UI Coach reference sheet
A concise map of 80 interaction, perception, cognition, behavior, and usability concepts. Open any entry for evidence, limitations, examples, and practical guidance.
Principles that explain how movement, target geometry, feedback, practice, and control mappings shape interaction speed and accuracy.
modelAffordancesAn affordance is a possible action supported by the relationship between an actor’s capabilities and an object or environment.Open reference 
principleConstraints PrincipleWell-designed constraints limit invalid actions or make their boundaries clear while preserving valid choice and recovery.Open reference 
principleDirect ManipulationDirect manipulation lets people act on visible objects through incremental, rapid, and reversible operations with immediate feedback.Open reference 
heuristicDoherty ThresholdRapid, meaningful system feedback helps sustain an interactive rhythm; the often-cited 400 ms value is historical guidance, not a universal boundary.Open reference 
usability heuristicFeedback PrincipleEvery meaningful action should produce timely, perceivable feedback that accurately communicates the resulting system state.Open reference 
lawFitts’s LawFor aimed movement, acquisition time tends to increase with target distance and decrease with target size along the movement axis.Open reference 
lawHick-Hyman LawIn practiced choice-reaction tasks, response time tends to grow with the information uncertainty of the possible stimulus-response alternatives.Open reference 
principleNatural MappingA mapping feels natural when the arrangement or movement of controls corresponds clearly to the arrangement or behavior of their effects.Open reference 
principlePostel’s LawAccept safe, unambiguous input variation where useful and produce predictable output, while rejecting ambiguity that threatens security or interoperability.Open reference 
lawPower Law of PracticePerformance commonly improves quickly during early practice and more slowly later, but individual learning is not universally described by one power function.Open reference 
principleProximity Compatibility PrincipleInformation that must be mentally integrated often benefits from perceptual proximity, while information needing separate treatment may benefit from separation.Open reference 
lawSteering LawMovement time through a constrained path tends to increase with path length and decrease with path width along the trajectory.Open reference 
principleStimulus-Response CompatibilityResponses are generally faster and less error-prone when the relationship between a signal and its control matches learned or spatial expectations.Open reference Principles that describe how people organize separate visual elements into groups, figures, paths, and coherent wholes.
principleChunkingOrganizing separate items into meaningful, familiar groups can make information easier to perceive, rehearse, and retrieve.Open reference 
principleCommon FateElements that move or change together tend to be perceived as belonging to the same group.Open reference 
principleFigure-Ground PrincipleVisual perception organizes a scene into a focal figure and surrounding ground, with contrast and boundaries influencing which region receives focus.Open reference 
principleLaw of ClosurePerception can complete missing contours or parts when the remaining structure supports a plausible whole.Open reference 
principleLaw of Common RegionElements enclosed by the same visible boundary tend to be perceived as a group, even when other grouping cues compete.Open reference 
principleLaw of ContinuityAligned elements and smooth paths tend to be perceived as continuing in the same direction rather than changing abruptly.Open reference 
principleLaw of PrägnanzAmbiguous visual input tends to organize into a stable, coherent form under the conditions present, often favoring relative simplicity or regularity.Open reference 
principleLaw of ProximityElements placed nearer one another tend to be perceived as related, especially when the spacing pattern is consistent and other cues do not override it.Open reference 
principleLaw of SimilarityElements sharing visible properties such as shape, color, size, or orientation tend to be perceived as belonging together.Open reference 
principleLaw of Uniform ConnectednessElements joined by a visible continuous connection tend to be perceived as one unit or as more strongly related than unconnected elements.Open reference 
principleSymmetry PrincipleSymmetrical regions tend to be perceived as coherent figures or paired units, especially around a clear axis.Open reference Research on how people notice differences, scan displays, interpret visual signals, and distinguish meaningful information from noise.
