedback has to be planned. All actions need to be confirmed, but in a manner that is unobtrusive.

Conceptual Models

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.

There are often multiple conceptual models of a product or device.

Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.

The major clues to how things work come from their perceived structure—in particular from signifiers, affordances, constraints, and mappings.

Conceptual models are valuable in providing understanding, in predicting how things will behave, and in figuring out what to do when things do not go as planned.

The System Image

The Designer’s Model, the User’s Model, and the System Image. The designer’s conceptual model is the designer’s conception of the look, feel, and operation of a product.

System image — What can be derived from the physical structure that has been built (including documentation).

The user’s mental model is developed through interaction with the product and the system image. Designers expect the user’s model to be identical to their own, but because they cannot communicate directly with the user, the burden of communication is with the system image.

Good conceptual models are the key to understandable, enjoyable products: good communication is the key to good conceptual models.

The Paradox of Technology

Technology offers the potential to make life easier and more enjoyable; each new technology provides increased benefits. At the same time, added complexities increase our difficulty and frustration with technology.

The Design Challenge

Design requires the cooperative efforts of multiple disciplines.

If the design team has representatives from all the constituencies present at the same time, it is often possible to reach satisfactory solutions for all the needs.

The Psychology of Everyday Actions

The Gulfs of Execution and Evaluation

When people encounter a device, they face two gulfs:

  • Gulf of Execution — where they try to figure out how to use it
  • Gulf of Evaluation — where they try to figure out what state it is in and whether their actions got them to their goal.

We bridge the Gulf of Execution through the use of signifiers, constraints, mappings, and a conceptual model.

The Seven Stages of Action

  1. Goal (form the goal)
  2. Plan (the action)
  3. Specify (an action sequence)
  4. Perform (the action sequence)
  5. Perceive (the state of the world)
  6. Interpret (the perception)
  7. Compare (the outcome with the goal)

Not all of the activity in the stages is conscious. Goals tend to be, but even they may be subconscious.

The action cycle can start from:

  • The top — establishing a new goal, in which case we call it goal-driven behavior. merge with below
  • The bottom —  triggered by some event in the world (data-driven or event-driven behavior)

The seven stages provide a guideline for developing new products or services. The gulfs are obvious places to start, for either gulf, whether of execution or evaluation, is an opportunity for product enhancement.

Human Thought: Mostly Subconscious

Declarative memory — memory for factual information

Procedural memory — could be factual, but usually recalling activities like how to open a door

Cognition and emotion cannot be separated. Cognitive thoughts lead to emotions: emotions drive cognitive thoughts.

Emotion interacts with cognition biochemically, bathing the brain with hormones, transmitted either through the bloodstream or through ducts in the brain, modifying the behavior of brain cells.

  • Hormones exert powerful biases on brain operation.
  • Tense/threatening situations — the emotional system triggers the release of hormones that bias the brain to focus upon relevant parts of the environment. The muscles tense in preparation for action.
  • Calm/nonthreatening situations — the emotional system triggers the release of hormones that relax the muscles and bias the brain toward exploration and creativity. Now the brain is more apt to notice changes in the environment, to be distracted by events, and to piece together events and knowledge that might have seemed unrelated earlier.

Human Cognition and Emotion

Three levels of processing:

  • Visceral level (lizard brain) — allows us to respond quickly and subconsciously, without conscious awareness or control.
  • Behavioural level — Learned skills, triggered by situations that match the appropriate patterns. Every action is associated with an expectation. 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.
  • Reflective level (conscious cognition) — where deep understanding develops, where reasoning and conscious decision-making take place. To the designer, reflection is perhaps the most important of the levels of processing.

The Seven Stages of Action and the Three Levels of Processing

The flow state occurs when the challenge of the activity just slightly exceeds our skill level, so full attention is continually required. Flow requires that the activity be neither too easy nor too difficult relative to our level of skill.

People as Storytellers

But even when there is no single causal act, that doesn’t stop people from assigning one (see Narrative Fallacy)

Everyone forms stories (conceptual models) to explain what they have observed (e.g. turning the oven to full to heat it quicker, not true).

Positive Psychology

To fail is to learn: we learn more from our failures than from our successes.

Eliminate all error messages from electronic or computer systems. Instead, provide help and guidance.

Falsely Blaming Yourself

Human error usually is a result of poor design: it should be called system error.

