Evolution as an Explanation for Human Behaviour (P1 - AO1): Definitions, Sexual Jealousy
- Evolution - changes in inherited characteristics in biological population over successive generations
- Natural Selection - characteristics that are inherited because they aid the survival of an organism in an environment e.g. aggression, which are passed on to the next generation
- Inheriting traits (aggression) can help survival when there are limited resources
- Being able to defend food, tools, land, and a mate would aid survival and reproduction
- Male rival showing interest in another man’s female = sexual jealousy in the relationship, male acts aggressively towards potential male rivals
- Male needs to pass on his genes
- His aggression is an evolved response to ensure he is the one to reproduce
Evolution as an Explanation for Human Behaviour: Supporting Evidence - Love Triangles (P1)
- Daly and Wilson (1989) analysed data from 8 studies about same-sex killings involving love traingles
- Found that 92% of murders were males killing males
- Supports sexual jealousy leading to aggression towards a rival being a survival trait (acts aggression to ensure he passes on his genes)
Evolution as an Explanation for Human Behaviour: Alternative Explanation - Dollard et al. (P1)
- Unable to explain aggression towards a stranger in the street
- Dollard et al (1939) proposes the frustration-aggression hypothesis as an alternative explanation
- Individual may displace their frustration on someone else (stranger in the street) if they were unable to express their aggression at the source of their frustration at the time
- Explains aggression that isn’t adaptive or involves the transmission of genes
AO3 ‹-› Evolution could explain this if the source of the frustration was a child = displace their frustration to ensure their child’s safety and the passing on of their genes
Evolution as an Explanation for Human Behaviour (P2 - AO1): Aggression Towards Partners, Parental Aggression
- Aggression towards partners can be explained using the evolutionary explanation
- Males can use ‘direct guarding’
- Restrict the movement of the female to prevent her from straying
- Coercive control
- Checking her phone and restricting her communications
- Negative Inducements - physical threats and actual violence
- Can explain why parents act aggressive if their offspring are threatened by other people -> aggression is an adaptive trait, enables them to protect their offspring and ensure their genes are passed on
Evolution as an Explanation of Human Behaviour: Supporting Evidence - Direct Guarding (P2)
- Wilson and Daly (1996) found that direct guarding can involve male vigilance over a partner’s behaviour (keeping tabs on their whereabouts, checking who they have been seeing, coming home early to check on them)
- Shows that males will behave aggressively towards females to ensure they have someone to reproduce with
Evolution as an Explanation for Human Behaviour: Alternative Explantion - Bandura (P2)
- Aggression acquired through the observation and imitation of role models
- More likely if the behaviour is gender typical (physical aggression in males)
- Shows that social factors (exposure to an aggressive role model) may be an influential factor when explaining human aggression
Evolution as an Explanation for Human Behaviour (Conclusion)
AO3 ‹+› Able to explain gender differences in aggression which have been seen consistently across different cultures
Aggressive and dominant males are more likely to gain status, females and be able to reproduce to pass on their genes
Less aggressive females (more cooperative) can increase their chances of survival by protecting their offspring as part of a social group
AO3 ‹-› Reduces the complex human behaviour of aggression down to a transmission of genes, fails to consider the interaction between genes and the environment - reductionist
Adoption Study: Heston - Aim, Sample (P1)
- Aimed to investigate whether nature or nurture was responsible for the development of schizophrenia (Sz)
- Final Sample:
- 47 participants, born to Sz mothers in an American psychiatric hospital and given up for adoption
- Matched with 50 controls (children given up for adoption with no Sz mothers) for sex, type of eventual placement, length of time in childcare
AO3 ‹+› 47 matched with a control group on sex, type of eventual placement and length of time in childcare, confident that having a mother with Sz is the only difference affecting participants and controls, increases internal validity
AO3 ‹-› sample of Sz mothers may be unrepresentative of all mothers with Sz (they gave their babies up for adoption due to being in a psychiatric unit), cannot generalise to Sz mothers who did not give their babies up for adoptions, lowers population validity
