2.3: Visibility

• Visibility - making the invisible state & behavior of software perceivable by the user
• Actions - the things the user can do in the interface
• State - the current configuration of the interface & its backend, which objects are selected or what data is in the model
• Feedback - the result of a user's actions, which might be a change in visible state or might simply be an acknowledgment of the action taking effect
• Affordances: low-level properties that tell you what a graphical object is and how to interact with it
• Self-disclosure: a technique for making a command language more visible, helping the user learn the available commands & syntax
• Information scent: visible properties of a link that indicate how profitable it will be to follow the link
• Information foraging theory:

  • the gathering of information can be modeled like animals gathering food
  • constantly evaluating & making decisions to maximize information collected against cost of obtaining it
• The quality of information scent depends on the user's particular goal.
• Modes: interface states in which the same action has different meanings
• Spotlight metaphor: attention focuses on one input channel at a time
• fovea: the user's field of vision
• Types of Feedback:

  • Low-level feedback
  • High-level feedback
• Low-level feedback: provided by a view object; shows that the interface took notice of the user's input, and is responding to it
• High-level feedback: the actual result of the user's action
• Perceptual fusion: two stimuli within the same perceptual cycle appear fused
• 100 milliseconds is a typical value for the perceptual processor's cycle time.
• The cycle time may also range from 50 - 200 milliseconds, based on the individual and on the stimulus.
• Visible View State: the current state of the user's interaction with the interface