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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?
Design is concerned with how things work, how they are controlled, and the nature of the interaction between people and technology. When done well, the results are brilliant, pleasurable products. When done badly, the products are unusable, leading to great frustration and irritation. Or they might be usable, but force us to behave the way the product wishes rather than as we wish.
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.
The problem with the designs of most engineers is that they are too logical. We have to accept human behavior the way it is, not the way we would wish it to be.
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.
Designers need to focus their attention on the cases where things go wrong, not just on when things work as planned.
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.
Experience is critical, for it determines how fondly people remember their interactions.
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.
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 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 people. We are used to thinking that properties are associated with objects. But affordance is not a property. An affordance is a relationship. Whether an affordance exists depends upon the properties of both the object and the agent.
Affordances determine what actions are possible. Signifiers communicate where the action should take place.
Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.
Cognition attempts to make sense of the world: emotion assigns value.
More and more evidence is accumulating that we use logic and reason after the fact, to justify our decisions to ourselves
The most basic level of processing is called visceral. This is sometimes referred to as “the lizard brain.” All people have the same basic visceral responses. These are part of the basic protective mechanisms of the human affective system, making quick judgments about the environment: good or bad, safe or dangerous.
With success, sure, we are pleased, but we often have no idea why we succeeded.
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
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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.
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Knowledge of—what psychologists call declarative knowledge—includes the knowledge of facts and rules.
Knowledge how—what psychologists call procedural knowledge—is the knowledge that enables a person to be a skilled musician, to return a serve in tennis, or to move the tongue properly when saying the phrase “frightening witches.”
Make something too secure, and it becomes less secure.
°C = (°F–30) / 2
How many people are involved? It could be any number, but the point is that each adds their bit of knowledge, slowly constraining the choices, recalling something that no single one of them could have done alone. Daniel Wegner, a Harvard professor of psychology, has called this “transactive memory.”
Skeuomorphic is the technical term for incorporating old, familiar ideas into new technologies, even though they no longer play a functional role.
Basically, it means that 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.
A slip occurs when a person intends to do one action and ends up doing something else. With a slip, the action performed is not the same as the action that was intended.
A mistake occurs when the wrong goal is established or the wrong plan is formed. From that point on, even if the actions are executed properly they are part of the error, because the actions themselves are inappropriate—they are part of the wrong plan. With a mistake, the action that is performed matches the plan: it is the plan that is wrong.
MODE-ERROR SLIPS A mode error occurs when a device has different states in which the same controls have different meanings: we call these states modes.
Poka-yoke translates as “error proofing” or “avoiding error.” One of the techniques of poka-yoke is to add simple fixtures, jigs, or devices to constrain the operations so that they are correct.
A major source of error, especially memory-lapse errors, is interruption. When an activity is interrupted by some other event, the cost of the interruption is far greater than the loss of the time required to deal with the interruption: it is also the cost of resuming the interrupted activity.
Multitasking, whereby we deliberately do several tasks simultaneously, erroneously appears to be an efficient way of getting a lot done. It is much beloved by teenagers and busy workers, but in fact, all the evidence points to severe degradation of performance, increased errors, and a general lack of both quality and efficiency.
James Reason likes to explain this by invoking the metaphor of multiple slices of Swiss cheese, the cheese famous for being riddled with holes (Figure 5.3). If each slice of cheese represents a condition in the task being done, an accident can happen only if holes in all four slices of cheese are lined up just right. In well-designed systems, there can be many equipment failures, many errors, but they will not lead to an accident unless they all line up precisely.
Engineers and businesspeople are trained to solve problems. Designers are trained to discover the real problems. A brilliant solution to the wrong problem can be worse than no solution at all: solve the correct problem.
Designers have developed a number of techniques to avoid being captured by too facile a solution. They take the original problem as a suggestion, not as a final statement, then think broadly about what the issues underlying this problem statement might really be (as was done through the “Five Whys” approach to getting at the root cause, described in Chapter 5). Most important of all is that the process be iterative and expansive. Designers resist the temptation to jump immediately to a solution for the stated problem. Instead, they first spend time determining what basic, fundamental (root)
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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 (Figure 6.1). This double diverge-converge pattern was first introduced in 2005 by the British Design Council, which called it the double-diamond design process model.
One comment: there is a difference between task and activity. I emphasize the need to design for activities: designing for tasks is usually too restrictive. An activity is a high-level structure, perhaps “go shopping.” A task is a lower-level component of an activity, such as “drive to the market,” “find a shopping basket,” “use a shopping list to guide the purchases,” and so forth.
Designers try hard to determine people’s real needs and to fulfill them, whereas marketing is concerned with determining what people will actually buy. What people need and what they buy are two different things, but both are important.
Even though the peeler was designed for someone with arthritis, it was advertised as a better peeler for everyone. It was. Even though the design was more expensive than the regular peeler, it was so successful that today, many companies make variations on this theme.
In an earlier era, there was close coupling between designers and users. Today, they are separated by barriers. Some companies prohibit designers from working with customers, a bizarre and senseless restriction. Why would they do this? In part to prevent leaks of the new developments to the competition, but also in part because customers may stop purchasing the current offerings if they are led to believe that a new, more advanced item is soon to come.
In every successful product there lurks the carrier of an insidious disease called “featuritis,” with its main symptom being “creeping featurism.”
