Evolutionary Altruism


  • Altruism is when you perform a behavior for someone (to increase their survival) at a cost to yourself (like getting hurt) without any clear benefit to yourself
  • Having altruistic individuals in your group builds social cohesion which can strengthen the group because you have individuals willing to sacrifice themselves to benefit the survival of the group
  • People can sacrifice their time to gather food for the whole group
  • People can put themselves in danger to ensure the survival of a group member

Prosocial Humans and Chimps (Warneken and Tomasello, 2006) PDF

  • Aim: Will humans and captive chimps help someone if given the opportunity?
  • Method: Experimenter makes it clear to the chimp and human that they need help with something
    • The dependent variable was whether the child or human helped the experimenter
  • Results: Human infants help most of the time
  • Chimps help when they understand the goal of the experimenter
  • Conclusion: Helping behavior may be innate and determined by genes which makes evolutionary sense since strong social bonds means groups may be more likely to survive
    • Altruism may have evolved from a common ancestor that both humans and chimps share
  • Evaluation: They only used captive chimps which may have been helping the experimenter (who was their caretaker) because they know the caretaker provides them with food
    • This experiment tells us nothing about how helpful wild chimps are
      • Follow up experiments have shown that wild chimps do help their fellow wild chimps and not just their caretakers

Here are some clips from the Warneken and Tomasello (2006) study

Evaluation of Evolutionary Arguments

  • Testing evolutionary theories of behavior is empirically difficult so researchers may be led astray by confirmation bias
  • We know little, if anything, about Homo sapien behavior - it is purely speculative
    • We can never know how extinct species behaved
  • Disregard the role of culture in shaping behavior
  • There is a tendency for researchers to anthropomorphize animal behavior
    • A famous example is elephants who stand around dead elephants for some time which can be interpreted as the elephants grieving

Evolutionary Disgust


  • Disgust is considered a basic emotion that is hard-wired to promote survival
  • Disgust helps us avoid rotten food that could make us sick and die
  • A survey showed that participants had the strongest disgust reactions to items that threaten the immune system like pathogens (Curtis et al., 2004) PDF

Nausea and Pregnancy (Fessler, 2006) PDF

  • Pregnant women get an influx of hormones that lowers the immune system's defenses when they are pregnant
  • This happens because the baby is a foreign object to the body and if the immune system wasn't weakened it would attack the baby
  • The researchers wanted to see if nausea compensates for the weakend immune system
  • Method: They showed pregnant women different scenarios like stepping on an earthworm (which is gross but not relevant to getting sick) and maggots on meat (food scenario related to getting sick)
  • Results: Highest disgust towards food scenarios
  • Conclusion: Nausea helps pregnant women avoid rotten food and compensates for their lowered immune system during the first trimester

Ethics and Genetics

  • Telling people their behavior is because of their genes has several ethical considerations
    • There can be anxiety for the parents and children
    • Should you tell parents that they have a short serotonin transporter gene and may have passed on this gene to their children?
  • Stigmas can be attached like for the 'psychopath gene'
    • It is unlikely that all males with XYY chromosomes are criminals
  • If genes are linked to intelligence then being told you have 'stupid genes' may make you feel powerless
Criminal Genes (Barnes et al., 2011)
  • Their research found that genes may affect whether people choose a life of crime
  • This kind of research can brand criminal gene possessors as incapable of changing because they are simply born criminals
  • Therefore criminals with these genes may be less inclined to change
    • They may even believe change isn't possible
  • Using the criminal gene argument in court could lead the jury to reduce the sentence for the offender because the crime wasn't his/her fault
    • Is this what psychological research should be used for?
Addiction Genes (Morozova et al., 2012)
  • PKNOX2 gene has been linked to addictive behavior
  • Children can acquire the PKNOX2 gene from their parents
  • Is it ethical to tell the parents that their genes may be responsible for their child's addition?
  • Telling substance abusers that it is because of their genes removes personal responsibility
  • They may feel powerless to break their addiction
Depressed Genes (Collier et al., 1996)
  • 5-HTT serotonin gene has two versions
  • Short version produces less serotonin
  • Long version produces more serotonin
  • Bipolar and depressed patients are more likely to have the short transporter gene
  • Telling patients they have the short transporter gene may be counterproductive to therapy because they feel they are destined to be depressed or bipolar by their genes
  • Telling parents may make them feel responsible for their child's mental disorder

Mental Workout

Mental Workout Grows Muscles (Wright and Smith, 2007)
  • Background: This study is related to mirror neurons, the same neurons can fire when you watch yourself exercise as when you actually do exercise
  • Aim: How does a mental workout compare to physical workout in terms of muscle growth
  • Method: Control group did physical exercise for 6 weeks and the Imagery group watched a video of themselves performing the workout for 6 weeks
    • The dependent variable was strength measured after 6 weeks
  • Results: Imagery group outperformed controls even though they did less physical exercise
  • Conclusion: Suggests that muscles (physiology) can interact with cognition (thinking about exercise) and become stronger without doing any physical work

