By Don Norman
https://www.goodreads.com/book/show/25224275-the-design-of-everyday-things
Human-centered design (HCD)
The total experience of a product covers much more than its usability:
- Aesthetics
- Fun
- Pleasure
- Enjoyment
- Emotion
Cost and schedule are critical, the need to pay attention to competition, and the importance of multidisciplinary teams.
The best products do not always succeed. Brilliant new technologies might take decades to become accepted.
To understand products, it is not enough to understand design or technology: it is critical to understand business.
Based on psychology, on the nature of human cognition, emotion, action, and interaction with the world, will remain unchanged.
2 of the most important characteristics of good design are:
- Discoverability: is it possible to even figure out what actions are possible and where and how to perform them?
- What does "it" do?
- How does "it" work?
- What operations are possible?
- Understanding: what does it all mean? How is the product supposed to be used? What do all the different controls and settings mean?
In the best cases, the products should also be delightful and enjoyable, which means that not only must the requirements of engineering, manufacturing, and ergonomics be satisfied, but attention must be paid to the entire experience, which means the aesthetics of form and the quality of interaction.
Design is concerned with how things work, how they are controlled, and the nature of the interaction between people and technology.
It is the duty of machines and those who design them to understand people. It is not our duty to understand the arbitrary, meaningless dictates of machines.
We have to accept human behavior the way it is, not the way we would wish it to be.
Design presents a fascinating interplay of technology and psychology…So we must design our machines on the assumption that people will make errors.
HCD is 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
- Requires good communication, esp. from machine to person, indicating:
- What actions are possible
- What is happening
- What is about to happen
Designers need to focus their attention on the cases where things go wrong, not just on when things work as planned.
HCD is a design philosophy. It means starting with a good understanding of ppl and the needs that the design is intended to meet. This comes through observation, for ppl themselves are often unaware of their true needs, even unaware of the difficulties they are facing.
HCD principle is to avoid specifying the problem as long as possible but instead to iterate upon repeated approximations.
Discoverability results from appropriate application of 5 fundamental psychological concepts:
- Affordances
- Signifiers
- Constraints
- Mappings
- Feedback
- Conceptual model of the system (provides true understanding)
Affordances make sense for interaction with physical objects. Affordance refers to the relationship between a physical object and a person (or any interacting agent, animal, machines, robots, etc.). An affordance is a relationship between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used.
The presence of an affordance is jointly determined by the qualities of the object and the abilities of the agent that is interacting. This relational definition of affordance gives considerable difficulty to many ppl.
Affordance IS NOT a property, it is a relationship.
An anti-affordance is the prevention of interaction.
To be effective, affordances and anti-affordances have to be discoverable or perceivable. If they can't be perceived, some means of signaling its presence is required: a signifier.
Affordances exist even if they are not visible. For designers, their visibility is critical: visible affordances provide strong clues to the operations of things. Perceived affordances help ppl figure out what actions are possible without the need for labels or instructions.
Affordances was a term coined by the insights of J.J. Gibson, an eminent psychologist who provided many advances to our understanding of human perception.
In Gibsonian psychology, an ecological approach to perception is taken, meaning the world contains the clues and the ppl simply pick them up through "direct perception".
Combined info, "information pickup", picked up by all of our sensory apparatus - sight, sound, smell, touch, balance, kinesthetic, acceleration, body position - determines our perceptions without the need for internal processing or cognition.
Signifiers specify how people discover those possibilities.
Signifiers are signs, perceptible signals of what can be done. Signifiers are of far more importance to designers than are affordances.
Designers need to know how to design things to make them understandable. They're trying to signify where the "touch" should take place. This is not the same thing as saying what action is possible.
People search for clues, for any sign that might help them cope and understand. It is the sign that is important, anything that might signify meaningful information.
Good design requires, among other things, good communication of the purpose, structure, and operation of the device to the users. That is the role of the signifier.
Signifiers refer to any mark or sound, any perceivable indicator that communicates appropriate behavior to a person. Signifiers can be deliberate and intentional.
