Human-computer interaction

Posted on May 20, 2022


4 main types.

  1. Selective: Tuning out other things to a select set of stimuli
  2. Sustained attention: Focusing on a single task for a long time
  3. Divided attention: Focusing on multiple tasks at once
  4. Executive attention: More organised sustained attention - having a plan/end goal in mind and tracking progress over a long term task

Focus determines how a system is interacted with, so grabbing attention in the right ways makes for effective interfaces.
How to keep attention:

  • Don’t clog the UI
  • Switch visuals often to keep it fresh
  • Make tasks intuitive, so less focus effort is needed to complete a task
  • Don’t overdo attention grabbing techniques, it can be annoying


Short term memory

  • Can hold ~4 things at a time
  • Used as a scratchpad for holding transitory information

Long term memory

  • Episodic: Events and experiences in sequential, serial form. How we remember / reconstruct past events.
  • Semantic: Collection of facts, concepts and skills, which are derived form episodic memory.

Commiting to long term memory

  • We need to make committing interface actions to long-term memory as effortless as possible.
  • Common design patterns can help: eg. people already know that blue text = hyperlink, exploit that pattern

Norman’s human action cycle

Norman's human interaction cycle

Focuses on two main aspects of UI interactions.

  • Gulf of evaluation: Psychological gap of interpreting a UI, and the expected result of performing an action.
  • Gulf of execution: Gap between the user’s goals and the means to execute them, ie. number of steps required to do something.

We can extract some design principles to optimise these aspects of a design.

  • Visibility: Users can tell the system’s current state and their possible options
  • Good conceptual model: Action outcomes are consistent in their presentation
  • Good mappings: Easy to determine an action’s outcome from it’s appearance and context
  • Provide feedback: Users get constant and consistent feedback on the effect of their actions

Gestalt laws of perceptual organisation

  1. Figure-ground principle: People segment vision into a “figure” (foreground) and “ground” (background)
  2. Similarity principle: form informs function (eg. blue hyperlinks)
  3. Proximity: Elements close to eachother have similar function
  4. Common region: Elements grouped together (eg. in boxes) have similar function
  5. Continuity: Objects on a line/curve ae continuous and similar
  6. Closure: Complex arranements are seen as a single pattern (eg. tiger image made of black stripes)
  7. Focal point principle: Attention is drawn to a standout element

Affordances and signifiers

  • Affordances: Functions an object allows us to do
  • Signifiers: Cues/hints as to an object’s affordances For example, a road has the affordance of being able to walk on it, but crossings act as a signifier as to where you should cross.
    A save icon is a common signifier, informing a user of the save button’s affordances.


Concepts that impact system design:

  • Feedback: Informing users of the effects of their actions
  • Constraint: eg. blurring non-focused activities
  • Mapping: Relate controls to their effects eg. dragging objects into a recycle bin
  • Consistency: Similar operations for similar elements for similar tasks

Nielsen’s usability principles:

  1. Visibility of system status
  2. Match system and real world: ie. use familiar language to user
  3. User control and freedom: Give escape routes such as an undo button
  4. Consistency and standards (especially consistency in the use of language)
  5. Help user recognise and recover from error
  6. Error prevention: eg. “Are you sure?” dialogue
  7. Recognition, not recall of action flows
  8. Flexibility and efficiency of use: eg. macros for advanced users
  9. Aesthetic and minimalist design
  10. Provide help and documentation

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