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Discoverability

The degree to which a person can determine what actions are possible and how to perform them.

Affordance

A relationship between the properties of an object and the capabilities of an agent that determines possible interactions.

Anti-affordance

A relationship that prevents or blocks an interaction (e.g., a glass wall blocking passage).

Signifier

A perceivable cue that communicates where or how an action should take place.

Feedback

Information that communicates the result of an action and the new state of the system.

Conceptual model

A simplified explanation of how a system works that helps people predict the effects of their actions.

System image

The information available to the user through the product, interface, documentation, signifiers, and behavior; how the designer communicates with the user.

Human-centered design

A design approach that begins with understanding people's needs, capabilities, and behavior, and iteratively develops solutions around them.

Gulf of execution

The gap between a person's goal and knowing what actions the system allows to achieve that goal.

Gulf of evaluation

The gap between the system's state and the person's ability to perceive, interpret, and determine whether the goal was achieved.

Mapping

The relationship between a control and the thing it affects.

Constraint

A limitation built into a design that reduces the chance of the wrong action being taken.

Goal

The outcome a person wants to accomplish.

Plan

The stage in which a person determines a general course of action to reach a goal.

Specify

The stage in which a person determines the specific action sequence needed to carry out a plan.

Perform

The stage in which the specified physical action is actually executed.

Perceive

The evaluation stage in which a person detects what happened in the world after an action.

Interpret

The evaluation stage in which a person makes sense of the perceived state.

Compare

The evaluation stage in which the interpreted outcome is compared with the original goal.

Seven stages of action

Goal, Plan, Specify, Perform, Perceive, Interpret, Compare.

Visceral level

The level of processing based on immediate sensory reaction — appearance, look, and feel of a product.

Behavioral level

The level of processing concerned with skilled use, performance, usability, and the experience of controlling a product.

Reflective level

The conscious level concerned with meaning, self-image, memory, interpretation, and the story a person tells about an experience.

Learned helplessness

A condition in which repeated failure leads people to believe they are incapable, so they may stop trying even when success is possible.

Positive psychology

An emphasis on positive emotional experience and human strengths, including how successful interactions support feelings of competence and control.

Norman door

A door whose identical handles on both sides give no clue whether to push or pull, illustrating a signifier/affordance mismatch.

Feedforward

Information given before an action that tells the user what actions are possible ("what can I do now?").

Six principles of interaction (Ch1)

Affordances, Signifiers, Constraints, Mappings, Feedback, Conceptual model.

What bridges the gulf of execution?

Signifiers, mappings, constraints, and conceptual models.

What bridges the gulf of evaluation?

Feedback and conceptual models.

Thermostat folk theory

Example showing users invent their own explanations when a system doesn't clearly explain itself.

Why examine design first, not the user?

Because repeated user failure usually reveals bad design, not incapable users — the central lesson of Chapter 1.