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SIMS 213: User Interface Design & Development
Marti Hearst Thurs, Feb 1, 2001
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Cooper Chapter 11 Scenarios Perpetual Intermediaries
Daily use vs Edge Case Perpetual Intermediaries The Importance of Precise Vocabulary Case study: Image processing tool Who are the Personas? Found some common goals Focus on a few key capabilities Matched to the capabilities of the system Had fewer features, but seemed most powerful!
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Cognitive Considerations
From Don Norman’s book, The Psychology (Design) of Everyday Things Affordances, Constraints, and Mappings Mental Models Action Cycle and Gulf of Execution
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Based on slide by Saul Greenberg
Mental Models People have mental models of how things work: how does your car start? how does an ATM machine work? how does your computer boot? Allows people to make predictions about how things will work Based on slide by Saul Greenberg
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Based on slide by Saul Greenberg
Mental Models Mental models built from affordances constraints mappings positive transfer cultural associations/standards instructions interactions Mental models are often wrong! Based on slide by Saul Greenberg
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Slide adapted from Saul Greenberg
Our mental models of how bicycles work can “simulate” this to know it won’t work Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
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People are always trying to explain things
Mental models often extracted from fragmentary evidence People find ways to explain things Computer terminal breaks when accessing the library catalog Sure your driving on the correct road
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Norman’s Action Cycle Human action has two aspects
execution and evaluation Execution: doing something Evaluation: comparison of what happened to what was desired
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Action Cycle start here Goals Execution Evaluation The World
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Action Cycle Goals Execution Evaluation The World Intention to act
start here Goals Execution Intention to act Sequence of actions Execution of seq uence of actions Evaluation Evaluation of interpretations Interpreting the perception Perceiving the state of the world The World
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Norman’s Action Cycle Execution has three stages:
Start with a goal Translate into an intention Translate into a sequence of actions Now execute the actions Evaluation has three stages: Perceive world Interpret what was perceived Compare with respect to original intentions
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Gulf of Evaluation The amount of effort a person must exert to interpret the physical state of the system how well the expectations and intentions have been met We want a small gulf!
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Based on slide by Saul Greenberg
Good Example Scissors affordances: holes for insertion of fingers blades for cutting constraints big hole for several fingers, small hole for thumb mapping between holes and fingers suggested and constrained by appearance positive transfer learnt when young conceptual model implications clear of how the operating parts work Based on slide by Saul Greenberg
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Based on slide by Saul Greenberg
Bad Example Digital Watch affordances four push buttons, not clear what they do contraints and mapping unknown no visible relation between buttons and the end-result of their actions negative transfer little association with analog watches cultural standards somewhat standardized functionality, but highly variable conceptual model must be taught; not obvious Based on slide by Saul Greenberg
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Digital Watch Redesigned for Affordances (Rachna Dhamija)
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Digital Watch Redesigned for Affordances (Ping Yee)
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Interface Metaphors Revisited
Definition of Metaphor application of name or descriptive term to an object to which it is not literally applicable Purpose function as natural models leverages our knowledge of familiar, concrete objects/experiences to understand abstract computer and task concepts Problem metaphor may portray inaccurate or naive conceptual model of the system A presentation tool is like a slide projector Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Interface Metaphors Use metaphors that matches user's conceptual task desktop metaphor for office workers paintbrush metaphor for artists... Given a choice, choose the metaphor close to the way the system works Ensure emotional tone is appropriate to users E.g., file deletion metaphors trashcan black hole paper shredder pit bull terrier nuclear disposal unit... Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Metaphors continued metaphors can be overdone! Common pitfalls overly literal unnecessary fidelity excessive interactions overly cute novelty quickly wears off overly restrictive cannot move beyond mismatched does not match user’s task and/or thinking Slide adapted from Saul Greenberg
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The Metaphor of Direct Manipulation
