Examine one explanation of
evolutionary behaviour
SAQ
Link back to principles of BLOA
 If we assume (a) that a predisposition for certain
behaviours is inherited and (b) that the principles of
evolution dictate that genetically based behaviours of
an individual who has reproduced are passed on (while
genetically based behaviours of unsuccessful individuals
are lost over time), then behaviours we observe today
should have evolutionary explanations.
 In Staller terms: If a behaviour exists today, then it must
have helped human survival and reproduction
 A behaviour that helps a species survive and reproduce
is known as adaptive
Evolutionary Psychology
 Applies Darwin’s theory of natural selection to human behaviour
 We often think of evolution having to do with primates such as in
Matsuzawa’s 2007 study (spatial memory in Chimps, pg. 57).
Chimps had a better spatial memory, which is required for their
survival to find food and be aware of dangers.
 Ex. Chartrand & Bargh (1999) studied the chameleon effect in
humans.
 The natural tendency to imitate each other's body postures, hand
gestures, speaking accents, etc.
 Study showed that people who engage more in imitative
behaviour rated the person they imitated higher in terms of
likeability, suggesting that imitating actually increased social
bonding, which is an important adaptive behaviour for the success
of the group
Fessler (2005)
 Aim: to investigate the nausea experienced by women in their first
trimester of pregnancy (a type of disgust reaction)
 Method: 496 healthy women between the ages of 18-50 were
asked 32 questions with specific ‘disgusting’ questions (ex.
Maggots on meat, the thought of rare meat on your dinner plate
)
 Controlled the confounding variable by asking the same
participants questions beforehand to make sure they weren’t
nauseous from morning sickness.
 No compensation offered to the women. Web-based
questionnaire.
 The sense of disgust is heightened when we have a reaction to
dangerous situations (or food)
 During the first term of pregnancy, the mother’s immune system is
lower because of specific hormones that are released to prevent
the mother’s body from killing the foreign genetic material (AKA
the ‘fetus’)
Fessler Cont’d…
 Results: More women were nauseated when it involved food.
 So (insert student’s name who is NOT paying attention here)
what does disgust and nausea have to do with evolution?!?!
 Fessler suggests that many of the diseases that are most
dangerous are food-borne, but our ancestors could not
afford to be picky about what they ate, as it was slim
pickings.
 Natural selection may have have helped to protect the
mother and fetus from getting sick by forcing the mother to
be picky about her food choices in the first trimester
(decreased the desire to eat certain foods which may have
increased risk of disease)
EXAMINE…
 Means that you should consider whether this evolutionary
theory can be supported or not. You should also explain
general problems in evolutionary explanations.
 With the partner sitting beside you, come up with some
critiques for evolutionary explanations
And here they are folks…
 It is difficult to test evolutionary theories and not much is
known about the life of early humans.
 Evolutionary explanations tend to focus on biological
factors and underestimate cultural influences.
 According to Davey (1974), disgust for spiders may be
explained by people’s need to find tangible causes of
illness and disease when causes are unclear.
Stringing evolution through the unit
 Connection:
 Oxytocin and trust (Explain, using examples, the function of 2
hormones on human behaviour) Could also use Newcomer et al
(1999), Experiment on cortisol and memory
 Oxytocin (secreted by the hypothalamus) has been linked to trusting other
people. Experimental manipulation of oxytocin levels has shown increase in
trust
 According to evolutionary psychologists, trust is an important social tool
in the relationship between humans.
 Trust is an adaptive mechanism as it helps humans to form meaningful
relationships at a personal and professional level.
 Betrayal disrupts bonds of trust and may result in the avoidance of the
person who has betrayed you, or you may end up on Jerry Springer.
Trust & Oxytocin
 Baumgartner et al. (2008): The role of oxytocin in trust in
economic behaviour
 Aim: To investigate the role of oxytocin after breaches of
trust in a trust game
 Method: Subjects played a trust game used by
economists and neuroscientists to study social interaction
 Player 1 (the investor) had the option of sharing their
money with a ‘trustee.’ If they did share, the investor’s
money was tripled. Then the trustee decides if the
money should be shared (trust) or not (violation of trust)
Method:
 Researchers conducted fMRI scans on 49 participants.
They received wither a placebo or oxytocin nasal spray.
