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Affordances define what actions are possible. Signifiers specify how people discover those possibilities: signifiers are signs, perceptible signals of what can be done.
Two of the most important characteristics of good 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?
the relevant components must be visible, and they must communicate the correct message: What actions are possible?
natural signals,
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.
Industrial design: The professional service of creating and developing concepts and specifications that optimize the function, value, and appearance of products and systems for the mutual benefit of both user and manufacturer
Interaction design: The focus is upon how people interact with technology. The goal is to enhance people’s understanding of what can be done, what is happening, and what has just occurred. Interaction design draws upon principles of psychology, design, art, and emotion to ensure a positive, enjoyable experience.
Experience design: The practice of designing products, processes, services, events, and environments with a focus placed on the quality and enjoyment of the total experience.
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.
So 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.
Designers need to focus their attention on the cases where things go wrong, not just on when things work as planned. Actually, this is where the most satisfaction can arise: when something goes wrong but the machine highlights the problems, then the person understands the issue, takes the proper actions, and the problem is solved.
Experience is critical, for it determines how fondly people remember their interactions.
Cognition and emotion are tightly intertwined, which means that the designers must design with both in mind.
Discoverability results from appropriate application of five fundamental psychological concepts covered in the next few chapters: affordances, signifiers, constraints, mappings, and feedback. But there is a sixth principle, perhaps most important of all: the conceptual model of the system.
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.
An affordance is a relationship. Whether an affordance exists depends upon the properties of both the object and the agent.
If an affordance or anti-affordance cannot be perceived, some means of signaling its presence is required: I call this property a signifier
Affordances determine what actions are possible. Signifiers communicate where the action should take place.
the term signifier refers to any mark or sound, any perceivable indicator that communicates appropriate behavior to a person.
Mapping is a technical term, borrowed from mathematics, meaning the relationship between the elements of two sets of things.
When the mapping uses spatial correspondence between the layout of the controls and the devices being controlled, it is easy to determine how to use them.
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.
Some natural mappings are cultural or biological, as in the universal standard that moving the hand up signifies more, moving it down signifies less, which is why it is appropriate to use vertical position to represent intensity or amount.
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.
feedback: some way of letting you know that the system is working on your request.
Poor feedback can be worse than no feedback at all, because it is distracting, uninformative, and in many cases irritating and anxiety-provoking.
Feedback is essential, but not when it gets in the way of other things, including a calm and relaxing environment.
A conceptual model is an explanation, usually highly simplified, of how something works.
Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.
system image.
Most important is the provision of a good conceptual model that guides the user when thing go wrong. With a good conceptual model, people 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.
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 same technology that simplifies life by providing more functions in each device also complicates life by making the device harder to learn, harder to use. This is the paradox of technology and the challenge for the designer.
The challenge is to use the principles of human-centered design to produce positive results, products that enhance lives and add to our pleasure and enjoyment. The goal is to produce a great product, one that is successful, and that customers love.
I first delve into human psychology and a simple conceptual model of how people select and then evaluate their actions. This leads the discussion to the role of understanding (via a conceptual model) and of emotions: pleasure when things work smoothly and frustration when our plans are thwarted. Finally, I conclude with a summary of how the lessons of this chapter translate into principles of design.
When people use something, they face two gulfs: the Gulf of Execution, where they try to figure out how it operates, and the Gulf of Evaluation, where they try to figure out what happened (Figure 2.1). The role of the designer is to help people bridge the two gulfs.
The gulfs are present for many devices. Interestingly, many people do experience difficulties, but explain them away by blaming themselves.
Blame themselves for being stupid or incapable.
We bridge the Gulf of Execution through the use of signifiers, constraints, mappings, and a conceptual model. We bridge the Gulf of Evaluation through the use of feedback and a conceptual model.
FIGURE 2.2. The Seven Stages of the Action Cycle. Putting all the stages together yields the three stages of execution (plan, specify, and perform), three stages of evaluation (perceive, interpret, and compare), and, of course, the goal: seven stages in all.
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)
So the hierarchy of goals is roughly: satisfy hunger; eat; cook; read cookbook; get more light. This is called a root cause analysis: asking “Why?” until the ultimate, fundamental cause of the activity is reached.
Opportunistic actions are less precise and certain than specified goals and intentions, but they result in less mental effort, less inconvenience, and perhaps more interest.
Most of the brain’s operations are subconscious, hidden beneath our awareness. It is only the highest level, what I call reflective, that is conscious.
Once skills have been overlearned, performance appears to be effortless, done automatically, with little or no awareness.
The earlier questions were memory for factual information, what is called declarative memory. The last question could have been answered factually, but is usually most easily answered by recalling the activities performed to open the door. This is called procedural memory.
We also tend to believe that thought can be separated from emotion. This is also false. Cognition and emotion cannot be separated. Cognitive thoughts lead to emotions: emotions drive cognitive thoughts.
