Bathtub control

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Bathtub control

• Users goals
• Warm bath
• Right amount of water
• Psychological variables
• Temperature water depth
• Physical variables
• Cold water flow rate
• Warm water flow rate

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Design exercise
Design the perfect bathtub control. 1. Assume
you have unlimited budget 2. Bath control only
no shower. 3. Think about mapping controls to
the users goals (physical variables).
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HCI Design Step 1

• Knowing the user
• Users are distinct individuals
• They have similar architectures
• Learning and memory for items is similar
• Motor, visual and hearing performance is similar
• HCI design is user-center Design
• Changing the system to fit the user.
• Not the other way around.

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What do we need to know about people?

• Perception
• Memory
• Vision
• Information Processing
• Mental Models
• Learning
• Skill
• Individual Differences

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Same or different?
A A
A A
A A
A a
A a
A B
Even simple decisions require thought and depend
on context
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Things that make us think
Jobs
Employment Opportunities
Job-o-Rama
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The Model of Human Processor

• The Perceptual System
• Seeing, hearing, touching, (smelling, tasting)
• The Motor System
• Movement
• The Cognitive System
• learning, reasoning, and problem-solving,

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Human Dimensions in Design Consideration

• Memory
• Motor processor
• Cognitive Processor
• Perceptual Processor

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What we need to know about users

• They forget
• They make mistakes
• Behavior is guided by prior knowledge

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They forget

• Short Term Memory
• limited duration (200ms - 30 sec)
• limited capacity (7 2 chunks)
• Design implications
• Misinterpreted and overused (e.g. menu size)
• Use to watch for memory demands of the UI
• it is hard to remember much information from one
  step in a process to another (leave information
  on the screen)
• Task chunking leads to closure

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Pay Attention .

• 5476926264

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What is the number?
5476926264

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Pay Attention .

• 505 646 6222

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What is the number?
505 646 6222

• Information can be grouped into chunked so that
  we can increase our short-term memory to 7 /- 2
  chunks

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Another Example

• T HEC ATR ANU PTH ETR EE

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What is the String?

• THE CAT RAN UP THE TREE
• T HEC ATR ANU PTH ETR EE
• Patterns and meanings helps to increase capacity
  of short-term memory.

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They forget

• Long Term Memory
• is organized and associative but imperfect
• recognition is easier than recall
• Design implications
• provide meaningful retrieval cues
• visibility is important (e.g. menus)
• but it has to make sense
• cues must be easily discriminated
• e.g. is it options or properties

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Memory

• Involves first encoding and then retrieving
  knowledge
• We dont remember everything - involves filtering
  and processing what is attended to
• Context is important in affecting our memory
  (i.e., where, when)
• Well known fact that we recognize things much
  better than being able to recall things
• Better at remembering images than words
• Why interfaces are largely visual

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Processing in memory

• Encoding is first stage of memory
• determines which information is attended to in
  the environment and how it is interpreted
• The more attention paid to something,
• And the more it is processed in terms of thinking
  about it and comparing it with other knowledge,
• The more likely it is to be remembered
• e.g., when learning about HCI, it is much better
  to reflect upon it, carry out exercises, have
  discussions with others about it, and write notes
  than just passively read a book, listen to a
  lecture or watch a video about it

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Context is important

• Context affects the extent to which information
  can be subsequently retrieved
• Sometimes it can be difficult for people to
  recall information that was encoded in a
  different context
• e.g., You are on a train and someone comes up to
  you and says hello. You dont recognize him for a
  few moments but then realize it is one of your
  neighbors. You are only used to seeing your
  neighbor in the hallway of your apartment block
  and seeing him out of context makes him difficult
  to recognize initially

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Activity

• Try to remember the dates of your grandparents
  birthday
• Try to remember the cover of the last two DVDs
  you bought or rented
• Which was easiest? Why?
• People are very good at remembering visual cues
  about things
• e.g., the color of items, the location of objects
  and marks on an object
• They find it more difficult to learn and remember
  arbitrary material
• e.g., birthdays and phone numbers

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Recognition versus recall

• Command-based interfaces require users to recall
  from memory a name from a possible set of 100s
• GUIs provide visually-based options that users
  need only browse through until they recognize one
• Web browsers, MP3 players, etc., provide lists of
  visited URLs, song titles etc., that support
  recognition memory

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The problem with the classic 7?2

• George Millers theory of how much information
  people can remember
• Peoples immediate memory capacity is very
  limited
• Many designers have been led to believe that this
  is useful finding for interaction design

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What some designers get up to

• Present only 7 options on a menu
• Display only 7 icons on a tool bar
• Have no more than 7 bullets in a list
• Place only 7 items on a pull down menu
• Place only 7 tabs on the top of a website page
• But this is wrong? Why?

