Testosterone - The Aggressive Hormone?

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Testestorone - The Aggressive Hormone?

• Rats are more aggressive when exposed to testosterone prenatally
• Rats will bite and attack more
• When you castrate male rates the aggression is reduced
• Castrated males lose social dominance (Albert et al., 1986)
• There is also a link between testosterone and aggression in primates (Higley et al., 1966)

Testosterone and Criminal Males (Dabbs et al., 1995)

• Aim: Is testosterone related to the type of violent crimes males commit?
• Method: Measured testosterone in the saliva of 692 male prisoners
  
  • Looked at the criminal records of the prisoners for violent and non-violent crimes
• Results: Found that testosterone levels predicted violent crimes like homicide and rape
• Conclusion: Testosterone levels may affect the types of violent crimes criminals commit
• Evaluation: What about testosterone and violent crimes in females?
  
  • What about effects of environment like upbringing by parents?
  • There is a confounding variable of motivation for committing crimes: senseless violence or acts of vengeance. It is arguably more horrific if someone goes around murdering for fun rather than to right a wrong they feel was done to them
  • This study had a huge sample size which is a strength
  • It is a correlational study and therefore cannot imply causation

Testosterone and Criminal Females (Dabbs and Hargrove, 1997)

• Aim: Is testosterone related to the type of violent crimes females commit and their behavior in prison?
• Method: Measured testosterone in the saliva of 87 female prisoners
  
  • Looked at the criminal records of the prisoners for violent and non-violent crimes
  • Added an extra category of defensive violent which they defined as females being violent towards a perpetrator had abused them in the past
• Results: Found that testosterone levels predicted violent crimes
  
  • Found that testosterone levels were related to their aggressive behavior in prison
• Conclusion: Testosterone levels may affect the violent behavior in and out of prison
• Evaluation: Considering females is a strength
  
  • What about effects of environment like upbringing by parents?
  • They fixed the confounding variable of motivation for committing crimes by adding the defensive violence category
    
    • Why didn't they use this category for the men in the 1995 study? Possible gender bias

Testosterone and Aggression Evaluation Studies

Testosterone and Wrestlers (Fry et al., 2011)

• Aim: Do testosterone levels change when you win a wrestling match?
• Method: Measure blood in testsoterone of 12 collegiate wrestlers before and after their match
• Results: Testosterone increased for both winners and losers but the winners had higher increases than the losers
• Conclusion: Suggests that winning increases your testosterone more so than losing does
• Evaluation: Is the testosterone related to how aggressive they were? Or is the testosterone only related to winning the match?
  
  • What about females? Only male wrestlers were used
  • This study supports the challenge hypothesis of testosterone which is explained later

Testosterone and Chess Players (Mazur et al., 1992)

• Aim: Do testosterone levels change when you win a chess match?
• Method: Measure testosterone in chess players
• Results: Chess players who won had higher testosterone than players who lost
• Conclusion: Chess is non-violent yet testosterone increased which suggests testosterone may be related to winning and gaining social status rather than just being more aggressive
• Evaluation: What about other non-violent games in other cultures?

Testosterone and Fairness (Eisenegger et al., 2010)

• Folk hypothesis of testosterone is that is it linked to aggression
• Aim: Can testosterone lead to fair behavior? Does the belief in the folk hypothesis affect behavior?
• Method: Human females received either testosterone or a placebo
  
  • They played an ultimatum game where participants had to choose how to divide money
  • The proposer could be fair or unfair (the dependent variable)
• Results: Females who received testosterone made fair offers
  
  • Females who received placebo made unfair offers
  • Females who believed they received testosterone made unfair offers
  • Femals who believed they received placebo made fair offers
• Conclusion: There is a social and biological factor at play in terms of testesterone and fairness
  
  • The biological factor of receiving testosterone increases fairness
  • The social factor of believing the folk hypothesis of testosterone affects fairness

Testosterone Overall Evaluation

• Testosterone has been linked to aggressive behavior in both animals and humans
  
  • Problem of causality in testosterone and aggression studies
  • Does having high testosterone cause you to be violent or does being violent raise your testosterone levels?
• The recent evidence favors a social status function of testosterone related to winning and losing rather than purely aggression

Serotonin and Sexuality

Serotonin and Sexual Orientation (Liu et al., 2011)

• Aim: Is serotonin related to sexual preference in rats?
• Method: Male mice were genetically manipulated to have a gene that produced normal amounts of serotonin or low amounts of serotonin
• The independent variable was whether the mice got manipulated to have a low or normal serotoning producing gene
• They placed the manipulated mice in cages with other male mice and/or female mice
• The dependent variable was which sexes the male mice chose to mount
• Results: Normal serotonin males mounted females 60-80% of the time and mounted males 20% of the time
• Low serotonin males lost their sexual preference for females and mounted both males and females equally 80% of the time
• Conclusion: Serotonin affects sexual preference in rats such that low serotonin mice become more bisexual than normal serotonin rats
• Evaluation: Cannot generalize these findings to humans and it would be unethical to genetically manipulate humans to test for the chemical roots of sexual preference
• What about female rats? Only male rats were used in this study

Here are some videos of the rats in Liu's study

Normal serotonin male chooses a female over a male - hetero rat

Low serotonin male mounts a male - homo rat?

Low serotonin male mounts both male and female - bisexual rat?

