Psychological perspectives - Biological Flashcards
(18 cards)
Biological Psychology
Studies how behavior and experiences arise from nervous system activity
Influenced by Darwin’s theories of evolution and genetics
Inherited traits enhance survival (e.g., aggression deters predators)
Charles Darwin and Evolutionary Theory
Charles Darwin introduced the theory of evolution through natural selection
Suggests that traits enhancing survival and reproduction are passed down to future generations
Genetic traits that provide an advantage (e.g., aggression for defense) are more likely to persist
His theory influenced biological psychology, linking genetics and behaviour.
Genes and Behaviour
Genes found in cell nuclei, responsible for inherited traits
Criminal behaviour may have genetic components
Biological psychology examines how DNA influences behaviour
Factors affecting behaviour: chromosomes, hormones
Sex vs. Gender
Sex: biological differences (e.g., XX or XY chromosomes, hormones)
Gender: culturally defined roles
Biological approach: gender behaviour is determined by biology.
DNA, Genes, and Chromosomes
Chromosomes carry DNA; DNA builds and maintains the body
Genes dictate physical traits
XYY Syndrome: extra Y chromosome in males, linked to impulsive behaviour.
The Warrior Gene (MAOA Gene)
Affects neurotransmitters (serotonin, dopamine, noradrenaline)
Low-activity MAOA (MAOA-L) linked to aggression
Brunner et al. (1993): Dutch family study linked MAOA deficiency to violent behaviour
Gene-environment interaction affects aggression
Brunner’s Theory (1993)
Studied 28 males from a Dutch family involved in violent criminal behavior
Found they had a mutation in the MAOA gene leading to low MAOA enzyme levels
Suggested a genetic link to aggression, but also emphasized environmental factors.
Concluded that genetics alone do not determine behaviour but interact with upbringing.
MAOA Gene Research
Cases et al. (1995): Mice with low MAOA had increased aggression
MAOA present in 1/3 of Western men, rarely in women
Not all aggression is explained by MAOA gene.
Theilgaard Study (1984)
Investigated links between XYY chromosome and aggression
Found little evidence supporting XYY males being more aggressive
Small sample size limits conclusions.
Correlation does not imply causation.
Twin Studies
Method used to identify genetic basis of behavior
Examines monozygotic (MZ, identical) and dizygotic (DZ, non-identical) twins
MZ twins share 100% genetic makeup; DZ twins share 50%
Twins are raised in the same environment, controlling social factors
Greater similarity in MZ twins compared to DZ twins suggests genetic influence.
Johannes Lange (1920s) Study
Studied 30 pairs of same-sex twins
17 pairs were DZ, the rest were MZ
At least one twin in each pair was a criminal
Results:
10 out of 13 MZ pairs both had criminal records
Only 2 out of 17 DZ pairs both had criminal records
Suggested strong genetic component to criminal behaviour.
Karl O. Christiansen (1977) Study
Examined 3,586 twin pairs in Denmark (born 1881-1910)
Found that:
If one MZ twin was criminal, the other had a 50% chance of also being criminal
If one DZ twin was criminal, the other had only a 20% chance.
Stronger correlation for violent crimes and long criminal careers.
David C. Rowe (1980s-1990s) Study
Investigated self-reported delinquency in twins
Found that MZ twins were more likely than DZ twins to both engage in delinquent activities
MZ twins reported having more delinquent peers than DZ twins
Suggested both genetic and social influences on delinquency.
Advantages of Twin Studies
Natural experiments due to biological relation of twins
Helped in preventing vulnerable disorders
Christiansen’s study supports a genetic basis for criminality
Lange’s study found MZ twins were more likely to both have served in prison (10/13 MZ vs. 2/17 DZ)
Disadvantages of Twin Studies
Early studies (e.g., Lange) lacked proper controls and validity
MZ and DZ twins were identified based on appearance, not DNA
Small sample sizes limit generalizability
Shared environments may contribute to criminality, making it difficult to isolate genetic effects.
Adoption Studies
Used to separate genetic and environmental influences
Studies children raised by adoptive parents with no genetic similarity.
Lombroso’s Criminal Theory
Criminal traits are inherited and identifiable through physical characteristics
Thieves: expressive faces, small eyes, manual dexterity
Murderers: cold, glassy stares, bloodshot eyes, hawk-like noses
Female criminals: ruthless, lustful, immodest, shorter, wrinkled, darker-haired
Sheldon’s Somatotype Theory
Body type influences personality and criminal behaviour
Mesomorph: muscular, prone to violent offences
Ectomorph: thin, linked to online crimes
Endomorph: larger, linked to sexual offences
