What is HCI

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What is HCI?

• The role of HCI is to enhance the quality of
  interaction between humans and computer systems
• We are especially concerned with the problems
  encountered by users while interacting with
  multiple channels of communication
• HCI involves input from other disciplines

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Other disciplines which contribute

• Cognitive science
• Cognitive psychology
• Sociology, Philosophy and Anthropology
• Artificial Intelligence
• Ergonomics and Human Factors
• Design
• Computing Science
• Linguistics

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of Multimedia Systems

• User Types and capabilities
• Mental Models
• Memory
• Navigation
• Training
• Ergonomics environment
• Prototyping

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1 User types

• Four main types of user
• Novice
• Casual
• Experienced
• Professional
• The above will be included in one of the
  following
• Discretionary
• Non-Discretionary

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2 Mental Models

• Guide the user on how to structure the
  interaction task
• Are built up through interaction
• Contain structural and functional models
• how it works
• knowing how to use it
• Precise model is built up through experience

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Feedback and observation

• Feedback helps the user to build up or confirm an
  existing model by presenting information about
  itself as it is used
• Public systems are usually placed where users can
  observe before trying it out
• Prime cause of errors is disagreement with user
  model and actual model

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3 Memory

• Short-term working storage
• Transient store of temporary data
• Rapid decay of information
• Half-life of about six seconds
• Limited (but variable) capacity
• Long-term knowledge
• Retrieval of structured data
• Slower than working storage

Dont expect users to remember much for
long Dont expect users to remember things quickly
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Use of Metaphors

• Meaningless information is more difficult to
  remember.
• Concepts are more difficult than objects to
  remember.
• Analogies, metaphors and icons are therefore
  better for to help explain the workings of a
  system.
• Meaning is taken more quickly and is easier to
  maintain in memory.

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Book-page Metaphor
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4 Navigation

• Problems of spatial disorientation
• Assessing how much information the system
  contains
• Distraction from goal directives
• Complexity in the interface

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Solutions to assist navigation

• Guided Tours
• History Lists
• Book marks
• Backtrack
• Overview Diagrams

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Navigation and interaction

• Explicit systems
• - Plain but all interaction is directly
  viewable
• Implicit (metaphor) systems
• - Advanced to look at, but all navigation
  and
• interaction needs to be hunted out by
  the user

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Passive applications

• Emphasis on simple linear progression
• e.g. forward and back (book-page structure)
• Press to move on, low cognitive load, little can
  go wrong
• Mainly sit back and watch auto- running on page
  load (media rich but little interaction)

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Highly interactive applications

• Non-linear exploration
• Diversity of actions on users part, user has to
  work. Interaction diversity leads to higher
  cognitive overhead
• Needs clear, selectable options

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User distractions

• There is always a danger that users may easily
  become side-tracked, or change direction due to
  new stimulation in a multimedia application. Too
  busy ?

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Follow Through
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5 Training

• Usability criteria
• how long does it take to learn
• the speed of performance
• what is the rate of errors
• how easy is the recovery
• subjective satisfaction
• how much is remembered
• how much is unused

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6 Ergonomics environment

• Health and safety requirements
• Task requirements
• Visual display
• Keyboard requirements
• Workstation layout and posture
• Lighting
• Room climate
• Noise
• Personal space

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7 Prototyping

• Interactive product design and construction is
  labour and time intensive -
• So you cannot afford many mistakes
• Prototyping as an iterative approach can be
  useful in managing blocks of work
• User centred design approach

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7 Prototyping

• Interactive product design and construction is
  labour and time intensive, mistakes are costly
• User centered design approach
• Tangible visible approach- depiction of intended
  system
• Helps to define user requirements at an early
  stage in development can include some interaction
• Can be used to elicit information from users
• Helps resolve uncertainty about whether it suits
  users needs
• Helps to verify design solutions

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User Feedback Design

• Early or Late?
• Early user feedback gives you time to incorporate
  changes
• Late user feedback is more precise, since the
  product is nearly ready
• Analytic or informal?
• Analysis of user feedback may be necessary
• Informal feedback may be all that is required

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Design rules in use

• The following slides show reported principles
  for user interface design as used in industry
• The information is split into
• Input/Output Dialogue
• Conceptual model General
• Idea generation

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Input/Output

• Minimise input movements
• Maximise input channels
• Be Visually attractive
• Use language carefully
• Maintain screen key consistency
• Use a highly visual interface

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Dialogue

• Use of menus and prompts
• Context-dependent messages
• User control
• Natural response time

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Conceptual model

• Use of analogy, metaphor
• Match user expectations, minimise surprises
• Start with user model, not the developer model
• Make examples concrete
• Novice-expert path

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General

• Easy to use, "user friendly"
• Make it as simple as possible (but no simpler)
• Follow standards wherever applicable
• The key is to understand the users needs and the
  users types of conceptual models

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Three different models

• When developing an interface, there are three
  different viewpoints
• The users conceptual model
• The programmer/developers model
• The interface/system designers model

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Types of models

• The users model may be unconsciously
  (intuitively) developed. An easy-to-use system
  should not impose any conscious modelling on the
  part of the user.
• The programmer and designer have consciously
  designed system models. Ease-of-use is still an
  issue, but not necessarily linked to intuition.

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The Users Conceptual Model

• Real-world experiences
• Tasks
• Processes
• Tools
• Results

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The Programmers Model

• Platform
• Operating System
• Development tools
• Practical User Interface Guidelines
• Hardware constraints
• Media limitations

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The Designers Model

• Users Conceptual Model
• Programmers Model
• User interface design principles
• User interface design guidelines

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The Users Model

• Developed through experience.
• Refined or redefined slowly.
• Transfer of expectations based on recognition of
  metaphor (e.g. Trashcan on Mac).
• Uncertainty, hesitation and frustration may
  result from mismatched metaphors.
• Model depends on education, training, previous
  exposure to machines.

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The Programmers Model

• Includes a thorough understanding of the
  underlying hardware and the library and operating
  system software.
• Model concentrates on the objects and
  relationships useful in implementing a product.
• The deeper technical levels must not be perceived
  by the user, so the programmer must be mindful of
  the design guidelines.

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The Designers Model

• Like an architect who must balance the
  requirements of the user and the builder, so the
  system designer must maintain multiple
  perspectives.
• Three main elements of the model are 136
• the look of the interface (visual
  representation)
• the feel of the interface (interaction
  techniques)
• the objects in the interface and their
  relationships