Transcript genes vs environment

Investigating the genetic basis
of behaviour
Lesson 1 Objectives
• To know the difference between nature
and nurture
• To know the terms genotype and
phenotype
• To understand why psychologists debate
genetic influences on behaviour
Nature or Nurture?
Watch this
Nature
Nurture
And the interaction
between them
Genes
Environment
Influences that occur outside
the individual could be
Pre-natal environment
Diet
Pollution
Family/peers
Media
The Current view
It is impossible to view human
characteristics and behaviour as
purely biological or environmental
• Each individual human has a genotype – this is
the genetic composition
• Each person has a phenotype which is what the
individual becomes when their genes interact
with the environment.
• http://www.youtube.com/watch?v=qyqbnDjId7g
Why is it a debate?
• It isn’t really because there is wide acceptance that
genes and the environment interact.
•
Our environment can affect our genes
•
Genes can affect our environment
• Psychologists disagree over the extent of genetic vs
environmental influences e.g they may agree that IQ is
down to both genes and environment but they disagree
on how much of it genes and how much is environment.
• ESSAY TIP 1 – Controversial Question
• How much of behaviour is determined by genes and how
much by environment?
Why is this a big question?
• A belief that intelligence is genetic could
lead to practice of eugenics – selective
breeding of humans.
• Likewise a belief that behaviour is purely
down to environment may lead to harsh
regimes based on conditioning people.
• See textbook for examples!
The Application of
Psychological knowledge
If we think a behaviour is mostly genetic, we
would treat it differently than if we thought
it was environmental (or learned)
For example think about….
Intelligence
Criminality
Homosexuality
Plenary
• Complete gap fill and questions 1-3 on
your handout.
Objectives Lesson 2
• To be able to explain the term heritability
estimate
• To describe and evaluate three pieces of
research into the genetic influences on
behaviour.
The Role of Genes in Human
Behaviour
NO – I said GENES
Twin Studies, adoption studies
and correlation
How they contribute to our
understanding of the debate
Twin and adoption studies look to see how
much of our INDIVIDUAL DIFFERENCES
are due to genes
• For example they want to know the reason
why I like oranges and you don’t. Is it more
nature than nurture or vice versa.
• The extent to which this DIFFERENCE is
due to genetic make-up is called a
Heritability Estimate.
THIS IS A BIOLOGICAL APPROACH
Comparing
• When we say we compare twins or children with
parents we mean on a measurable variable and
because we are psychologists this will be
something to do with behaviour for example
• Intelligence
• Aggression
• Introversion/extroversion
• Sense of humour
• Mental illnesses such as depression or
schizophrenia
Whatever it is you need some kind of test to give
both parties that will give a number representing
a behaviour
Twin studies
With twin studies there are 2 methods
1.comparing Monozygotic twins with Dyzygotic twins
• Eg
• MZ 0.86
• DZ 0.46
What does this indicate? .
2.Comparing Monozygotic twins reared together with
monozygotic twins reared apart
Eg
Together 0.86
Apart 0.74
What does this indicate?
Adoption studies
• With adoption studies we tend to compare
the adopted child with the biological
mother and the adoptive mother to see
which correlation coefficient is highest
• Eg
• Child and adoptive mother 0.42
• Child and biological mother 0.72
• Answer questions 4 and 5 on your
handout
• Mental Illness
• Joseph (2004) the concordance rates for
Schizophrenia is 40% for MZ twins and
7% for DZ twins.
• However Tienari et al (1994) provide
evidence of the diathesis stress model
which encompasses both genes and
environment.
Further Evaluation
Do twins, siblings and adopted and
biological children always share
the same environment?
What do you think ??
http://www.psychexchange.co.uk/vi
deos/view/20460/
So how do we explain the fact
that MZ twins reared together
do not always show perfect
concordance rates ?
The Human Genome
Examples of the effects of genes on
human behaviour
• Intelligence
• Chorney et al (1998) have identified
individual genes associated with a high IQ
through gene mapping.
• However Turkheimer (2003) states socioeconomic status is more important when
accounting for variance in IQ scores.
• Mate preference
• Evolutionary studies like that of Buss
(1989) suggests that adaptive behaviours
are passed on in our genes e.g women
preferring ambition and industriousness
• However, Buss also found cultural
variances and exceptions – 22% of
women did not prefer ambition and
industriousness.
Plenary
• Answer questions 6-8 on your handout.
Objectives Lesson 3
• To be able to describe and evaluate 3
pieces research into environmental
influences on behaviour
• To understand the term ‘neural plasticity’
• Aggression – Social Learning Theory
• Bandura’s classic bobo doll study
illustrates the importance of vicarious
reinforcement and the environment on our
behaviour
• THIS IS A BEHAVIOURIST APPROACH
• However Coccaro et al (1997) suggest
50% of variance in aggressive tendencies
is due to genes.
• Neural plasticity
• This is the ability of the brain (as in it’s
physical structure) to change according to
experiences and environmental factors
• For example in Maguire et al 2000 the
hippocampi of London Taxi drivers were
found to be larger.
• Evaluation ?
Research Study
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Blakemore and Cooper (1970)
See page 70 of textbook
What is the key message of this study?
THAT NURTURE CREATES NATURE !!
Evaluation ??
• Answer question 9-12 on your handout.
Objectives Lesson 4
To understand how genes and the
environment can interact with each other.
To prepare an essay plan for the question
Discuss the influence of genetic factors on
human behaviour (22)
Nurture affects nature!
• Look at pg 72 of your textbook
• Look at the picture of identical twins
separated at birth
• Environmental factors such as stress or
poor diet can switch on certain genes
which are then passed on to the next
generation. This is called epigenetics
Nature affects Nurture
• Do parents treat all their young children exactly the same
way? Why? Why not?
• Reactive influence - Genetic factors like temperament
can create a microenvironment.
• e.g an aggressive child may be treated with more
aggression.
Nature affects Nurture
• Passive Influence - Genetically determined behaviour of
parents might influence environment.
• e.g mental disorder of parent may cause environment
which triggers disorder in child.
• Active influence Genes may influence actively selected
parts of unshared environments in siblings – niche
picking e.g Child with high IQ seeks challenging books,
sporty child prefers outdoor activities – this has the effect
of increasing the genetic characteristic.
Overall
• Many examples demonstrate the
interaction between genes and
environment.
• Another good example is Phenylketonuriathis prevents the amino acid phenylalanine
being metabolised causing brain damage.
• However if this is detected at birth it can
be prevented through diet. So is it due to
nature or nurture?
Plenary
• Complete the gap fill on your handout and
then start work on your essay plan.
Key word check
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Epigenetics
Reactive influence
Passive Influence
Active influence
Microenvironment
Niche-picking
• Watch this
• Bear in mind the debate!