Meditation and Gamma Waves

Meditation and Gamma Waves (Lutz et al., 2004)
  • Aim: Investigate effects of meditation (cognition) on the brain (physiology)
  • Method: Compare buddhist monks who meditated long-term with 10 control participants who had just learned to meditate
    • The control participants were asked to practice meditation for 1 hour a day for 1 week
    • Used EEG recordings to compare brain activity of long-term (monks) and short-term (controls) meditators
  • Results: Monks and 2 control participants had higher gamma wave activity
    • When the control participants stopped meditating their gamma wave activity returned to normal whereas the monks' gamma wave activity remained high
  • Conclusion: Meditation (cognition) can have a permanent change on physiology (the gamma waves) if practiced enough
    • Gamma waves are supposedly related to higher reasoning ability, better memory, self-control, happiness and compassion

Oxytocin - The Prosocial Hormone?

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Oxytocin and Trust (Kosfeld et al., 2005)

  • Aim: Does oxytocin affect trust in humans?
  • Method: Humans were given either oxytocin intranasally or a placebo
  • The independent variable was what chemical the humans received
  • The dependent variable was their behavior in a trust game: do you trust the investor?
  • In the trust game the participant was an investor who could choose to invest 4 monetary units and possibly get 12 monetary units in return
  • Results: The oxytocin group was more willing to trust the investor
  • Conclusion: This suggests that oxytocin increases our feelings of trustworthiness in others
  • Evaluation: The participants did not earn the money they used in the study
  • You can argue that people are more careful with money they have earned themselves
  • They did a follow up study to ensure that oxytocin was not just increasing riskier behavior

Oxytocin and Empathy (Domes et al., 2007)

  • Aim: Does oxytocin affect empathy in humans?
  • Method: Humans were given either oxytocin intranasally or a placebo
  • The independent variable was what chemical the humans received
  • The dependent variable was their performance on an empathy test called the reading the mind in the eyes test
put reading mind in eyes test pics here
  • Participants took the reading mind in eyes test before the spray and one week later after they were given the spray
  • Results: Oxytocin group scored higher on the reading mind in the eyes test
  • Conclusion This suggests that when oxytocin levels are elevated we become better at reading the emotions in people's eyes
  • Evaluation: Well-controlled study that established a baseline of empathy for all participants before administering the spray
  • Is the reading the mind eyes test the best measure of empathy?
  • Empathy is related to feeling what others may be experiencing and not just reading emotions from eyes
  • The study therefore lacks some external validity


Oxytocin Genes and Empathy (Rodrigues et al., 2009)

  • Aim: Do people with different oxytocin producing genes have different empathy capacities?
  • Method: They compared two gene groups AA/AG genes have low oxytocin and GG genes produce more oxytocin
  • The independent variable was the gene group
  • The dependent variable was their performance on the reading the mind in the eyes test
  • Another dependent variable was their trait empathy measured by a questionnaire
  • Results: The GG group scored higher on the reading the mind in the eyes test
  • The GG group also scored higher on the empathy questionnaire
  • Conclusion: Naturally higher levels of oxytocin produced by your genes increases your empathy level
  • Evaluation: Well-controlled study that used 2 measures of empathy to establish a cause and effect relationship between the genes and empathy
  • Is the reading the mind eyes test the best measure of empathy?
  • Empathy is related to feeling what others may be experiencing and not just reading emotions from eyes
  • The study therefore lacks some external validity
  • To add external validity researchers could give participants the opportunity to help someone else in distress which would be a more ecologically valid way of measuring empathy

Oxytocin and Generosity (Zak et al., 2007)

  • Aim: Does oxytocin increase generosity to strangers?
  • Method: Give participants oxytocin or a placebo intranasally and have them split money
  • The independent variable was whether participants received placebo or oxytocin
  • Participants are given 10 USD that they can choose to split with a stranger of keep for themselves
  • The dependent variable was how much participants gave to the stranger
  • Results: Oxytocin group gave larger amounts to the stranger, they were 80% more generous than the placebo group
  • Conclusion: Having higher oxytocin levels can increase generosity in humans toward strangers
  • Evaluation: Well-controlled study to establish a cause and effect relationship between oxytocin and generosity
  • Lacks some ecological validity because the participants did not have a normal social interaction with the strangers

Oxytocin Research Evaluation

  • There is a problem of reductionism. Most research on oxytocin focuses only on positive social behavior
  • There is evidence that oxytocin can actually lead to antisocial behavior
  • Participants who were given oxytocin and won a game where more likely to gloat (Shamay-Tsoory et al., 2009)
  • The participants were happy about the opponent losing and rubbed it in their face
  • Oxytocin has been suggested as a treatment for antisocial behavior like autism
  • Shamay-Tsoory's work shows that it is important not to assume that oxytocin is exclusively positive

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 Flash Video

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