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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

  • DOET 4:

  • Knowing What to Do


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Today's Forecast

  • Lecture: DOET 4, Knowing What To Do

  • Random surprise visits to zee Wheel of Pain* ...

  • * (und Fear)


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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


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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.


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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.


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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 ... ?


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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.


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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 ... ?


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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.


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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 ... ?


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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)


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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.


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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 ... ?


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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?


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