Adoption Study: Heston - Procedure (P2)
- Data collected for each individual through:
- School records
- Psychiatric hospital records
- Interviews
- Personality inventory
- Diagnosis of Sz only given if the raters (2 psychologists and Heston) agreed -> blindly and independently rated each participant
- Participants scored on psycho-social disability
- Participants born to Sz mothers -> scored an average of 65.2, rate of Sz was 10.6%
- Controls -> scored an average of 80.1, rate of Sz was 0%
- Concluded that his findings support the influence of genes in Sz as his findings matched the concordance rates of Sz in the general population if a child has one Sz parent
AO3 ‹+› data collected from several different sources (interviews, school records, personality inventory), detailed quantitative and qualitative data allowed psychiatrists to collate the data to make an informed diagnosis for Sz, increases validity of findings
AO3 ‹-› possibility that the selective placement meant the adopted children were often placed with families similar to their birth family, he may have overestimated the role of genes in the development of Sz, similar environmental factors may have contributed to its development
Adoption Study: Heston (Conclusion)
AO3 ‹+› Adoptions occurred naturally, no direct manipulation of the child’s behaviour or placement, ethical
AO3 ‹-› Findings may lead to stigma for adopted individuals with Sz mothers (seen as less socially able)
Hormones as an Explanation of Aggression: Testosterone (P1 - AO1)
- Hormones -> chemical messengers secreted by glands and travel in the bloodstream
- Affect mood, metabolism and growth
- Production of testosterone increases with the onset of puberty in males
- Produced in spurts, levels can rise suddenly and have an effect within minutes
- Shortly after birth, testosterone stimulates cell growth in the amygdala and hypothalamus (important structures in processing and regulation of emotion)
- High testosterone linked to high aggression
Hormones as an Explanation for Aggression: Supporting Evidence - Dabbs (P1)
- Dabbs (1987) took saliva samples from 89 male prisoners (violent and non-violent offenders) to measure testosterone
- 10/11 violent prisoners had higher levels of testosterone compared to non-violent prisoners
- Supports link between higher levels of testosterone and violence, measured objectively using saliva samples
Hormones as an Explanation for Aggression: Refuting Evidence (P1)
- Higley et al (1996) found that individuals with elevated testosterone levels exhibited signs of aggression, but rarely committed aggressive acts, suggests cognitive and social factors play a mediating role
- Refutes the idea that higher testosterone automatically results in more violence an aggression , other factors play a role
Hormones as an Explanation for Aggression: Cortisol, Oestradiol (P2 - AO1)
- Cortisol:
- Produced in the adrenal glands, manages stress levels
- Seems to inhibit aggression = low cortisol linked with increased aggression
- Dual-hormone hypothesis (Carré and Mehta, 2011) states that aggression is an interaction between cortisol and testosterone -> high levels of testosterone lead to high levels of aggression only when cortisol is blocked, testosterone’s influence on aggression blocked when cortisol is high
- Oestradiol:
- Type of oestrogen found in women
- Associated with dominance, motivation and physical aggression -> some research suggests a positive correlation between oestradiol and aggression
Hormones as an Explanation for Aggression: Supporting Evidence - Barzman et al, Weakness (P2 - AO3)
AO3 ‹+›
- Barzman et al (2013) tested 17, 7-9 yrs old boys in a psychiatric hospital for testosterone and cortisol levels in saliva
- Cortisol levels showed a greater morning-to-evening decline in aggressive boys compared to other boys
- Supports the idea that lower cortisol levels may lead to more aggressive behaviour -> objective data, free from researcher bias, increases credibility
AO3 ‹-›
- Evidence of the link between hormones and aggression is usually correlational
- Do not allow for cause and effect statement to be made
- Direction of effects is unclear (high testosterone causes high aggression or vice versa)
Hormones as an Explanation for Aggression
AO3 ‹+› Scientifically credible,
U.A. development pf chemical treatment for aggression (Depo-Provera, artificial progesterone, treat sex offenders)
AO3 ‹-› Simplifying the complex human behaviour of aggression down to hormones is biologically reductionist, holistic view more beneficial (personality and exposure to aggression which may be socially learned)
