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Glossary » Psychology


(human error) the result of any action whose consequences are not what was intended by the person performing the action. Errors are commonly classified as slips (automatic processes interfering with an action) or mistakes (failures in reasoning or selection of…

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an empirical study designed to relate cause and effect by ruling out as many alternative causes as possible and by actually manipulating the cause to obtain the effect, as opposed to merely finding a correlation between the two that may…

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external validity

the degree to which the results of a study can safely be generalized to apply to settings and parameters outside those of the original study, such as to other populations, times, places, similar tasks, and other measurement instruments.

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a range of devices are capable of observing a person’s pupil to determine the direction of their gaze.

Eye-tracking can be used for input, by directly controlling a pointer on the screen, or even for communicating the gaze direction to

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face validity

the apparent appropriateness of an experimental design in resolving the question it is intended to address, at a subjective level.

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Fitts’ Law

T = k log2(D/S + 0.5), k ~ 100 msec.

T = time to move the hand to a target
D = distance between hand and target
S = size of target

Fitts’ Law is a model to…

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fundamental attribution error

the tendency for people to blame themselves rather than external factors for problems they have. In computer terms, the tendency to blame the user rather than the technology or its design when users have trouble with computers.

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gestalt principles

principles of perception that address the interpretation of arrangements and relationships of objects; the whole is greater than the sum of the parts. Some of the common principles are:

good continuation – objects along a common path form a unit

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a family of techniques for modeling and representing the knowledge necessary for a person to perform a task. GOMS is an acronym that stands for Goals, Operators, Methods, and Selection Rules, the components of which are used as the building…

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gulf of evaluation

the psychological gap that must be crossed to interpret a user interface display: interface -> interpretation -> evaluation. In other words, the process of perception.

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gulf of execution

the psychological gap that must be crossed to manipulate a user interface appropriately: goals -> plans -> action specification -> operate interface. In other words, the processes of motor control. The idea here is that representations on the screen should…

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developing a habit, a fixed pattern of responses to given situations, which becomes fast and automatic but can lead to user errors when those patterned responses don’t apply, as in modal systems.

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Hawthorne effect

the tendency for people to improve their performance after any change when they know their performance is being studied — a common potential confound when testing user interface changes for whether they represent an improvement or not.

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Hick’s Law

(1) H = log2(n + 1).
(2) H = Σ pi log2(1/pi + 1).

H = the information-theoretic entropy of a decision.
n = the number of equally probable alternatives.
pi = the probability of alternative i…

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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…

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information anxiety

stress caused by the inability to access or understand the information you need, caused by information overload, lack of clear organization to information, insufficient information, excessively difficult presentation of information, etc.

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information processing model

in cognitive psychology, the idea of breaking down human behavior into 3 primary systems: perception, cognition, and motor control (action). These systems are similar to the computer’s input, processing, and output. Cognition, in this model, can do hidden mental processing…

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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…

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inter-observer reliability

or inter-coder reliability; the degree to which 2 observers record the same data (or in some cases, draw the same conclusions) in the same circumstances. Lack of reliability in observations can indicate that observers are missing important details, that they…

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internal validity

the degree to which the design of a study allows you to accurately attribute an observation to a specific cause rather than alternative causes. An undesirable alternative cause for your result is known as a “confound”.

An example is to…

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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…

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Keystroke Level Model. A simple GOMS technique dealing mainly with observable events and organized as a single stream of sequential operators. KLM is easy to learn and can provide fast, but crude, task execution times.

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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…

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Likert scale

a type of survey question where respondents are asked to rate the level at which they agree or disagree with a given statement. For example:

I find this software easy to use.
strongly disagree 1 2 3 4 5 6

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locus of attention

or focus of attention; the single source or location of sensory input that a person attends to at a given time, such as the point in space that they’re looking at and able to devote mental resources to interpreting. In…

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