(the represented system) Chapter 8: Displays Attention Display (the represented system) Perception Mental model Senses System

Objectives Power of representation Display variables and the match to the task Display design principles Perceptual Mental model Attention Memory Types of displays and how to apply the principles

Power of representation A good representation captures essential elements and leaves out the rest Good representations allow people to concentrate on essential elements and ignore the irrelevant Poor representations can be misleading, out of sight out of mind Solving a problem simply means representing it so as to make the solution transparent (Simon, 1981)

Game of 15 Using digits 1,2,3,4,5,6,7,8,9 Each player takes a digit in turn Once a digit is taken it cannot be used by the other player The first player that has three digits that sum to 15 wins Sample game: Player A takes 8, Player B takes 2, A takes 4, B takes 3, A takes 5 What should B do?

Player A = X, Player B=O O X X X O

Player A, Player B 3 8 4 9 5 1 6 2 7

Displays: Applications Internet Cockpits Cars Maps Control rooms …

Display variables Location (superimposed) Color Dimensionality (2-D vs 3-D) Motion (what and how) Intensity (contrast between elements) Modality (e.g., visual vs. auditory) Coding (e.g., analog vs. digital) No one best display configuration, but depends on the match to the task

Display principles Display principles: General strategies for improving display effectiveness though consideration of human limits and capabilities Categories of principles: Perceptual Mental model Attention Memory

Display design principles Perceptual principles 1) Absolute judgement (maximum of 5-7 levels) 2) Top-down processing (Highlight the unexpected) 3) Redundancy gain (Multiple cues or modes) 4) Discriminability (ratio of similar to dissimilar features) Attention principles 5) Minimizing information access cost (minimize “distance” between variables) 6) Proximity compatibility principle (link variables through common location, color, or other code) 7) Principle of multiple resources (distribute information between mental resources) Mental model principles 8) Principle of pictorial realism (configure to match system/mental model, thermometer) 9) Principle of the moving part (match movement to system/mental model, aircraft and altimeter) 10) Ecological interface design (display provides an externalized and normative mental model) Memory principles 11) Predictive aiding (show future states rather than force people to estimate) 12) Knowledge in the world (displayed information rather than rely on memory) 13) Consistency (same cues should have same meaning, red is for danger)

Perceptual principles Absolute judgement (maximum of 5-7 levels) Top-down processing (Highlight the unexpected) Redundancy gain (Multiple cues or modes) Discriminability (ratio of similar to dissimilar features)

What is wrong with this graph

Problems of discriminability