genetic factors aggression eval Flashcards
Eval nature or outure
Several lines of evidence on this spread point to genes as direct causes of aggression. These include twin and adoption studies. Twin studies consistently show significantly higher concordance rates for MZ twins compared with DZs (e.g. Cocarro et al. 1997). Evidence also includes research on the MAOA gene. Brunner et al. (1993) have shown that this genetic low-activity variant is associated with higher levels of physical aggression (violent crimes such as rape, attempted murder and physical assault). Finally there are animal studies. MAOA knockout mice have higher serotonin levels and are hyperaggressive (Godar et al. 2014).
However, there is also evidence that environmental factors are important. Criticisms of twin studies support this view. The equal environments assumption may be wrong, because MZ twins’ aggressive behaviour is reinforced more equally than DZs’. This means concordance rates are inflated. Early childhood trauma also plays a role. Frazetto et al. (2007) found that adults with the low-activity variant were only aggressive if childhood trauma ‘triggered’ the gene’s influence. At the very least environmental factors affect whether or not genes are expressed.
Therefore, ultimately, it could be argued that environmental factors are more important because, though we may have predispositions, these are only expressed in certain conditions.
Eval research support
One strength is support fir the role of the MAOA gene in aggression. Research on the facing page shows that the low activity variant of the MAOA found that the converse is also true men with low activity and high activity vairants of the MAOA gene took part in a Money distributing game. Men with the high activity variant MAOA were more cooperative and made fewer aggressive moves than the low activity patryicpants. This findings support the relationship between MAOA gene activity and aggression
Counterpoint?
However the study nay Mertains et al also showed that non genetic factors are crucial they nouns that even participants with the low activity MAOA variant behaved co operatively rather than aggressibles when they were made aware that others in the study were banging co operatively. Knowledge of a social norm partly determined how aggressive or copoerative MAOA-L participants were. Therefore genes are influenced by enviromanl factors that are at least as important as aggression.
Complex link eval
One limitation of the MAOA - serotrinn aggression link is that the precise mechanism is unclear.
On teh previous spread research linked aggression with low levels of serotonin. But the MAOA L gene causes low acuity of the MAO A enzyme which in turn should lead to higher serotonin because the low activity enzyme does not deactivate seotinn. Leaving more serotonin for the synaptic transition in people with teh MAOAL variant it may be more accurate to say their serotonin levels are disrupted rather than they are lower or higher than normal this shows that the relationship between the MAOA gene serotonin and aggression is not yet fully understood
Problems with twin studies
Another limitation of teh genetic explanation is that twin studies may lack validity
In every pair of twins both individuals share the same environment as each other however DZ twins may not share their environment to the same extent as MZ twin share theirs. We assume they di and this is called the equal environments assumption. But the assumptions may be wrong because one aspects off the environment is the way twins are treated by others. MZ twins are treated very similarly espicallly by parents. SZ are treated in less similar ways. This means that concordance rates are inflated and genetic influences on aggression may not be as great as twin studies suggests
