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HCI: Mental Models


Mental models can furnish a problem space - a mental structure of possible ... Models can be derived from perception, or from language or imagination. ... – PowerPoint PPT presentation

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Title: HCI: Mental Models

HCI Mental Models
  • Sang Won Lee
  • Jessica SheffieldMichael Stryker
  • October 5, 2006

Chapters 5 and 6
  • Notational Systems--The Cognitive Dimensions of
    Notations Framework, by Alan Blackwell and Thomas
  • Users Mental Models The Very Ideas, by Stephen
    J. Payne

Notational Systems
  • Support the activity of designers based on an
    understanding of the process of design
  • Cognitive Dimensions notations framework
  • Describes necessary (though not sufficient)
    conditions for usability
  • Derives usability predictions from the structural
    properties of a notation, the properties and
    resources of an environment, and the type of

  • To offer a comprehensible, broad-brush evaluation
  • To use terms that were readily comprehended by
  • To be applicable not just to interactive devices,
    but also to paper-based notations and other
    noninteractive information systems
  • To be theoretically coherent
  • To distinguish between different types of user

Cognitive Dimensions framework
  • Set of discussion tools for use by designers and
    people evaluating designs to improve the quality
    of discussion
  • Better terms with which to think about issues and
    discuss them
  • Reminder of issues to be discussed
  • Effective discussion tools include
  • Shared vocabulary
  • Standard examples
  • Trade-offs

Components of Notational Systems
  • Interaction language or notation
  • Environment for editing the notation
  • Medium of interaction
  • Subdevices
  • Helper devices (offer a new notational view)
  • Redefinition devices (allow the main notation to
    be changed)

CDs framework
  • Are the users intended activities adequately
    supported by the structure of the information
  • If not, what design maneuver would fix it, and
    what trade-offs would be entailed?
  • Evaluation
  • Classify intended activities
  • Analyze cognitive dimensions
  • Decide whether the requirements of the activities
    are met

Notation-use activity
  • Incrementation
  • Transcription
  • Modification
  • Exploratory design
  • Searching
  • Exploratory understanding

Notational Dimensions
  • Viscosity resistance to change
  • Visibility ability to view components easily
  • Premature commitment constraints on the order of
    doing things
  • Hidden dependencies important links between
    entities are not visible
  • Role-expressiveness the purpose of an entity is
    readily inferred

Notational Dimensions
  • Error-proneness the notation invites mistakes
    and the system gives little protection
  • Abstraction types and availability of
    abstraction mechanisms
  • Secondary notation extra information in means
    other than formal syntax
  • Closeness of mapping closeness of representation
    to domain

Notational Dimensions
  • Consistency similar semantics are expressed in
    similar syntactic forms
  • Diffuseness verbosity of language
  • Hard mental operations high demand on cognitive
  • Provisionality degree of commitment to actions
    or marks
  • Progressive evaluation work-to-date can be
    checked at any time

Case Study
  • Compared textual (BASIC) and box-and-wire
    (LabVIEW) rocket trajectory programs
  • Viscosity
  • Hidden dependencies
  • Premature commitment
  • Commitment to layout
  • Commitment to connections
  • Commitment to choice of construct
  • Abstraction
  • Secondary notation
  • Visibility and juxtaposability

Current Status
  • Dissemination
  • Clarification and formalization
  • Coverage
  • Analysis tools
  • Beyond CDs misfit analysis

(No Transcript)
Users Mental Models
  • Mental models as
  • Topic important and still under-researched
    aspect of the cognitive program
  • Theory offers important insights into discourse
    comprehension and inference

Scientific foundations
  • Idea 1 Mental content vs. cognitive architecture
    (mental models as theories)
  • It is important to try to systematically
    investigate what people believe to be true about
    particular domains (such as interactive devices).
  • Emphasis on mental content over mental structure
  • Example students models of ATMs

Scientific foundations
  • Idea 2 Models vs. methods (mental models as
    problem spaces)
  • Mental models can furnish a problem space - a
    mental structure of possible states of the world
    that the user can search in order to plan their
  • Automatic (rule-based) versus controlled
    (skill-based) behavior
  • Examples Reverse Polish Notation (RPN)

Scientific foundations
  • Idea 3 Models vs. descriptions (mental models as
  • Mental models might in some sense share the
    structure of the physical world that they
    represent (analog representation)
  • Example The spoon is to the left of the fork
    and The knife is to the left of the spoon
    knife spoon fork

Scientific foundations
  • Idea 4 Models of representations (mental models
    can be derived from language, perception, or
  • Models can be derived from perception, or from
    language or imagination.
  • Text comprehension readers (or listeners) first
    form representations of the text itself and then
    compute a mental model of the meaning of the text
  • The model represents the situation described by
    the language, rather than the language itself

Detailed description
  • Idea 5 Mental representations of
    representational artifacts
  • Yoked state space (YSS) text is a
    representational artifact, and to use it one
    needs a mental representation of the structure of
    the text, the situation described by the text,
    and the mapping between the two
  • Goal space
  • Device space
  • Example Text-editing on a word processor

Detailed description
  • Idea 6 Mental models as computationally
    equivalent to external representations
  • Task-relative versions of informational and
    computational equivalence

Case study
  • Yoked state spaces analysis of calendar design
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