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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
      • A follow up experiment by Warneken and Tomasello showed that wild chimps do help their fellow wild chimps

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
    • An 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?

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