Human Factors Lecture Notes

Rich Halstead-Nussloch

8 April 1996

Chapters 3-6 Plus

Chapter 3 - Cognitive Frameworks

• HIP (Pg. 63)
  • Input or stimuli
  • Encoding
  • Comparison
  • Response Selection
  • Response Execution
  • Output
• Extending Attention & Memory (pg. 64)

Memory, HIP, and HCI

• Memory
  • Sensory store
  • STM
  • LTM
• HIP and HCI (Pg. 67)
  • Representation and mental models
  • Learning
  • Interface metaphors and conceptual models

Broadening the Cognitive Framework

• Human factors to human actors
• Real people in real situations, etc.
• Distributed cognition--working on teams.
  • Situational: Situation awareness
  • Information propagation
  • Breakdowns

Perception and Representation Chapter 4

• Visual perception - Cognitive Action
  • Constructivist--Perceptions are constructed:
    • Environmental information and sensory input
    • Stored information from memory
  • Ecological--Perceptions are "picked up" from environmental information

Context and Gestalt

• Context: Exercise 4.2, page 78
• Gestalt Laws:
  • Proximity -- Grouping
  • Similarity -- Grouping
  • Closure -- Form and figure vs. Background
  • Continuity -- Form and figure vs. Background
  • Symmetry -- Form and figure vs. Background

Ecological Approach

• Users are constantly engaged in actions to understand and deal with events over time.
• We bring in information from all senses.
• Affordances:
  • What objects have to make obvious how they are used, e.g., "Push" on a door.
  • Affordances can be more or less perceptually obvious.

Representation and Interface

• Constructivist and Gestalt approaches posit an "Internal Representation" in the user.
• GUI designers need to include critical cues in an interface to produce a correct internal representation.
• Understand perceptual depth (pg. 82-88)
• Understand graphical coding (pg. 88-96)

Attention and Memory
Chapter 5

• Focusing and guiding attention
  • Important -- Too much information available
  • User interface
    • Structure information for navigation, e.g. menus
    • Spatial and temporal cues, e.g., groups
    • Color, e.g., red for danger
    • Alerting, e.g., flashing

Automatic vs. Controlled Cognitive Processing

• Automatic--e.g., making a corner in a car
  • Fast
  • Demands minimal attention
  • Unavailable to consciousness
• Controlled--e.g., mental arithmetic
  • Relatively slow
  • Requires attention
  • Requires conscious control

Memory Constraints

• Levels of processing theory--Learning is positively related to meaningfulness:
  • Familiarity--How often seen
  • Imagery--Ability to evoke common images
• Meaningful
  • Interfaces, i.e., not UNIX
  • Icons

Meaningful Icons

• Context
• Task and Function see pg. 113
• Representational form
  • Resemblance
  • Exemplar
  • Symbolic
  • Arbitrary
• Underlying concept
• Best of both worlds

Recognition versus Recall--Overcoming Memory Constraints

• Recognition--Identifying or selecting an item from the environment or interface
• Recall--Remembering or generating a command or action sequence from what's inside the head
• Recognition is easier than recall
• For user interface design, there are trade-offs as in Table 5.2, page 119

Memory and Action

• External (visual) vs. internal (non-visual)
• Cognitive aids--External memory aids, e.g., checklists, notes
• Cognitive mnemonics--Internal memory aids, e.g., "Never eat soggy waffles."
• Novices--Make exploration cues visual
• Experts--Rich, internal knowledge of how to access and interpret information

Chapter 6 - Knowledge and Mental Models

• Forms of knowledge representation
  • Analogical, e.g., images
  • Propositional, e.g., statements
  • Distributed, e.g., networks
• Knowledge organization
  • Semantic networks, e.g., hierarchies of objects
  • Schemata, e.g., script for a restaurant

Mental Models

• A small-scale model of reality carried in an organism's head
• Structural--The composition of an object and/or how it works, e.g., subway map
• Functional--How to use an object, e.g., procedure or task description

Mental Models

• Value and utility
  • People learn rules or gist, not details
  • What is learned is vague, difficult to articulate
  • A mental model aids both designers and users
• Mental models in process control
  • Skill-based--Interaction norms
  • Rule-based--Process A resolves situation B
  • Knowledge-based--Conscious analysis to resolve unexpected situations