Signifiers provide valuable clues as to the nature of the world and of social activities.
Affordances are the possible interactions between ppl and the environment. Some affordances are perceivable, some are not.
Perceived affordances often act as signifiers, but they can be ambiguous.
Signifiers signal things, in particular what actions are possible and how they should be done. Signifiers must be perceivable, else they fail to function.
In design, signifiers are more important than affordances, for they communicate how to use the design. Creative designers incorporate the signifying part of the design into a cohesive experience.
Mapping is a technical term, borrowed from mathematics, meaning the relationship between the elements of two sets of things. It is an important concept in the design and layout of controls and displays.
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.
Natural mappings take advantage of spatial analogies, leading to immediate understanding. Other natural mappings follow from the principles of perception and allow for the natural grouping or patterning of controls and feedback.
Groupings and proximity are important principles from Gestalt psychology that can be used to map controls to functions:
- Groupings: related controls should be grouped together
- Proximity: controls should be close to the item being controlled
NOTE: What is natural to one culture is not necessarily natural for another!
A device is easy to use when the set of possible actions is visible, when the controls and displays exploit natural mappings.
The principles are simple but rarely incorporated into design. Good design takes care, planning, thought, and an understanding of how people behave.
Feedback is some way of letting you know that the system is working on your request, or done with your request. It is communicating the results of an action. It is a well-known concept from the science of control and information theory.
The human nervous system is equipped with numerous feedback mechanisms, including:
- Visual
- Auditory
- Touch sensors
- Vestibular (body equilibrium)
- Proprioceptive systems that monitors body position and muscle and limb movements
Feedback MUST be immediate: even a delay of a tenth of a second can be disconnecting. If the delay is too long, ppl often give up.
Feedback MUST also be informative.
Poor feedback can be worse than no feedback at all, bc it is distracting, uninformative, and in many cases, irritating and anxiety-provoking. Too much feedback can be even more annoying than too little. Machines that give too much feedback are like backseat drivers. Too many announcements cause ppl to ignore all of them, or wherever possible, disable all of them, which means that critical and important ones are apt to be missed.
Feedback has to be planned. Feedback MUST also be prioritized, so that unimportant info is presented in an unobtrusive fashion, but important signals are presented in a way that does capture attention.
A conceptual model is an explanation, usually highly simplified, of how something works, a prototype. It doesn't have to be complete or even accurate as long as it is useful.
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. The most important conceptual models are the ones that reside in the minds of the ppl who are using the product, so they're also "mental models". They're conceptual models in ppl's minds that represent their understanding of how things work. Diff ppl may hold diff mental models of the same item. Sometimes the models can even be in conflict within a single person.
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. A good conceptual model allows us to predict the effects of our actions.
There is no need to understand the underlying physics or chemistry of each device we own, just the relationship between the controls and the outcomes.
The combined information available to the users is called the system image. The user's conceptual model comes from the system image, through the interaction w/the product, reading, searching for online, information, and from whatever manuals are provided.
Designers expect the user's model to be identical to their own, but bc they cannot communicate directly w/the user, the burden of communication is w/the system image.
It is up to the designer to provide the appropriate information to make the product understandable and usable. Most important is the provision of a good conceptual model that gudies the user when things go wrong.
With a good conceptual model, ppl can figure out what has happened and correct the things that went wrong.
Good conceptual models are the key to understandable, enjoyable products: good communication is the key to good conceptual models.
Technology offers the potential to make life easier and more enjoyable; e/new technology provides increased benefits. At the same time, added complexities increase our difficulty and frustration w/technology.
The same tech that simplifies life by providing more functions in each device also complicates life by making the device harder to learn, harder to use.
The hardest part of producing a product is coordinating all the many, separate disciplines, e/with diff goals and priorities. E/discipline has a diff perspective of the relative important of the many factors that make up a product.
