Textbook of Usability

114 terms

Glossary

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