Genetic Factors In Aggression Flashcards
What are genes and what do they produce
Genes are sections of DNA. Dna produces ‘instructions’ for general physical features of an organism, such as eye colour or height as well specific physical features like levels of neurotransmitters or size of brain regions? This may impact on psychological features such as aggression. Genes are inheritedm
Is there evidence of aggression being genetic?
Yes - this is shown through twin and adoption studies. As well as studying specific genes which are related to aggression
How are males and females different genetically and how does this implicate aggression?
Their differences lie in their genotype and the pair of genes that decides whether we are male or female is XY and XX and early psychologists believed that the genetic cause for aggression lied in the Y chromosome. They were also particularly interested in XYY individuals who have an extra Y chromosome and are referred to as ‘super males’. Court brown discovered 314 patients with thr double Y and said they should be hospitalised due to increased aggression
What has happened recently regarding selective breeding
Psychologists have used selective breeding to find out that aggression is a trait that can be transmitted from parent to offspring - supports genetic explanation
How have twin studies helped
The focus on twin studies have looked at the incidence of aggression displayed by MZ twins to DZ twins. MZ share 100% and DZ share 50. Differences in rates of aggression between these sets have indicated that aggression has a genetic element
What did coccaros twin study find?
He studied pairs of male adult twins who were either MZ or DZ. He found that the concordance rate for aggression ,defined as a direct physical assault, was 50% for MZ twins and 19% for DZ twins. And verbal aggression incidences was 28% for MZ and 7% for DZ. This suggests a genetic component
How do adoption studies help explain that
Similarities between adopted child and their biological parents suggest that genetic influences are operating and similarities between an adopted child and their adoptive parents suggest that environmental influences operate. Rhee and Waldman carried out meta analysis of adoption studies of direct aggression and anti social behaviour and found genetic influence accounted for 41%.
What are the candidate genes for aggression
MAOA gene - responsible for the production of the protein monoamine oxidase. This protein allows the metabolism of noradrenaline, serotonin and dopamine. A dysfunction in this gene can result in these neurotransmitters not being broken down. If adrenaline not broken down we have too much. This can cause hypersensitivity and May overreact to situations. Dopamine as well, if not broken down is linked to aggressive behaviour.
What happens if there is low activity of this candidate gene
More likely to be aggressive.
Strengths of genetic explanations
Abundance of research support - coccaro et al supports the role of genetics and aggression as the concordance rate of physical aggression in the form of criminal behaviour for MZ twins was much higher than DZ twins suggesting the role of nature in aggression
Scientists like godar et al have refined selective breeding by specifically removing certain genes in mice, this has been done on the MAOA gene. The MAOA knockout mice showed increased aggression and also lower levels of serotonin, demonstrating the relationship between genes and neurotransmitters. When serotonin reestablished, behaviour returned to normal. Supports genetics
Weakness
Not all research supports genetic factors for aggression - with regards to the extra Y chromosome yutes, thielgaard researched them and found it was related to increased height, not aggression. This shows we can’t make generalisations about aggression as this research shows no link.
Twin studies lack validity - every pair of twins share the same environment whereas DZ may not share it to the same extent. MZ treated the same way compared to DZ, especially if not the same seggs. Therefore aggression due to same genes and SAME environment, which may contribute to their aggression, compared to DZ twins. This explain lack validity as it also measures environmental influences