- One discipline argues that it must be usable and understandable
- Another that it must be attractive
- Another that it has to be affordable
- Another reliable
- Others to be able to be manufactured and serviced
- Distinguishable from competing products
- Superior in critical dimensions such as price, features, reliability, appearance
Overall, ppl need to want to purchase it. It doesn't matter how good a product is if, in the end, nobody uses it.
The successful product has to satisfy all of these requirements.
Another hard part is to convince ppl to understand the viewpoints of others, to abandon their disciplinary viewpoint and to think of the design from the viewpoints of the person who buys the product and those who use it.
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. It is when the disciplines operate independently of one another that major clashes and deficiencies arise.
The "Gulf of Execution" is where we try to figure out how it operates.
We bridge the gulf of execution through the use of signifiers, constraints, mappings, and a conceptual model.
The "Gulf of Evaluation" is where we try to figure out what happened. This gulf reflects the amount of effort that the person must make to interpret the physical state of the device and to determine how well the expectations and intentions have been met.
What are the major design elements that help bridge the gulf of evaluation? Feedback and a good conceptual model.
The difficulties reside in the design, not in the ppl attempting to use the design.
Different emotions arise at different stages, and show which stages are primarily located at each of the three levels of processing:
- Visceral: for the elementary levels of motor action performance and perception
- Behavioral: for the levels of action specification and initial interpretation of the outcome
- Reflective: for the development of goals, plans, and the final stage of evaluation of the outcome
Both execution & evaluation require understanding: how the item works & what results it produces. They can both affect our emotional state.
All the 7 stages of action are conscious steps we take.
- Goal: form the goal
- Plan: the action Determine which of the many possible plans of action to follow
- Determine which of the many possible plans of action to follow
- Specify: an action sequence
- Perform: the action sequence
- Perceive: the state of the world
- Interpret: the perception
- Compare: the outcome with the goal
There are 3 stages of execution that follow from the 1) goal: 2) plan, 3) specify, and 4) perform.
Evaluating what happened has 3 stages: 5) perceiving what happened in the world; 6) tyring to make sense of it or interpreting it; 7) comparing what happened with what was wanted.
Event-driven behavior: the sequence starts with the world, causing evaluation of the state and the formulation of the goal. The trigger was an environmental event.
Root cause analysis: asking "why?" until the ultimate, fundamental cause of the activity is reached. Also, it is asking what the "real goal" is.
Goal-driven behavior: the action cycle starting from the top, by establishing a new goal. The cycle starts with the goal, and then goes through the 3 stages of execution.
Data-driven behavior or event-driven behavior: the cycle starts with the goal and then goes through the 3 stages of execution.
The 7 stages of action 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.
Because they are for humans, designs are apt to be faulty, difficult to use, difficult to understand.
Many of our beliefs about how ppl behave - including beliefs about ourselves - are wrong.
Most of our brain's operations are subconscious, hidden beneath our awareness. It's only the highest level, what we call reflective, that is conscious. Conscious attention is necessary to learn most things, but after a few tries, we can get to a state of "over-learning". Once the skill is over-learned, then it could be performed from "muscle memory", or with little effort, almost subconsciously.
How do we know what we do not know so rapidly? Yet some things that we do know can take a long time to retrieve?
Declarative memory: memory for factual information.
Procedural memory: recalling activities performed in sequence, like opening a door.
Human thought is not all conscious. Thought cannot be separated from emotion.
Cognitive thoughts lead to emotions: 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.
The emotional system is a powerful information processing system that works in tandem with cognition. Cognition attempts to make sense of the world: emotion assigns value. Cognition provides understanding: emotion provides value judgments.
We use logic and reason after the fact, to justify our decisions to ourselves (to our conscious minds) and to others.
Subconscious processing is one of our strengths. It is good at detecting general trends, recognizing relationships between what we now experience and what has happened in the past.
Subconscious thought is biased toward regularity and structure, and it is limited in formal power.
Conscious thought is quite different, it is slow, and labored. We slowly ponder decisions, think through alternatives, compare different choices.
Both conscious and subconscious modes of thought are powerful and essential aspects of human life. Both can provide insightful leaps and creative moments. Yet both are prone to errors, misconceptions, and failures.
