It's all about Interactions
- How the system accept input
- How the user respond to the input
- How the system output
- Device-free AI
- Don't need user input to perform user's desired action
- Device-free but tracking user movements
- Eye-tracking interface
- Hand-tracking interface
Interactions in HCI are defined by
- Communication, direct/indirect
- Dialogue + feedback/batch
- Task oriented
7 Stages of Action
- Deciding the goal
- Intention to act
- Sequence of actions
- Execution of the actions
- Perceiving the state of the world
- Interpreting the perception
- Evaluating the outcome
Gulf of Evaluation: the gap between the idea of doing an action (mental model) and that act coming to fruition Gulf of Execution: the ease of noting whether the purpose of the devise has been accomplished
In the rhetoric of the GOMS model, bridging the gulf of execution means that the user must form intentions, specify action sequences, execute actions, and select the right interface mechanisms (GOMS stands for Goals, Operators, Methods and Selection Rules).
- Memory parameters
- decay time of an item
- storage capacity in items
- code type
- Processor parameter
- Cycle time
Fastman (1frame/50msec) ~ Middleman (1frame/100msec) ~ Slowman (1frame/200msec)
- Animations are the result of the perceptual processor speed being slower than the frame rate of still pictures being shown, so that it creates an illusion of animation.
- Fitts' Law
- A predictive model of human movement primarily used in human–computer interaction and ergonomics
- This scientific law predicts that the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target
- Proposed to quantify the difficulty of a target selection task
- Used to model the act of pointing, either by physically touching an object with a hand or finger, or virtually, by pointing to an object on a computer monitor using a pointing device.
- The Power Law of Practice
- Users can learn and get better at the interface
- Or the interface is bad but the users will naturally somehow learn to work around it (if there are still any around lol, and level of satisfaction is not considered here)
- Uncertainty Principle
- Decision time increases with uncertainty duh
- Also dependent on information-theoretic entropy of the decision (H)
- For n equally probable alternatives, H can be calculated by Hick's law
- For n alternatives with diff probabilities, H can be calculated like usual probability problems.
- When well designed, the interface almost disappears, enabling users to concentrate on their work, exploration, or pleasure.
- Good designs generate positive feelings of success, competence, mastery and clarity in the user community.
- Visibility of system status
- The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.
- Match between system and the real world
- The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
- User control and freedom
- Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.
- Consistency and standards
- Users should not have to wonder whether different words, situations, or actions mean the same thing.
- Follow platform conventions.
- Error prevention
- Even better than good error messages is a careful design which prevents a problem from occurring in the first place.
- Recognition rather than recall
- Make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.
- Flexibility and efficiency of use
- Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.
- Aesthetic and minimalist design
- Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.
- Help users recognize, diagnose, and recover from errors
- Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
- Help and documentation
- Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.
- People no time to learn new system
- Systems need to be easy to use, to learn, and without errors.
- Designers have difficulty thinking like users
- they can't unlearn something xD