theories and practice of interactive media 13 october 2003 kathy e. gill
TRANSCRIPT
Theories and Practice of Interactive Media
13 October 2003
Kathy E. Gill
Agenda Review assignments HCI theory, continued Affordances Human limits (memory)
Assignment review (1/3)
Journal Pew Reading
What should newspapers be doing to increase reader interaction/involvement?
What is the proper role of “local” news media today?
Assignment review (2/3)
Crawford Speaking : monitor pixels/rez Animation: not necessarily interactive,
often distracting Thinking : pattern recognition v logic Hyperlinks : a “weak” form of thinking?
Assignment review (3/3)
“The task in interactivity design is the same as in any art: to create, not an exact duplicate of reality in all its confusion and messiness, but an image or representation of reality that focuses the user’s mind on some singular truth. The designer deliberately distorts reality in a manner reflecting the designer’s own point of view.” (Crawford, p33)
Theories in HCI - recap Must explain and/or predict human
behavior in the human-computer system Must work in a wide variety of task
situations Must work within broad spectrum of
system designs and implementations
Two general models Stages of interaction (Norman)
Norman’s theories are broader than computer systems
Syntactic/semantic model (Shneiderman)
Norman’s seven-stage model
Physical activity
Execution
ActionSpecification
Intention
Goals
Evaluation
Interpretation
PerceptionMental activity
expectation
GoalsPhysicalSystem
gulf ofexecution
Gulf of Execution Do actions provided by system
correspond to the intentions of the user?
Gulf: amount of effort exerted to transform intentions into selected and
executed actions
GoalsPhysicalSystem
gulf ofevaluation
Gulf of Evaluation Can feedback be interpreted in terms of
intentions and expectations? Gulf: amount of effort exerted to
interpret feedback
Bridging Gulf of Execution
Hick’s Law : number of choices affects the size of the Gulf of Execution Relationship between number of signals
and human response time [usabilityfirst.com/glossary/main.cgi?function=display_term&term_id=266 and http://muse.widener.edu/~crn0001/ed488/L10/L10_4.htm]
Bridging the Gulf of Evaluation Number and quality of feedback items
affects size of Gulf
Design questions How easily can a user
Determine the function of the system? Tell what actions are possible? Determine mapping from intention to selection? Perform the action? Tell what state the system is in? Determine mapping from system state to
interpretation? Tell if system is in the desired state?
Norman on Design (1/2)
Visibility Can I see the state of application (or web
page) and my alternatives for actions Good conceptual model
Does the system have consistent presentation of operations and results and does the system make sense to the users
Norman on Design (2/2)
Good mappings What are the relations between
Actions and results Controls and their effects System state and what is visible
Feedback Full and continuous feedback about results
of actions
Object-Action Interface Schneiderman’s evolving theory An explanatory model
First - understand the task Second - represent via metaphor Third - make action options visible
Direct manipulation design Visually represent the world of action
Objects of interest shown on screen Actions of interest shown on screen
Rapid execution of actions Actions are reversible Interaction accomplished through
Pointing Selecting Dragging
Why does it work? According to Schneiderman:
It engages human perceptual recognition Human vision is an effective way to learn
and understand the world
Pluses Novices gain basic functionality quickly Users feel in control of the system Users experience less anxiety because
the system is comprehensible and reversible
Users see the results of their actions and can determine if they are furthering their goals
Cautions Careful with metaphors Some work : trash can (exception) Some have short lives : USAir web,
Boo.com [http://www.boo.com/boo/]
Some don’t : Bob
Good interactive design Helps users build the correct conceptual
model of the system Makes the right parts visible Provides memory aids to user Provides good feedback Accommodates errors
Conceptual Model (1/2)
Conceptual Model (2/2)
Design model : belongs to the designer System image : the actual system User's model : developed through
interaction with the system Examples : refrigerators, thermostats,
hot-cold taps
Question: Think of some badly designed thing
(object, software, web site). What principles did its designer fail to heed?
Think of some well-designed thing. How did its designer apply Norman's principles of good design?
Affordances Term invented by JJ Gibson (1977,
1979) refers to the relationship of actionable properties between the world and actor
Part of nature; may or may not be visible or known
Perceived Affordances Introduced by Norman, Psychology of
Everyday Things, 1988 Is an action possible or not possible Does the user perception reflect reality The “non-verbal language of objects”
[http://cyberwriter.com/TFM/2001/01-06.html]
Visibility Hidden features Hidden navigation Strive for transparency
Memory Aids Why do we need to discuss memory
aids? Long-term versus short-term memory
Challenge : “overcoming” habit Macintosh Word 6; Freehand/Illustrator
Use knowledge in the head and in the world
Knowledge in the head Affordances Natural mappings Constraints
Cultural, Semantic, Physical, Logical
Knowledge in the world (1/3)
Cultural constraints Brought up by Dan and others in
reading;conventions vary by culture Semantic constraints
Relies on context Example: lego motorcycle - put rider facing
forward
Knowledge in the world (2/3)
Physical constraints Square pegs and round holes :) Fitt’s Law: Apple menus v Windows menus
[www.joelonsoftware.com/uibook/chapters/fog0000000063.html]
Jodi : 330 days (Orbitz)
Knowledge in the world (3/3)
Logical constraints (mapping)
Chunking as design tool Aids in information processing and
memory Grouping reduces effect of Hick’s Law
Example: week-3-structured_info.html
Feedback, Errors To Come!
Summary Communication models need to
incorporate feedback and intent Interactive systems must minimize the
Gulf of Execution and the Gulf of Evaluation in order to be successful
Visibility is key