Norman (1988) borrowed the term affordance from cognitive psychology and he applied it to the design of physical as well as virtual environments and products. Norman made the concept dependent not only on the physical capabilities of an actor, but also dependent on the actor’s own beliefs, experiences, goals, plans, and values. The designer of virtual environments and virtual products cares about perceived affordances, whether the user perceives that some action actually is possible or not. In product design, where one deals with real, physical objects, there can be both real and perceived affordances.

Some familiar everyday examples of affordance include our natural understanding that buttons are for pushing, cords and handles are for pulling, cylinders are for rolling, knobs are for turning, and switches are for flipping. All these designed objects invite us to act in the intended way. Here action and perception are linked together through real-world objects that provide action possibilities.

The concept affordance has rapidly spread within the fields of human–machine interaction, and interaction design. In graphical, screen-based interfaces, all that the designer has available is control over perceived affordances
[IDTheories, p.42]

We have a tendency to analyse design retrospectively as opposed to prospectively—and in the process over-interpret for rational attributes such as logic and uniformity. If we did view design prospectively, as in fact design practice demands, we would see that complexity precedes, accompanies and follows design action. Complexity is contextual, situated and dynamic and therefore cannot be isolated in processes or artifacts. That is design and designers’ actions respond to complex situations. What we find is that the process is not pre-determined as complex, symmetrical or simple in structure, rather it is a dynamic process that is improvisational and responsive to the changing design situation. An active stance is required in design. Such design strategies have come to be understood as reflective, embodied, or contextual in practice.
[ComplexityDesign, p.67]

Design is a human activity that addresses human and social experience. A re-orientation away from tasks and efficiency in design objectives is required to address the fuller aim of responding to complex human experience.
[ComplexityDesign, p.76]

Plain language and information design are critical to successful websites.
[TechCommUX, p.198]

We are not our users, and users will always surprise you.
[TechCommUX, p.193]

Little usability equals usability testing; big usability equals UX. Little information architecture (IA) equals organizing the content of a website; big IA means creating the site that works for its users. Little plain language equals plain language seen as only about short sentences and small words; big plain language is plain language as UX where people can (1) find what they need, (2) understand what they find, and (3) act appropriately on that understanding.
[TechCommUX, p.196]

Center for Plain Language, “About.” https://centerforplainlanguage.org/about/

When you’re creating a site, your job is to get rid of the question marks.
[DontMakeMeThink, p.8]

There’s almost always a plausible rationale—and a good, if misguided, intention—behind every usability flaw.
[DontMakeMeThink, p.11]

If you can’t make something self-evident, you at least need to make it self- explanatory.
[DontMakeMeThink, p.14]

In reality, though, most of the time we don’t choose the best option—we choose the first reasonable option, a strategy known as satisficing.

Satisficing. Economist Herbert Simon coined the term (a cross between satisfying and sufficing) in Models of Man: Social and Rational (Wiley, 1957).

[DontMakeMeThink, p.17]

If you can make something significantly clearer by making it slightly inconsistent, choose in favor of clarity.
[DontMakeMeThink, p.30]

In the face of limited time and attention, everything that’s not part of the solution must go.
[DontMakeMeThink, p.35]

“Scent of information.” This term comes from Peter Pirolli and Stuart Card’s “information foraging” research at Xerox PARC in which they drew parallels between people seeking information (“informavores”) and animals following the scent of their prey.
[DontMakeMeThink, p.40]

The main thing you need to know about instructions is that no one is going to read them—at least not until after repeated attempts at “muddling through” have failed. And even then, if the instructions are wordy, the odds of users finding the information they need are pretty low.

