Table 1 PGLS analyses of the effects of body temperature and activity period on brain size, while controlling for various confounding effects. Variables with significant effects (P < 0.05) are highlighted in in bold. The 95% confidence intervals for the 100 trees are shown in brackets. λ is Pagel’s lambda

All species (n = 153)

Intercept

0.767 (0.765, 0.769)

0.175 (0.173, 0.177)

4.401 (4.348, 4.453)

< 0.001 (<0.001, <0.001)

Body mass (log-10)

0.552 (0.552, 0.552)

0.020 (0.020, 0.020)

27.843 (27.806, 27.881)

< 0.001 (<0.001, <0.001)

Taxon (Reptile)

0.272 (0.271, 0.274)

0.234 (0.230, 0.239)

1.168 (1.150, 1.185)

0.247 (0.240, 0.254)

Activity period(nocturnal)

0.343 (0.340, 0.346)

0.138 (0.137, 0.138)

2.492 (2.476, 2.508)

0.014 (0.013, 0.015)

Body temperature (T_b)

0.007 (0.007, 0.008)

0.004 (0.004, 0.004)

1.949 (1.927, 1.972)

0.055 (0.052, 0.058)

AP (nocturnal) x T_b

-0.019 (-0.019, -0.019)

0.006 (0.006, 0.006)

-3.430 (-3.446, -3.414)

<0.001 (<0.001, <0.001)

λ = 0.796 (0.785, 0.807); R² = 0.846 (0.845, 0.846)