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like a parallel processor is waiting to hear your name ... Riding a bike. Driving a car. Cognitive tasks can be automatic. Reading ....and, and... – PowerPoint PPT presentation

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Title: HCI 5

HCI 5 6
  • Attention and memory
  • and
  • Knowledge and Models

The Cocktail Party Effect
  • Allows you to hear your name mentioned through
    the rumble of the crowd
  • Like being interrupt driven like a parallel
    processor is waiting to hear your name
  • Allows you to focus on one conversation above
    all others

Attention Two types
  • Focused attention
  • we choose which stream of information, among all
    the streams of information, to attend to.
  • Divided attention
  • carrying on one conversation while
    intermittently attending to other details
  • Skilled, expert behavior enables divided
  • Drive and talk on cell phone

Attention Additional properties
  • Voluntary
  • We decide to pay attention to something else
  • Involuntary
  • Some stimulus grabs our attention, forcing itself
    into our consciousness

Attention and HCI
  • Our attention has a bearing on how effectively we
    interact with the system
  • Can we attract the users attention to the
    salient parts of the interface?

Guiding attention
  • Structure guides attention
  • Structure information in the interface to make it
    easy to navigate and find the salient parts
  • Not too much, not too little
  • Group or order into meaningful parts
  • Using Gestalt principles of proximity,
    similarity, closure, continuity, symmetry

Guiding attention Other approaches
  • Spatial cues
  • Temporal cues
  • Color
  • Alerting techniques and other highly annoying,
    distracting junk like flashing, reverse video,
    beeps, clicks, whirrs, alarms...

Structure Methods in general
  • Important information should be displayed in a
    prominent place
  • Less important information should be displayed in
    a less prominent place
  • Rarely needed information should be available on

Multitasking Handling interruptions
  • Activity in an aircraft cockpit is different than
    everyday activities it is the domain of highly
    skilled, highly motivated, expert users and
    highly constrains behavior.
  • Activities are hierarchically structured into
    primary and secondary activities
  • The task being attended to is foregrounded
    while the others are said to be suspended

Multitasking difficulties
  • Where was I before I was interrupted?
  • Results in missed steps or repeated steps
  • Most frequently occurs when the interrupted
    activity is one that is automated like when you
    are driving a familiar stretch of road, start
    thinking about something else and suddenly
    realize that you dont know if youve passed a
    certain landmark

What was I cooking?
  • Quan Tran
  • Everyday task
  • Interruptions frequent
  • Ingredients similar in appearance
  • How do you bring someone back to the right place
    in the recipe?

Reminder strategies
  • Cognitive aids
  • Lists
  • Post-its
  • Knots
  • Chairs in the way
  • External representations that gain attention
  • Normans Knowledge in the world

Reminder difficulties
  • Norman Reminders consist of signal and
  • Many tasks are not necessarily sequential in
    nature they dont have a prescribed, required

Automatic processes
  • Highly practiced tasks become automatic
  • Fast
  • Minimal attention required
  • Unavailable to consciousness!
  • Sensory motor tasks can be automatic
  • Riding a bike
  • Driving a car
  • Cognitive tasks can be automatic
  • Reading .and, and.

Stroop effect
  • One automatic cognitive process (reading the
    word) conflicts with another cognitive process
    (perceiving the color)

Automatic vs controlled processes
  • Controlled processes
  • Affected by the brains limited capacity
  • Require attention
  • Require conscious control
  • Automatic processes
  • Fast
  • Unaffected by the brains limited capacity
  • Do not require attention
  • Unavailable to consciousness!
  • VERY difficult to change once learned!
  • Once changed may revert in times of stress!

  • Meaningfulness affects the ability to remember
  • Meaningfulness attributes
  • Familiarity frequency of occurrence
  • Associated imagery ability of the word to
    illicit images

Meaningfulness guideline
  • Consider context, culture and the user
  • An application within a specific design culture
    should be cast in terms of the language of that

Icon Meaningfulness
  • Context of use
  • Provides a constraint
  • Task it is used in
  • Provides a constraint
  • Surface form of representation
  • Underlying concept that is represented

Icon Representational form
  • Concrete
  • It looks like what it is
  • Abstract
  • It maps to some memorized meaning arrows, lines
  • Arrows and line represent some dynamic or action
  • Combination is most memorable once learned

