Design of Everyday Things Framework

Foundational design principles for creating products that are intuitive, discoverable, and understandable. The "bible of UX" — applicable to physical products, software, and any human-designed system.

Core Principle

Good design is actually a lot harder to notice than poor design, in part because good designs fit our needs so well that the design is invisible. When something works well, we take it for granted. When it fails, we blame ourselves — but the fault is almost always in the design.

The foundation: Design must bridge the gap between what people want to do and what the product allows them to do. The best designs are discoverable (you can figure out what to do) and understandable (you can figure out what happened).

Scoring

Goal: 10/10. When reviewing or creating designs, rate 0-10 based on discoverability, understandability, and error prevention. A 10/10 means users can figure out what to do without instructions, understand what happened, and recover from errors easily. Always provide current score and improvements to reach 10/10.

The Two Gulfs

Every interaction with a product requires bridging two gulfs:

USER                                    PRODUCT
  │                                        │
  ├──── Gulf of Execution ────────────────→│
  │     "How do I do what I want?"         │
  │                                        │
  │←──── Gulf of Evaluation ──────────────┤
  │     "What happened? Did it work?"      │

Gulf of Execution

The gap between what users want to do and what the product lets them do.

Questions users ask:

What can I do here?
How do I do it?
Which control do I use?
How do I operate this control?

Bridging strategies:

Clear signifiers showing what's possible
Natural mappings between controls and outcomes
Constraints preventing wrong actions
Familiar conceptual models

Gulf of Evaluation

The gap between what the product did and what users understand happened.

Questions users ask:

What happened?
Did it work?
Is this what I wanted?
What state is the system in now?

Bridging strategies:

Immediate, visible feedback
Clear system state indicators
Meaningful error messages
Progress indicators

Design goal: Make both gulfs as narrow as possible. The ideal design requires zero bridging — action and understanding are immediate.

See: references/two-gulfs.md for gulf analysis exercises.

Seven Fundamental Design Principles

1. Discoverability

Definition: Can users figure out what actions are possible and how to perform them?

Five components of discoverability:

Affordances
Signifiers
Constraints
Mappings
Feedback

(Each detailed below)

Test: Put a new user in front of your product. Can they figure out what to do within 10 seconds? If not, discoverability is broken.

Anti-pattern: "The user manual explains it." If users need a manual, the design failed.

2. Affordances

Definition: The relationship between the properties of an object and the capabilities of the agent (user) that determine how the object could be used.

Key insight: Affordances exist whether or not they are perceived. A door affords pushing whether or not you know to push it. What matters is perceived affordance.

Types:

Type	Definition	Example
Real affordance	Physical capability exists	A button affords pressing
Perceived affordance	User believes capability exists	A raised area looks clickable
Hidden affordance	Capability exists but isn't obvious	Right-click context menu
False affordance	Appears to afford action but doesn't	A decorative element that looks clickable
Anti-affordance	Prevents action	A barrier that blocks movement

Digital applications:

Element	Affordance	How to Signal
Button	Affords clicking/tapping	Raised, colored, shadow, hover state
Text field	Affords text input	Border, placeholder text, label
Link	Affords navigation	Color, underline, cursor change
Slider	Affords dragging	Handle, track, visual range
Scroll area	Affords scrolling	Scroll bar, fade at edge, partial content

Common failures:

Flat design removes perceived affordances (is it a button or a label?)
Touch targets that are too small (fat finger problem)
No visual distinction between interactive and decorative elements

See: references/affordances.md for affordance design patterns.

3. Signifiers

Definition: Signals that communicate where the action should take place.

Key insight: Affordances determine what's possible. Signifiers communicate where and how.

If affordances are what you CAN do, signifiers show you HOW to do it.

Types:

Type	Definition	Example
Deliberate signifier	Designed to communicate	"Push" label on door, placeholder text
Accidental signifier	Unintentional but informative	Worn path in grass (people walk here)
Social signifier	Other people's behavior	Line of people indicates entrance

Digital signifiers:

Signifier	What It Communicates	Example
Cursor change	This is interactive	Pointer → hand on links
Hover state	This responds to interaction	Button color change on hover
Placeholder text	What to type here	"Enter your email..."
Icons	Function of the element	Magnifying glass = search
Labels	What this control does	"Submit", "Cancel", "Next"
Color	Status or category	Red = error, green = success
Position	Relationship and hierarchy	Close button in top-right corner

Design rule: When in doubt, add a signifier. It's better to over-communicate than to leave users guessing.

See: references/signifiers.md for signifier patterns and examples.

4. Mappings

Definition: The relationship between controls and their effects.

Natural mapping: When the spatial layout of controls matches the layout of the thing being controlled.

