Chapter 9: Progressive Segmenting & Elimination
Progressive segmenting repeatedly divides the set until the target remains. Elimination scanning is the most common form.
Common techniques
- Halving (binary split)
- Quartering (quadrants)
- Scan-direct (many groups)
Trade-offs
- Fast once learned, but higher cognitive load.
- Can be confusing for beginners.
- Works best for large grids (64+ items).
Example: 64 items with 4-switch elimination
- Select quadrant (16 items remain)
- Select sub-quadrant (4 items remain)
- Select item
Elimination scanning offers logarithmic efficiency: big grids become fast once learned.
Switch count trade-off: 2 switches means more steps, 4 or 8 switches means fewer steps if the user can reliably control them.
Efficiency Snapshot (64 items)
| Method | Max Presses | Average Presses |
|---|---|---|
| Linear | 64 | 32 |
| Row‑Column (8×8) | 16 | 9 |
| Elimination (4‑switch) | 3 | 3 |
Rule of thumb: use the maximum number of switches a user can reliably control. More switches mean fewer steps.
Demo
🎮 Experience elimination scanning speed with a 64-item grid.