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IM's Life [一期一會]

[IMS5302]2006.4.11.

The remaining notes for Norman's book...



There were four different classes of constraints - physical, semantic, culture, and logical. [Norman, p.84]

The value of physical constraints is that they rely upon properties of the physical world for their operation; no special training is neccessary. With the proper use of physical constraints there should be only a limited number of possible actions - or, at least, desired actions can be made obvious, usually by being especially salient. ... The physical constraint prevents the wrong action from succeeding only after it has been tried. [Norman, p.84]

Semantic constraints rely upon our knowledge of the situation and of the world. [Norman, p.85]

We can place slips into one of six categories: capture errors, description errors, data-driven errors,associative activation errors, loss-of-activation errors, and mode errors.[Norman, p.107]

Thought and memory are closely related, for thought relies heavily upon the experiences of life. [Norman, p.115]

"Schema Theory" or "Frame Theory" or "Semantic Networks" or "Propositional Encoding": The essence of the theory consists of three beliefs, all reasonable and supported by considerable evidence: (1) that there is logic and order to the individual structures (this is what the schema or frame is about); (2) that human memory is associative, with each shema pointing and referring to multiple others to which it it related or that help define the components (thus the term "network"); and (3) that much of our power for deductive thought comes from using the information in one schema to deduce the properties of another (thus the term "propositional encoding"). [Norman, p.115-116]

Shallow structures(the menu of ice cream): there are many alternative actions, but each is simple; there are few decisions to make after the single top-level choice. The majot problem is to decide which action to do. [Norman, p.121]

Narrow structures(the cookbook recipe): A narrow structure arises when there are only a small number of alternatives, perhaps one or two. If each possibility leads to only one or two further choices, then the resulting tree structure can be said to be narrow and deep. [Norman, p.121]

Moral: it isn't easy to force unwanted behabior upon people. And if you are going to use a forcing function, make sure it works right, is reliable, and distinguishes legitimate violations from illegitimate ones. [Norman, p.134-135]

Put the required knowledge in the world. Don't require all the knowledge to be in the head. Yet do allow for more efficient operation when the user has learned the operations, has gotten the knowledge in the head. [Norman, p.140]

Use the power of natural and artificial constraints: physical, logical, semantic, and culture, Use forcing functions and natural mappings. [Norman, p.140]

Narrow the gulfs of execution and evalution. Make things visible, both for execution and evalution. On the execution side, make the options readily availble. On the evaluation side, make the results of each action apparent. Make it possible to determine the system state readily, easily, and accurately, and in a form consistent with the person's goals, intentions, and expectations. [Norman, p.140]

If everyday design were ruled by aesthetics, life might be more pleasing to the eye but less comfortable; if ruled by usability, it might be more comfortable but uglier. [Norman, p.151]

Designers go astray for several reasons: First, the reward structure of the design community tends to put aesthetics first. Design collections feature prize-winning clocks that are unreadable, alarms that cannot easily be set, can openers that mystify. Second, designers are not typical users. They become so expert in using the object they have designed that they cannot believe that anyone else might have problems; only interaction and testing with actual users thoughout the design process can forestall that. Third, designers must please their clients, and the clients may not be the users. [Norman, p.151]

All of us develop an everyday psychology - professionals call it "folk phychology" or, sometimes, "naive psychology" - and it can be as erroneous and misleading as the naive physics...Worse, actually. As human beings, we have access to our conscious thoughts and beliefs but not to our subconscious ones. Conscious thoughts are often retionalizations of behavior, explainations after the fact. We tend to project our own rationalizations and beliefs onto the actions and beliefs of others. But the profesional should be able to realize that human beliefs and behavior are complex and that the individual is in no position to discover all the relavant factors. There is no substitude for interaction with and study of actual users of a proposed design. [Norman, p.155]

There is a big different between the expertise required to be a designer and that required to be a user. In their work, designers often become expert with the device they are designing. Users are often expert at the task they are trying to perform with the device. [Norman, p.156]

Even when the designers become users, their deep understanding and close contact with the device they are designing means that they operate it almost entirely from knowledge in the head. The user, especially the first-time or infrequent user, must rely almost entirely on knowledge in the world. That is a big difference, fundamental to the design. [Norman, p.157]

There is no such thing as the average person. This poses a partocular problems for the designers, who usually must come up with a single design for everyone; the task is difficult when all sorts of people are expected to use the item. [Norman, p.161]

