Experimentally verified ESEs are preferentially conserved by natural selection. (a) Motif z-scores (greater z indicates greater conservation), based on mouse-human comparisons, show a strong quantitative correlation (Spearman ρ = 0.422, permutation test P-value = 0.045) with splicing inclusion rates as measured experimentally in . (b) K
values, also based on mouse-human comparisons, show a far weaker correlation (ρ = -0.0725, P-value = 0.606). Black lines indicate regression fits. While the two motifs with the highest splicing inclusion rates do exhibit below-average K
values, this is the only apparent effect, indicating that COMIT scores are better for assessing functional motifs.