Field
Overlap and complementarity, separated
How much two searches over one sample share is measured as the net of two effects: ground both of them find, and configurations the joint search reaches that neither slice contains. Pin the first search at its own answer and search the second, and the two separate exactly — the pinned supremum cancels, so the split adds back to the original number on every draw. The control the whole scale is anchored on reads zero because its two components are several times larger and cancel, and the split depends on which of the two searches is pinned while their difference does not.
Two effects in one number
How much two searches over one sample share is measured as the net of two things — ground both of them find, and configurations only the joint search reaches. One extra supremum per draw separates them exactly.
What a zero is made of
Two disjoint dictionaries of independent columns read an excess of 0.000116 and are made of an overlap of 0.000583 and an interaction of 0.000467. The control the whole scale is anchored on reads zero because two effects cancel.
A split that depends on the order
Run the second search first and pin that instead, and the same draw gives a different overlap and a different interaction — with the same difference. And one pair has no second order at all.