Cognitive Foundations

When to Use This Skill

• Explaining why a design works or fails (grounded in research, not opinion)
• Evaluating cognitive load or working memory demands
• Predicting user performance (Fitts, Hick-Hyman)
• Diagnosing mental model misalignment
• Justifying design decisions to stakeholders with evidence
• Understanding attention, perception, or memory failures

Output Contracts

For Single-Principle Analysis

## Cognitive Principle: [Name]

**Principle**: [1-sentence explanation]

**Evidence in Design**: [Where/how this applies]

**Implication**: [Specific, actionable recommendation]

**Confidence**: [High/Medium/Low] — [rationale]

For Cognitive Audit (Comprehensive)

## Cognitive Audit: [Screen/Flow Name]

### Working Memory Load
- Items requiring recall: [count]
- Cross-screen memory demands: [Y/N]
- Verdict: [Acceptable / High / Overloaded]

### Attention Demands
- Preattentive features for critical info: [Y/N]
- Competing attention demands: [list]
- Change blindness risk: [areas where changes may go unnoticed]

### Mental Model Alignment
- Expected user model: [what users likely think]
- System behavior: [what actually happens]
- Gap: [mismatch, if any]

### Predictive Laws
- Fitts's Law concerns: [target size/distance issues]
- Hick's Law concerns: [choice overload areas]

### Gulf Analysis
- Gulf of Execution: [unclear how to act?]
- Gulf of Evaluation: [unclear what happened?]

### Violations of Nielsen's Heuristics
| Heuristic | Violation | Severity |
|-----------|-----------|----------|
| ... | ... | 1-4 |

### Recommendations
1. [Highest priority fix]
2. [Second priority]
3. [Third priority]

For Explaining a Failure

## Failure Analysis: [What Went Wrong]

**Observed Behavior**: [What users did]

**Cognitive Explanation**: [Which principle explains this]

**Root Cause**: [Design element that caused it]

**Fix**: [Specific change]

Quick Reference: Predictive Laws

Quick Reference: Nielsen's 10 Heuristics

Quick Reference: Working Memory

• Capacity: ~4 chunks (not 7)
• Duration: ~20 seconds without rehearsal
• Test: Count items user must hold in mind across screens/steps

• "Remember this code and enter it on the next page"
• Multi-step forms without visible progress/state
• Complex comparisons requiring mental tracking

Quick Reference: Preattentive Features

• Color (hue, saturation)
• Size (length, area)
• Orientation (angle)
• Motion (flicker, direction)
• Shape (curvature, enclosure)

Cognitive Load Checklist

Common Violations → Principle

Process

1. Identify cognitive demands — What is the interface asking the user to perceive, remember, decide, or do?
2. Match to principles — Which cognitive constraints or laws apply?
3. Evaluate alignment — Does the design respect or violate these?
4. Recommend changes — Specific modifications grounded in the principle

Deep Reference Files

• PSYCHOLOGY.md — Perception, memory, attention, biases, emotion, motivation
• HCI-THEORY.md — Norman's model, predictive laws, error theory, research methods, heuristics

Primary Sources

• A Feature-Integration Theory of Attention.md — Treisman & Gelade on preattentive processing (informs: Quick Reference: Preattentive Features)
• Judgment under Uncertainty- Heuristics and Biases.md — Kahneman & Tversky on cognitive biases (informs: PSYCHOLOGY.md § Decision Making)

Key Researchers

• Don Norman: Affordances, gulfs, emotional design
• Daniel Kahneman: Dual process theory, heuristics and biases
• Stuart Card: GOMS, information foraging, Fitts's Law
• Anne Treisman: Feature integration, preattentive processing
• Jakob Nielsen: Usability heuristics, discount usability
• Ben Shneiderman: Direct manipulation, golden rules

Remember

• Cognitive science explains why design principles work
• Individual differences exist—design for variability, not averages
• Lab findings may not generalize (ecological validity matters)
• Theory informs but doesn't replace observing real users
• When in doubt, reduce cognitive load—users have less capacity than you think