Glossary

114 terms

A B C D E F G H I J K L M N P R S T U V W

A

A/B Testing — Randomised comparison of design variants on live users
Accessibility — Design that works for users with disabilities
Aesthetic-Usability Effect — Aesthetically pleasing designs are perceived as more usable
Affordance — Action possibilities a design communicates to users
AI Usability — Usability principles specific to AI-powered interfaces
Alert Fatigue — Habitual dismissal of alerts due to excessive volume
Anchoring — Cognitive bias where initial information disproportionately influences judgement
Automation Bias — Tendency to accept automated recommendations without sufficient scrutiny

B

Between-Subjects Design — Experimental design where each participant experiences only one condition
Biophilic Design — Architecture that incorporates natural elements to promote wellbeing
Bounded Rationality — Rational decision-making constrained by limited time, information, and cognition

C

Card Sorting — Research method for validating information architecture
Change Blindness — Failure to notice visual changes that coincide with disruption
Chartjunk — Visual elements in a chart that don't represent data
Checklist — External memory aid that prompts required steps
Choice Architecture — Deliberate design of how choices are presented
Choice Overload — Paralysis and dissatisfaction from too many options
Chunking — Grouping information into meaningful units to extend memory capacity
Cleveland-McGill Hierarchy — Ranking of visual encodings by perceptual accuracy
Clinical Decision Support — Software systems that assist clinical decision-making
Cognitive Bias — Systematic deviation from rational decision-making
Cognitive Load — The amount of working memory resources used
Cognitive Load Theory — Framework for understanding working memory demands in learning and interaction
Cognitive Walkthrough — Expert review method focused on learnability
Cogulator — Free tool that automates GOMS and cognitive modelling analysis
Colour Vision Deficiency — Impaired ability to distinguish certain colours
Contrast — Difference in luminance or colour between an object and its background
CPM-GOMS — GOMS variant modelling parallel perceptual, cognitive, and motor operations
Crew Resource Management — Training for team-based safety performance

D

Dark Cockpit Principle — Normal state shows nothing; only anomalies attract attention
Dark Patterns — Interface designs that manipulate users against their interests
Dashboard Design — Aggregating multiple data displays for monitoring and decision support
Data-Ink Ratio — Proportion of graphic ink devoted to actual data
Default Effect — Users disproportionately accept default options
Divided Attention — Attempting to process multiple tasks simultaneously
Doherty Threshold — Response times under 400 ms keep users engaged

E

Effect Size — Magnitude of a difference or relationship, independent of sample size
Electronic Health Record — Digital system for recording and managing patient clinical data
Evidence Hierarchy for Design — Levels of evidence supporting design decisions
Evidence-Based Design — Applying research evidence to architectural decisions
Evolved Design Practice — Design knowledge accumulated through centuries of cultural selection
Explainability — An AI system's ability to communicate its reasoning to users

F

Fail-Safe Design — Design that defaults to a safe state when failure occurs
Fitts's Law — Predicts the time to point at a target based on size and distance
Five-User Rule — Five participants find ~85% of major usability problems
Foveal Vision — High-acuity vision limited to ~2 degrees of visual angle
Framing Effect — The way options are described influences choice

G

Gestalt Principles — Laws describing how the visual system groups elements
Golden Ratio — Proportion (~1.618) used in classical architecture and design
GOMS — Framework for analysing expert task performance: Goals, Operators, Methods, Selection rules

H

Heuristic Evaluation — Expert inspection method using usability heuristics as criteria
Hick's Law — Predicts decision time based on the number of choices
Human Error — Predictable failure modes in human performance
Human Factors Engineering — Discipline applying human capabilities knowledge to system design
Human-Centred Design — Design approach that puts users at the centre

I

IEC 62366 — International standard for medical device usability engineering
Inattentional Blindness — Failure to perceive visible but unexpected objects
Information Architecture — The organisation and labelling of content for findability
ISO 9241 — International standard for ergonomics of human-system interaction

J

Jakob's Law — Users spend most time on other sites and expect yours to work the same

K

Keystroke-Level Model — Simplest GOMS variant: sum operator times to predict task time

L

Lapse — A memory failure — forgetting a step or losing track of progress
Long-Term Memory — The permanent store of knowledge and experience
Lynch's Five Elements — Paths, edges, districts, nodes, and landmarks for navigable environments

M

Mental Model — A user's internal representation of how a system works
Miller's Law — The magical number seven, plus or minus two
Mistake — A planning error — the intention itself was wrong
Model Human Processor — Engineering model of human information processing
Motor Control — Neural and muscular system that executes planned movement

N

Nielsen's 10 Heuristics — Jakob Nielsen's 10 usability principles for evaluation
Norman's Design Principles — Don Norman's principles linking psychology to design

P

Palladio's Proportions — Andrea Palladio's classical system of room proportions
Peak-End Rule — People judge experiences by their peak and end, not the average
Post-Occupancy Evaluation — Systematic assessment of a building's performance after occupancy
Postel's Law — Be conservative in what you do, liberal in what you accept
Power Law of Practice — Performance improves as a power function of practice trials
Pre-Attentive Processing — Visual features detected in parallel within ~250 ms
Predictive Modelling — Predicting usability outcomes without human testing
Progressive Disclosure — Revealing information in stages as users need it

R

Reason's Swiss Cheese Model — Safety as multiple imperfect layers of defence
Recognition over Recall — Showing options is easier than requiring users to remember them
Redundancy Effect — Presenting the same information in multiple formats can increase load

S

Satisficing — Choosing the first option that meets a minimum threshold
Selective Attention — Focusing on one source of information while ignoring others
Sensory Memory — Brief, high-capacity buffer for incoming sensory information
Serial Position Effect — Items at the start and end of a list are remembered best
Severity Rating — Prioritising usability problems by impact and frequency
Shneiderman's 8 Golden Rules — Ben Shneiderman's principles of interface design
Signifier — A perceivable cue that communicates an affordance
Slip — An execution error where intention is correct but action fails
Small Multiples — Series of similar charts for cross-comparison
Sparklines — Word-sized data graphics embedded in text or tables
Split-Attention Effect — Cognitive burden when related information is spatially separated
Statistical Power — Probability of detecting a real effect if one exists
Steering Law — Predicts time to move through a constrained path
System Usability Scale — 10-item standardised usability questionnaire

T

Tesler's Law — Every application has an irreducible amount of complexity
Think-Aloud Protocol — Asking participants to verbalise their thoughts during tasks
Throughput — Measure of pointing device performance combining speed and accuracy
Trust Calibration — Matching user trust to the actual reliability of an automated system

U

Universal Design — Design usable by all people without adaptation or specialised design
Usability — How easy and pleasant a system is to use
Usability Testing — Empirical evaluation by observing users performing tasks
User Experience — All aspects of a person's interaction with a product

V

Vigilance Decrement — Decline in detection performance during sustained monitoring
Visual Hierarchy — Arrangement of elements to signal relative importance
Visual Search — The process of locating a target among distractors
Vitruvian Triad — Firmitas, utilitas, venustas — the three qualities of good design
Von Restorff Effect — Distinctive items are remembered better than similar ones

W

Wayfinding — The process of navigating through an environment to a destination
WCAG — Web Content Accessibility Guidelines
Weber's Law — Just-noticeable difference is a constant proportion of stimulus intensity
Within-Subjects Design — Experimental design where each participant experiences all conditions
Working Memory — The cognitive workspace that holds information in active use