The ability of conscious attention is limited: focus on one thing and you reduce your attention to others. Psychologists call the phenomenon "selective attention". Excessive focus leads to a kind of tunnel vision, where peripheral items are ignored. [Norman, p.164]

If you can't not put the knowledge on the device, then develop a cultural constraint: standardize what has to be kept in the head. [Norman, p.170]

Creeping featurism is the tendency to add to the number of features that a device can do, often extending the number beyond all reason. There is no way that program can remain usable and understandable by the time it has all of those sepcial-purpose features. [Norman, p.173]

Creeping featurism is disease, fatal if not treated promptly. There are some cures, but as usual, the best approach is to pratice preventive medicine. The problem is that the disease comes so natually, so innocently. Analyze a task, and you see how it can be made easier. Why, adding features seems so virtuous, following the very preachings of this book, simply trying to make life easier for everyone. But with extra features comes extra complexity. Each new feature adds yet another control, or display, or button, or instruction. Complexity probably increases as the square of the features: double the number of features, quadruple the complexity. Provide ten times as many features, multiply the complexity by one hundred. [Norman, p.173-174]

There are two paths to treating featurism. One is aviodance, or at the least, great restraint. The second path is organization. [Norman, p.174]

There is nothing particularly special about the computer; it is a machine, a human artifact, just like the other sorts of things we have looked at, and it poses few problems that we haven't encountered already. But designers of computer systems seem particularly oblivious to the needs of users, particularly susceptible to all the pitfalls of design. The professional design community is seldom called in to help with computer products. Instead, designs is left in the hands of engineers and programmers, people who usually have no experience, and no expertise in designing for people. [Norman, p.177]

The best computer programs are the ones in which the compputer itself "disappears", in which you work directly on the problem without having to be aware of the computer. [Norman, p.180]

There are three requirements for a (computer) system to be explorable. [Norman, p.183-184]
1.In each state of the system, the user must readily see and be able to do the allowable actions. The visibility acts as a suggestion, reminding the user of possiblities and inviting the exploration of new ideas and methods.
2.The effect of each action must be both visible and easy to interpret. This property allows users to learn the effects of each action, to develop a good mental model of the system, and to learn the causal relationships between actions and outcomes. The system image plays a critical role in making such learning possible.
3.Actions should be without cost. When an action has an undesirable result, it must be readily reversible. This is especially important with computer systems. In the case of an irreversible action, the system should make clear what effect the contemplated action will have prior to its execution; there should be enough time to cancel the plan. Or the action should be difficult to do, nonexplorable. Most actions should be cost-free, explorable, discoverable.

Design should:,[Norman, p.188]
Make it easy to determine what actions are possible at any moment(make sure of constraints).
Make things visible, including the conceptual model of the system, the alternative actions, and the results of actions.
Make it easy to evaluate the current state of the system.
Follow natural mappings between intentions and the required actions; between actions and the resulting effect; and between the information that is visible and the imperpretation of the system state.
In other words, make sure that (1) the user can figure out what to do, and (2) the user can tell what is going on.

Seven pricinples for transforming difficult tasks into simple ones [Norman, p.188-189]
1.Use both knowledge in the world and knowledge in the head.
2.Simplify the structure of tasks.
3.Make things visible: bridge the gulfs of Execution and Evaluation.
4.Get the mapping right.
5.Exploit the power of constraints, both natural and artificial.
6.Design for error.
7.When all else fails, standardize.

Exploit natural mappings. Make sure that the user can determine the relationship: [Norman, p.199]
Between intentions and possible actions
Between actions and their effects on the system
Between actual system state and what is perceivable by sight, sound, or feel
Between the preceived system state and the needs, intentions, and expectations of the user.

Everyday tasks are not difficult because of their inherent complexity. Thery are difficult only because they require learning arbitrary relationships and arbitary mappings, and because they sometimes require precision in their execution. The difficulties can be avoided through design that makes obvious what operations are neccessary. Good design exploits constraints so that the user feels as if there is only one possible thing to do - the right thing, of course. The designer has to understand and exploit natural constraints of kinds. [Norman, p.216]

And enjoy yourself. Walk around the world examining the details of design. Take pride in the little things that help; think kindly of the person who so thoughtfully put them in. Realize that even details matter, that the designer may have had to fight to include something helpful. Give mental prizes to those who practice good design: send flowers. Jeer those who don't: send weeds. [Norman, p.217]

Done!
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