HCI 5

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HCI 5 6

• Attention and memory
• and
• Knowledge and Models

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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

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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
  attention
• Drive and talk on cell phone

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Attention Additional properties

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

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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?

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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

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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...

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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
  request

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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

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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

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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?

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Reminder strategies

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

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Reminder difficulties

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

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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.

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Stroop effect

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

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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!

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Memory

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

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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
  culture.

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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

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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

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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
  concept

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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

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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

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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

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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)

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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
  nodes

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Imagists vs propositionalists

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

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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
  rotation
• Research results? Controversial and unclear.

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And now for something completely different The
connectionists!

• Yeh, yeh, sure, sure the truth is that both
  images and propositions are important to human
  thinking
• But underlying images and propositions is a
  neural network of nodes
• Images and propositions are emergent properties
  of that network.

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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.

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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

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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
  scenarios

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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

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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

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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.

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Model types

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

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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

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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

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Rasmussen

• 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)

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The End!
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