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 Action Specification Intention Goals Evaluation Interpretation Perception Mental activity expectation

Goals Physical System gulf of execution 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

Goals Physical System gulf of evaluation 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

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 [ 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” [

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 [ 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