Table S2.

Slopes of allometric relationships for raw data and phylogenetically independent contrasts

			Raw data			Phylogenetically independent contrasts
Dependent variable	Independent variable	Region	Slope ± SE	r2	P value	Slope ± SE	r2	P value
Neuron density	VGM	PF	−0.256 ± 0.068	0.738	0.0132	−0.328 ± 0.073	0.801	0.0065
		Int	−0.315 ± 0.088	0.720	0.0157	−0.324 ± 0.113	0.620	0.0355
		Occ	−0.313 ± 0.112	0.610	0.0381	−0.289 ± 0.147	0.435	0.1070
VGM	Neurons	PF	1.290 ± 0.118	0.960	0.0001	1.405 ± 0.153	0.944	0.0002
		Int	1.349 ± 0.173	0.924	0.0006	1.297 ± 0.218	0.876	0.0019
		Occ	1.285 ± 0.210	0.872	0.0017	1.158 ± 0.240	0.824	0.0047
VWM	Other cells, WM	PF	1.176 ± 0.222	0.848	0.0032	1.206 ± 0.303	0.760	0.0105
		Int	1.241 ± 0.254	0.827	0.0045	1.310 ± 0.347	0.740	0.0130
		Occ	1.137 ± 0.211	0.853	0.0030	1.158 ± 0.198	0.837	0.0021
VWM	Neurons	PF	1.656 ± 0.298	0.860	0.0026	1.765 ± 0.415	0.783	0.0081
		Int	1.644 ± 0.208	0.926	0.0005	1.695 ± 0.258	0.896	0.0012
		Occ	1.557 ± 0.260	0.878	0.0019	1.553 ± 0.271	0.868	0.0023
Neurons, PF	Neurons, NPF		0.917 ± 0.220	0.776	0.0088	0.779 ± 0.210	0.733	0.0139
Other cells, PF WM	Other cells, NPF WM		0.966 ± 0.256	0.739	0.0131	0.914 ± 0.237	0.749	0.0119

All functions calculated without human data points (n = 7). Neuron density in neurons per cubic millimeter. V_GM, volume of cortical gray matter (cubic millimeters). V_WM, volume of subcortical white matter (cubic millimeters). Int, intermediate region; NPF, nonprefrontal region; Occ, occipital region; and PF, prefrontal region.