 Subjects played against different trustees in the trust
game, as well as a computer in a risk game.
 In 50 % of the games, their trust was broken. Subjects
received feedback on this from experimenters during
their games.
Results of Baumgartner
 Participants in the placebo group were likely to show less
trust after feedback on betrayal. They invested less.
 Participants in the oxytocin group continued to invest at
similar rates after receiving feedback on a breach of
trust.
 The fMRI scans showed decreases in responses in the
amygdala (which is involved in emotional processing
and has many oxytocin receptors)
Baumgartner Evaluation:
 Oxytocin could explain why people are able to restore
trust and forgive in long-term relationships
 Scanner research maps brain activity, but nothing
definite can be confirmed about what it really means.
 Too reductionist: giving oxytocin like this in an experiment
may not reflect natural physiological processes. The
function of oxytocin is far more complex and it is too
simplistic to say that it is the trust hormone.
How could homosexuality be
adaptive behaviour?
 If evolution is adaptive, then how can homosexuality be
genetically transmitted when it seems more likely to
prevent reproduction?
 the presence of an individual homosexual person in the
family offers some kind of reproductive advantage to
others in the family
 Ex. Sharing resources and care for others, which increases
the reproductive capabilities for the family, rather than
reproducing themselves
Evolution of Homosexuality Cont’d
 Zietsch et al. (2008) suggest that the idea that the genes which
incline a man towards homosexuality are advantageous in a
heterosexual man – perhaps somehow increasing his attractiveness
to women.
 Link to another study which shows that women are more
attracted to men with more feminine faces at certain times
during their menstrual cycle.
 When we inherit some of the genetic predisposition for
homosexuality, but do not consider ourselves homosexual, we
have inherited some characteristics normally associated with
the opposite sex, and these somehow make us more attractive
to members of the opposite sex.
 Men may, therefore , be attracted to women who have the
stereotypically masculine features of competitiveness and
sexual willingness.
Does nurture or nature determine
gender identity?
 Money (1974)  Crane, pg 37
 Longitudinal Study on David Reimer
 A boy who lost his penis during a circumcision accident
 Money suggested his parents give him a sex change
 Money was not upfront with the parents about his intentions
 to prove that nurture determines gender identity, not
nature
 When David grew up, he displayed masculine behaviour
 Findings: Psychosexual development is determined by
chromosomes and hormones.
Homicide Adaptation Theory (HAT)
 We are genetically predisposed to kill other humans in specific
situations because it increases the chances of our own survival
until we can reproduce; in some cases, by killing those who are
competing with our own children for resources, we increase
the chance of our genes being passed on through our
children.
 Cost-Benefit Analysis: There are significant costs to homicide
that makes the theory less likely to be valid.
HAT Critique…
 Durrant (2009) found that a possible weakness of this
theory is the idea that some behaviours which have
evolved over time are not adaptations to increase
survival or reproductive success, but are by-products of
evolution.
 So…. Maybe homicide has no advantage
Testing Evolutionary Psychology…
 How? Carry out a Cost-Benefit Analysis
 Weigh the the +’s and –’s of killing somebody
 IF there are more costs than benefits, it seems unlikely that the
behaviour is the result of successful adaptation.
 Ex. It has been argued that rape cannot be an adaptive
behaviour as the costs outweigh the benefits.
 Durant gives the example that attempting to kill will expose an
individual to potential harm that might result in their own death,
which is hardly adaptive, nor is the risk of being ostracized by a
social group.
 THUS,Durant concludes that HAT is unlikely to be correct
Class Interactive
 You will be given one piece of paper.
 Try and solve the first anagram on your own when I say
go.
 When you are done the first one, flip the paper over and
raise your hand.
 Wait for the next instruction.
Class Interactive
 Link to Seligman study for homework
 What is learned helplessness?
 Sense of powerlessness brought on by a traumatic event or
persistent failure to succeed.
 Thought to be one of the leading causes of depression
Homework:
 Read the following article summarizing Seligman’s study.
It can be used for both the CLOA and BLOA. Explain
why.
 Seligman
 Can evolution be used to explain Seligman?
What about a reductionist approach?
 Wednesday & Thursday: BLOA wrap-up
 Friday: In-Class SAQ and ERQ