Interaction

1
Interaction

• Interaction concerns
• how the user communicates with the system,
• how the system responds
• Interaction is a key differences between
  computers and other artefacts
• Consider communication between people
• Different styles
• giving orders
• consolation
• telling off.
• Throw in a few artefacts, devices e.g., phones,
  letters.
• Interaction devices and styles are not inherently
  superior to others
• As with many issues in HCI will represent a
  trade-off
• Device.
• Cost.
• Context.

2
Input/Output devices

• Input-
• Keyboard, including chord
• Speech
• Handwriting
• Scanner
• Mouse,Trackball, Joystick
• Touch screen
• Light pen
• Digitizing tablet
• Touchpad
• Eyegaze
• Gesture
• Head Mounted Display
• Output-
• Screens text, images, 3D images
• Audio - sound, voice

3
Interaction Styles

• 3 categories, eight styles
• Key-modal
• Menu-based interaction
• Question-and-answer
• Function-key interaction
• Voice-based
• Direct Manipulation
• Graphical direct manipulation
• Forms fill-in
• Linguistic
• Command-line interaction
• Text-based natural language

4
Interaction Styles

• Direct Manipulation
• Objects displayed on screen
• Actions are applicable to the objects
• User can manipulate each independently
• Less constraints
• Examples include
• Typical desktop
• Spreadsheets

5
Graphical Direct Manipulation

• Direct manipulation
• From batch input we have moved to highly
  interactive means of communication such as direct
  manipulation (DM), and VR.
• In these contexts the user is constantly
  providing instruction and receiving feedback on
  the status of those instructions.
• Rapid feedback is a fundamental feature of DM.
• Shneiderman coined the phrase in 1982 and
  describes its features as
• visibility of the objects of interest
• incremental action at the interface with rapid
  feedback
• reversibility of all actions, to allow
  exploration without penalty
• syntactic correctness of all actions, so that
  every user action is a legal operation
• replacement of complex command languages with
  actions to manipulate directly the visible
  objects.
• First commercially successful DM UI developed by
  Macintosh.
• Pre-dated by Xerox Star.

6
Interaction Styles

• How many user interfaces blend styles
• Word uses function keys
• Speech input is becoming more common.
• Windowing systems use menus.
• Also applications within applications.
• E.g., web based applications.
• Design constraints. Fit to task
• E.g., walk up and use.
• Low bandwidth display, e.g., command line.
• Cognitive Considerations

7
Model of interaction.

• Traditionally models in cognitive science.
• Norman (1986) developed a theory of cognitive
  action
• Can be used to approximate stages of cognitive
  activity when interacting with the environment. a
  seven stage cycle of action
• Establishing the goal to be achieved
• Forming the intention to achieve a goal
• Specifying action sequence(s)
• Executing the action sequence(s)
• Perceiving the state of the system
• Interpreting the state
• Evaluation of system state against respect to
  goals and intentions.

8
Gulfs

• Gulf of execution
• Knowing what you want to do.
• Knowing how to do it.
• Intention generation.
• Action specification.
• Interface mechanism.
• Gulf of evaluation.
• Comparison of goals with the state of the system
  or environment.
• Interface display.
• Interpretation.
• Evaluation.

9
The cycle
10
Supplementary notesPrinciples

• Gould and Lewis (1985)
• Early and continual Focus on Users and Tasks.
• close commitment to understanding what users do
  in the course of their task, role, and job
  performance.
• Integrated Design.
• greater communication between designers, human
  factors staff, technical writers etc.
• not a compartmentalisation of roles within
  development.
• For human factors staff it entails becoming more
  involved in the design process rather than simply
  assessing completed systems.
• HF staff should develop a deeper understanding of
  the constraints that developers face.
• For designers it entails a willingness to accept
  human factors input at all stages and to attempt
  to understand their concerns and motivations.

11
Principles, Dix

• Three principles
• Learnability
• the ease with which new users can begin effective
  interaction and achieve maximal performance
• Flexibility
• the multiplicity of ways the user and system
  exchange info.
• Robustness
• the level of support provided the user in
  determining successful achievement and assessment
  of goals.

12
Learnability

• Predictability
• determining effect of future actions based on
  past interaction history
• Synthesizability
• assessing the effect of past actions
• immediate vs. eventual honesty
• Familiarity
• how prior knowledge applies to new system
• guessability affordance
• Generalizability
• extending specific interaction knowledge to new
  situations
• Consistency
• likeness in input/output behaviour arising from
  similar situations or task objectives

13
Flexibility

• Dialogue initiative
• freedom from system imposed constraints on input
  dialogue
• system vs. user pre-emptiveness
• Multithreading
• ability of system to support user interaction for
  more than one task at a time
• concurrent vs. interleaving multimodality
• Task migratability
• passing responsibility for task execution between
  user and system
• Substitutivity
• allowing equivalent values of input and output to
  be substituted for each other
• representation multiplicity equal opportunity
• Customizability
• modifiability of the user interface by user
  (adaptability) or system (adaptivity)

14
Robustness

• Observability
• ability of user to evaluate the internal state of
  the system from its perceivable representation
• browsability defaults reachability
  persistence operation visibility
• Recoverability
• ability of user to take corrective action once an
  error has been recognized
• reachability forward/backward recovery
  commensurate effort
• Responsiveness
• how the user perceives the rate of communication
  with the system
• Stability
• Task conformance
• degree to which system services support all of
  the user's tasks
• task completeness task adequacy

15
Heuristics, Guidelines and Principles

• Heuristics
• Often useful.
• Solve a specific problem.
• Symptomatic of a craft based approach to design.
• Try something, if it works use again.
• If it doesnt discard or reformulate.
• Example.
• To ensure that information in the computer is
  what the user thinks it is, try using only one
  mode.

16
Heuristics, Guidelines and Principles

• Guidelines.
• Serve as normative procedure for designing
  aspects of the restricted interface elements.
• Newman and Lamming (1995) see them as packaged
  research
• Guidelines cannot guarantee their application
  will results in increased performance.
• Entails that we still have perform usability
  testing.

17
Heuristics, Guidelines and Principles

• Principles should have
• Theoretical basis
• Predictive
• Prescriptive
• Validated
• Scoped
• Relevant