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# 425: HCI 1 - PowerPoint PPT Presentation

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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Presentation Transcript

• DOET 4:

• Knowing What to Do

• 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

• 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

• There are four main types of everyday constraints:

• Physical

• Semantic

• Cultural

• Logical

Let's take a look at each of these.

• 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 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 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 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 ... ?

• 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 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 ... ?

• 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)

• 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

• 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 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?