Emotion interacts w/cognition biochemically, via hormones through bloodstream or ducts in the brain, modding the behavior of the brain cells.
Hormones exert powerful biases on brain ops. Thus, in tense threatening situations, the emotional system triggers the release of hormones that bias the brain to focus upon relevant parts of the environment.
Subconscious and conscious systems of cognition:
| Subconscious | Conscious |
|---|---|
| Fast | Slow |
| Automatic | Controlled |
| Multiple resources | Limited resources |
| Controls skilled behavior | Invoked for novel situation |
A positive emotional state is ideal for creative thought.
A brain in a negative emotional state provides focus.
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.
3 levels of processing:
- Visceral
- Behavioral
- Reflective
AKA "the lizard brain". E/one has the same basic visceral responses. These are part of the protective mechanisms of the human affective system, making quick judgements about the env.
The visceral system allows us to respond quickly and subconsciously, w/out conscious awareness or control.
Visceral learning takes place primarily by sensitization or desensitization through such mechanisms as adaptation and classical conditioning.
These responses give rise to the startle reflex.
The visceral level responds to the immediate present and produces an affective state, relatively unaffected by context or history. It simply assesses the situation.
The visceral level is tightly coupled to the body's musculature - the motor system.
This is also the cause for "fight or flight".
Tension of the body includes, negative state = tense; positive state = relaxed. We often determine our own state by noting our own musculature.
Visceral responses are fast and completely subconscious, they are precursors to emotion.
For designers, the visceral response is about immediate perception.
The style matters: appearances, whether sound or sight, touch or smell, drive the visceral response.
This has nothing to do with how usable, effective, or understandable the product is. It is all about attraction or repulsion. Great designers use their aesthetic sensibilities to drive these visceral responses.
Engineers and other logical ppl tend to dismiss the visceral response as irrelevant. VISCERAL RESPONSES MATTER!
The behavioral level is the home of learned skills, triggered by situations that match the appropriate patterns. Actions and analyses at this level are largely subconscious.
When playing sports, our responses occur far too quickly for conscious control: it is the behavioral level that takes control.
When we perform a well-learned action, all we have to do is think of the goal and the behavioral level handles all the details.
For designers, the most critical aspect of the behavioral level is that every action is associated with an expectation.
The information in the feedback loop of evaluation confirms or disconfirms the expectations.
Behavioral states give rise to a feeling of control when there is good understanding and knowledge of results, and frustration and anger when things do not go as planned.
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. Expectations play an important role in our emotional lives.
The reflective level is the home of conscious cognition. This is where deep understanding develops, where reasoning and conscious decision-making take place.
Reflection is cognitive, deep, and slow. A reflection is looking back over them, evaluating the circumstances, actions, and outcomes, often assessing blame or responsibility.
The highest levels of emotions come from the reflective level, for it is here that causes are assigned and where predictions of the future take place. Emotion and cognition are tightly intertwined.
Reflective responses are part of our memory of events. Memories last far longer than the immediate experience or the period of usage, which are the domains of the visceral and behavioral levels. It is reflection that drives us to recommend a product, to recommend that others use it - or perhaps avoid it.
Advertisers hope that the strong reflective value associated with a well-known, highly prestigious brand might overwhelm our judgment, despite a frustrating experience in using the product.
The behavioral level, which is the home of interaction, is also the home of all expectation-based emotions, of hope and joy, frustration and anger.
Understanding arises at a combination of the behavioral and reflective levels. Enjoyment requires ALL three.
High-level reflective cognition can trigger lower-level emotions. Lower-level emotions can trigger higher-level reflective cognition.
At the lowest level are the visceral levels of calmness or anxiety when approaching a task or evaluating the state of the world.
Then in the mid levels are the behavioral ones driven by expectations on the execution side - for example hope and fear - and emotions driven by the confirmation of those expectations on the evaluation side - for example relief or despair.
At the highest level are the reflective emotions, ones that assess the results in terms of the presumed causal agents and the consequences, both immediate and long-term.