Representational form mapping
  • Resemblance an analogous image.
  • Exemplar selected as a typical example
  • Subject to context
  • Symbolic the thing referred to is a higher level
    abstraction (cracked wine glass)
  • Arbitrary bear no resemblance to the underlying

Recognition vs recall
  • Recognition Knowledge in the world
  • Recall Knowledge in the head
  • Tradeoffs between them (Norman)
  • Retrievability
  • Learning
  • Efficiency of use
  • Ease of use at first encounter
  • Aesthetics

Proof of use ofKnowledge in the world
  • Skilled interface users cannot recite the options
    available they must search for them!
  • Skilled UNIX users can execute a series of
    commands but cannot provide a list of what to do

Types of memory
  • Episodic memory
  • Storage of autobiographical experiences, objects,
    images (others) that were personally encountered.
  • Semantic memory
  • General knowledge built up through a lifetime

One of the BIG questions
  • How is knowledge held in memory?
  • The way it is stored affects
  • How it is accessed
  • How long it takes to access it
  • The way in which it can be used
  • What can be reasoned about
  • The effectiveness of the reasoning
  • (others)

Knowledge representations
  • Analogical
  • A symbolic representation
  • Picture-like images
  • Propositional
  • A symbolic representation
  • Abstract, language-like statements
  • Distributed
  • Considered to be sub-symbolic
  • Networks of nodes
  • Knowledge is implicit in the connections between

Imagists vs propositionalists
  • Imagists believe that images play an important
    (but probably not exclusive) role in human
  • Propositionalists believe that images are a
    by-product, propositions underlie and are really
    responsible for thinking

Imagists vs propositionalistsMental rotations
  • Imagists believe that the degrees of rotation of
    an image, not the image complexity, determines
    the amount of time it takes to do the rotation
  • Propositionalists believe that the image
    complexity, not the degrees of rotation,
    determines the amount of time it takes to do the
  • Research results? Controversial and unclear.

And now for something completely different The
  • Yeh, yeh, sure, sure the truth is that both
    images and propositions are important to human
  • But underlying images and propositions is a
    neural network of nodes
  • Images and propositions are emergent properties
    of that network.

Why worry about this?
  • If you know the way that knowledge is
    represented, organized and retrieved then perhaps
    it is possible to develop interfaces that
    facilitate thinking and problem solving.

Knowledge organization
  • It must be organized, otherwise you couldnt
    answer a series of seemingly unrelated questions
    in a short period of time
  • It could be semantically organized
  • It could be organized in schema

Knowledge organization (cont)
  • Semantic networks
  • Knowledge is represented as a network of nodes
    and links
  • The nodes are objects or classes of objects
  • The links are relationships between the objects
  • Schemata
  • Network of knowledge based on experience
  • Facilitate our understanding of everyday events
  • Scripts are types of schemata that describe

Mental models and Schemata
  • Schemata are too inflexible how can they
    possibly inform us on all the different
    variations found in everyday life?
  • How could schemata explain humans ability to
    handle unique or novel situations?
  • Mental models try to account for this dynamic
    aspect of life by being dynamically created, on
    the fly, from schemata

Images and Mental models
  • Mental models are constructed when we need to
    make inferences or predictions about the future
  • Mental models can have a mental simulation run
    on them to predict future states of a system
  • An image is a one-shot, one-off representation of
    the state of affairs at one point in time

Models and error
  • Remember Normans system image?
  • Example in book
  • Developing expectations about performance of a
    voice mail system...
  • Using an answering machine model
  • Delivered unexpected results.

Model types
  • Structural
  • Allows reasoning about how it works
  • Functional
  • Allows reasoning about how to use the system

Model types (cont)
  • Structural
  • Allows reasoning about how it works
  • Internalize a model of how the system is
    functionally structured
  • Useful for repair of the system
  • Requires a great deal of effort to learn
  • Requires a great deal of effort to use
  • Context free

Model types (cont)
  • Functional
  • Allows reasoning about how to use the system
  • AKA the task-action mapping model
  • Context dependent
  • Used to infer about novel situations by comparing
    the familiarity of the task domain not how the
    device works

  • Addresses reducing human error in the control of
    complex systems
  • All about process control operators (like nuclear
    power plants)
  • Sees it as a matte of skill level
  • Skill based behavior (automatic)
  • Rule based behavior (previously experienced)
  • Knowledge based behavior (novel situation)

The End!
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