tools-only Cognitive Psychology Reference
Deep dive into how minds work—perception, memory, attention, decision-making, and emotion.
Perception
Visual Perception
Preattentive Features (Treisman) Detected in <200ms, parallel processing:
- Color
- Orientation
- Size
- Motion
- Curvature
- Enclosure
Design implication: Use these for critical, must-see information.
Gestalt Principles How we group visual elements:
- Proximity: Close things belong together
- Similarity: Similar things belong together
- Continuity: We follow smooth paths
- Closure: We complete incomplete shapes
- Common fate: Things moving together belong together
- Figure/ground: We separate foreground from background
Design implication: Layout communicates relationship. Use grouping intentionally.
Change Blindness We fail to notice changes during visual disruption (saccades, blinks, scene cuts).
Design implication: Don't rely on users noticing changes. Animate or highlight transitions.
Inattentional Blindness We miss unexpected stimuli when focused elsewhere. (Gorilla experiment, Simons & Chabris)
Design implication: Important new elements need to demand attention, not just appear.
Attention
Selective Attention (Broadbent, Treisman)
- We can only deeply process one stream at a time
- Selection happens early (filtering) and late (weighting)
- Attention is a limited resource that depletes
Attentional Capture Some stimuli grab attention involuntarily:
- Sudden onset
- Motion
- High contrast
- Personal relevance (your name, faces)
Design implication: Use attention capture sparingly; it's powerful but disruptive.
Divided Attention
- Possible for low-demand tasks
- Impossible for high-demand tasks
- Talking while driving degrades both
- "Multitasking" is rapid task-switching with costs
Design implication: Don't require attention in multiple places simultaneously.
Memory Systems
Sensory Memory
- Iconic (visual): ~250ms, high capacity
- Echoic (auditory): ~3-4 seconds
Design implication: Brief exposures can be processed if attention follows quickly.
Working Memory (Baddeley)
Components:
- Phonological loop: Verbal/acoustic information (~2 seconds without rehearsal)
- Visuospatial sketchpad: Visual and spatial information
- Central executive: Attentional control
- Episodic buffer: Integration across modalities
Capacity: 4±1 chunks (Cowan), not 7±2 (that's short-term memory slots)
Chunking: Meaningful groups expand effective capacity. "FBI-CIA-IBM" = 3 chunks, not 9 letters.
Design implication:
- Don't exceed 4 items for active manipulation
- Support chunking through meaningful grouping
- Externalize memory when possible (show, don't require recall)
Long-Term Memory
Types:
- Episodic: Personal events (what you had for breakfast)
- Semantic: Facts and knowledge (Paris is in France)
- Procedural: Skills and how-to (riding a bike)
Encoding:
- Depth of processing matters (Craik & Lockhart)
- Elaboration strengthens encoding
- Emotional events are remembered better
- Spacing effect: Distributed practice > massed practice
Retrieval:
- Cue-dependent: Context aids recall
- Reconstruction: Memory is not playback, it's reconstruction
- False memories are possible and common
Design implication:
- Recognition is easier than recall
- Consistent contexts aid retrieval
- Don't assume users remember accurately
Prospective Memory
Remembering to do something in the future.
- Event-based: "When I see the store, buy milk"
- Time-based: "At 3pm, call the doctor"
Both are unreliable without external cues.
Design implication: Don't rely on users remembering future actions. Remind them.
Decision Making
Dual Process Theory (Kahneman)
System 1:
- Fast, automatic, effortless
- Associative, intuitive
- Parallel processing
- Emotional, stereotyping
- Always running
System 2:
- Slow, deliberate, effortful
- Rule-based, analytical
- Serial processing
- Logical, calculating
- Lazy, avoids engagement
Design implication: Most interface use is System 1. Design for intuition, not analysis.
Heuristics and Biases
Availability Heuristic Judging probability by ease of recall.
- Recent events seem more likely
- Vivid events seem more likely
- If I can think of examples, it must be common
Representativeness Heuristic Judging probability by similarity to prototype.
- Base rate neglect
- Conjunction fallacy
- Hot hand fallacy
Anchoring Initial values bias subsequent estimates.
- Even arbitrary anchors influence judgment
- Adjustment is insufficient
- First numbers seen matter
Loss Aversion Losses loom larger than gains (~2x).
- We prefer avoiding losses to acquiring gains
- Endowment effect: We overvalue what we have
- Status quo bias: Change feels like loss
Framing Effects How options are presented changes choices.
- "90% survival" vs "10% mortality"
- Gain frame vs loss frame
- Default options strongly influence choice
Design implication: You're always framing. Do it intentionally and ethically.
Choice Architecture (Thaler & Sunstein)
- Defaults matter: Most people stick with defaults
- Expect error: Design for mistakes
- Give feedback: Show consequences of choices
- Map complex choices: Make comparison easier
- Structure complex choices: Break down, sequence, categorize
- Incentives: Make costs and benefits salient
Learning and Expertise
Skill Acquisition (Fitts & Posner)
Stages:
- Cognitive: Deliberate, error-prone, attention-demanding
- Associative: Patterns forming, errors decreasing
- Autonomous: Automatic, parallel, attention-free
Design implication: Interface should support all stages, not optimize for just one.
