Core characteristics of interaction design: Recap
- Users should be involved through the whole development of the product
- Specific usability and user experience goals need to be indentified, clearly documented and agreed at the beginning of the project
- Iteration is needed throughout the core activities
Usability Goals: Recap
- Effective to use (effectiveness)
- Efficient to use (efficiency)
- Safe to use (safety)
- Have a good utility (utility)
- Easy to learn (learnability)
- Easy to remember how to use (memorability)
Principles of Interaction Design
- How do we create elegant solutions to complex interaction problems?
- How do interaction designers succeed at creating great designs that are powerful and aesthetically appealing?
Interaction design principles
- A way of conceptualizing usability is in terms of design principles
E.g. feedback
- Design principles are derived from a mix of theory-based knowledge, experience, and common sense.
- the do\'s and dont\'s of in interaction design
- intended to help designers explain and improve the design
- not intended to specify how to design an actual interface.
Maxim
公理，无法证明
- Design principles can be used to guide design decisions
- Design principles do not prescribe specific outcomes; they function within the context of a particular design project.
- Design principles guide interaction designers and help them make decisions that are based on established citeria
Gulfs and Principles
- Design principle can be used to determine if there are gulfs of execution or evaluation
- Gulfs of execution relate to the effectiveness principles
- Gulfs of evaluation relate to the efficiency principles
Don Norman (1988) - the Design of Everyday Things
- Visibility -- don\'t hide buttons
E.g. bank web site
- Feedback -- so you don\'t re-hit buttons
- Constrains -- grey-out options in different modes
- Mapping -- between controls and effects
- Consistency -- right mouse click always behaves same
- Affordances -- give a clue as to the use
E.g. pushing a button
Similar to Nielson\'s 10 usability principles (2001).
(1) Visibility
- The more visible functions are, the more likely users will be able to know what to do next.
功能越可视，用户越容易了解如何去做
- When functions are "out of sight", it makes them more difficult to find and know how to use.
- Norman\'s example: controls of a car
- 对驾驶员：仪表盘等
- 对行人：转向灯等
(2) Feedback
- Send information back to the user about what has to be done
- Include sound, highlighting, animation, and combinations of these
- Deciding which combinaitons are apporopriate for different kinds of activities and interactivities is central.
- Using feedback in the right way can also provide the necessary visibility for user interaction.
What everyday life would be like without feedback?
(3) Constraints
- Restrict the possible actions that can be performed 限制有可能的错误操作
USB
- Helps prevent user from selecting incorrect options
Deactivating certain menu options by shadeing them
- Three main types (Norman 1999)
-
Physical -- the way physical objects restrict the movement of things
E.g. inserting a CD, door hinges
-
Logical -- rely on people\'s understanding of the way the world works
disabling menu options in certain modes; colour coding wires/sockets to connect to appliances
-
Cultural -- rely on learned conventions
E.g. red for danger
- Once learned and accepted by a cultural group, they become universally accepted conventions.
- the use of windowing for displaying information
- the use of icons on the desktop to reresent operations and documents
-
(4) Mapping
- Relationship between controls and their effects in the real world
- Nearly all artifacts need some kind of mapping
(5) Consistency 一致性
- Interface should use similar elements for similar tasks; Easier to learn and use
E.g. always use ctrl key plus first initial of the command for an operation: ctrl+S fro Save, ctrl+O for Open
- Difficult to maintain across different applications
E.g. Office, Excel, World
(6) Affordance
An affordance is an action that an individual can potentially perform in their environment. However, the more exact meaning depends on whether the word is used to refer to any such action possibility or only to those which the actor is aware of, both of which are common uses.
Example: Scissors
- First the user goal needs to be considered. To an angry user, the scissor might afford throw weapon, rather than a paper cutter
- Affordance will simply by observation, remind the user of similar items in size and form.
Affordance can be misinterpreted, if the user does not have the conventional knowledge, or even worse, if he has a conventional behavior that makes him want to touch the sharp edges.
Affordance: to give a clue
- An attribute of an object that allows people to know how to use it
- Originally used for physical objects -- buttons, door handles etc.
- Used now as "perceived" affordances
- scrollbars to afford moving up and down
- icons to afford clicking on
- These are more like learned conventions. 习得性规范
Activity -- physical affordances 课堂练习
Study an ovject from the classroom.
Write down the answer to therse questions:
- What does the object do? How do you know?
- Would you know what to do if you had never encountered this device before?
- How does the object afford?
- Are controls visible?
- Is there feedback?
- What constraints are there?
Framework for Design Principles
General Idea of a User Interface: Recap
Comprehensibility
Maxim
- An interface design that is easy to comprehend will be efficient and effective
- If a user does not understand the interface it will be useless
- A design\'s comprehensibility is highly dependent on the way in which the interface communicates its funcionality to the user
-
Comprehensibility Learnability
- Learnability and comprehensibility are recursive: we start with comprehensibility which affects learnability, which will inturn increase comprehensibility.
Principles of Interaction Design
- Effectiveness / Usefulness
- Utility
- Safety
- Flexibility
- Stability
- Efficiency / Usability
- Simplicity
- Memorability
- Predictability
- Visibility
Design Principle Categories
Effectiveness/Usefullness
Maxim
Effectiveness describes the usefullness of a design
- The effectiveness goal stipulates that a design must fulfill the user\'s needs by affording the required functionality
Gestalt Principles of Perception
Figure-Ground: Basic premise
- We perceive our environment by differentiating between objects and their backgrounds
Usability Principles
- Similar to design principles, which inform the design ... but
- Usability principles are used mainly as the basis for evaluating systems
- Keep it simple
- 设计原则：事前
- 可用性原则：事后，检验可用性目标是否实现
10 Usability Principles (Nielson 2001)
- Visibility of system status
- Match between system and real
- User control and freedom
- Consistency and standards
- Help users recognize, diagnose and recover from errors
- Error prevention
- Recognition rther than recall
- Flexibility and efficiency
- Aesthetic and minimalist design
- Help and documentation
Usability Summary
You should now be able to
- Define HCI adn interaction design
- Identify important usability and user experience goals for a product
- Critically evaluate and interface design