Primate brain architecture and selection in relation to sex

Table 1 Stepwise multiple regression models: brain components

	Brain components (dependent variables)
Independent variables included in the best model	Pons	Medulla oblongata	Cerebellum	Mesencephalon	Diencephalon	Telencephalon
Total brain volume minus the dependent variable	b = 1.233	b = 0.734	b = 1.030	b = 0.646	b = 0.841	b = 1.090
	t = 21.016	t = 17.239	t = 22.734	t = 20.520	t = 30.225	t = 28.424
	p << 0.001	p << 0.001	p << 0.001	p << 0.001	p << 0.000	p << 0.001
Sexual size dimorphism	b = -0.240	b = 0.369	-	b = 0.168	b = 0.140	b = -0.182
	t = -2.421	t = 5.093		t = 3.134	t = 3.294	t = -3.227
	p = 0.026	p << 0.001		p = 0.006	p = 0.005	p = 0.005
Female group size	--	--	--	--	b = -0.064	b = 0.119
					t = -2.143	t = 3.259
					p = 0.048	p = 0.005
Male group size	--	--	--	--	b = 0.043	b = -0.062
					t = 2.021	t = -2.335
					p = 0.060	p = 0.033
Whole model	F_(2,18) = 258.21	F_{(2, 18)} = 260.89	F_(1,19) = 516.82	F_(2,18) = 317.32	F_(4,16) = 409.56	F_(4,16) = 352.48
	R² = 0.966	R² = 0.967	R² = 0.964	R² = 0.972	R² = 0.990	R² = 0.989
	p << 0.001	p << 0.001	p << 0.001	p << 0.001	p << 0.001	p << 0.001

The table shows results from separate multiple regression models based on independent contrasts investigating the effects of four independent variables on six different main components of the primate brain.
The models were constructed by sequentially removing variables, keeping those with p ≤ 0.1. Each column contains one best regression model relating to that specific brain component. Numbers to the right of each independent variable are the partial regression coefficients for that specific variable, and the numbers in the bottom row give statistics for the multiple regression models. Dashes indicate variables excluded from the final best models because they had a partial regression p > 0.1.

ISSN: 1741-7007