Table 4.
Twin correlations for the RTs on the Eriksen flanker task, and the flanker interference score (flanker effect).
| Zygosity | N Twin1 | N Twin2 | Overall RT | Flanker effect |
| MZM | 29 | 31 | 0.38 | 0.12 |
| DZM | 20 | 19 | -0.01 | -0.07 |
| MZF | 41 | 41 | 0.35 | 0.09 |
| DZF | 14 | 15 | 0.18 | 0.52 |
| DOS | 25 | 26 | 0.55 | 0.04 |
Note: MZM = monozygotic males; DZM = dizygotic males; MFZ = monozygotic females; DZF = dizygotic females; DOS = opposite sex pairs. N Twin 1 is the number of first born twins per zygosity group; N Twin 2 is the number of second born twins.