If a person performs an inappropriate action, the design should maximise the chance that this can be discovered and then rectified. This requires good, intelligible feedback coupled with a simple, clear conceptual model. When people understand what has happened, what state the system is in, and what the most appropriate set of actions is, they can perform their activities more effectively.

The Seven Stages of Action → Seven Fundamental Design Principles

The Seven Stages of Action as Design Aids. Each of the seven stages indicates a place where the person using the system has a question. The seven questions pose seven design themes.

  1. What do I want to accomplish?
  2. What are the alternative action sequences?
  3. What action can I do now?
  4. How do I do it?
  5. What happened?
  6. What does it mean?
  7. Is this okay? Have I accomplished my goal?

The information that helps answer questions of execution (doing) is feedforward. The information that aids in understanding what has happened is feedback.

The insights from the seven stages of action lead us to seven fundamental principles of design:

  1. Discoverability  — It is possible to determine what actions are possible and the current state of the device.
  2. 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.
  3. 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.
  4. Affordances — The proper affordances exist to make the desired actions possible.
  5. Signifiers — Effective use of signifiers ensures discoverability and that the feedback is well communicated and intelligible.
  6. 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.
  7. Constraints — Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

Knowledge in the Head and in the World

Not all of the knowledge required for precise behavior has to be in the head. Knowledge is both in the head and in the world.

Knowledge is in the World

Whenever knowledge needed to do a task is readily available in the world, the need for us to learn it diminishes.

People function through their use of two kinds of knowledge:

  • Knowledge of (declarative) — includes the knowledge of facts and rules (e.g red traffic light means stop).
  • Knowledge how (procedural) — e.g. knowledge that enables a person to be a skilled musician or to return a serve in tennis.

The Structure of Memory

Memory is knowledge in the head.

Short-term or Working Memory

The traditional measures of STM capacity range from five to seven, but from a practical point of view, it is best to think of it as holding only three to five.

Long-term Memory

How well we can ever recover experiences and knowledge from LTM is highly dependent upon how the material was interpreted in the first place.

It has long been known that rehearsal of material—mentally reviewing it while still active in working memory (STM)—is an important component of the formation of long-term memory traces.

It is relatively easy to bias people so that they form false memories, “remembering” events in their lives with great clarity, even though they never occurred.

How people use their memories and how they retrieve knowledge:

  1. Memory for arbitrary things — the items to be retained seem arbitrary, with no meaning and no particular relationship to one another or to things already known.
  2. Memory for meaningful things — the items to be retained form meaningful relationships with themselves or with other things already known.

Memory for Arbitrary and Meaningful Things

The most effective way of helping people remember is to make it unnecessary. Conscious thinking takes time and mental resources. Experts minimise the need for conscious reasoning.

Natural Mapping

Natural mappings are those where the relationship between the controls and the object to be controlled (the burners, in this case) is obvious.

  • 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.

Usability is not often thought about during the purchasing process.

Knowing What to do: Constraints, Discoverability, and Feedback

Knowledge in the world — perceived affordances and signifiers, the mappings between the parts that appear to be controls or places to manipulate and the resulting actions, and the physical constraints that limit what can be done.

Knowledge in the headconceptual models; cultural, semantic, and logical constraints on behavior; and analogies between the current situation and previous experiences with other situations.

These four classes of constraints—physical, cultural, semantic, and logical—seem to be universal, appearing in a wide variety of situations. Constraints are powerful clues, limiting the set of possible actions.

The thoughtful use of constraints in design lets people readily determine the proper course of action, even in a novel situation.

Physical Constraints

Physical constraints are made more effective and useful if they are easy to see and interpret, for then the set of actions is restricted before anything has been done.

Cultural Constraints

Each culture has a set of allowable actions for social situations.

Guidelines for cultural behavior are represented in the mind by schemas, knowledge structures that contain the general rules and information necessary for interpreting situations and for guiding behavior.

Semantic Constraints

Semantics is the study of meaning. Semantic constraints are those that rely upon the meaning of the situation to control the set of possible actions.

Logical Constraints

There are no physical or cultural principles here; rather, there is a logical relationship between the spatial or functional layout of components and the things that they affect or are affected by.

A usable design starts with careful observations of how the tasks being supported are actually performed, followed by a design process that results in a good fit to the actual ways the tasks get performed. The technical name for this method is task analysis.