effectAesthetic-Usability EffectPeople often judge a visually coherent interface as easier to use, especially before or during early interaction.Open reference 
phenomenonAttentional CaptureA salient or abrupt event can draw attention away from the current goal, with capture shaped by stimulus properties and the observer’s attentional set.Open reference 
phenomenonChange BlindnessSubstantial changes can go unnoticed when they occur during a visual interruption, across views, or outside focused attention.Open reference principleCommon FateElements that move or change together tend to be perceived as belonging to the same group.Open reference principleFigure-Ground PrincipleVisual perception organizes a scene into a focal figure and surrounding ground, with contrast and boundaries influencing which region receives focus.Open reference principleLaw of PrägnanzAmbiguous visual input tends to organize into a stable, coherent form under the conditions present, often favoring relative simplicity or regularity.Open reference 
effectPicture-Superiority EffectPictures are often remembered better than comparable words when they are recognizable, relevant, and tested under suitable conditions.Open reference 
phenomenonPreattentive ProcessingSome basic visual features can be detected rapidly across a display before focused inspection of each individual item.Open reference principleProximity Compatibility PrincipleInformation that must be mentally integrated often benefits from perceptual proximity, while information needing separate treatment may benefit from separation.Open reference 
theorySignal Detection TheoryDetection depends on both sensitivity to signal versus noise and a decision criterion that trades misses against false alarms.Open reference 
modelVisual SearchVisual search performance depends on how a target is represented, how similar distractors are, and how attention is guided through the display.Open reference 
lawWeber’s LawAcross an approximate range, the smallest detectable change in a magnitude often scales with the starting magnitude rather than remaining a fixed absolute amount.Open reference Effects and models that explain what receives attention, what gets missed, and how goals compete with visual interruption.
phenomenonAttentional BlinkA second target in a rapid stream is often missed when it appears shortly after a first target that receives attention.Open reference phenomenonAttentional CaptureA salient or abrupt event can draw attention away from the current goal, with capture shaped by stimulus properties and the observer’s attentional set.Open reference 
phenomenonBanner BlindnessPeople can ignore page regions that resemble advertising or other routinely irrelevant content, even when those regions contain useful information.Open reference phenomenonChange BlindnessSubstantial changes can go unnoticed when they occur during a visual interruption, across views, or outside focused attention.Open reference 
phenomenonCocktail-Party EffectPeople can follow one information stream amid competition, while personally relevant unattended material may sometimes capture awareness.Open reference 
theoryFlowFlow is a deeply absorbed experience associated with clear goals, immediate feedback, concentrated attention, and a workable balance of challenge and skill.Open reference 
phenomenonInattentional BlindnessPeople focused on a demanding task can fail to notice an unexpected, fully visible event outside their current attentional goal.Open reference phenomenonPreattentive ProcessingSome basic visual features can be detected rapidly across a display before focused inspection of each individual item.Open reference 
phenomenonSelective AttentionAttention prioritizes some available information for deeper processing while other visible or audible information receives less processing.Open reference modelVisual SearchVisual search performance depends on how a target is represented, how similar distractors are, and how attention is guided through the display.Open reference 
effectVon Restorff EffectAn item that differs from otherwise similar surrounding items is often more likely to be noticed or remembered.Open reference Findings about temporary storage, recall, recognition, practice, spacing, and the way presentation changes what people remember.
principleChunkingOrganizing separate items into meaningful, familiar groups can make information easier to perceive, rehearse, and retrieve.Open reference 
theoryCognitive LoadCognitive load describes demands placed on limited working-memory resources while a person learns or performs a task.Open reference 
theoryDual CodingVerbal and nonverbal representations can create partly independent, connected memory codes that support later understanding and retrieval.Open reference 
principleEncoding SpecificityRetrieval improves when available cues overlap with information and context encoded during learning.Open reference 
modelForgetting CurveAccessible memory for newly learned material often declines rapidly at first and more gradually later when there is no effective review or retrieval.Open reference 
effectGeneration EffectInformation people generate themselves is often remembered better than comparable information they only read.Open reference 
modelIntrinsic Cognitive LoadIntrinsic cognitive load is the working-memory demand created by interacting elements that are inherent to what must be understood or performed.Open reference 
theoryLevels of ProcessingMemory often improves when encoding engages meaning and relationships rather than only surface appearance or sound.Open reference 
lawMiller’s LawImmediate-memory performance is limited and can improve through meaningful recoding, but Miller’s ‘seven plus or minus two’ is not a universal UI item limit.Open reference 
effectPeak-End RuleRetrospective evaluation of an experience can be disproportionately influenced by its most intense moment and its ending rather than its full duration.Open reference effectPicture-Superiority EffectPictures are often remembered better than comparable words when they are recognizable, relevant, and tested under suitable conditions.Open reference lawPower Law of PracticePerformance commonly improves quickly during early practice and more slowly later, but individual learning is not universally described by one power function.Open reference 
effectPrimacy EffectItems encountered early in a sequence often receive a recall advantage, partly because they can receive more rehearsal or distinctive context.Open reference 
effectRecency EffectRecently presented items often receive a recall advantage when they remain accessible at the time of test.Open reference 
usability heuristicRecognition Rather Than RecallMake relevant objects, actions, and options visible or readily retrievable so people do not have to recall them unaided.Open reference 
effectSerial-Position EffectRecall often varies by an item’s position in a sequence, with advantages for early and recent items under many test conditions.Open reference 
modelShort-Term MemoryShort-term memory refers to limited retention of information over a brief interval when it has not yet become durable long-term knowledge.Open reference 
effectSpacing EffectLearning episodes separated across time often support longer retention than the same practice concentrated into one session.Open reference 
effectTesting EffectActively retrieving learned information can improve later retention more than spending the same time restudying it.Open reference effectVon Restorff EffectAn item that differs from otherwise similar surrounding items is often more likely to be noticed or remembered.Open reference 
modelWorking MemoryWorking memory is a limited system for temporarily maintaining and manipulating information needed by the current task.Open reference 
effectZeigarnik EffectInterrupted goals may remain mentally active and prompt resumption, but unfinished tasks do not show a reliable universal memory advantage.Open reference Models and heuristics for understanding limited mental resources, task complexity, and where a system should carry unavoidable work.
