Things that couple tend to fall into step. Measure how strongly, and you can say something about what happens next.
Same four numbers. Different fields.
Proteins
K = bond strength. R = fold stability. Predicts disease mutations.
Sleep
K = neural coupling. R separates all 5 sleep stages. One EEG channel.
Music
K = rhythmic coupling. R = groove. Why some beats make you move.
Chemistry
K = atomic coupling. Predicts 31 bond energies, 1.78% error.
Physics
K = force coupling. The star tetrahedron produces the Standard Model.