Table 5. Bivariate regressions of vestibular shape vs. volume and of semicular canal volume vs. length.

Both ordinary least-square linear regressions (OLS) and phylogenetic generalized least-square regressions (PGLS) are provided for the whole anthropoid sample, as well as hominids and non-hominids separately. Vestibular shape is represented by the first three principal components (bgPC), while vestibular volume (Vol) is represented by its log-transformed cube root. Semicular canal volume (VolSC) and length (L) are represented by the log-transformed cube root and the log-transformed length, respectively, of the three semicircular canals together. For each regression, the coefficient of determination (R²), the significance of the slope (p), and the slope and intercept values with their corresponding standard error (SE) and 95% confidence intervals (CI) are included. Regressions bolded when significant at p<0.05. For bgPCs vs. VOL regressions, a significant correlation denotes allometry, while for VOLSC vs. L regressions there is allometry when the correlation is significant and the 95% CI for the slope excludes unity.

	R2	p	slope	SE	95% CI		intercept	SE	95% CI
OLS
Anthropoids (n = 142)
bgPC1 vs. ln Vol	0.635	<0.001	5.257	0.335	4.600	5.914	−6.191	0.399	−6.973	−5.409
bgPC2 vs. ln Vol	0.008	0.146	0.453	0.309	−0.154	1.060	−0.533	0.368	−1.254	0.188
bgPC3 vs. ln Vol	0.000	0.385	0.192	0.220	−0.239	0.622	−0.226	0.261	−0.738	0.287
ln VolSC vs. ln L	0.288	<0.001	0.897	0.118	0.666	1.128	−2.328	0.429	−3.169	−1.487
Hominids (n = 30)
bgPC1 vs. ln Vol	0.480	<0.001	6.496	1.233	4.079	8.913	−7.781	1.797	−11.303	−4.259
bgPC2 vs. ln Vol	0.026	0.195	−1.400	1.054	−3.466	0.666	2.307	1.538	−0.708	5.322
bgPC3 vs. ln Vol	0.039	0.153	−0.720	0.490	−1.681	0.240	1.036	0.714	−0.365	2.436
ln VolSC vs. ln L	0.251	0.003	0.621	0.190	0.249	0.992	−1.084	0.705	−2.465	0.297
Non-hominids (n = 112)
bgPC1 vs. ln Vol	0.058	0.006	1.990	0.709	0.601	3.380	−2.645	0.785	−4.183	−1.108
bgPC2 vs. ln Vol	0.010	0.152	−1.027	0.712	−2.422	0.368	1.061	0.788	−0.482	2.605
bgPC3 vs. ln Vol	0.046	0.013	1.332	0.529	0.295	2.368	−1.466	0.585	−2.613	−0.319
ln VolSC vs. ln L	0.219	<0.001	0.454	0.080	0.297	0.611	−0.783	0.291	−1.352	−0.213
PGLS
Anthropoids (n = 27)
bgPC1 vs. ln Vol	0.261	0.004	3.401	1.065	1.314	5.488	−3.719	1.376	−6.416	−1.022
bgPC2 vs. ln Vol	0.003	0.416	0.625	0.756	−0.858	2.107	−1.27	0.962	−3.155	0.615
bgPC3 vs. ln Vol	0.063	0.111	−0.727	0.440	−1.589	0.135	0.879	0.570	−0.238	1.996
ln VolSC vs. ln L	0.437	<0.001	0.502	0.109	0.288	0.716	3.144	0.124	2.901	3.388
Hominids (n = 5)
bgPC1 vs. ln Vol	0.221	0.240	4.440	3.042	−1.521	10.402	−4.627	4.499	−13.445	4.192
bgPC2 vs. ln Vol	0.036	0.760	−1.144	3.421	−7.850	5.561	1.892	4.990	−7.888	11.672
bgPC3 vs. ln Vol	0.062	0.687	−0.392	0.883	−2.122	1.338	0.596	1.309	−1.970	3.162
ln VolSC vs. ln L	0.553	0.093	0.631	0.259	0.124	1.138	2.920	0.327	2.279	3.561
Non-hominids (n = 22)
bgPC1 vs. ln Vol	0.008	0.294	1.376	1.276	−1.125	3.877	−1.674	1.512	−4.639	1.290
bgPC2 vs. ln Vol	0.030	0.445	0.763	0.978	−1.154	2.679	−1.444	1.152	−3.701	0.814
bgPC3 vs. ln Vol	0.020	0.500	−0.419	0.610	−1.616	0.777	0.577	0.730	−0.854	2.008
ln VolSC vs. ln L	0.504	<0.001	0.634	0.134	0.371	0.896	3.052	0.137	2.784	3.320