Aggression Booklet 2: Genetic explanations Flashcards
What are the basics of the genetic explanation?
-Some scientists believe aggression can be inherited through genes
-This is investigated through twin and adoption studies
Why do we use twin studies?
-By looking at twin studies we can examine twins raised together in the same environment
-By looking at MZ and DZ twins we can see whether genetics play a role in aggression, since DZ share 50% and MZ share 100%
-Therefore a higher concordance rate with MZ twins indicates a genetic basis
What do 4 different concordance rates indicate?
-MZ twins have 100% concordance rate: behaviour purely genetic
-MZ twins have concordance rate less than 100%: behaviour must be at least partly down to environment
-MZ twins have significantly higher concordance rate than DZ twins: Behaviour must be at least partly down to genes
-MZ twins and DZ twins have similar concordance: Behaviour must be down to environment
What study is used for AO1 twin studies research in aggression?
Coccaro
What was found in Coccaro
-Studied adult male MZ and DZ twins for aggressive behaviour
-Found that concordance rate for MZ twins 50% compared to 19% DZ twins
What do the results of Coccaro demonstrate?
-Showed that genetics do play a role in aggression as those more genetically similar are more likely to be aggressive compared to hose less genetically similar
What can you talk about in AO1 twin studies for bonus marks?
EQUAL ENVIRONMENTS ASSUMPTION
What is the issue: equal environments assumption
Studies assume both MZ and DZ twins share an environment 100% the same, isn’t necessarily true since they will share different interests personalities and friends etc.
Why can we use adoption studies?
-By looking at adoption studies, allows us to look at children adopted to see whether more similar in terms of aggression to biological or adoptive parent
-Allows us to see which is more important: genetics or environment
What is the main research study for adoption studies?
Mednick, Gabrielli and Hutchings
What was found in Mednick, Gabrielli and Hutchings?
-Carried out adoption study over 14000 participants
-Researchers studied criminal records of all children adopted outside biological family between 1924 and 1947
-Found that having a criminal biological father increased risk of child’s criminality and aggression more than having an adoptive criminal father
What did the findings of Mednick, Gabrielli and Hutchings show?
It showed that genetics are a factor influencing aggression, as even under a non aggressive environment, being raised by a non aggressive father, they were still aggressive suggesting it had been inherited (nature)
What three things can be talked about in AO1 for genetic explanations?
-Twin studies
-Adoption studies
-Genes
What is the main gene associated with aggression?
The MAOA Gene (Monoamine oxidase A)
How was the MAOA gene linked to aggression?
Has been implicated in aggression as it was found that mice with the gene were extremely aggressive
What does the MAOA gene do?
-It affects levels of neurotransmitters
-MAOA is an enzyme that breaks down NT in the brain, including serotonin (this is controlled by MAOA gene)
Is the MAOA gene rare?
NO, this is a common misconception! We all have the MAOA gene though we may have different variants of this gene
-One example of a variant is MAOA-L variant: leads to reduced MAOA enzyme
-Other example is MAOA-H variant: leads to increased MAOA enzyme
How do MAOA gene variants icnrease aggression?
Because it leads to an imbalance of serotonin, increasing aggression
How is the MAOA-L variant said to icnrease aggression?
-By having less of the enzyme MAOA, it is not breaking down serotonin as much, leading to higher amounts of serotonin which has been shown to cause increased aggression
Does high serotonin levels cause aggression or low levels of serotonin?
Arguably both do, so a better explanation would be that an “imbalance” in serotonin levels causes aggression
what term must be used when referring to genetics?
Inheritance
Twin, adoption studies and MAOA-L gene are not genetic factors, what are they?
They are simply evidence that genetics are a factor in aggression (DON’T FORGET THIS!)
What are the evaluations of genetic explanations of aggresion?
😂Evidence to support (Cases et al)
😂Evidence to support (Brunner)
😢/😂Deterministic (no free will / cause and effect)
😢Reductionist
What was found in the study Cases et al?
-Genetically engineered mice with MAOA-L, found these had atypical serotonin levels and behaviour
-Showing that there’s a genetic influence on aggression as having defective MAOA gene is found to increase levels of aggression
What was found in study Brunner?
-Studied 28 male members of a large Dutch family repeatedly involved in aggressive violent crime such as rape, murder and assault
-Found these man had MAOA-L
-Adds to validity of genetic factors in aggression as men with defective MAOA-L gene increased levels of aggression
-Causing less of enzyme and therefore increased serotonin
