Table 3. Percentage of variance (R²) accounted for by combinations of predictors regressed to deviations in roughness.

(ΔR_d). For each row, we tested the null hypothesis that R² = 0 for each entry in the table, with a Bonferroni correction for multiple tests. Bold indicates that R² was significantly different from 0. The overall α of the test was 0.05. The Bonferroni-corrected level for each was 0.007 = 0.05/7. We did not apply Bonferroni correction for all 49 tests as the results in each column are not independent.

VAF	Observer
	CP	JG	MF	MSL	PJN	TA	YXH
$R_c^2$	35	57	45	40	34	25	70
$R_s^2$	63	41	32	42	19	30	45
$R_m^2$	2	17	19	16	15	8	18
$R_p^2$	12	15	24	14	29	2	57
$R_{s,c}^2$	71	58	47	43	41	30	80
$R_{m,c}^2$	44	58	45	40	34	26	70
$R_{m,s}^2$	72	41	33	42	22	30	46
$R_{p,c}^2$	73	57	45	43	40	32	78
$R_{p,s}^2$	73	48	37	42	37	30	72
$R_{p,m}^2$	19	29	37	24	43	10	71
$R_{m,s,c}^2$	74	59	47	44	41	30	81
$R_{p,s,c}^2$	73	61	51	43	42	32	81
$R_{p,m,c}^2$	81	58	45	47	44	32	78
$R_{p,m,s}^2$	77	49	40	43	44	30	76
$R_{p,m,s,c}^2$	82	66	53	48	44	33	81