Group affected icons together when an icon array must be read exactly
For retrieve tasks in part-whole risk displays, use grouped affected icons on icon arrays to improve fidelity and mitigate slow or inaccurate counting for exact readers.
- purpose:refine
- basis:empirical
- task:retrieve
- quality:fidelity
- lever:layout-structure
- operator:part-whole
- reading-mode:exact
advice
Grouped icons in icon arrays
Place the affected icons together when viewers need an exact read from an icon array. For example, show the highlighted people as one contiguous block in a 10×10 matrix instead of scattering them across the grid when the task is to read the count or percentage quickly.
reason
Why grouped icons work for exact reading
Grouped icons reduce the search and counting effort needed to find all affected cases. Scattered icons can still show randomness, but they slow exact reading.
Mechanism: A contiguous block lets viewers read the affected portion as one chunk instead of scanning the whole array mark by mark.
Evidence: The paper states that when icons are used to show affected individuals within a population, grouping the affected individuals together improves accuracy in numeric estimates and speed of processing relative to distributing them throughout the array (Lipkus, 2007).
context
Use when exact counts matter more than randomness
- User Goal: Read an exact affected count or percentage.
- Task: Identify how many people are affected within a fixed population.
- Data: Binary affected versus unaffected cases within a known total.
- Chart Setting: An icon array or pictograph, often a fixed matrix.
- Audience: Readers making exact or near-exact readings from the display.
- Success Criterion: Faster and more accurate count or percentage reading.
exceptions
Do not use when the display must show randomness
Break it when: The display needs to show randomness in where cases occur. Why: The source notes that affected icons are sometimes distributed throughout the array specifically to show randomness.
costs
Tradeoffs of grouping icons
Sacrifice: You give up the visual impression of random occurrence.
Risk: The grouped block can look more orderly than the underlying event pattern.
Mitigation: Use the grouped layout only when exact reading speed and accuracy matter more than showing randomness.
mistakes
Common failure mode in icon arrays
Mistake: Scattering affected icons across the array when exact count reading is the job. Why it fails: Viewers must search and count across the full grid.
check
How to test the icon arrangement
Failure Sign: Readers trace across the grid or recount affected icons before answering.
Quick Check: Time a reviewer reading the same value from grouped and scattered versions.
Stronger Test: Compare exact count or percentage answers from both versions.
fix
What to change
- Move the highlighted icons into one contiguous region of the array.
- Keep the affected and unaffected totals within the same fixed array.
- If showing randomness is the message, keep the scattered pattern and stop using the array for exact reading.