Table 3.
Twin studies that evaluate proactive aggression arranged according to year of publication.
| Study | Year | n | Age(s) | Sex | Region | PA Instrument |
PA Genetic Contribution | Findings |
|---|---|---|---|---|---|---|---|---|
| Brendgen et al. [78] | 2006 | 344 | 6 | M/F | North America | TRI | 41% | The majority of genetic effects (34%) were due to physical aggression, which was common to PA and RA; genetic influences specific to PA were limited. |
| Baker et al. [79] | 2008 | 1219 | 10 | M/F | North America | RPQ | 0% to 50% | PA exerted a greater genetic influence than RA, and child-report PA data showed the greatest fit among report types. Male PA scores were higher than female scores across all report types. |
| Tuvblad et al. [80] | 2009 | 1241 | 10, 12 | M/F | North America | RPQ | 32% to 48% | PA becomes increasingly stable over time, compared to RA, which appears to be influenced more strongly by environmental factors. |
| Bezdjian et al. [81] | 2011 | 1219 | 10 | M/F | North America | RPQ | 18% to 37% | PA was associated with psychopathic traits, but only for child-reported measures. Both heritable and non-shared environmental influences were found for PA and psychopathic traits, suggesting etiological differences in young twins. |
| Paquin et al. [82] | 2014 | 1110 | 6, 7, 9, 10, 12 | M/F | North America | TRI | 39% to 45% | The contributions of unique PA influences were limited (0.2% to 9.4%), but factors common to PA and RA showed persistent associations during childhood. |
| Paquin et al. [83] | 2017 | 1110 | 6, 7, 9, 10, 12 | M/F | North America | TRI | 47% to 64% | Genetic factors that influence baseline and developmental PA are independent of each other. |