425: HCI 1

1. 425: HCI 1 • DOET 4: • Knowing What to Do

2. Today's Forecast • Lecture: DOET 4, Knowing What To Do • Random surprise visits to zee Wheel of Pain* ... • * (und Fear)

3. 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

4. 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.

5. 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.

6. 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 ... ?

7. 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.

8. 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 ... ?

9. 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.

10. 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 ... ?

11. 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)

12. 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.

13. 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 ... ?

14. 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?