80/20
The 80/20 rule is useful for focusing resources and, in turn, realizing greater efficiencies in design.
principle of accessibility
The principle of accessibility asserts that designs should be usable by people of diverse abilities, without special adaptation or modification.
Forgiveness
Forgiveness is achieved when designs minimize the occurrence and consequences of errors.
Aesthetic-usability effect
The aesthetic-usability effect describes a phenomenon in which people perceive more-aesthetic designs as easier to use than less-aesthetic designs—whether they are or not.
Aesthetic designs
Aesthetic designs are more effective at fostering positive attitudes than unaesthetic designs, and make people more tolerant of design problems.
Affordance
When the affordance of an object or environment corresponds with its intended function, the design will perform more efficiently and will be easier to use. Conversely, when the affordance of an object or environment conflicts with its intended function, the design will perform less efficiently and be more difficult to use.
Biophilia
Consider the biophilia effect in the design of all environments, but in particular, environments in which learning, healing, and concentration are paramount. Although nature imagery seems to suffice in lieu of real nature exposure, the latter should be favored when possible as it is more likely to produce a strong generalizable effect.
High ceilings
Conspicuous ceiling height — that is, noticeably low or noticeably high ceilings — promotes different types of cognition, with high ceilings promoting abstract thinking and creativity and low ceilings promoting concrete and detail-oriented thinking.
General vs specific
The group in the high-ceilinged room tended to focus on general product characteristics, whereas the group in the low-ceilinged room tended to focus on specific features.
Creativity vs detail-oriented work
For tasks that require creativity and out-of-the-box thinking (e.g., research and development) favor large rooms with high ceilings. For tasks that require detail-oriented work (e.g., surgical operating room) favor smaller rooms with lower ceilings.
Display
In environments where noise or stress can interfere with concentration, consider chunking critical display information in anticipation of diminished short-term memory capacity.
Confirmation dialogs
Confirmations are primarily used to prevent a class of errors called slips, which are unintended actions. Confirmations slow task performance, and should be reserved for use with critical or irreversible operations only.
Confirmation dialog screens
The message should end with one question that is structured to be answered Yes or No, or with an action verb that conveys the action to be performed (the use of OK and Cancel should be avoided for confirmations).
Avoid overusing confirmations
Use confirmations to minimize errors in the performance of critical or irreversible operations. Avoid overusing confirmations to ensure that they are unexpected and uncommon; otherwise, they may be ignored.
Consistency
Consistency enables people to efficiently transfer knowledge to new contexts, learn new things quickly, and focus attention on the relevant aspects of a task.
Constrains for better selection
dimming or hiding options that are not available at a particular time effectively constrains the options that can be selected. Proper application of constraints in this fashion makes designs easier to use and dramatically reduces the probability of error during interaction.
Customization
Conceal expert methods to the extent possible to minimize complexity for beginners. When systems are complex and frequently used, consider designs that can be customized to conform to individual preference and levels of expertise.
Convergence
the high degree of convergence indicates a stable environment—one that has not changed much over time—and designs that closely approximate the optimal strategies afforded by that environment. The result is a rate of evolution that is slow and incremental, tending toward refinements on existing convergent themes.
Radical vs minor changes
Stable environments with convergent system designs are receptive to minor innovations and refinements but resist radical departures from established designs. Unstable environments with no convergent system designs are receptive to major innovations and experimentation, but offer little guidance as to which designs may or may not be successful.
When is design by committee better?
Design by committee is preferred when projects are quality-driven, requirements are complex, consequences of error are serious, or stakeholder buy-in is important. For example, NASA employs a highly bureaucratized design process for each mission, involving numerous working groups, review committees, and layers of review from teams of various specializations. The process is slow and expensive, but the complexity of the requirements is high, the consequences of error are severe, and the need for stakeholder buy-in is critical.
Autocracy vs Democracy
Autocracy is linear and fast, but risky and prone to error. Democracy is iterative and slow, but careful and resistant to error. Both models have their place depending on the circumstances.