One important emotional state is the one that accompanies complete immersion into an activity, a state that social scientist Mihaly Csikszentmihalyi has labeled "flow".
When in the "flow" state, ppl lose track of time and the outside environment. They are at one with the task they are performing.
The task is at the proper level of difficulty: difficult enough to provide a challenge and require continued attention, but not so difficult that it invokes frustration and anxiety.
When the results of our actions are evaluated against expectations, the resulting emotions affect our feelinlgs as we continue through the many cycles of action.
Ppl are innately disposed to look for causes of events, to form explanations and stories.
Stories resonate with our experiences and provide examples of new instances.
From our experiences and the stories of others, we tend to form generalizations about the way ppl behave and things work.
We attribute causes to events, and as long as these cause-and-effect pairings make sense, we accept them and use them for understanding future events.
Conceptual models are a form of story, resulting from our predisposition to find explanations. These models are essential in helping us understand our experiences, predict the outcome of our actions, and handle unexpected occurrences.
Conceptual models are often constructed from fragmentary evidence, with only a poor understanding of what is happening, and with a kind of naive psychology that postulates causes, mechanisms, and relationships even where there are none.
In the absence of external info, ppl can let their imagination run free as long as the conceptual models they develop account for the facts as they perceive them.
Ppl try to find causes for events. They tend to assign a causal relation whenever 2 things occur in succession, even if there really was no relationship between the two.
The tendency to repeat an action when the first attempt fails can be disastrous, so feedback is very important.
Often ppl will use their own conceptual models of the world to determine the perceived causal relationship between the thing being blamed and the result.
It seems natural for ppl to blame their own misfortunes on the environment. It seems equally natural to blame other ppl's misfortunes on their personalities.
When things go right, ppl credit their own abilities and intelligence. When they see things go well for someone else, they sometimes credit the environment, or luck.
Learned helplessness refers to the situation which ppl experience repeated failure at a task. As a result, they decide the task cannot be done, at least not by them: they are helpless. They stop trying.
Sometimes all it takes to get such a feeling of helplessness are a few experiences that accidentally turn out bad.
The problem is that once failure starts, it is soon generalized by self-blame. The vicious cycle starts: if you fail at something, you think it is your fault. Therefore you think you can't do the task. Next time you have to do a task, you believe you can't, so you don't even try. You're trapped in a sel-fulfilling prophecy.
When something doesn't work, it can be considered an interesting challenge, or perhaps just a positive learning experience.
We need to remove the word failure from our vocab., replacing it instead with learning experience. To fail is to learn: we learn more from our failures than from our successes.
"Fail often, fail fast!". Failures are essential part of exploration and creativity.
It is possible to avoid failure, to always be safe, but that is also the route to a dull, uninteresting life. In design, make sure to follow this philosophy:
- Do not blame ppl when they fail to use your products properly
- Take ppl'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 msgs
- Allow ppl to continue with their task
- Don't impede progress
- Help make it smoot and continuous
- Never make ppl start over
- Assume that what ppl 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 for the ppl you interact with
Invariably ppl feel guilty and either try to hide the error or blame themselves for "stupidity" or "clumsiness". Nobody likes to be observed performing badly.
The idea that a person is at fault when something goes wrong is deeply entrenched in society. That's why we blame others and even ourselves. Unfortunately, the idea that a person is at fault is embedded in the legal system.
Humans err continually; it is an intrinsic part of our nature. System design should take this into account.
Blaming the person without fixing the root, underlying cause does not fix the problem.
Eliminate the term human error, instead talk about communication and interaction: what we call an error is usually bad communication or interaction.
Why can't the interaction between a person and a machine be thought of as collaboration?
Designers have a special obligation to ensure that the behavior of machines is understandable to the ppl using them.
We insist that ppl perform abnormally, to adapt themselves to the peculiar demands of machines, which inc always giving precise, accurate info. Humans are particularly bad at this, yet when they fail to meet the arbityrary, inhuman requirements of machines, we call it human error. No, it is design error.