effectChoice OverloadLarge or difficult choice sets can reduce decision confidence or action when options are hard to compare and preferences are uncertain.Open reference principleChunkingOrganizing separate items into meaningful, familiar groups can make information easier to perceive, rehearse, and retrieve.Open reference theoryCognitive LoadCognitive load describes demands placed on limited working-memory resources while a person learns or performs a task.Open reference 
modelExtraneous Cognitive LoadExtraneous cognitive load is mental work caused by how information or a task is presented rather than by the relationships that must be learned.Open reference modelIntrinsic Cognitive LoadIntrinsic cognitive load is the working-memory demand created by interacting elements that are inherent to what must be understood or performed.Open reference lawMiller’s LawImmediate-memory performance is limited and can improve through meaningful recoding, but Miller’s ‘seven plus or minus two’ is not a universal UI item limit.Open reference 
heuristicOccam’s RazorWhen explanations or designs account for the same requirements equally well, prefer the one that depends on fewer unnecessary assumptions.Open reference 
usability heuristicProgressive DisclosureProgressive disclosure presents the information and controls needed now, then reveals additional detail when the user asks or the task reaches it.Open reference 
heuristicTesler’s LawSome task complexity is irreducible, so design determines whether the system, the user, or an organization carries that work.Open reference modelWorking MemoryWorking memory is a limited system for temporarily maintaining and manipulating information needed by the current task.Open reference Research on how framing, defaults, reference points, ownership, and choice structure influence judgment and selection.
effectAnchoring EffectAn initial numeric or categorical reference can pull later estimates and judgments toward it, even when adjustment should be larger.Open reference effectChoice OverloadLarge or difficult choice sets can reduce decision confidence or action when options are hard to compare and preferences are uncertain.Open reference 
modelCognitive BiasCognitive bias is an umbrella term for systematic patterns in judgment that can depart from a task-relevant normative standard.Open reference 
effectDecoy EffectAdding an option that is clearly worse than one target option on relevant attributes can shift preference toward that target.Open reference 
effectDefault EffectA preselected or no-action option is often chosen more frequently than an otherwise comparable alternative.Open reference 
effectEndowment EffectOwnership or a sense of possession can increase the value assigned to an item relative to the value assigned before ownership.Open reference 
effectFraming EffectChoices can change when equivalent outcomes are described through different gain, loss, survival, or mortality frames.Open reference lawHick-Hyman LawIn practiced choice-reaction tasks, response time tends to grow with the information uncertainty of the possible stimulus-response alternatives.Open reference 
effectLoss AversionIn many risky choices, losses relative to a reference point influence value more strongly than comparable gains, with magnitude varying by context.Open reference 
heuristicPareto PrincipleOutcomes are often unevenly distributed, so a minority of causes, tasks, or defects may account for a large share of observed impact.Open reference 
modelSatisficingPeople often stop searching when they encounter an option that meets an acceptable threshold rather than exhaustively finding the theoretical optimum.Open reference theorySignal Detection TheoryDetection depends on both sensitivity to signal versus noise and a decision criterion that trades misses against false alarms.Open reference 
biasStatus Quo BiasPeople may prefer an existing state or previously chosen option beyond what its attributes alone would predict.Open reference Effects that describe progress, immersion, unfinished goals, remembered experiences, time pressure, and other forces that shape continued action.
