2 by sex) thus were constrained to be the same across cohorts. First it was tested whether the correlation in opposite-sex twins could be equated to the expectation above (i.e. testing for qualitative sex effects). Next, it was tested whether the relative sizes of the genetic components could be equated across sexes, that is, whether h m2 = h f2 and d m2 = d f2. Lastly, it was tested whether non-additive genetic effects were present, by comparing the fit of the model with a model in which d 2 = 0.Table 1Twin correlations for the IRT-based Neuroticism and Extraversion scoresCohortTwin pairsTraitrMZ N95 % CIrDZ N95 % CI7. FINNISH TWINSM–MNeuroticism0.4319980.39–0.470.2048620.16–0.23Extraversion0.4419990.40–0.480.1448610.11–0.17F–FNeuroticism0.4822260.45–0.520.1946580.16–0.22Extraversion0.5222270.49–0.550.1546630.12–0.18AllNeuroticism0.4642240.43–0.480.1995200.17–0.21Extraversion0.4842260.46–0.510.1495240.12–0.1712. MCTFRM–MNeuroticism0.539220.47–0.600.175060.05–0.28Extraversion0.529220.45–0.580.235060.11–0.34F–FNeuroticism0.4510540.38–0.520.265800.15–0.37Extraversion0.5110540.45–0.570.135800.02–0.25AllNeuroticism0.4819760.44–0.530.2210860.14–0.30Extraversion0.5219760.47–0.560.1710860.09–0.2515. NTRM–MNeuroticism0.4511240.40–0.500.228550.14–0.29Extraversion0.4711230.42–0.520.138550.06–0.21F–FNeuroticism0.5122490.47–0.540.2313910.17–0.28Extraversion0.4922480.46–0.520.2013920.14–0.26M–FNeuroticism–––0.2120440.16–0.26Extraversion–––0.1420440.09–0.19AllNeuroticism0.4933730.46–0.520.2242900.18–0.25Extraversion0.4833710.46–0.510.1642910.13–0.1918. QIMR adolescentsM–MNeuroticism0.513040.42–0.590.272520.15–0.38Extraversion0.493040.40–0.570.182520.06–0.30F–FNeuroticism0.393290.29–0.480.192680.07–0.30Extraversion0.453290.36–0.530.192680.07–0.31M–FNeuroticism–––0.214630.13–0.30Extraversion–––0.124630.03–0.21AllNeuroticism0.446330.38–0.500.229830.16–0.28Extraversion0.476330.40–0.530.169830.09–0.2219. QIMRadultsM–MNeuroticism0.4511820.40–0.500.118890.04–0.19Extraversion0.4811820.43–0.530.198890.11–0.26F–FNeuroticism0.4820750.45–0.520.2214350.17–0.28Extraversion0.4820750.44–0.510.1614350.11–0.21M–FNeuroticism–––0.1318270.08–0.18Extraversion–––0.1418270.09–0.19AllNeuroticism0.4732570.44–0.500.1641510.13–0.19Extraversion0.4832570.45–0.510.1641510.12–0.1921. STRM–MNeuroticism0.5431880.51–0.560.1848410.15–0.21Extraversion0.5431880.51–0.560.2548410.22–0.28F–FNeuroticism0.4528300.42–0.490.1646250.13–0.19Extraversion0.4428300.41–0.480.2046250.17–0.23AllNeuroticism0.5160180.49–0.530.1994660.17–0.21Extraversion0.5260180.50–0.540.2694660.23–0.28 r MZ correlation in monozygotic twin pairs, r DZ correlation in dizygotic twin pairs, N number of twin pairs (pairs are included with personality data for both twins and with data for one twin), 95 % CI 95 % confidence interval, M–M male–male twin pairs, F–F female–female twin pairs, M–F male–female twin pairs, All twin pairs combined across gender