the feeling of working directly on the task An interface that behaves as though the interaction was with a real-world object rather than with an abstract system Central ideas visibility of the objects of interest rapid, reversible, incremental actions manipulation by pointing and moving immediate and continuous display of results Almost always based on a metaphor mapped onto some facet of the real world task semantics) Slide adapted from Saul Greenberg
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Object-Action vs Action-Object
Select object, then do action interface emphasizes 'nouns' (visible objects) rather than 'verbs' (actions) Advantages closer to real world modeless interaction actions always within context of object inappropriate ones can be hidden generic commands the same type of action can be performed on the object eg drag ‘n drop: my.doc move Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Direct manipulation Representation directly determines what can manipulated Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Phone list List metaphor Rolodex metaphor Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Games Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Direct Manipulation Xerox Star: pioneered in early '80s, copied by almost everyone simulates desktop with icons in and out baskets file folders and documents calculators printers blank forms for letters and memos small number of generic actions applicable system wide move, copy, delete, show properties, again, undo, help eg same way to move text, documents, etc property sheets pop-up form, alterable by user What you see is what you get (WYSIWYG) Slide adapted from Saul Greenberg
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Slide adapted from Saul Greenberg
Xerox Star continued Star's observers: objects understood in terms of their visual characteristics affordances, constraints actions understood in terms of their effects on the screen causality intuitively reasonable actions can be performed at any time conceptual model A subtle thing happens when everything is visible: the display becomes reality Slide adapted from Saul Greenberg
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Is direct manipulation the way to go?
Some Disadvantages Ill-suited for abstract operations spell-checker? Tedium manually search large database vs query Task domain may not have adequate physical/visual metaphor Metaphor may be overly-restrictive Solution: Most systems combine direct manipulation and abstractions word processor: WYSIWYG document (direct manipulation) buttons, menus, dialog boxes (abstractions, but direct manipulation “in the small”) Slide adapted from Saul Greenberg
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Conventional Applications: A Mix
Slide adapted from Saul Greenberg
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Based on slide by Saul Greenberg
Guidelines for Design Provide a good conceptual model allows users to predict consequences of actions communicated thorugh the image of the system Make things visible relations between user’s intentions, required actions, and results should be sensible consistent meaningful (non-arbitrary) make use of visible affordances, mappings, and constraints remind person of what can be done and how to do it Based on slide by Saul Greenberg
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Slide adapted from Saul Greenberg
Summary Good Representations captures essential elements of the event / world deliberately leave out / mute the irrelevant appropriate for the targetted users, their task, and their interpretation Metaphors use our knowledge of the familiar and concrete to represent abstract concepts need not be literal have limitations that must be understood Direct manipulation visibility of the objects of interest rapid, reversible, incremental actions manipulation by pointing and moving immediate and continuous display of results Slide adapted from Saul Greenberg
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Raskin on Cognition Cognitive Engineering
Ergonomics: sizes and capabilities of the human body Cognetics: Ergonomics of the mind Applied side of cognitive science
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Image from Newsweek, Jan 2001
Raskin on Cognition Cognitive Conscious / Unconscious Examples? Differences? Locus of Attention What is it? Why is it important for HCI? Image from Newsweek, Jan 2001
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Cooper on error dialog boxes
Why are they problematic? How related to locus of attention? What are the alternatives? Cooper is talking to programmers “Silicon Sanctimony” You should feel as guilty as for using a goto – an admission of failure in design
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Umm, thanks for the warning,
but what should I do? What happens when you cancel a cancelled operation? Do I have any choice in this? Uhhh… I give up on this one
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Inane Dialog Boxes
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Slide adapted from Saul Greenberg
Silly Help Midwest Microwave's online catalog Slide adapted from Saul Greenberg
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ClearCase, a source-code control system
from Rational Software
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Slide adapted from Saul Greenberg
“HIT ANY KEY TO CONTINUE” Slide adapted from Saul Greenberg
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Next Time: Design
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