Glossary » Design Principles

indication

showing what item would be selected if the user were to click. Analogous to hiliting the current selection, indication highlights as the user mouses over items, helping the user to accurately make selections.

individual differences

people vary in a number of ways that can have an impact on the design of a user interface, and rather than trying to design for “the average user”, it is often better to understand how people vary to design…

individualization

modifying a system to suit the needs and preferences of a single individual user.

information efficiency

the minimum amount of information the computer needs from the user divided by the amount of information the specific user interface requires from the user, with values ranging from 0 to 1. A good interface has an efficiency close to…

information overload

a state of having too much information, such that a person is overwhelmed. When information is available in enormous quantities (as on the web) and not clearly structured, people have difficulty finding relevant information and grasping important principles embedded in…

information race

a method of measuring optimal task times in an application by having 2 expert users compete to complete the task as fast as possible.

informed consent

permission from a participant in a user study to participate and to have data collected about them, with that permission hinging on the fact that they have been fully informed of the nature and risks of the study and their…

intelligent cut and paste

applied to text editing, a version of cut and paste that simplifies selection and saves keystrokes. When a word is selected and cut from a sentence, instead of leaving spaces on either side of the word, one of the spaces…

interlock

an error-prevention mechanism that forces operations to occur in sequence, the first of which makes the second operation safer, such as a TV set that can’t be dismantled without first turning it off (as per Don Norman).

intrusiveness

the property of a perceptual signal that enables it to draw attention from other activities. Perceptually, a sound or a bright flash can draw attention from people even when they are attending to something else. This property is useful for…

intuitive

a term used loosely to refer to user interfaces that are easy to understand without training. An interface may sometimes be intuitive due to some inborn perceptual skill (e.g. loud noises make us pay attention) or at least some common…

inverted pyramid process

An iterative process oriented around exploring a wide variety of alternatives. Rather than build a single prototype and testing, in the inverted pyramid process, you build lots of low-cost alternatives, such as thumbnails, evaluate them, then refine to the next…

ISO 13407 Human-Centered Design Process

a standard established by the International Standards Organization for how user research should be involved in designing products.

The standard specifies an iterative cycle of these 4 activities:

…

ISO 9126 Software Engineering Product Quality

a standard that defines specific terms for evaluating software quality, under these 6 categories: functionality, reliability, usability, efficiency, maintainability, and portability.

ISO 9241

“Ergonomics requirements for office work with visual display terminals (VDTs)”; a set of international standards for using computers, including hardware, visual display, and interaction guidelines, developed by the International Standards Organization (ISO).

ISO TR 18529

“Human-centered lifecycle process descriptions”, a standard developed by the International Standards Organization that defines a “Usability Maturity Model”, a set of practices in the design lifecycle to be human-centered and involve appropriate evaluation.

The standard defines individual components within these…

iterative design

the idea that design should be done in repeated cycles where, in each cycle, the design is elaborated, refined, and tested, and the results of testing at each cycle feed into the design focus of the next cycle.

This is…

kinesthetic feedback

knowledge people have about the position and movement of their bodies based on nerves in their joints and muscles (also known as proprioception). Such feedback may play a role in hand-eye coordination, the use of input devices, and reaction to…

KISS

keep it simple, stupid! The extremely popular principle of simplicity applicable to any area of design and engineering.

Know Thy User

a mantra for usability specialists; understand your audience and design for them. Don’t make assumptions about your users. Go out and meet them. Gather data. Perform user testing. Understand how they differ, what their goals are, what their needs are,…

latching

the capability of a control to be set in a specific position (or state) and to remain in that position; the opposite of a spring-loaded mode.

latency

same as delay — a measure of the time it takes for a message to be transmitted across a network. The variance of the latency is also an important measure.

learnability

a measure of the degree to which a user interface can be learned quickly and effectively. Learning time is the typical measure. User interfaces are typically easier to learn when they are designed to be easy to use based on…

learned helplessness

when a person has repeated experiences of failure at a task or skill and learns to assume that they aren’t capable, when in fact they may simply need to be taught from a different point of view or to break…

learning time

the amount of time it takes to acquire a new skill or piece of knowledge up to a given level of mastery. Since nothing is ever learned perfectly, target levels of mastery must be defined, such as the ability to…