Examples:

Mapping Quality	Example	Why It Works/Fails
Natural	Steering wheel turns car direction	Direct spatial correspondence
Natural	Volume slider (up = louder)	Matches mental model
Poor	Light switch panel (which switch = which light?)	No spatial correspondence
Poor	Stovetop controls in a row (which knob = which burner?)	Layout doesn't match

Digital mapping principles:

Controls should be near what they affect
Layout of controls should mirror layout of content
Direction of action should match expectation (scroll down = content moves up)
Grouping related controls together

Mapping techniques:

Technique	How It Works	Example
Proximity	Control near target	Edit button next to content
Spatial	Layout mirrors real world	Map controls match compass directions
Cultural	Follows conventions	Red = stop/danger, green = go/safe
Sequential	Follows natural order	Steps 1, 2, 3 from left to right (or top to bottom)

See: references/mappings.md for mapping analysis exercises.

5. Constraints

Definition: Limiting the possible actions to prevent errors.

Four types of constraints:

Type	Mechanism	Example
Physical	Shape/size prevents wrong action	USB plug only fits one way (USB-C both ways)
Cultural	Social norms guide behavior	Red means stop, green means go
Semantic	Meaning restricts options	A rearview mirror only makes sense facing backward
Logical	Logic limits choices	Only one hole left for last screw (process of elimination)

Digital constraints:

Constraint Type	Implementation	Example
Input validation	Restrict what can be entered	Date picker vs. free text
Disabled states	Gray out unavailable options	"Submit" disabled until form valid
Progressive disclosure	Show options only when relevant	Payment fields after selecting "Buy"
Forced sequence	Steps must be completed in order	Wizard/stepper with locked steps
Undo/redo	Allow reversal	Gmail "Undo send"

The power of constraints: Every constraint you add is one less error the user can make.

Design rule: Make it impossible to do the wrong thing, rather than punishing users for doing the wrong thing.

See: references/constraints.md for constraint design patterns.

6. Feedback

Definition: Communicating the results of an action back to the user.

Feedback must be:

Immediate: Within 0.1 seconds for direct manipulation
Informative: Tells user what happened and current state
Appropriate: Not too much (annoying) or too little (confusing)
Non-intrusive: Doesn't block the user's workflow

Types of feedback:

Type	When to Use	Example
Visual	Most actions	Button press animation, color change, checkmark
Auditory	Important events, confirmations	Success chime, error sound, notification
Haptic	Touch devices, confirmation	Vibration on key press, force feedback
Progress	Long operations	Progress bar, spinner, skeleton screen

Digital feedback patterns:

Situation	Feedback Needed	Example
Button click	Visual state change	Button depresses, color changes
Form submission	Success/error message	"Saved!" toast or inline error
Loading	Progress indicator	Spinner, skeleton screen, percentage
Error	What went wrong + how to fix	"Invalid email. Please check format."
Hover	Interactive element indicator	Background color change, underline
Drag	Object follows cursor	Element moves with mouse

Common failures:

No feedback at all (did my click register?)
Delayed feedback (makes system feel broken)
Unclear feedback (something happened but what?)
Too much feedback (every action triggers alert)

Response time guidelines:

0.1s: Feels instantaneous (direct manipulation)
1.0s: Noticeable delay (show cursor change)
10s: Attention wanders (show progress bar)
10s: User leaves (show percentage, allow background)

See: references/feedback.md for feedback design patterns.

7. Conceptual Models

Definition: The user's mental model of how a product works.

Three models:

Model	Held By	Description
Design model	Designer	How the designer thinks it works
User's model	User	How the user thinks it works
System image	Product	What the product actually communicates

Goal: User's model should match the design model. The system image is the bridge.

When models match:

Users predict outcomes correctly
Users recover from errors easily
Users feel confident and in control

When models mismatch:

Users are confused and frustrated
Users blame themselves
Users give up or call support

Example: Thermostat

Design model: Set temperature, system maintains it
Common user model: Higher setting = faster heating (wrong!)
Result: Users crank thermostat to 90°F hoping for faster warmth

Building correct conceptual models:

Use familiar metaphors (desktop, folder, trash)
Make system state visible
Provide clear feedback
Use consistent behavior (same action = same result)
Progressive disclosure (simple model first, details available)

See: references/conceptual-models.md for model design frameworks.

Human Error

Norman's key insight: There is no such thing as "human error." There is only bad design.

When someone makes an error, look for the design flaw, not the person's flaw.

