3.26 Perception/decoding: Preattentive search & patterns

  • What “pops” (Healy 2018, Ch. 1.3.2)
    • Inspect and discuss Figure 1.18.
    • Some contrasts (color, size, angle) easier to see than others (See Figure 1.16)
    • Consequences: Multiple mappings/channels (size, angle, elongation, movement) may overtax the viewer’s capacity (See Figure 1.19)
    • Think carefully before representing different variables and their values by shape, color etc.
  • Gestalt rules (Healy 2018, Ch. 1.3.3)
    • Humans generally want to identify groupings/classifications/entities than can be treated as the same thing
      • Proximity: Things that are spatially near to one another seem to be related.
      • Similarity: Things that look alike seem to be related.
      • Connection: Things that are visually tied to one another seem to be related.
      • Continuity: Partially hidden objects are completed into familiar shapes.
      • Closure: Incomplete shapes are perceived as complete.
      • Figure and Ground: Visual elements are taken to be either in the foreground or the background.
      • Common Fate: Elements sharing a direction of movement are perceived as a unit.
      • Inspect and discuss Figure 1.20 and 1.21
    • Keep those in mind when we interpret graphs ourselves.


Healy, Kieran. 2018. Data Visualization: A Practical Introduction. Princeton University Press.