Slips
Minimize slips by providing clear feedback on actions. Make error messages clear, and include the consequences of the error, as well as corrective actions, if possible.
Feedback loops
A key lesson of feedback loops is that things are connected—changing one variable in a system will affect other variables in that system and other systems.
Fitts’ Law
Consider Fitts’ Law when designing systems that involve pointing. Make sure that controls are near or large, particularly when rapid movements are required and accuracy is important.
5 Hat racks
The five hat racks principle asserts that there are a limited number of organizational strategies, regardless of the specific application: category, time, location, alphabet, and continuum.
Functional
The descriptive interpretation is that beauty results from purity of function and the absence of ornamentation. The prescriptive interpretation is that aesthetic considerations in design should be secondary to functional considerations.
Hick’s Law
Hick’s Law states that the time required to make a decision is a function of the number of available options. It is used to estimate how long it will take for people to make a decision when presented with multiple choices.
Time critical procedures
In training people to perform time-critical procedures, train the fewest possible responses for a given scenario. This will minimize response times, error rates, and training costs.
Hierarchies
There are three basic ways to visually represent hierarchy: trees, nests, and stairs.
Highlighting, bolding and italics
Highlight no more than 10 percent of the visible design; highlighting effects are diluted as the percentage increases… Bolding is generally preferred over other techniques as it adds minimal noise to the design and clearly highlights target elements… Italics add minimal noise to a design, but are less detectable and legible. Underlining adds considerable noise and compromises legibility, and should be used sparingly if at all.
Noise + pricing
the degree to which the shop windows were filled with mannequins, clothes, price tags, and signage was inversely related to the average price of the clothing and brand prestige of the store.
Minimalism + affluence
To promote associations of high value, favor minimalism for affluent and well-educated audiences and horror vacui for poorer and less-educated audiences, and vice versa.
Environments
Design environments that minimize distractions, promote a feeling of control, and provide feedback. Emphasize stimuli that distract people from the real world, and suppress stimuli that remind them of the real world.
Iteration and failure
In fact, there is often more value in failure, as valuable lessons are learned about the failure points of a design. The outcome of design iteration is a detailed and well-tested specification that can be developed into a final product.
Patterns
Humans tend to add order and meaning to patterns and formations that do not exist outside their perception.
Modular designs
The benefits of modular design are not without costs: modular systems are significantly more complex to design than nonmodular systems. Designers must have significant knowledge of the inner workings of a system and its environment to decompose the systems into modules, and then make those modules function together as a whole.
Group resistance
The not invented here (NIH) syndrome is an organizational phenomenon in which groups resist ideas and inputs from external sources, often resulting in subpar performance and redundant effort (i.e., “reinventing the wheel”).
Why NIH?
Four social dynamics underlie NIH: belief that internal capabilities are superior to external capabilities; fear of losing control; desire for credit and status; and significant emotional and financial investment in internal initiatives.
Avoiding NIH
The best way to address NIH is prevention. Rotate and cross-pollinate team members on a project basis. Engage outsiders in both the strategy and the evaluation stages of the design process to ensure fresh perspectives and new thinking. Encourage team members to regularly interact with the wider community (e.g., conferences). Formalize regular competitor reviews and environmental scanning to stay abreast of the activities of competitors and the industry in general. Consider open innovation models, competitions (e.g., Netflix Prize), and outside collaborations to institutionalize a meritocratic approach to new ideas.
Defaults, Feedback, Incentives, Choices, Goals
Defaults — Select defaults that do the least harm and most good. Feedback — Provide visible and immediate feedback for actions and inactions. Incentives — Avoid incentive conflicts and align incentives to preferred behaviors. Structured Choices — Provide the means to simplify and filter complexity to facilitate decision making. Visible Goals — Make simple performance measures clearly visible so that people can immediately assess their performance against a goal state.
Ockham’s razor
Ockham’s razor asserts that simplicity is preferred to complexity in design. … Implicit in Ockham’s razor is the idea that unnecessary elements decrease a design’s efficiency, and increase the probability of unanticipated consequences.
