Table 2.

Brother and twin pair analyses

Analysis	Global intelligence	Logical intelligence	Verbal intelligence	Visuospatial intelligence	Technical intelligence
Brother pairs
n	268,496	257,591	257,352	257,351	255,635
b	0.172	0.177	0.143	0.114	0.113
95% CI	0.168–0.176	0.173–0.181	0.140–0.147	0.110–0.118	0.108–0.117
R2	0.27	0.23	0.20	0.16	0.18
DZ twin pairs
n	1,715	1,676	1,676	1,676	1,672
b	0.136	0.152	0.104	0.054	0.096
95% CI	0.089–0.182	0.103–0.202	0.057–0.152	0.005–0.104	0.047–0.144
R2	0.30	0.25	0.21	0.15	0.19
MZ twin pairs
n	1,432	1,391	1,394	1,394	1,377
b	0.128	0.114	0.113	0.099	0.060
95% CI	0.084–0.172	0.062–0.166	0.059–0.166	0.039–0.159	0.003–0.118
R2	0.66	0.53	0.46	0.37	0.43
Bivariate heritability
r (DZ)	0.14	0.14	0.13	0.08	0.08
r (MZ)	0.20	0.21	0.20	0.13	0.13
Heritability	0.14	0.15	0.14	0.10	0.10
Shared environment	0.07	0.06	0.06	0.03	0.03
Non-shared environment	0.79	0.79	0.80	0.87	0.87

The association between cardiovascular fitness and cognitive performance within brother and twin pairs. r²=adjusted coefficient of determination; b=regression coefficient presented with 95% confidence intervals. Bivariate heritability: By comparing correlation coefficients (r) between dizygotic (DZ) and monozygotic (MZ) twin pairs, bivariate heritability and contribution of shared and non-shared environment for associations between cardiovascular fitness and intelligence scores wee calculated. env=environment.