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Why?

• Inappropriate application of the theory
• People can scan lists of bullets, tabs, menu
  items till they see the one they want
• They dont have to recall them from memory having
  only briefly heard or seen them
• Sometimes a small number of items is good design
• But it depends on task and available screen estate

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Personal information management

• Personal information management (PIM) is a
  growing problem for most users
• Who have vast numbers of documents, images, music
  files, video clips, emails, attachments,
  bookmarks, etc.,
• Major problem is deciding where and how to save
  them all, then remembering what they were called
  and where to find them again
• Naming most common means of encoding them
• Trying to remember a name of a file created some
  time back can be very difficult, especially when
  have 1000s and 1000s
• How might such a process be facilitated taking
  into account peoples memory abilities?

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Personal information management

• Memory involves 2 processes
• recall-directed and recognition-based scanning
• File management systems should be designed to
  optimize both kinds of memory processes
• e.g., Search box and history list
• Help users encode files in richer ways
• Provide them with ways of saving files using
  colour, flagging, image, flexible text, time
  stamping, etc

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Is Apples Spotlight search tool any good?
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Design implications

• Dont overload users memories with complicated
  procedures for carrying out tasks
• Design interfaces that promote recognition rather
  than recall
• Provide users with a variety of ways of encoding
  digital information to help them remember where
  they have stored them
• e.g., categories, color, flagging, time stamping

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Mental models

• Users develop an understanding of a system
  through learning and using it
• Knowledge is often described as a mental model
• How to use the system (what to do next)
• What to do with unfamiliar systems or unexpected
  situations (how the system works)
• People make inferences using mental models of how
  to carry out tasks

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Mental models

• Craik (1943) described mental models as internal
  constructions of some aspect of the external
  world enabling predictions to be made
• Involves unconscious and conscious processes,
  where images and analogies are activated
• Deep versus shallow models (e.g. how to drive a
  car and how it works)

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Everyday reasoning and mental models

• You arrive home on a cold winters night to a
  cold house. How do you get the house to warm up
  as quickly as possible? Set the thermostat to be
  at its highest or to the desired temperature?
• (b) You arrive home starving hungry. You look in
  the fridge and find all that is left is an
  uncooked pizza. You have an electric oven. Do you
  warm it up to 375 degrees first and then put it
  in (as specified by the instructions) or turn
  the oven up higher to try to warm it up quicker?

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Heating up a room or oven that is
thermostat-controlled

• Many people have erroneous mental models
  (Kempton, 1996)
• Why?
• General valve theory, where more is more
  principle is generalised to different settings
  (e.g. gas pedal, gas cooker, tap, radio volume)
• Thermostats based on model of on-off switch model

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Heating up a room or oven that is
thermostat-controlled

• Same is often true for understanding how
  interactive devices and computers work
• Poor, often incomplete, easily confusable, based
  on inappropriate analogies and superstition
  (Norman, 1983)
• e.g. elevators and pedestrian crossings - lot of
  people hit the button at least twice
• Why? Think it will make the lights change faster
  or ensure the elevator arrives!

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Exercise ATMs

• Write down how an ATM works
• How much money are you allowed to take out?
• What denominations?
• If you went to another machine and tried the same
  what would happen?
• What information is on the strip on your card?
  How is this used?
• What happens if you enter the wrong number?
• Why are there pauses between the steps of a
  transaction? What happens if you try to type
  during them?
• Why does the card stay inside the machine?
• Do you count the money? Why?

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How did you fare?

• Your mental model
• How accurate?
• How similar?
• How shallow?
• Payne (1991) did a similar study and found that
  people frequently resort to analogies to explain
  how they work
• Peoples accounts greatly varied and were often
  ad hoc

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Memory

• Human Memory Arguments
• keyboard entry requires someone to remember the
  name of the item
• screen selection only requires someone to
  recognize the item
• long command sequences hard to learn and to hold
  in the users head

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Just enough Psychology(So far)

• People make mistakes because they can easily get
  distracted by changes in the task context.

