hci g

hci g

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A standard operator in a keystroke-level model (KLM), P represents the act of pointing, that is, moving a cursor with a mouse. It was empirically determined to average 1100 msec by Card, Moran, and Newell (1980b, 1983), but it can also be calculated with Fitts’ Law.

participatory design

A design movement primarily associated with Scandinavia, in which future users of the artifacts being designed participate in the original design work.

PERT chart

Program Evaluation Review Technique, a methodology developed by the U.S. Navy in the 1950s to manage the Polaris submarine missile program. A similar methodology, the Critical Path Method (CPM), which was developed for project management in the private sector at about the same time, has become synonymous with PERT, so that the technique is known by any variation on the names: PERT, CPM, or PERT/CPM. These methods are used in cognitive modeling to depict the parallel operation of perceptual, cognitive, and motor operators, with resource allocation and information-flow constraints.

PIE model

An example of an abstract formal model—that is, one that is used to analyze a class of systems and usability problems rather than specifying a particular system. The PIE model was developed at York University in the mid-1980s and was one of the first steps in a new stream of formal method work in human-computer interaction (HCI) that began at that time. See: http://www.hcibook.com/alan/topics/formal/


Something (a physical artifact, electronic record, or human memory) that explicitly or tacitly maintains the current position within a formal or informal process. See: http://www.hcibook.com/alan/topics/triggers/


a technique used during the design of interactive systems in which the designer adopts a computational perspective on the task objects in a scenario.


When being trained as a carpenter or a nurse, for example, one shares a practice. At the same time, each individual who possesses a practice keeps it up and changes it as well. It is practice that allows us to talk about more than just individual skills, knowledge, and judgment, and not just about a “generic” human being. Practice is shaped historically, which is of particular relevance for design and use of computer applications.

preattentive processing

The rapid detection of visual features theorized to occur in parallel before the operation of selective attention.

predictive model

A model that allows metrics of human performance to be determined analytically without undertaking time-consuming and resource-intensive experiments.

Problem Behavior Graph

A graphical depiction of search through a problem space.

problem solving

Searching through a problem space from a known start state to a desired end state, or one of a set of desired end states, applying operators of uncertain outcome to move from state to state. Problem solving typically refers to a path through the problem space that includes explorations of deadend paths and backing up to prior states. (see skilled behavior for a contrasting type of behavior)

problem space

A mental representation of a problem, including the start state, the goal state, and the operators or moves that allow transitions between states. According to Newell and Simon’s (1972) theory of problem solving, humans solve problems by constructing and searching a problem space.

procedural knowledge

Also called “how to do it” knowledge. The knowledge of which operators to perform to move from a known start state to a desired state in a problem space.

Production system

A programming language made up of conditional statements. If all conditions are satisfied, then action is taken.


In cognitive-dimensions analysis, a statement of what is required (in cognitive-dimensions terms) to support a given generic activity. The profile of an activity states for each cognitive dimension whether that dimension is material and, if so, what value it should have (e.g., for modification, viscosity must be low, visibility must be high, etc.).

progressive evaluation

In the cognitive-dimensions framework, the ability to review or test a partially complete structure, to check on progress to date it is important for novices, and becomes less so as one gains experience. Some systems allow only a complete design to be reviewed; others allow a review at any stage.

propagation of representations

A component of information-processing activity in which sequences of transformations from one representational form (or medium) to another result in information-processing activity. Hutchins claims that “representational states are propagated from one medium to another by bringing the states of the media into coordination with one another” (1995a, 117).

propositional representations

Representations that have a more-or-less arbitrary structure; for example, a word or a sentence in a natural language. See also analog representations.


an operational model of a design or software development proposal, usually created for testing and feedback purposes

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