theoryFlowFlow is a deeply absorbed experience associated with clear goals, immediate feedback, concentrated attention, and a workable balance of challenge and skill.Open reference 
effectGoal-Gradient EffectMotivated effort can increase as a salient, valued goal appears closer, although progress framing and context shape the pattern.Open reference 
phenomenonParadox of the Active UserPeople often begin productive action immediately instead of investing first in broad instruction that might improve later efficiency.Open reference 
heuristicParkinson’s LawWork can expand to occupy the time made available, making bounded scope and explicit completion criteria useful planning constraints.Open reference effectPeak-End RuleRetrospective evaluation of an experience can be disproportionately influenced by its most intense moment and its ending rather than its full duration.Open reference effectZeigarnik EffectInterrupted goals may remain mentally active and prompt resumption, but unfinished tasks do not show a reliable universal memory advantage.Open reference Models and design principles that explain how prior experience, conceptual structure, familiarity, and information cues guide behavior.
modelAffordancesAn affordance is a possible action supported by the relationship between an actor’s capabilities and an object or environment.Open reference phenomenonBanner BlindnessPeople can ignore page regions that resemble advertising or other routinely irrelevant content, even when those regions contain useful information.Open reference 
modelConceptual ModelsA conceptual model is the designed explanation of a system’s objects, relationships, actions, and state that the interface presents to users.Open reference 
modelInformation ScentInformation scent is the perceived value of a cue for predicting whether a path will lead toward the information a person seeks.Open reference 
heuristicJakob’s LawPeople bring expectations learned from other products, so familiar conventions often reduce the effort needed to begin using a new interface.Open reference 
modelMental ModelsA mental model is a person’s internal, partial representation of how a system works and what actions will produce.Open reference principleNatural MappingA mapping feels natural when the arrangement or movement of controls corresponds clearly to the arrangement or behavior of their effects.Open reference phenomenonParadox of the Active UserPeople often begin productive action immediately instead of investing first in broad instruction that might improve later efficiency.Open reference modelSatisficingPeople often stop searching when they encounter an option that meets an acceptable threshold rather than exhaustively finding the theoretical optimum.Open reference 
principleSignifiersSignifiers are perceivable cues that communicate where an action can occur, how to perform it, or what state an object is in.Open reference principleStimulus-Response CompatibilityResponses are generally faster and less error-prone when the relationship between a signal and its control matches learned or spatial expectations.Open reference Practical principles for clarity, simplicity, error resistance, visibility, and consistency that come from HCI practice rather than one experiment.
effectAesthetic-Usability EffectPeople often judge a visually coherent interface as easier to use, especially before or during early interaction.Open reference modelConceptual ModelsA conceptual model is the designed explanation of a system’s objects, relationships, actions, and state that the interface presents to users.Open reference principleConstraints PrincipleWell-designed constraints limit invalid actions or make their boundaries clear while preserving valid choice and recovery.Open reference principleDirect ManipulationDirect manipulation lets people act on visible objects through incremental, rapid, and reversible operations with immediate feedback.Open reference heuristicDoherty ThresholdRapid, meaningful system feedback helps sustain an interactive rhythm; the often-cited 400 ms value is historical guidance, not a universal boundary.Open reference modelExtraneous Cognitive LoadExtraneous cognitive load is mental work caused by how information or a task is presented rather than by the relationships that must be learned.Open reference usability heuristicFeedback PrincipleEvery meaningful action should produce timely, perceivable feedback that accurately communicates the resulting system state.Open reference modelInformation ScentInformation scent is the perceived value of a cue for predicting whether a path will lead toward the information a person seeks.Open reference heuristicJakob’s LawPeople bring expectations learned from other products, so familiar conventions often reduce the effort needed to begin using a new interface.Open reference modelMental ModelsA mental model is a person’s internal, partial representation of how a system works and what actions will produce.Open reference heuristicOccam’s RazorWhen explanations or designs account for the same requirements equally well, prefer the one that depends on fewer unnecessary assumptions.Open reference heuristicPareto PrincipleOutcomes are often unevenly distributed, so a minority of causes, tasks, or defects may account for a large share of observed impact.Open reference heuristicParkinson’s LawWork can expand to occupy the time made available, making bounded scope and explicit completion criteria useful planning constraints.Open reference principlePostel’s LawAccept safe, unambiguous input variation where useful and produce predictable output, while rejecting ambiguity that threatens security or interoperability.Open reference usability heuristicProgressive DisclosureProgressive disclosure presents the information and controls needed now, then reveals additional detail when the user asks or the task reaches it.Open reference usability heuristicRecognition Rather Than RecallMake relevant objects, actions, and options visible or readily retrievable so people do not have to recall them unaided.Open reference principleSignifiersSignifiers are perceivable cues that communicate where an action can occur, how to perform it, or what state an object is in.Open reference heuristicTesler’s LawSome task complexity is irreducible, so design determines whether the system, the user, or an organization carries that work.Open reference