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Human Computer Interaction

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4) The feedback is used to amend the initial design. ... Alice cried eagerly. ' You take some flour.' 'Where do you pick the flower? ... – PowerPoint PPT presentation

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Title: Human Computer Interaction


1
Human Computer Interaction
  • Jon Ivins
  • DMU

2
Overview
  • What is HCI?
  • Problems faced by designers
  • Cognitive issues
  • Definitions
  • Physical factors
  • Some guidelines

3
HCI Designers
  • 1) try to anticipate as many likely problems as
    possible.
  • 2) A prototype design is produced.
  • 3) Users are invited to try the prototype and
    comment on the efficiency of the design.
  • 4) The feedback is used to amend the initial
    design.
  • 5) The process is repeated until the users are
    completely satisfied.

4
Problems
  • Above is inefficient and expensive
  • a) if only a subset of users are involved, they
    can become used to the HCI and not identify
    difficulties that a new user may experience
  • b) how does the designer know when to stop the
    iteration?
  • Allied to point b) is
  • c) how do we measure user satisfaction?

5
A Definition and yet more issues
  • The engineering process of designing
    interactive computer systems so they are
    efficient, pleasing, easy to use and do what
    people want. Sutcliffe.
  • What are the core issues
  • Why bother about it anyway?
  • Are there any guidelines?

6
Core issues
  • What are the facets of a person which affects
    HCI?
  • How do we analyse what people do with computers
    and their interfaces?
  • What are the user needs?
  • How do we specify an interface?
  • How do we design an interface?
  • How do we evaluate an interface?
  • What is a good interface?
  • How do we ensure good quality for HCI on a
    consistent basis? Can we?

7
Why Bother with HCI?
  • Less user frustration
  • A lower number of errors
  • Greater productivity
  • Economy
  • Health and Safety issues e.g. stress
  • Poor HCI System failure and/or inefficiency
  • Poor HCI does not sell products

8
Human Information Processing
  • How is bread made?
  • I know that! Alice cried eagerly. You take
    some flour.
  • Where do you pick the flower? the White Queen
    asked. In a garden, or in the hedges?
  • Well it isnt picked at all, Alice explained,
    its ground.
  • How many acres of ground? said the White Queen.
  • Lewis Carroll - Through The Looking Glass

9
Human Short Term Memory
  • short retention time of around 200 ms
  • contents can be refreshed within 70 ms
  • capacity is 7 items /- 2 items
  • capacity can be increased by using tricks
  • there are two sub-systems one for language and
    one for visual-spatial data
  • STM for language tends to be LIFO based
  • Poor retention of visual detail
  • Retention best if images/words together.

10
HCI and STM
  • Minimise distraction during tasks and
    memorisation
  • Do not overload STM
  • Structure information
  • Images need to be accompanied by text.

11
Human Long Term memory
  • Infinite (?) capacity
  • Frequently used information can be retrieved very
    rapidly while less frequent items take longer to
    recall
  • Age slows down memory recall
  • It appears to be a two-stage process based upon
    recognition (usually started by cues) and recall
    (the actual retrieval).
  • It appears that there is a background processor
    to retrieve items as we can do other things while
    recalling information

12
  • Recalling one item often prompts the recall of
    related items
  • It is possible that there are two types of LTM
    associative ( for concepts) and analogue (for
    physical objects)

13
Sutcliffe recommends the following HCI guidelines
  • )Memorisation is helped by enriching the
    information during learning
  • )Reasoning and understanding what is being
    remembered helps retention
  • )structuring information helps categorical memory
  • )Use techniques like keywords as recall cues
  • )Visual images with text aid recall
  • )Consistency of association creates better
    contexts for memorisation and recall

14
Physical factors 1
  • The 5 senses
  • Which are important to HCI?
  • The Brain
  • 15 billion cells, each with 150 connections
  • complex
  • sensors appear to do pre-processing
  • pragmatic approach needed

15
Physical factors 2
  • The Eyes
  • 400-700nm
  • optimum performance in middle of range
  • brightness is subjective
  • contrast is based on luminance
  • C(Lmax-Lmin)/(Lmax Lmin)
  • Visual acuity (12 point at 0.5 m)
  • poor peripheral vision

16
  • Eyes characteristics lead to
  • only one image at a time
  • people cannot deal with detail in 2 simultaneous
    windows
  • movement alerts peripheral vision and, hence, the
    user
  • retina can detect edges easily
  • moving images attract attention
  • Icons must have clean edges and be simple

17
Interaction
  • depends upon the computer system being used,
  • the software being used and
  • the human user
  • Norman (1986) argues there are 2 gulfs
  • When the user is faced with what to do next - the
    interface should prompt the user
  • When the user evaluates an action they have
    performed - the interface should make the effects
    of user action explicit

18
Sutcliffe (1995) offers the following principles
  • Consistency - reduces learning and increases
    recognition
  • Compatibility - how well the HCI design matches
    the users expectations from previous experience
  • Predictability - HCI prompts user and suggest
    actions
  • Adaptability - The user should be in control and
    computer adapts to pace of work, skill level etc.
  • Economy and error prevention - self evident
  • User Control - linked to predictability but
    allows the user to backtrack and recover from
    errors e.g. the UNDO command
  • Structure - to reduce complexity and give order.
    Only relevant information is shown to the user.

19
References
  • Many good textbooks available in library
  • Best is Jenny Preece et al
  • Sutcliffe is also a good text
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