Types of Errors

Slips: Correct intention, wrong action

Slip Type	Cause	Example	Design Fix
Action slip	Wrong action on right target	Click "Delete" instead of "Edit"	Separate destructive actions
Memory lapse	Forget step in sequence	Forget attachment after writing "attached"	Gmail's attachment reminder
Mode error	Right action, wrong mode	Type in caps lock	Show mode state clearly
Capture error	Familiar action overrides intended	Drive to old office on autopilot	Interruptions at decision points

Mistakes: Wrong intention, executed correctly

Mistake Type	Cause	Example	Design Fix
Rule-based	Apply wrong rule	Use formula for wrong situation	Provide context, confirm
Knowledge-based	Incomplete/wrong mental model	Misunderstand how system works	Better conceptual model
Memory lapse	Forget goal or plan	Forget why you opened the fridge	Provide reminders, history

Design for Error

Error prevention:

Constraints that make errors impossible
Undo/redo for all actions
Confirmation for destructive actions
Sensible defaults
Forgiving input (accept variations)

Error recovery:

Clear error messages (what happened + how to fix)
Don't erase user's work on error
Allow partial saves
Easy reset to known good state

Error message checklist:

See: references/human-error.md for error prevention patterns.

The Seven Stages of Action

Norman's model for how humans interact with products:

1. GOAL      → "I want to adjust the temperature"
2. PLAN      → "I'll use the thermostat"
3. SPECIFY   → "I'll press the up arrow"
4. PERFORM   → (presses button)
   ─── Gulf of Execution ───
5. PERCEIVE  → (sees display change)
6. INTERPRET → "The number went up"
7. COMPARE   → "Is this what I wanted?"
   ─── Gulf of Evaluation ───

Design implications:

Stages 1-3 (execution): Support with clear signifiers, mappings, constraints
Stage 4 (action): Support with good affordances
Stages 5-7 (evaluation): Support with clear feedback, system state

Use as evaluation tool: Walk through each stage for any interaction. Where does the user get stuck?

See: references/seven-stages.md for stage-by-stage analysis.

Human-Centered Design (HCD) Process

Norman's design process:

Observation → Idea Generation → Prototyping → Testing → (iterate)

1. Observation

Watch real users in real contexts
Don't ask what they want (they don't know)
Look for workarounds, frustrations, adaptations
Focus on activities, not individual tasks

2. Idea Generation

Generate many ideas (diverge before converge)
Don't criticize during ideation
Build on others' ideas
Defer judgment

3. Prototyping

Quick, cheap, disposable
Test concepts, not polish
Paper prototypes for early ideas
Interactive prototypes for validation

4. Testing

Test with real users (not designers)
5 users reveal 85% of problems
Observe behavior, not just opinions
Iterate based on findings

Key principle: The design process is iterative. You'll go through multiple cycles, each time refining the design based on what you learn.

Common Mistakes

Mistake	Why It Fails	Fix
No signifiers	Users can't find features	Add visual cues for every interactive element
No feedback	Users don't know if action worked	Respond to every action within 0.1s
Blaming users	Ignores design flaws	Look for design cause of every "user error"
Feature creep	Complexity overwhelms	Apply constraints, progressive disclosure
Inconsistency	Breaks conceptual model	Same action = same result everywhere
Ignoring context	Designed for ideal conditions	Observe real usage environments

Quick Diagnostic

Audit any design:

Question	If No	Action
Can users figure out what to do?	Poor discoverability	Add signifiers, improve affordances
Do users understand what happened?	Gulf of evaluation too wide	Add feedback, show system state
Can users recover from errors?	No error tolerance	Add undo, confirmation, clear messages
Does the control layout match the output?	Poor mapping	Reorganize controls to match spatial layout
Are impossible/irrelevant options hidden?	Missing constraints	Disable, hide, or remove invalid options

Reference Files

two-gulfs.md: Gulf analysis exercises, bridging strategies
affordances.md: Affordance types, design patterns
signifiers.md: Signifier patterns, examples, best practices
mappings.md: Natural mapping analysis, spatial layout
constraints.md: Constraint types, digital implementations
feedback.md: Feedback patterns, timing, modality
conceptual-models.md: Model design, metaphors, mental models
human-error.md: Error types, prevention, recovery
seven-stages.md: Stage analysis, evaluation tool
case-studies.md: Door handles, thermostats, digital products

About the Author

Don Norman, PhD is co-founder of the Nielsen Norman Group and director of The Design Lab at UC San Diego. He coined the term "user experience" while at Apple in the 1990s. The Design of Everyday Things (originally published in 1988 as "The Psychology of Everyday Things") is considered the most influential design book ever written and is required reading in virtually every design program worldwide. Norman has served as VP of Advanced Technology at Apple and has been a professor at Northwestern, UC San Diego, and KAIST (Korea).

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