Book - The Design of Everyday Things

The Design of Everyday Things by Don Norman — Notes (in progress)

Discoverability — Is it possible to figure out what actions are possible and how to perform them?

Understanding — What does it mean? How is the product supposed to be used? What do all the different controls and settings mean?

Industrial Design — Optimizing function, value, and appearance for the user’s and manufacturer’s benefit

Interaction Design — Enhancing people’s understanding of what can be done, what is happening, and what has just occurred

Experience Design — Quality and enjoyment of the total user experience

Human-Centered Design (HCD) — A process that ensures design matches the needs and capabilities of the intended users.

The Three Mile Island nuclear disaster was caused by poor design.

Affordance

A relationship between the properties of an object and the capabilities of an agent that determines the space of possibilities for how the object could be used.

• Anti-affordance — the prevention of interaction
• To be effective, both affordances and anti-affordances must be perceivable
• Rooted in Gibsonian psychology (an ecological approach to perception)

Example: Scissors. The holes afford finger insertion (affordance), their relative sizes indicate which fingers go where (signifier/mapping), and fingers are the only logical thing that fits (constraint).

Signifier

Any mark, sound, or other perceivable indicator that communicates appropriate behavior to a person.

Example: A bookmark. As an intentional signifier it marks someone’s place; as an unintentional signifier it reveals how much of the book remains.

Mapping

A relationship between the elements of two sets of things (e.g., a set of light switches and the lights they control).

Natural mapping — uses grouping and proximity (cf. Gestalt psychology) to make relationships immediately understandable.

Feedback

Communicating the results of an action; the system letting a user know it is working on their request.

Feedback should be:

• Immediate and informative
• Planned and prioritized — unimportant feedback should be unobtrusive; important feedback should be obtrusive

Conceptual Model

A simplified explanation of how something works (e.g., file and folder icons on a computer).

• The same person may hold multiple, potentially conflicting mental models of the same object
• System image — the combined information available to a user (appearance, past experience, etc.) from which they form their conceptual model

Designer should bridge two “gulfs”:

Gulf of Execution — trying to figure out how an object operates. Bridge through signifiers, constraints, mapping, and a conceptual model.

Gulf of Evaluation — trying to figure out what happened as a result of their interaction with the object. Bridge through feedback and a conceptual model.

The Seven Stages of the Action Cycle

Goal
  │
  ├── EXECUTION
  │     ├── Plan    — "What are the possible action sequences?"
  │     ├── Specify — "What action can I do now?"
  │     └── Perform — "How do I do it?"
  │
  └── EVALUATION
        ├── Perceive  — "What happened?"
        ├── Interpret — "What does it mean?"
        └── Compare   — "Is it OK? Have I achieved my goal?"

• Most behavior involves multiple feedback loops — results of one activity direct the next; goals spawn subgoals; plans spawn subplans
• Goal-driven (top-down) — starts by establishing a new goal
• Event-driven (bottom-up) — starts by perceiving an event
• Opportunistic actions — take advantage of circumstances; less precise but require less mental effort

Root cause analysis — asking “why?” repeatedly until the fundamental cause of an action is reached.

Feedforward helps answer questions of execution; feedback helps answer questions of evaluation.

Declarative memory - Memory for facts; e.g. the name of the street you live on

Procedural memory - Memory for action; e.g. recalling which side your doorknob is on by mentally acting out opening the door

Overlearning — continued practice after initial mastery, resulting in performance that feels effortless and automatic.

The Three Levels of Mental Processing

1. Visceral

• Basic, subconscious protective mechanisms; makes quick good/bad, safe/dangerous judgements
• Tightly connected to the motor system
• For design: Style and aesthetics matter — immediate perception drives visceral response
• Action cycle stages: Perform, Perceive

2. Behavioral

• Largely subconscious learned skills triggered by pattern-matching
• For design: Every action is associated with an expectation that must be managed with feedback
• Action cycle stages: Specify, Interpret

3. Reflective

• Conscious cognition; deep and slow — often occurs after an event
• Evaluates circumstances, actions, and outcomes to assign value judgements
• For design: Reflective memories of an experience are often more important than the objective reality of it
• Action cycle stages: Plan, Compare

Recommended reading: Emotional Design (Norman)

• Cognition attempts to make sense of the world; emotion provides value judgements
• We craft narratives (attributing causes to events) to understand our experiences, then generalize these into models of how things behave — which are often erroneous
  • Example: The misconception that turning a thermostat to maximum heats/cools a room faster
• We tend to blame ourselves for failures with everyday objects — often incorrectly — leading to learned helplessness

On Errors & Feedback

• Humans err constantly; no system should be designed so that a single action can cause calamity
• Human tendency to repeat a failed action can be dangerous — hence “panic bars” on emergency exit doors
• Target feedback within 0.1 seconds of a user action (even if it’s just a progress indicator)
• Under-predict completion time — show the upper end of the estimated range
• Prefer guidance messages over error messages; assume partial correctness and move forward
• Accommodate the full variety of ways a user might complete a task

“The paradox of technology: the more functions a device has, the harder it is to learn — making it simultaneously more and less useful.”

The Seven Fundamental Principles of Design

1. Discoverability — It is possible to determine what actions are possible and the current state of the device.
2. Feedback — Full and continuous information about results and current state; after an action, the new state is easy to determine.
3. Conceptual Model — The design projects all information needed to build a good mental model, leading to understanding and a sense of control.
4. Affordances — The proper affordances exist to make desired actions possible.
5. Signifiers — Effective signifiers ensure discoverability and that feedback is well communicated and intelligible.
6. Mappings — The relationship between controls and actions follows principles of good mapping, enhanced through spatial layout and temporal contiguity.
7. Constraints — Physical, logical, semantic, and cultural constraints guide actions and ease interpretation.