Examples

Forcing Functions

e.g. starting a car — the driver must have some physical object that signifies permission to use the car.

Interlocks

e.g. Dead man’s switch — requires the operator hold down a spring-loaded switch to enable operation of the equipment

Whereas a lock-in keeps someone in a space or prevents an action until the desired operations have been done, a lockout prevents someone from entering a space that is dangerous, or prevents an event from occurring.

Using Sound as Signifiers

Sometimes everything that is needed cannot be made visible. Enter sound: sound can provide information available in no other way.

Skeuomorphic

Skeuomorphic is the technical term for incorporating old, familiar ideas into new technologies, even though they no longer play a functional role. (e.g. switch designs in UI, engine sounds in electric sports cars)

Human Error? No, Bad Design

Root Cause Analysis

Root cause analysis — investigate the accident until the single, underlying cause is found.

  • Flawed because most accidents do not have a single cause. There are usually multiple things that went wrong, multiple events that, had any one of them not occurred, would have prevented the accident.

Why does the root cause analysis stop as soon as a human error is found? If a machine stops working, we don’t stop the analysis when we discover a broken part.

The Five Whys

When searching for the reason, even after you have found one, do not stop: ask why that was the case. And then ask why again. Keep asking until you have uncovered the true underlying causes.

Two Types of Errors: Slips & Mistakes

Memory lapses can lead to either slips or mistakes, depending upon whether the memory failure was at the highest level of cognition (mistakes) or at lower (subconscious) levels (slips).

Human error — any deviance from “appropriate” behavior.

Slips

Slips occur when the goal is correct, but the required actions are not done properly: the execution is flawed.

Action-based slips — the wrong action is performed.

Memory-lapse — memory fails, so the intended action is not done or its results not evaluated.

Tend to occur more frequently to skilled people than to novices because slips often result from a lack of attention to the task. Skilled people tend to perform tasks automatically.

Mistakes

Mistakes occur when the goal or plan is wrong.

Rule-based mistake — new procedures have to be invoked or when simple problems arise, we can characterise the actions of skilled people as rule-based.

Knowledge-based mistake — the problem is misdiagnosed because of erroneous or incomplete knowledge.

Memory-lapse mistakes — take place when there is forgetting at the stages of goals, plans, or evaluation.

We make decisions based upon what is in our memory. But retrieval from long-term memory is actually a reconstruction rather than an accurate record. As a result, it is subject to numerous biases.

Never underestimate the power of social pressures on behavior, causing otherwise sensible people to do things they know are wrong and possibly dangerous.

Hindsight makes events seem obvious and predictable. (see Hindsight Bias)

Designing for Error

It is relatively easy to design for the situation where everything goes well, the tricky part is to design for when things go wrong.

  • Understand the causes of error and design to minimise those causes.
  • Do sensibility checks. Does the action pass the “common sense” test?
  • Make it possible to reverse actions—to “undo” them—or make it harder to do what cannot be reversed.

Adding Constraints To Block Errors

Prevention often involves adding specific constraints to actions. (e.g. different vehicle fluids often have different colours so that they can be distinguished.)

Reason’s Swiss Cheese Model of Accidents. Accidents usually have multiple causes, whereby had any single one of those causes not happened, the accident would not have occurred. Unless the holes all line up perfectly, there will be no accident.

We can decrease accidents and make systems more resilient by designing them to have extra precautions against error (more slices of cheese), less opportunities for slips, mistakes, or equipment failure (less holes), and very different mechanisms in the different subparts of the system (trying to ensure that the holes do not line up).

Design redundancy and layers of defence: that’s Swiss cheese.

  • The metaphor illustrates the futility of trying to find the one underlying cause of an accident (usually some person) and punishing the culprit.
  • Instead, we need to think about systems, about all the interacting factors that lead to human error and then to accidents, and devise ways to make the systems, as a whole, more reliable.

Design Thinking

Good designers never start by trying to solve the problem given to them: they start by trying to understand what the real issues are.

They don’t try to search for a solution until they have determined the real problem, and even then, instead of solving that problem, they stop to consider a wide range of potential solutions.

The Double-Diamond Model of Design

Designers often start by questioning the problem given to them: they expand the scope of the problem, diverging to examine all the fundamental issues that underlie it. Then they converge upon a single problem statement.