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Motor Processor

• Human Motor Performance Arguments
• items that are co-selected should be close
• small items are hard to select
• selection while holding the mouse button down is
  a harder motor task

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Geometry and Movement

• Small targets are harder (and slower) to hit with
  a mouse than big target
• long mouse movements are slower than short ones
• icons pack differently from text strings
• more keystrokes take longer to type
• switching between mouse and keyboard is slow

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Fitts LawMT a b log2(2A/W) where MT
movement time a,b regression coefficients A
distance of movement from start to target center
W width of the target
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Perceptual Processor

• Human Visual Performance Arguments
• important items stand out by varying properties
  of items, e.g., color, shape
• user search guided by organization of screen
  elements, e.g., users eye navigates from left to
  right and top to bottom

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Perceptual Processor

• Anything that is seen by our eyes has to be
  processed
• The processing difficulty depends the complexity
  of the visual scene and on our previous memory of
  the scene

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Visual Processing Speed

• Images that we already are familiar with simply
  match to images stored in our memory
• the processing time is fast
• the processing effort is low

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Visual Processing Speed

• For native English readers, the character on top
  right is processed faster
• For native Chinese readers, the character on the
  bottom right is processed faster

A
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Pay Attention!

• I am going to show the next slide as fast as I can

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M
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Take out a pencil and draw the character you just
saw
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Pay Attention!

• I am going to show the next slide as fast as I can

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Take out a pencil and draw the character you just
saw
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Visual Processing Speed

• English character has same complexity as Chinese
  character.
• Because the English character simply needs to be
  mapped to a similar character in our memory, the
  visual understanding speed is much shorter
• Chinese students will, of course, be faster with
  the Chinese characters

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What do you see?
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What information do you memorize?

• Location of element
• Shape of element
• Relationship of element to other elements on
  screen
• Pictures of icons
• Colors

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Human Processing of Complex Visual Scenes

• The time it takes to visually understand a scene
  depends on the number of unique elements that we
  must visually identify in the scene
• If we have already learned the scene, we record
  it as one element
• Words are recorded as a single element.
• One graphical component many have several unique
  components.

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An Example of a Complex Visual Scene
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Control Panel for Desktop Video Conferencing

• Too many elements to learn
• Elements located all over screen
• each individual location and relationship to
  other elements has to be learned
• Elements not clustered or ordered so that
  sub-groupings can be learned

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Design implication

• Provide external representations at the interface
  that reduce memory load and facilitate
  computational offloading

e.g. Information visualizations have been
designed to allow people to make sense and rapid
decisions about masses of data
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Galitz Graphical Design Principles

• Principles come from the way the human visual
  system works
• Principles relate to
• HOW HARD IT IS TO PROCESS VISUAL SCENE
• HOW MUCH OF SCENE CAN BE MATCHED TO MEMORY

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Organization of Screen Elements

• Balance
• Symmetry
• Regularity
• Predictability
• Sequentiality
• Economy
• Unity
• Proportion
• Simplicity
• Groupings

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The Stoop Effect Tells Us

• People have a hard time overcoming well practiced
  skills (like reading)
• We need to design applications that match
  acquired skills and work habits
• User testing is a good way of determining if our
  designs violate over learned skills

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Cognitive Processor

• Problem-Solving Arguments
• problems can be hard to solve if represented
  poorly
• if the user has to map their problem
  representation into a different one on the
  screen, the problem will be harder to do
• Learning Arguments
• Automatic learning

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Problem-Solving

• it should be possible to select operations
  relevant to goals
• it should be possible to know what an operation
  has actually done

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The dog is facing west. Make him face east by
changing the positions of just two matches. His
tail must remain up!
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Solution!
Assumptions can make easy things hard.
We dont always know what our users assumptions
are.
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And/Or questions
Enter your question


Enter your question Which students are from
Texas and New Mexico


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Who is from New Mexico and Texas?
Who is from New Mexico or Texas?
Texas
New Mexico
Texas
New Mexico
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And/Or Method

• Thirty-six participants from a temporary agency
• Word processing but no database experience
• Were asked to test a new database program which
  used English.
• Forty problems
• Equal numbers of And (Intersection) and Or
  (Union) divided between one or two database
  attributes

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And/Or Results
Actual use
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Attention

• big changes are more noticeable
• information presented close to where the user is
  looking is more likely to be read
• auditory signals cannot be ignored as easily as
  visual signals

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