Deliberate Practice (Ericsson)
- Not just repetition—focused improvement
- Immediate feedback essential
- Pushing beyond comfort zone
- 10,000 hours is oversimplified but directionally correct
Transfer of Learning
- Near transfer: Similar contexts (easier)
- Far transfer: Different contexts (harder, rarer)
- Expertise is often surprisingly domain-specific
- Abstract principles transfer better than specific procedures
Expert Blindness (Curse of Knowledge)
Experts forget what it's like not to know.
- Hard to predict novice confusion
- Obvious to expert ≠ obvious to novice
- Jargon becomes invisible
Design implication: Always test with actual novices.
Language and Communication
Language Processing
Reading:
- Skilled readers process word shapes, not letters
- Eye movements: Fixations (~250ms) and saccades
- Predictable words processed faster
- Context enables prediction
Comprehension:
- Proposition-based, not word-based
- Inference-dependent
- Schema-driven (we fill in gaps)
- Limited by working memory
Design implication: Write for scanning, not reading. Use predictable structures.
Pragmatics (Grice)
Cooperative Principle—speakers assume:
- Quality: Truth
- Quantity: Right amount of information
- Relation: Relevance
- Manner: Clarity
Violating these creates confusion or implies hidden meaning.
Design implication: Error messages and instructions should follow these maxims.
Ambiguity
- Lexical: "Bank" (river or financial)
- Syntactic: "Flying planes can be dangerous"
- Referential: "Put it there" (what? where?)
Design implication: Be explicit. Context doesn't always disambiguate.
Reasoning and Problem Solving
Mental Models (Johnson-Laird)
- We simulate scenarios mentally
- Models are incomplete and biased
- We consider few alternatives
- Counterexamples are hard to generate
Design implication: Support exploration of alternatives. Don't rely on users imagining them.
Confirmation Bias
We seek evidence that confirms our beliefs.
- Selective search
- Selective interpretation
- Selective recall
Design implication: Present disconfirming information actively; users won't seek it.
Problem Solving
Means-Ends Analysis:
- Identify difference between current and goal state
- Find operator to reduce difference
- Apply and repeat
Functional Fixedness: We see objects in their typical functions only.
Set Effects: Past solutions bias current approaches (Einstellung effect).
Design implication: Prior experience both helps and constrains. Consider fresh perspectives.
Emotion and Motivation
Affect and Cognition
Emotional processing:
- Faster than cognitive evaluation
- Influences attention, memory, decision-making
- "How do I feel about it?" is a valid heuristic
Mood congruence:
- We remember mood-congruent information
- We make mood-congruent judgments
- Positive mood → broader thinking
- Negative mood → narrower, analytical thinking
Design implication: Emotional responses to interfaces are legitimate data.
Motivation
Intrinsic vs. Extrinsic:
- Intrinsic: Activity is its own reward
- Extrinsic: Activity serves external goal
- Overjustification: External rewards can undermine intrinsic motivation
Self-Determination Theory (Deci & Ryan):
- Autonomy: Control over one's actions
- Competence: Feeling effective
- Relatedness: Connection to others
Design implication: Support autonomy and competence; don't just add rewards.
Flow (Csikszentmihalyi)
Optimal experience when:
- Challenge matches skill
- Clear goals
- Immediate feedback
- Deep concentration
- Loss of self-consciousness
- Altered sense of time
Design implication: Match difficulty to user skill level. Enable focus.
Embodied Cognition
Mind-Body Connection
Cognition is not just in the head:
- Bodily states influence judgment (warm cup → warm feelings)
- Gestures aid thinking (not just expression)
- Physical manipulation aids understanding
- Spatial metaphors are grounded in physical experience
Extended Mind (Clark & Chalmers)
Cognition extends into the environment:
- Notebook as memory
- Calculator as arithmetic
- Interfaces as cognitive tools
Design implication: Interfaces are cognitive extensions. Design them as such.
Situated Cognition
Thinking happens in context:
- Environment provides cues and scaffolding
- Knowledge is often tied to situations
- Transfer requires abstraction
Design implication: Consider the context of use, not just the interface in isolation.
Individual Differences
Cognitive Abilities
- Working memory capacity varies
- Processing speed varies
- Spatial ability varies
- These affect learning and performance
Cognitive Styles
- Field dependent/independent
- Verbal/visual preference
- Holistic/analytic processing
- Styles are preferences, not fixed traits
Age-Related Changes
- Processing speed decreases
- Working memory capacity decreases
- Crystallized knowledge increases
- Expertise can compensate for decline
Accessibility Considerations
- Cognitive load affects everyone, some more than others
- Attention disorders, learning differences, cognitive impairments
- Design for the margins; everyone benefits
Design implication: Don't assume a single cognitive profile. Design for variability.