Table 1. Twin correlations and approximated variance components.
| Intrapair twin correlations | Variance component estimates | Sample (numbers of pairs) | |||||
|---|---|---|---|---|---|---|---|
| MZ | DZ | h2 | c2 | e2 | MZ | DZ | |
| Rotation | 0.33 (0.26–0.41) | 0.21 (0.14–0.28) | 0.25 | 0.09 | 0.67 | 520 | 714 |
| Rotation/Visualisation | 0.38 (0.31–0.46) | 0.22 (0.14–0.28) | 0.34 | 0.05 | 0.62 | 521 | 714 |
| Visualisation | 0.45 (0.38–0.51) | 0.22 (0.15–0.29) | 0.45 | 0.00 | 0.55 | 516 | 711 |
| 2D | 0.47 (0.40–0.53) | 0.25 (0.18–0.31) | 0.44 | 0.02 | 0.53 | 526 | 724 |
| 3D | 0.41 (0.33–0.48) | 0.20 (0.13–0.27) | 0.41 | 0.00 | 0.59 | 508 | 697 |
| Overall Bricks | 0.56 (0.49–0.61) | 0.27 (0.20–0.33) | 0.56 | 0.00 | 0.44 | 522 | 720 |
Intraclass twin correlations (95% confidence intervals) for MZ and DZ twins, for the Bricks composites. Variance component estimates are heritability (h2: double the difference between the MZ and DZ correlations, constrained not to exceed the former–MZ twins are genetically identical, so heritability cannot exceed their correlation), shared environment (c2: the MZ correlation minus h2), and unique environment + error of measurement (e2: 1-h2-c2). Sample sizes shown are complete pairs, after exclusions and data cleaning.