Human-Computer Interaction: Human Information Processing, Mental Models, and Performance Evaluation

Comprehensive vocabulary flashcards covering human information processing, Norman's interaction framework, mental and conceptual models, Fitts's and Hick-Hyman predictive laws, GOMS/KLM, and usability evaluation metrics.

Human-Computer Interaction (HCI)

The study of how humans interact with computer systems and how those systems should be designed to support human goals, focusing fundamentally on the relationship between the human, the computer, and the interaction process.

Human Information-Processing System

A conceptual framework that models human interaction as a sequential flow of information: Sensory Input $\rightarrow$ Perception $\rightarrow$ Cognition $\rightarrow$ Decision Making $\rightarrow$ Motor Response.

Sensation

The low-level process through which physical sensory receptors (such as the eyes, ears, and skin) detect raw stimuli and physical signals from the environment.

Perception

The process of organizing, structuring, and interpreting sensory signals so that they become meaningful information (such as recognizing a red octagonal shape as a stop sign).

Cognition

The higher-level mental processes involved in processing, storing, and applying perceived information, including understanding, reasoning, memory, learning, pattern recognition, and problem-solving.

Decision Making

The cognitive stage where a user evaluates interpreted information against their goals and prior knowledge to select an intended course of action.

Motor Response

The physical execution of a decided action through bodily movement, such as moving a mouse cursor, tapping a touchscreen, typing on a keyboard, or speaking a voice command.

Human-Computer Interaction Cycle

A continuous feedback loop in which the user acts on the computer, the computer processes the action and outputs a response, and the user senses, interprets, and evaluates that response before initiating the next action.

Feedback

Information communicated by a system that reveals the outcome or state resulting from a user's action, thereby reducing uncertainty about whether and how the command was processed.

Immediate Feedback vs. Delayed Feedback

Immediate feedback appears promptly upon user action (e.g., a button visually depressing), whereas delayed feedback provides interim status information when processing takes time (e.g., a progress bar showing percent completion).

Norman's Seven Stages of Action

Donald Norman's interaction framework comprising: (1) Form the Goal, (2) Form the Intention, (3) Specify the Action, (4) Execute the Action, (5) Perceive the System State, (6) Interpret the System State, and (7) Evaluate the Outcome.

Gulf of Execution

The gap between what a user wants to achieve and how easy or difficult the system makes it to discover and perform the necessary physical actions.

Gulf of Evaluation

The gap between the physical state of the system and the user's ability to perceive, interpret, and determine whether their original goal was successfully accomplished.

Visibility

The core HCI principle stating that interface controls and functions must be noticeable and discoverable; hidden controls may effectively be treated as non-existent by users.

Affordance

The actual physical or functional properties of an object or interface element that determine what actions are possible (e.g., a button can be clicked, a text field can accept input).

Signifier

Any perceivable indicator, label, or visual cue that communicates where and how an action should be performed (e.g., a raised bevel indicating a clickable button or a magnifying glass signifying search).

Cognitive Model

An analytical representation of how users think, remember, perceive, reason, decide, and act when interacting with an interface.

Mental Model

A user's internal psychological understanding or belief about what a system does and how it operates, which may be simplified and technically inaccurate yet functional for task completion.

Designer's Model

The designer's conceptualization and intended specification of how the system operates, including its workflows, states, rules, and expected user pathways.

System Image

The physical, observable interface and behavior of the system (including visual layout, labels, documentation, error messages, and feedback) through which the user constructs their mental model.

Actual System

The underlying technical implementation of a product, including source code, database structures, APIs, server interactions, and hardware operations.

Mental Model Mismatch

A situation where a user's internal expectation of system behavior contradicts how the system actually operates, leading to user errors, hesitation, and frustration.

Familiar Metaphor

An interface design strategy that maps real-world physical concepts (such as desktops, folders, trash cans, or shopping carts) onto digital systems to leverage existing user knowledge.

Human Performance

The measurement of how efficiently, accurately, and effectively a person accomplishes tasks while interacting with a system, evaluated across multiple complementary dimensions.

Speed (Performance Dimension)

A dimension of human performance measuring how quickly a user completes a designated task or operation.

Accuracy (Performance Dimension)

A dimension of human performance evaluating whether a user executes a task correctly according to system and task requirements.

Error Rate (Performance Dimension)

A measure of how frequently users make mistakes during task completion, calculated as: $\text{Errors per Task} = \frac{\text{Total Errors}}{\text{Total Tasks}}$.

Effort (Performance Dimension)

The amount of physical exertion and cognitive workload required by a user to complete an interactive task.

Task Success

A binary or proportional performance metric indicating whether a user successfully reaches their intended end goal, regardless of completion duration.

Fitts's Law

A predictive model of human motor performance specifying that movement time ($T$) to select a target is a logarithmic function of target distance ($D$) and target width ($W$): $T = a + b \log_2\left(1 + \frac{D}{W}\right)$.

Index of Difficulty (Fitts's Law)

The logarithmic term in Fitts's Law, $\log_2\left(1 + \frac{D}{W}\right)$, which quantifies the motor precision difficulty of reaching a target based on its relative distance and size.

Hick–Hyman Law

A cognitive model predicting that decision-making time ($T$) increases logarithmically as the number of available options ($n$) increases: $T = a + b \times \log_2(n + 1)$.

GOMS Model

An analytical task analysis framework representing routine procedural user tasks through four components: Goals (desired outcomes), Operators (atomic actions), Methods (action sequences), and Selection rules (heuristics for choosing between methods).

Keystroke-Level Model (KLM)

A specialized, simplified form of GOMS that estimates the total execution time of routine tasks performed by experienced users by summing standard durations of atomic physical and mental operations.

Usability Metric

A quantifiable, objective or subjective measure used to assess how easily, effectively, and satisfactorily real users interact with an interface.

Task Completion Time

A quantitative usability metric measuring the total elapsed time required by a user to finish a defined task from initiation to completion.

Task Success Rate

The percentage of task attempts that successfully achieve the intended outcome, computed as: $\text{Task Success Rate} = \left(\frac{\text{Successful Attempts}}{\text{Total Attempts}}\right) \times 100$.

Efficiency (Usability)

A usability measure reflecting the relationship between successful task completion and the expenditure of user resources such as time, number of steps, and required assistance.

User Satisfaction

A subjective measure of how comfortable, pleased, and confident users feel while interacting with a system, typically assessed through rating scales, questionnaires, and interviews.

Perceived Workload

A subjective evaluation of the mental, physical, temporal, and cognitive effort a user feels was required to carry out a specific interaction or task.