design-everyday-things

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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:

• 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:

• 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

Further Reading

This skill is based on Don Norman's foundational design principles. 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 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).