Conditioning
There are three basic operant conditioning techniques: positive reinforcement, negative reinforcement, and punishment… Negative reinforcement increases the probability of a behavior by associating the behavior with the removal of a negative condition; fastening a seat belt in a car silences an annoying buzzer… Positive and negative reinforcement should be used instead of punishment whenever possible. Punishment should be reserved for rapidly extinguishing a behavior, or it should not be used at all.
Universal product codes
The use of Universal Product Codes, also known as bar codes, dramatically reduces the performance load associated with consumer transactions: products no longer need price tags, cashiers no longer need to type in prices, and inventory is automatically updated.
Confusion
Designers and managers often confuse the business maxim “the customer is always right” with “the user is always is right.” This is a dangerous confusion, since what helps people perform well and what people like is often not the same thing.
Designing for users
The design that seeks to accommodate everybody generally accommodates nobody well.
Exposure and priming
Exposure to words related to politeness made people more polite, and exposure to words to related to rudeness made people ruder. Priming is an effective means of influence when the stimulus introduced activates concepts that are consistent with a preexisting need or goal.
Progressive disclosure
Progressive disclosure keeps displays clean and uncluttered and helps people manage complexity without becoming confused, frustrated, or disoriented. For example, infrequently used controls in software interfaces are often concealed in dialog boxes that are invoked by clicking a More button.
Prospects and refuge
In natural environments, prospects include hills, mountains, and trees near open settings. Refuges include enclosed spaces such as caves, dense vegetation, and climbable trees with dense canopies nearby. In human-created environments, prospects include deep terraces and balconies, and generous use of windows and glass doors. Refuges include alcoves with lowered ceilings and external barriers, such as gates and fences.
Problems
There are three kinds of problems for which satisficing should be considered: very complex problems, time-limited problems, and problems for which anything beyond a satisfactory solution yields diminishing returns.
City spaces
It may be no coincidence that the parks, resorts, and golf courses of the world all resemble savannas—they may reflect an unconscious preference for the look and feel of our ancestral, east-African home.
Recursion
Naturally occurring self-similarity is usually the result of a basic algorithmic process called recursion. Recursion occurs when a system receives input, modifies it slightly, and then feeds the output back into the system as input.
Primacy and recency effect
The improved recall for items at the beginning of a list is called a primacy effect. The improved recall for items at the end of a list is called a recency effect.
Lighting
Objects that are depicted with top-down lighting look natural, whereas familiar objects that are depicted with bottom-up lighting look unnatural.
Logging
Event logging increases the visibility of what the computer is doing and how it is performing, but it also consumes computing resources, which interferes with the performance being measured.
Inconspicuously observing
asking people what they think about a set of new product features is a highly invasive measure that can yield inaccurate results. By contrast, inconspicuously observing the way people interact with the features is a minimally invasive measure, and will yield more reliable results.
Low-invasive vs high-invasive measures
Use low-invasive measures whenever possible. Avoid high-invasive measures; they yield questionable results, reduce system efficiency, and can result in the system adapting to the measures.
Pricing
The law of demand predicts that given two equivalent products, a lower price will increase demand and a higher price will decrease demand. The Veblen effect is one exception to this law.
Options
The principle of visibility is based on the fact that people are better at recognizing solutions when selecting from a set of options, than recalling solutions from memory. When it comes to the design of complex systems, the principle of visibility is perhaps the most important and most violated principle of design.
System status visibility
Design systems that clearly indicate the system status, the possible actions that can be performed, and the consequences of the actions performed. Immediately acknowledge user actions with clear feedback. Avoid kitchen-sink visibility.
Fail actively or passively
The weakest link in a system can function in one of two ways: it can fail and passively minimize damage, or it can fail and activate additional systems that actively minimize damage.
Weakest link
consider the weakest link principle when designing systems in which failures affect multiple elements. Use the weakest link to shut down the system or activate other protective systems. Perform adequate testing to ensure that only specified failure conditions cause the weakest link to fail.