genetic factors in aggression

what are the female and male chromosomes?

• female - XX

• male - XY

early psychologists believed the cause of aggression could lie in the __ chromosome

Y

what are individuals with an XYY chromosome known as and how are they more predisposed to aggressive behaviour? (2)

• ‘super males’

• more predisposed as they have an extra Y chromosome

what supporting evidence from twin studies is there for aggression?

• researcher compared concordance rates between monozygotic and dizygotic twins for criminal behaviour

• MZ twins had 50% concordance, whereas DZ had 19% for physical aggression

• MZ twins are genetically identical so more likely to display criminal behaviour, supporting role of genetics in aggression

what gene is suggested to carry the aggression trait?

the MAOA gene (a variant of this is known as the ‘warrior gene’)

what is the role of the MAOA gene? (2)

• produces the protein monoamine oxidase A

• this protein metabolises adrenaline, serotonin, and dopamine

what is the effect if adrenaline isn’t metabolised? (3)

• levels can become too high

• causes hypersensitivity in fight or flight response

• individuals may overreact to an external stimulus and perceive a threat where one doesn’t exist

what is the effect if serotonin isn’t metabolised? (2)

• levels become low

• this has been implicated in reduction of control over impulsive behaviour

what is the effect if dopamine isn’t metabolised? (2)

• levels can become too high

• this is linked to aggressive behaviour

how does the diathesis-stress explain aggression? (2)

• suggests each person has a set amount of genes/genetic makeup that makes them vulnerable to aggression

• the amount of exposure to trauma in early life depends how many aggressive behaviours they exhibit/how aggressive they are

what supporting research is there for the diathesis-stress model?

• a researcher found an association between higher levels of antisocial aggression and low levels of activity of the MAOA gene variant in adult males

• only the case in those who had experienced significant childhood trauma (e.g. sexual or physical abuse) during the first 15 years of life

• supporting research further increases credibility of explanation

what is the weakness of the supporting research for the diathesis-stress model?

• gender bias is present as study was only conducted on males

• we can’t understand how genes and the environment are linked in women

• diathesis-stress model has low ecological validity

what is a strength of the diathesis-stress model being holistic?

• model takes into account genetic and environmental factors into influencing aggression

• aggression is a complex and multi-layered, and by taking into account multiple factors, diathesis-stress is a well detailed and fuller explanation of aggression

• this increases the ecological validity of the explanation