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425: HCI 1. DOET 4: Knowing What to Do. Today's Forecast. Lecture: DOET 4, Knowing What To Do Random surprise visits to zee Wheel of Pain * ... * (und Fear). Knowing What to Do. When encountering new objects, how do we know what to do? KITH

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425 hci 1
425: HCI 1
  • DOET 4:
  • Knowing What to Do
today s forecast
Today's Forecast
  • Lecture: DOET 4, Knowing What To Do
  • Random surprise visits to zee Wheel of Pain* ...
  • * (und Fear)
knowing what to do
Knowing What to Do
  • When encountering new objects, how do we know what to do?
    • KITH
      • We've learned how to use a similar object.
      • We take a course to learn how to use it.
    • KITW
      • The object teaches us: instructions, labels, a manual, popup help, etc.
    • The design of the object can help us figure out what to do with it.
      • How? By intelligent/effective use of affordances and natural constraints.
        • Affordances - suggest range of possibilities of what to do
        • Constraints - limit the number of choices of what to do
          • put together a jigsaw puzzle
          • disassemble and reassemble a door lock for rekeying
          • build a spaceship out of legos
classification of everyday constraints
Classification of Everyday Constraints
  • There are four main types of everyday constraints:
    • Physical
    • Semantic
    • Cultural
    • Logical

Let's take a look at each of these.

physical constraints
Physical Constraints
  • Physical constraints rely on physical reality to limit the user's set of possible physical actions.
    • To close a screwtop bottle, you must turn the cap clockwise; to open it, you must turn the cap counterclockwise.
    • To insert a key in a lock you must push the correct end into the keyhole. To open the lock, you must turn the key (counter)clockwise.
    • To open a door you must turn the doorknob, or raise/lower the handle.
  • Physical constraints work best (at helping us know what to do) when they are easy to see and interpret.
semantic constraints
Semantic Constraints
  • Semantic constraints rely on the meaning of a situation to limit the user's set of possible actions.
    • For a semantic constraint to work, the user (obviously) needs to understand the meaning of the situation and of the world in which it is embedded.
    • When an alarm sounds, the meaning of the situation drives one to act in a certain way (get alarmed; fight or flight!) and NOT to act in another way (sit down and relax).
    • Other examples ... ?
cultural constraints
Cultural Constraints
  • Cultural constraints rely upon cultural conventions to limit the user's set of possible actions.
    • Which side of the road to drive on
    • Which way to read a sign (page, etc.): left to right, right to left, top to bottom, bottom to top
    • How to type on a computer keyboard (Z location, diacriticals, etc.)
  • Guidelines for cultural behavior are stored as schemas.

Schema: a memory-based knowledge structure that contains rules and instructions for interpreting situations and guiding behavior.

    • Other psychologists call schemas scripts or frames.
logical constraints
Logical Constraints
  • Logical constraints rely on rational logic to limit the user's set of possible actions.
    • Logical contraints are what enables natural mappings to work.
      • A naturally mapped stovetop – one whose knobs clearly map to its burners – works not because of physical, semantic, or cultural constraints, but because of logic: the spatial relationship between controls (knobs) and targets (burners).
  • How do semantic constraints differ from logical constraints?
    • Examples ... ?
ice name that constraint
ICE: Name that Constraint!
  • What types of constraints help us know what to do in these situations: Physical? Semantic? Cultural? Logical? (Hybrid?)
    • Stop at red traffic light; go at green.
    • Stand and bow to the Japanese executive you're having lunch with.
    • Fill your brake fluid reservoir.
    • Yield (or don't yield) to another car in traffic.
    • Communicate a work concern to your boss, not your boss's boss.
    • Change a bike tire (for the first time) without any instructions.
    • Don't make sudden movements if someone's pointing a gun at you.
    • Don't start eating dinner until an opening prayer has been said.
    • Choose D in a multiple-choice exam if A, B, and C are all wrong.
applying affordances and constraints to ets
Applying Affordances and Constraints to ETs
  • Applying well-designed affordances and constraints to everyday things can dramatically increase their usability.
  • Doors and light switches are good case studies.
    • All too often they are poorly designed (in terms of usability).
      • How about in this room?
    • Other examples of ETs that are often poorly designed ... ?
visibility and feedback
Visibility and Feedback
  • Along with affordances and constraints, visibility and feedback also contribute a great deal to knowing – or not knowing – what to do with a device.
  • Memory jog:
    • Affordance: a property of a device that enables it to be used.
    • Constraint: a property of a device that limits its usage.
    • Visibility: the degree to which a device's intended use is visible (apparent) to the user.
    • Feedback: information a device communicates back to users about actions they have taken. (vid1, vid2, vid3)
making visible the invisible
Making Visible the Invisible
  • Key parts of devices are sometimes invisible for aesthetic reasons.
    • Designers like to hide seams, cracks, handles, switches, etc.
  • But the usability of many of these devices would be dramatically improved by making these parts visible.
    • Has it ever taken you a full minute to find an on/off switch?
  • Without good visibility/feedback, users can run into problems:
    • Have trouble remembering their place in a sequence of steps
    • Have trouble remembering what needs to be done next
    • Have trouble checking info for correctness and changing it if necessary
  • A good visual display takes care of a lot of these problems.
    • When Norman wrote this book, visual displays were not as sophisticated or user friendly (high usability) as they are today.
using sound for visibility
Using Sound for Visibility
  • When things cannot be made visually visible, designers should consider making them sonically visible.
    • It would be difficult to visually inform (quickly, efficiently, all at once) 1,000 people in a big building of the outbreak of a fire.
    • But a sonic alarm does the trick nicely.
      • Except for deaf people.
    • A fire alarm is an extreme example of sonic visibility; more subtle:
      • The click of a door bolt sliding into place.
      • The funny sound a car makes when something is mechanically awry.
      • The whistle of a tea kettle when the water's boiling.
      • The change in tone when a vacuum cleaner hose is clogged.
      • Cell phone ring tones.
      • Other examples ... ?
using sound for visibility14
Using Sound for Visibility
  • The use of sound for visibility is currently quite primitive.
    • Exceptions:
      • Some video games have very sophisticated sonic visibility.
      • Music as an aid to debugging complex program code.
      • Earcons - icons for the ear
      • Other examples ... ?
    • One big challenge with using sound for visibility:
      • Sounds, unlike visuals, extend beyond the user's border.
      • Unless the user is wearing headphones or has volume set very low, the sounds emanating from a device can be heard by anyone in earshot.
        • This can be very (very!) annoying and disruptive ...
        • Suggestions for how to get around this?