Your objective should always be to eliminate instructions entirely by making everything self-explanatory, or as close to it as possible. When instructions are absolutely necessary, cut them back to the bare minimum.
[DontMakeMeThink, p.46]

Where debates about what people like waste time and drain the team’s energy, usability testing tends to defuse most arguments and break impasses by moving the discussion away from the realm of what’s right or wrong and what people like or dislike and into the realm of what works or doesn’t work. And by opening our eyes to just how varied users’ motivations, perceptions, and responses are, testing makes it hard to keep thinking that all users are like us.
[DontMakeMeThink, p.91]

Whenever you’re designing, you’re dealing with constraints. And where there are constraints, there are tradeoffs to be made.
[DontMakeMeThink, p.120]

One difference between User Centered Design and User Experience Design is their scope. UCD focused on designing the right product and making sure that it was usable. UX sees its role as taking the users’ needs into account at every stage of the product life cycle, from the time they see an ad on TV, through purchasing it and tracking its delivery online, and even returning it to a local branch store.
[DontMakeMeThink, p.152]

Two of the most important characteristics of design are discoverability and understanding. 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?
[EverydayThings, p.3]

Design is concerned with how things work, how they are controlled, and the nature of the interaction between people and technology.
[EverydayThings, p.5]

Human-centered design is a design philosophy. It means starting with a good understanding of people and the needs that the design is intended to meet. This understanding comes about primarily through observation, for people themselves are often unaware of their true needs, even unaware of the difficulties they are encountering.
[EverydayThings, p.9]

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). An affordance is a relationship between the properties of an object and the capabilities of the agent that determines just how the object could possibly be used.
[EverydayThings, p.11]

The presence of an affordance is jointly determined by the qualities of the object and the abilities of the agent that is interacting.
[EverydayThings, p.11]

Affordances exist even if they are not visible. For designers, their visibility is critical: visible affordances provide strong clues to the operation of things.
[EverydayThings, p.13]

Affordances determine what actions are possible. Signifiers communicate where the action should take place.
[EverydayThings, p.14]

Good design requires, among other things, good communication of the purpose, structure, and operation of the device to the people who use it. That is the role of the signifier.
[EverydayThings, p.14]

Whatever their nature, planned or accidental, signifiers provide valuable clues as to the nature of the world and of social activities. For us to function in this social, technological world, we need to develop internal models of what things mean, of how they operate.
[EverydayThings, p.17]

In design, signifiers are more important than affordances, for they communicate how to use the design. A signifier can be words, a graphical illustration, or just a device whose perceived affordances are unambiguous. Creative designers incorporate the signifying part of the design into a cohesive experience. For the most part, designers can focus upon signifiers.
[EverydayThings, p.19]

Natural mapping, by which I mean taking advantage of spatial analogies, leads to immediate understanding. For example, to move an object up, move the control up.
[EverydayThings, p.22]

Groupings and proximity are important principles from Gestalt psychology that can be used to map controls to function: related controls should be grouped together. Controls should be close to the item being controlled.
[EverydayThings, p.22]

A conceptual model is an explanation, usually highly simplified, of how something works. It doesn't have to be complete or even accurate as long as it is useful. The files, folders, and icons you see displayed on a computer screen help people create the conceptual model of documents and folders inside the computer, or of apps or applications residing on the screen, waiting to be summoned. In fact, there are no folders inside the computer—those are effective conceptualizations designed to make them easier to use.
[EverydayThings, p.25]

Simplified models are valuable only as long as the assumptions that support them hold true.
[EverydayThings, p.26]

With a good conceptual model, people can figure out what has happened and correct the things that went wrong. Without a good model, they struggle, often making matters worse.
[EverydayThings, p.32]

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 of 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. Affordance. 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, enhances as much as possible through spatial layout and temporal contiguity.
7. Constraint. Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

[EverydayThings, p.72-73]

Good designers never start by trying to solve the problem given to them: they start by trying to understand what the real issues are.
[EverydayThings, p.218]

Designing for people with special needs is often called inclusive or universal design. Those names are fitting, for it is often the case that everyone benefits.
[EverydayThings, p.246]

Designers need to make things that satisfy people's needs, in terms of function, in terms of being understandable and usable, and in terms of their ability to deliver emotional satisfaction, pride, and delight. In other words, the design must be thought of as a total experience.
[EverydayThings, p.293]

Our technologies may change, but the fundamental principles of interaction are permanent.
[EverydayThings, p.298]