During the solution phase of their studies, they first expand the space of possible solutions, the divergence phase. Finally, they converge upon a proposed solution.

Human Centered Design

The process of ensuring that people’s needs are met, that the resulting product is understandable and usable, that it accomplishes the desired tasks, and that the experience of use is positive and enjoyable.

This is where the human-centered design process comes into play: it takes place within the double-diamond diverge-converge process.

Observation

Understand the nature of the problem.

Research about the customer and the people who will use the products under consideration.

Observing potential customers activities, attempting to understand their interests, motives, and true needs.

Design research supports both diamonds of the design process.

  • The first diamond, finding the right problem, requires a deep understanding of the true needs of people.
  • Once the problem has been defined, finding an appropriate solution again requires deep understanding of the intended population, how those people perform their activities, their capabilities and prior experience, and what cultural issues might be impacted.

Idea Generation

This exercise might be done for both of the double diamonds: during the phase of finding the correct problem, then during the problem solution phase.

Generate numerous ideas. It is dangerous to become fixated upon one or two ideas too early in the process.

Be creative without regard for constraints.

Question everything.

Testing

Like prototyping, testing is done in the problem specification phase to ensure that the problem is well understood, then done again in the problem solution phase to ensure that the new design meets the needs and abilities of those who will use it.

Iteration

The role of iteration in human-centered design is to enable continual refinement and enhancement.

Failure is encouraged. “Fail frequently, fail fast.”

The Difference Between Tasks and Activities

Activity  — high-level structure, e.g. go shopping

Task — lower-level component of an activity (e.g. drive to the market, find a shopping basket)

Well-designed devices will package together the various tasks that are required to support an activity, making them work seamlessly with one another, making sure the work done for one does not interfere with the requirements for another.

Don Norman's Law of Product Development

The day a product development process starts, it is behind schedule and above budget.

The way to handle the time crunch that eliminates the ability to do good up-front design research is to separate that process from the product team: have design researchers always out in the field, always studying potential products and customers. Then, when the product team is launched, the designers can say, “We already examined this case, so here are our recommendations.”

Design in the World of Business

The design of technology to fit human needs and capabilities is determined by the psychology of people. Yes, technologies may change, but people stay the same.

Featurism

Creeping featurism — the tendency to add to the number of features of a product, often extending the number beyond all reason.

Causing factors:

  • Existing customers like the product, but express a wish for more features, more functions, more capability.
  • Customers are satisfied, but sales are declining because the market is saturated: everyone who wants the product already has it.

Jeff Bezos, the founder and CEO of Amazon.com, calls his approach “customer obsessed.” Everything is focused upon the requirements of Amazon’s customers. The competition is ignored, the traditional marketing requirements are ignored. The focus is on simple, customer-driven questions: what do the customers want; how can their needs best be satisfied; what can be done better to enhance customer service and customer value?

Technology changes the way we do things, but fundamental needs remain unchanged.

There is another problem: the general conservatism of large companies. Most radical ideas fail: large companies are not tolerant of failure. Small companies can jump in with new, exciting ideas because if they fail, well, the cost is relatively low.

Two Forms of Innovation

Incremental — the design is tested, problem areas are discovered and modified, and then the product is continually retested and remodified.

Radical Innovation — Incremental innovation starts with existing products and makes them better. Radical innovation starts fresh, often driven by new technologies that make possible new capabilities.

  • Radical innovation is what many people seek, for it is the big, spectacular form of change. But most radical ideas fail,

In to the Future

Although technology is continually introducing new means of doing things, people are resistant to changes in the way they do things.

Consider three simple examples: social interaction, communication, and music. These represent three different human activities, but each is so fundamental to human life that all three have persisted throughout recorded history and will persist, despite major changes in the technologies that support these activities. They are akin to eating: new technologies will change the types of food we eat and the way it is prepared, but will never eliminate the need to eat.

Needles Features and Needles Models

But a business that makes and sells durable goods faces a problem: As soon as everyone who wants the product has it, then there is no need for more. Sales will cease. The company will go out of business.

Ford explained that he wanted to find the parts that were still in good shape. The company could save money if they redesigned these parts to fail at the same time as the others.

Making things fail is not the only way to sustain sales.

In today’s environmentally sensitive world, the full life cycle of the product must be taken into consideration. (see The Circular Design Guide from IDEO)