Table 4.
Twin correlations, standardized ACE variance components, and genetic and nonshared environmental correlations between GPA and personality traits.
| Twin Correlations | Standardized Variance Components | % Covariance due to A | ||||||
|---|---|---|---|---|---|---|---|---|
| Variable | MZ | DZ | A | C | E | rG | rE | |
| GPA | ||||||||
| Girls | .74 | .45 | .56 | .17 | .26 | |||
| Boys | .72 | .38 | .69 | .04 | .27 | |||
| Achievement | ||||||||
| Striving | ||||||||
| Girls | .46 | .03 | .42 | .00 | .58 | .69 | .15 | 88 |
| Boys | .40 | .23 | .42 | .00 | .58 | .41 | .19 | 94 |
| Self-Control | ||||||||
| Girls | .44 | .06 | .41 | .00 | .59 | .60 | .14 | 87 |
| Boys | .30 | .18 | .32 | .00 | .68 | .39 | .12 | 77 |
| Aggression | ||||||||
| Girls | .51 | .25 | .44 | .05 | .51 | -.38 | -.02 | 86 |
| Boys | .52 | .10 | .51 | .00 | .49 | -.29 | -.18 | 72 |
Note. GPA = grade point average; MZ = monozygotic; DZ = dizygotic; A = additive genetic variance; C = shared environmental variance; E = nonshared environmental variance; rG = genetic correlation; rE = nonshared environmental correlation.