Serotonin and Risky Behavior

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Serotonin and Risky Male Behavior in Monkeys (Higley et al., 1996)

• Aim: Is serotonin related to taking risks?
• Method: A field study where they followed male monkeys who were migrating to new social groups
• Measured the serotonin by extracting cerebrospinal flluid by placing needles in their spines
• The independent variable was dividing the monkeys into high, mid-high, mid-low and low serotonin groups
• The dependent variables were how aggressive the monkeys were observed to be, number of scars they had and death
• Results: 11/49 of the monkeys who died had low serotonin levels
• Conclusion: Monkeys with low levels of serotonin are more likely to take risks like fighting with other monkeys
• Evaluation: This field study has high ecological validity but lacks the control of lab experiments
  
  • Sex difference - What about female monkeys?
  • External validity - Do these results generalize to human males?

Serotonin and Risky Female Behavior in Monkeys (Westergaard et al., 1999)

• Aim: Is serotonin related to taking risks for females?
• Method: Observational study of captive monkeys
• The independent variable was the species of monkey: rhesus monkeys or pigtailed macaques
• Rhesus monkeys are known to be aggressive
• Pigtailed macaques are known to be friendly
• The dependent variable was the level of serotonin they measured in the cerebrospinal fluid like Higley et al., 1996
• Another dependent variable was how aggressive the monkeys behaved and how many wounds they had
• They placed each monkey in same sex groups to see how they behaved
• Results: Rhesus monkeys were more aggressive and had more wounds
• Rhesus monkeys had less serotoninthan pigtailed macaques
• Conclusion: Serotonin inhibits risky behavior in females as well
• Evaluation: This field study has high ecological validity but lacks the control of lab experiments
  
  • External validity - Do these results generalize to human females?

Serotonin and Gambling Monkeys (Long et al., 2009)

• Aim: Test if serotonin levels are related to gambling risks in a controlled environment
• Method: They manipulated the amount of serotonin the monkeys could produce by forcing a certain type of diet
• Tryptophan is the raw material required to produce serotonin and is found in certain foods
• The independent variable was the tryptophan level of the diet which was high or low in tryptophan
• High tryptophan meant more serotonin should be produced than the low tryptophan diet
• The dependent variable was the choice the monkey made in the gambling task
• In the gambling task the monkey could choose a safe option which would guarantee they would get a normal amount of juice
• There was a riskier option where they could get a low or high amount of juice
• Results: The low tryptophan group chose the risky option whereas the high tryptophan group chose the safe option
• Conclusion: Levels of tryptophan as determined by diet can affect serotonin levels and risky behavior
• Evaluation: Lab experiment had a high amount of control but a small sample size (only 3 monkeys) and low ecological validity
• Do these results generalize to humans?

Hippocampus and Spatial Navigation

Hippocampus and Spatial Navigation (Maguire et al., 2000)

• Aim: Does the hippocampus play a role in spatial navigation?
• Method: The independent variable was the group of people and how much they had been navigating - they compared London taxi drivers to a control group
• The dependent variable was the hippocampus size
• Results: They found that taxi drivers have a larger posterior hippocampus than the control group
• The size of the posterior hippocampus positively correlated with how long the taxi drivers had been working as taxi drivers
• Conclusion: This suggests that the posterior hippocampus has the localized function of spatial navigation
• The longer you spend taxi driving the more it affects the posterior size of the hippocampus
• This suggests that practicing navigation (a form of cognition) affects hippocampus size (physiology)
• You can also use this study for the syllabus point of an interaction of cognition and physiology

Broca's Area

• Aim: Broca noticed some patients had problems with speech production and he wanted to find out if their impediment was related to the brain
• Method: Dissected the brains of the patients to look for lesions
• Results: He found that there was an overlapping damaged area in the left frontal lobe of the patients
• Evaluation: MRI results of Broca's patients showed more damage than just Broca's area (Dronkers et al., 2007)
  
  • Dronkers results suggests that the speech production difficulty of Broca's patients may be due to more extensive brain damage than just Broca's area
  • Plaza et al., (2009) found that patients other brain areas took over the function of Broca's area if their Broca's area was damaged
• Conclusion: Broca's area is localized for some aspects of speech production but Broca's aphasia can be a combination of various lesions to brain areas beyond Broca's area
• Here is a video of Broca's patients demonstrating a lack of speech fluency

Biological Research Methods

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• Lab Experiments
  
  • Vontrolled studies that attempt to find cause and effect relationships between independent and dependent variables
• Neuroimaging allow you to find brain regions (biological correlates) of behavior
• PET
• fMRI
• Correlational studies allow you to test the role of genetics vs. environment on behavior
• Twin studies - twins reared apart to test the effect of genetic vs. environment on their behavior
• Any differences found between twins reared apart are considered environmental
• Family studies
• Lesion studies allow you to find biological correlates of behavior, we assume the missing behavior and damaged brain area are related
• Phineas Gage's personality changed because of damage to his frontal lobe area
• HM
• Clive Wearing

Biological Principles

• Behavior is biologically determined by physiological processes such as the nervous system neurotransmitters (e.g. serotonin) and the endocrine system (hormones e.g. adrenalin increases heart rate and fight or flight response)
• "All that is psychological is first physiological" (Sperry)
• Patterns of behavior can be inherited through genetics
• Some patterns of behavior may be a result of natural selection
• The study of animals can inform our understanding of human behavior
• Psychologists use rats and monkeys for a lot of research but the results cannot always be generalized to humans