Most accidents are attributed to human error, but in almost all cases human error was the direct result of poor design
When you have trouble with things — whether it’s figuring out whether to push or pull a door — it’s not your fault. Don’t blame yourself: blame the designer. When we see an object we’ve never used before, how do we know how to use it? The appearance of the device should provide the critical clues required for its proper operation — knowledge has to be both in the head and in the world.
Conceptual Model. The human mind is a wonderful organ of understanding. A good conceptual model can make the difference between successful and erroneous operation of many devices in our life. Design is an act of communication between the designer and the user, except that all the communication has to come about the the appearance of the device itself.
Feedback. It is fundamental to show the effect of an action.
Constraints. The best way of making something easy to use is to restrict the possible choices. Want to prevent people from damaging their camera by inserting the SD card backwards? Make it impossible to do wrong. Rule of thumb: when instructions have to be pasted on something, it is badly designed.
I concentrate on one component: making things that are understandable and usable.
The door illustrates one of the most important principles of design: visibility. The correct parts must be visible, and they must convey the correct message.
Complex things may require explanation, but simple things should not. When simple things need pictures, labels or instructions, the design has failed.
Conceptual models. The designer model is the designer’s conceptual model. The user’s model is the mental model developed through interaction with the system. The system image results from the physical structure that has been built (including documentation, instructions and labels). The thing is that the designer can’t communicate directly with the user, and all communication happens through the system image.
Design of a car vs Design of a digital watch. When there are more functions than controls, labelling becomes difficult or impossible.
Natural Mapping, by which I mean taking advantage of physical analogies and cultural standards, leads to immediate understanding.
I’ve studied people making errors. Invariably people feel guilty and either try to hide the error or blame themselves for “stupidity” or “clumsiness”.
If an error is possible, someone will make it. The designer must assume that all possible errors will occur and design so as to minimise the chance of error in the first place, or its effect once it gets made.
Find an explanation, and we are happy. Once we have an explanation—correct or incorrect—for otherwise discrepant or puzzling events, there is no more puzzle, no more discrepancy. As a result, we are complacent, at least for a while.
The basic idea is simple. To get something done, you have to start with some notion of what is wanted, the goal that has to be achieved. Then, you have to do something in the world, that is, take action to move yourself or manipulate someone or something. Finally, you check to see that your goal is made. So, there are four different things:
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the goal
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the action that is done to the world
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the world itself
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the check of the world
Execution and Evaluation.
Does the system provide actions that corresponds to the intention of the user? The difference between the intentions and the allowable actions is called the Gulf of Execution.
Does the system show information about its state in way that’s easy to get, to interpret and to use? The Gulf of Evaluation represents the effort that the user must exert to interpret the physical state of the system.
Knowledge of and knowledge how. Declarative knowledge, subconscious knowledge.
short term memory 5 to 7 items
Mental models simplify learning, in part because the details of the required behaviour can be derived when needed. The power of mental models is that they let you figure out what to do in novel situations.
smartphone!
Natural mapping. stove example.
If a design depends upon labels, it may be faulty. Labels are important and often necessary, but the appropriate use of natural mapping can minimise the need for them. Wherever labels seem necessary, consider another design.
Physical constraints, semantic constraints, social constraints, logical constraints
doors!
Architects and designers seem to prefer designs that are visually elegant and win prizes.
Visibility, make relevant parts visible. Feedback, Give each action an immediate and obvious effect.
Mode errors (vim airline)
The decision tree for playing chess is deep and wide. Although, not everyday activity must be deep and wide: we can have either shallow decision trees (ordering an ice cream) or narrow decision trees (starting a car)
Don’t punish the person for making an error. Don’t take offence. But first of all, don’t ignore it. Try to design the system to allow for errors. Realize that normal behaviour isn’t always accurate. Design so that errors are easy to discover and corrections are possible.
Tinkering with keyboard design is a popular pastime. But none of these innovations takes hold because the qwerty keyboard, while deficient, is good enough. Although its anti jamming motivation no longer holds, it does put many common letter pair onto opposing parts of the keyboard, so that while finger can start typing while the other one is still finishing.
Think of it as designing with your future selves in mind
Selective attention: did their attention to one set of variables cause them to neglect another?
When simple things need instructions, it is a sign of bad design
Each problem alone isn't a big deal. But the total sum of all the trivial mal-design unnecessarily adds to the trauma of everyday life
Faucet sign: "Do not adjust controls, put hand under spout" Elegance or understandability?
Creeping Feature-ism. With extra features come extra complexity: 10 new features, increase complexity by 100 hundred.
Write down how to setup audio/video system: too many components, too much complexity. Tuner cassette deck television VCR CD player seem to be designed in relative isolation. Put them all together and there is chaos. (False image of technical sophistication: God complex)
In fact, the best computer programs are the ones in which the computer itself disappears, in which you work directly on the problem without having to be aware of the computer.
Xerox Star was a breakthrough is usability, but too expensive and too slow.
How many buttons on a mouse?
Make the computer invisible.
Design should: - Make it easy to determine what actions are possible at any moment - Make things visible, including the conceptual model, the alternate actions and the results of actions. - Make easy to evaluate the status of the system - Follow natural mappings between intentions and required actions.
The designer must pay attention to how many things a person can hold in memory at one time
Digital display makes easier to read correct time, but analog give a better sense of how much time has elapsed. Analog mapping is arbitrary, but a standard.
Over-automation. When you automate everything, who watches the automators?
The system should provide actions that match intentions. People are very good at creating mental models of how things work: the designer should help them make the correct interpretations. The system image is very important.
Importance of standardisation. Backward Clock.
Timing of standardisation. Standardise too soon: locked into primitive technology, added inefficient error-inducing rules. Standardise too late: it's too late (change standard for expressing time)
Easy looking is not necessarily easy to use.
Writing method affects style. Hand written letters had longer sentences, computer written ones are shorter.
We are surrounded with objects of desire, not objects of use.