Strive to minimize the chance of inappropriate actions in the first place by using affordances, signifiers, good mapping, and constraints to guide the actions.
If a person performs an inappropriate action, the design should maximize the chance that this can be discovered and then rectified.
This requires good, intelligible feedback coupled with a simple, clear conceptual model.
We are creative and imaginative, not mechanical and precise. Machines require precision and accuracy; ppl don't.
It is easy to design devices that work well when e/thing goes as planned. The hard and necessary part of design is to make things work well even when things do not go as planned.
E/stage of action requires its own special design strategies and, in turn, provides its own opportunity for disaster:
- What do I want to accomplish?
- What are the alternative action sequences?
- What action can I do now?
- How do I do it?
- What happened?
- What does it mean?
- Is this okay? Have I accomplished my goal?
How should the design convey the info required to answer the user's question? Through appropriate constraints and mappings, signifiers and conceptual models, feedback and visibility.
The info that helps answer questions of execution (doing) is feedforward.
Feedforward is accomplished through appropriate use of signifiers, constraints, and mappings. The conceptual model plays an important role.
The info that aids in understanding what has happened is feedback.
Feedback is accomplished through explicit info about the impact of the action.
Both feedforward and feedback need to be presented in a form that is readily interpreted by the ppl using the system.
The presentation has to match how ppl view the goal they are trying to achieve and their expectations.
Info must match human needs.
The 7 fundamental design principles:
- Discoverability: determine what actions are possible and the current state
- Feedback: full and continuous info about the results of actions and the current state
- After an action is executed, it is ez to determine the new state
- Conceptual Model: projects all the info needed leading to understanding and feeling of control
- Enhances both discoverability and evaluation of results (feedback)
- Affordances: exist to make the desired actions possible
- Signifiers: ensures discoverability and that the feedback is well communicated and intelligible
- Mappings: relationships between controls and their actions
- Enhanced as much as possible through spatial layout and temporal contiguity
- Constraints: providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation
When evaluating a product or a service's failure, ask at which of the 7 stages of action does it fail? Which design principles are deficient? Ask how the difficulty came about.
It is easy to find fault: the key is to be able to do things better.
The result may appear to be poor design, but it may actually arise from poor comms.
"Don't criticize unless you can do better!"
Good design requires consideration of the entire system to ensure that the requirements, intentions, and desires at each stage are faithfully understood and respected at all the other stages.
We combine knowledge in the head w/knowledge in the world, bc neither alone will suffice.
The psychologists Ray Nickerson and Marilyn Adams found easy to demonstrate the faulty nature of human knowledge and memory with different experiments, one of them asking if ppl could tell which penny was the real one in a group of many pennies with different looks. Most of them failed.
This is bc not all the knowledge required for precised behavior has to be in the head to be that a penny = one cent. It can be distributed - partly in the head, partly in the world, and partly in the constraints of the world.
Precise behavior can emerge from imprecise knowledge for 4 reasons:
- Knowledge is both in the head and in the world
- Much of the knowledge a person needs to do a task can be derived from the info in the world
- Great precision is not required
- Natural constraints exist in the world
- Knowledge of cultural constraints and conventions exists in the head
Bc behavior can be guided by the combo of internal and external knowledge and constraints, ppl can minimize the amt of material they must learn, as well as the completeness, precision, accuracy, or depth of the learning.
They also can deliberately organize the environment to support behavior.
We arrange things so that we don't need to have complete knowledge, or we rely upon the knowledge of the surrounding ppl, copying their behavior or getting them to do the required actions.
Simplified models are the key to successful application. Natural mappings can present info in the world in a manner readily interpreted and usable.
Best new approach to deal with design to either eliminate or minimize human error: resilience engineering.
Norman’s Law: the day the product team is announced, it is behind schedule and over its budget.
Everyone wants radical innovation, but the truth is, most radical innovations fail, and even when they do succeed, it can take multiple decades before they are accepted. Radical innovation, therefore, is relatively rare: incremental innovation is common.