Table 2.
Means (SDs) for vocabulary, block design, and brain volumes
| MZ (N = 224) |
DZ (N = 119) |
Singletons (N = 217) |
Siblings of twins (N = 89) |
p | |
|---|---|---|---|---|---|
| Vocabulary | 11.4 (2.8)* | 11.5 (2.6) | 12.3 (3.0)* | 12.0 (3.0) | 0.03 |
| Range | 4–18 | 5–18 | 2–19 | 5–18 | |
| Block design | 11.3 (2.8)* | 11.9 (3.0) | 12.2 (2.9) | 12.3 (3.0) | 0.02 |
| Range | 4–19 | 3–19 | 4–19 | 5–19 | |
| Gray matter + white matter | 1172.5 (106.5) | 1146.1 (105.9) | 1164 (117.5) | 1165.8 (118.6) | 0.41 |
| Range | 894.7–1470.4 | 816.3–1417.7 | 891.3–1473.1 | 920.4–1495.6 | |
| Gray matter | 736.5 (66.2) | 725 (70.1) | 728 (78.1) | 732.6 (75.1) | 0.68 |
| Range | 430.5–910.3 | 492.9–904.5 | 563.1–935.8 | 583.3–981.6 | |
| White matter | 435.9 (55.8) | 421.1 (53.3) | 435.9 (54.4) | 433.2 (55.9) | 0.22 |
| Range | 322.3–586.4 | 286.7–576.9 | 302–612.9 | 329.4–605.4 | |
| Frontal gray matter | 232.3 (21.3) | 228.8 (22.6) | 230.5 (25.2) | 231.2 (24.6) | 0.78 |
| Range | 143.2–288.8 | 155.9–286.6 | 173–298.7 | 178.8–310.3 | |
| Frontal white matter | 167.3 (22.6) | 161.6 (20.3) | 167.4 (21) | 167.1 (22.3) | 0.21 |
| Range | 125.4–227.5 | 112.8–217.9 | 113.1–238.2 | 125.7–234.4 | |
| Parietal gray matter | 123.1 (13) | 124.2 (13.2) | 122.6 (15.4) | 124 (14.8) | 0.81 |
| Range | 89.8–154.8 | 95.1–167.9 | 91.6–169.6 | 93.7–177 | |
| Parietal white matter | 83.9 (11.8) | 82.9 (11.3) | 85 (11.2) | 84.5 (11.9) | 0.57 |
| Range | 58.2–115.1 | 56.9–114.6 | 57.6–120.6 | 62.1–125.6 | |
| Temporal gray matter | 190.5 (18.5) | 186.5 (20.2) | 187.8 (20.4) | 189.7 (20) | 0.52 |
| Range | 88.4–245.2 | 117.8–232.5 | 138.6–246.1 | 150.7–264.5 | |
| Temporal white matter | 94 (12.3) | 91 (12.7) | 93.9 (12.4) | 93.6 (12.9) | 0.35 |
| Range | 69.1–131 | 65.9–130.6 | 64.7–134.8 | 67.4–129.3 | |
| Lateral ventricles | 11.5 (6.6)* | 10.2 (5.1) | 10.6 (5.9) | 8.4 (4.1)* | 0.0001 |
| Range | 2.9–41.5 | 3–31.6 | 2.8–35.9 | 3.3–27.2 | |
| Caudate nucleus | 9.9 (1.1) | 9.8 (1.1) | 9.8 (1) | 9.9 (1.1) | 0.96 |
| Range | 7.7–13.7 | 7.3–12.3 | 7–12.6 | 7.4–13 |
*
Groups with significant mean differences (p < 0.05) for a measure compared to the total sample