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 fails, users blame themselves — but the fault is almost always in the design. Great design bridges the gap between what people want to do and what the product allows: it is discoverable (you can figure out what to do) and understandable (you can figure out what happened).

Scoring

Goal: 10/10. Score 2 points per satisfied row of the Quick Diagnostic (5 rows = discoverability, evaluation, error recovery, mapping, constraints). Bands: 9-10 = users act without instructions, understand every outcome, and recover from any error; 5-6 = one gulf or error path is broken; <=3 = users must consult a manual or routinely blame themselves. Report the current score and the diagnostic rows failing it.

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. Users ask: What can I do here? Which control do I use?

Bridge with: clear signifiers, natural mappings, constraints, familiar conceptual models.

Gulf of Evaluation

The gap between what the product did and what users understand happened. Users ask: What happened? Did it work? What state is the system in?

Bridge with: immediate visible feedback, clear system-state indicators, meaningful error messages, progress indicators.

Design goal: Make both gulfs as narrow as possible — action and understanding should be 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? Its five components — affordances, signifiers, constraints, mappings, feedback — are detailed below.

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

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

2. Affordances

Definition: The relationship between an object's properties and a user's capabilities that determines how the object could be used.

Key insight: Affordances exist whether or not they are perceived — what matters for design is perceived affordance.

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

Digital applications:

Element	Affordance	How to Signal
Button	Clicking/tapping	Raised, colored, shadow, hover state
Text field	Text input	Border, placeholder text, label
Scroll area	Scrolling	Scroll bar, fade at edge, partial content

Common failures: flat design erasing perceived affordances (button or label?), too-small touch targets, interactive and decorative elements that look identical.

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

3. Signifiers

Definition: Signals that communicate where the action should take place. Affordances determine what you CAN do; signifiers show you WHERE and HOW.

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

Digital signifiers:

Signifier	What It Communicates	Example
Cursor change + hover state	This is interactive	Pointer → hand on links; button color change
Icons + labels	Function of the element	Magnifying glass = search; "Submit", "Cancel"
Color + position	Status, category, hierarchy	Red = error, green = success; close button top-right

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

See: references/signifiers.md when deciding which signifier to add to an unclear control.

4. Mappings

Definition: The relationship between controls and their effects. Natural mapping means the spatial layout of controls matches the layout of what they control.

Mapping Quality	Example	Why It Works/Fails
Natural	Volume slider (up = louder)	Matches mental model
Poor	Light switch panel	No spatial correspondence to lights
Poor	Stovetop knobs in a row	Layout doesn't match burner positions

Digital principles: controls near what they affect, layout mirroring content, direction matching expectation (scroll down = content moves up), related controls grouped.

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 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.

Type	Mechanism	Example
Physical	Shape/size prevents wrong action	USB plug only fits one way
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 the last screw

Digital constraints:

Constraint	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
Forced sequence + undo	Steps in order; allow reversal	Wizard with locked steps; Gmail "Undo send"

Design rule: Every constraint you add is one less error the user can make — make wrong actions impossible rather than punishing them.

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 0.1s for direct manipulation), informative, appropriately dosed, and non-intrusive.

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

Digital feedback patterns:

Situation	Feedback Needed	Example
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."

Response times: 0.1s feels instantaneous; 1s is a noticeable delay (change cursor); 10s loses attention (show progress bar); over 10s users leave (show percentage, allow backgrounding).

Common failures: no feedback (did my click register?), delayed feedback (feels broken), unclear feedback, alert overload.

See: references/feedback.md when an action gives no clear result and you need the right feedback type and timing.

7. Conceptual Models

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

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: The user's model should match the design model; the system image is the only bridge. Matching models let users predict outcomes and recover from errors; mismatches breed confusion, self-blame, and support calls.

Example (thermostat): design model — set a temperature, the system maintains it; common user model — higher setting heats faster (wrong), so users crank it to 90°F.

Build correct models with: familiar metaphors (desktop, trash), visible system state, clear feedback, consistent behavior, progressive disclosure.

See: references/conceptual-models.md when the user's model diverges from how the product works. For fully worked teardowns (door handles, thermostats, digital products), see references/case-studies.md.

Human Error

Norman's key insight: there is no such thing as "human error" — only bad design. When someone errs, 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	Habit overrides intention	Drive to old office on autopilot	Interrupt 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	Reminders, history

Design for Error

Prevent: constraints that make errors impossible, undo/redo everywhere, confirmation for destructive actions, sensible defaults, forgiving input. Recover: clear error messages, never erase the user's work, partial saves, easy reset to a known good state.

Error message checklist:

• Says what went wrong (in human language)
• Says how to fix it
• Doesn't blame the user
• Preserves user's work
• Provides alternative path

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: support stages 1-3 with signifiers, mappings, and constraints; stage 4 with good affordances; stages 5-7 with feedback and visible state. Walk any interaction through each stage to find where users get stuck.

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

Human-Centered Design (HCD) Process

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

Two specifics that change how you run this loop: in Observation, don't ask users what they want (they don't know) — watch for workarounds and frustrations in real contexts. In Testing, use real users not designers — 5 reveal ~85% of problems, so observe behavior over opinions and iterate.

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

Further Reading

For the complete framework:

• "The Design of Everyday Things" by Don Norman (Revised & Expanded Edition, 2013)
• "Emotional Design" by Don Norman (design and emotion)

About the Author

Don Norman, PhD is co-founder of the Nielsen Norman Group, director of The Design Lab at UC San Diego, and a former VP of Advanced Technology at Apple, where he coined the term "user experience." The Design of Everyday Things (1988, revised 2013) is widely considered the most influential design book ever written and is required reading in design programs worldwide.