2.2: Learnability

• The conventional model for human memory has two components:

  Working memory & long-term memory
• Learning - the process of putting information & procedures into long-term memory
• Working memory - where one does their conscious thinking
• The capacity of working memory is roughly 7 ± 2 things (technically called "chunks")
• Maintenance rehearsal - repeating the items to yourself; requires attention
• Long-term memory - least understood part of human cognition; contains the mass of our memories
• Elaborative rehearsal - seeks to make connections with existing chunks
• Chunks - the elements of perception and memory; represents the activation of past experience
• Recognition: remembering with the help of a visible cue

  (also known as "knowledge in the world")
• Recall: remembering something with no help from the outside world

  (also known as "knowledge in the head")
• A more learnable interface would have smaller gulfs of execution & evaluation.
• Interaction Styles:

  • Command language
  • Menus & Forms
  • Direct manipulation
• Command language: the earliest computer interfaces

  Job control languages for early computers, which later evolved into the Unix computer line
• Menus & Forms: an interface which presents a series of menus or forms to the user
• Direct Manipulation: user interacts with visual representation of data objects
• Direct manipulation is defined by three principles:

  1. A continuous visual representation of the system's data objects.
  2. The user interacts with the visual representation using physical actions or labeled button presses.
  3. The effects of actions should be rapid, incremental, reversible, and immediately visible.
• Direct manipulation is powerful as it exploits the perceptual & motor skills of the human machine - depending less on linguistic skills than command or menu/form interfaces.
• Learnability can be strongly affected by difficulties of building a model.
• A model of a system is a way of describing how the system works.
• A model;

  • specifies what the parts of the system are
  • how those parts interact to make the system do its intended function
• Models in UI Design:

  • System model / implementation model
  • Interface model / manifest model
  • User model / conceptual model
• Learnability Principles:

  • Cues that communicate the system model
  • Consistency
• Cues that communicate the system model:

  • Affordances
  • Natural Mapping
  • Visibility
  • Feedback
• Consistency:

  • Internal, external, metaphorical
  • Speak the user's language
  • Metaphors
  • Platform Standards
• Drag & Drop:

  A powerful direct manipulation tool but has little visibility
• Types of Feedback:

  • Visual
  • Audio
  • Haptic - conveyed by sense of touch
• Consistency: also called the "principle of least surprise"
• Three kinds of consistency:

  • internal consistency
  • external consistency
  • metaphorical consistency
• Internal consistency: consistency within your application
• External Consistency: consistency with other apps on the same platform
• Metaphorical Consistency: consistency with your interface metaphor or similar real-world objects
• Metaphors: one way to bring the real world into your interface