Transcript biological_approach.

The Biological Approach
Specification details:
Basic assumptions of the biological approach including:
the influence of genes, biological structures and
neurochemistry on behaviour, genotype and phenotype,
genetic basis of behaviour, evolution and behaviour.
What is the biological approach?
• The biological approach combines psychology and
biology to provide *physiological explanations for
human behaviour.
• Biological psychology tries to explain how we think,
feel and behave in terms of physical factors within
the body.
*Physiology: the study of the body and its parts and how they
function
Basic assumptions
• Everything psychological is at first biological
• Investigates how biological structures and
processes within the body impact on behaviour.
• Much of human behaviour has a physiological
cause
• Genes affect behaviour and influence individual
psychological differences between people.
• Psychologists should study the brain, nervous
system and other biological systems, e.g.
hormones, chemicals acting on the brain
• The mind lives in the brain
Genetic basis of behaviour
Psychologists are interested in trying to determine
and provide evidence for the extent to which
behaviours, or a characteristic such as intelligence,
are the product of inheritance (genes), or
environmental influences
Methods of investigating the genetic
basis of behaviour
Twin studies
Family studies
Adoption studies
Selective breeding
Twin studies
Psychologists are interested in studying twins in
order to investigate the genetic basis of behaviour
Zygote
A fertilised egg
Monozygotic
(MZ)
One zygote –
these twins are
formed when a
fertilised cell
splits into two
and forms two
separate
embryos
Dizygotic (DZ)
Two zygotes –
these twins are
formed when
two separate
eggs both
become
fertilised by
different sperm
cells
Twin studies
Concordance rates: agreement
between
This refers to the extent to which
a pair of twins share similar traits
or characteristics
i.e. there should be 100%
concordance rates between
MZ twins if a particular
characteristic /trait is a
genetic one
DZ twins will show lower
concordance rates
Comparisons can be made
between twins raised
together and twins raised
apart
Family studies
• 1869 - Francis Galton ‘…all
natural abilities are
inherited’
• This is a simplistic viewpoint
– Galton later had to agree
that any resemblance
between family relatives
could be a result of both
genes and shared
environment
• However, with alcoholism
for example, there is a
suggestion of a biological
predisposition to the
addiction
Adoption studies
These studies involve comparing a trait or
characteristic between adopted children and their
biological or adoptive parents.
Selective breeding
• This method involves artificially
selecting male and female
animals for a particular trait.
• These animals are then put
together in order to breed and
produce offspring.
• Selective breeding has been used
to demonstrate how a number of
behavioural characteristics may
have a genetic basis. e.g. ‘maze
bright’ rats
Genetic basis of behaviour
• There is evidence from twin, family and adoption
studies to suggest that certain behaviours, for
example, intelligence, are genetically determined
• Research has shown that the environment can play
more of a role in determining behaviour than
genetics
• Selective breeding studies have demonstrated how
a number of behavioural characteristics, for
example aggression, can have a genetic basis
Genotype and phenotype
• The basic units of heredity are called genes
• Genes function in pairs and the recombination of
genes from parents to offspring provides the basis
for genetic variability
• Genes only determine the potential for
characteristics (genotype)
• The observable characteristics of an individual
(phenotype) depend on the interaction of genetic
and environmental factors.
What is a Genotype?
•The actual set of genes an individual has, or
is made up of, is a genotype.
•The genetic material is made up of DNA, for
sexually reproducing organisms, which are
given by the sperm and egg of the parents.
What is a Phenotype?
• An individual's anatomical features
or observed traits, such as
behavioural and physical
characteristics (shape, metabolic
activities, size, and colour, etc.),
fall under an individual's
phenotype.
• These behavioural characteristics
and physical attributes are what
determines an individual's ability
to reproduce and survive in the
environment.
The Difference between Genotypes
and Phenotypes
•The genotype is the genetic programming
that provides the phenotype
•To a large extent, an individual's phenotype is
determined by its genotype.
•However, genes are only part of the equation
Genotype + environment = phenotype
Example
• Hair is a good example.
• An individual's genes
determines whether or not they
have hair on their head, but
how long this hair remains
depends on environmental
factors, such as excess sunlight,
chemicals used on the head, or
poor diet.
• This shows that phenotype is
influenced by the environment
Twins
• Identical twins are another good example of the
interaction between inheritance (genotype) and
environment.
• They have the same genetic makeup and they look alike,
but they possess different phenotypes.
• Identical twins have differences that allow those who are
close to them to tell them apart. Also, their fingerprints
are different.
• Twins are genetically the same - any differences you may
see between them – for example in personality, tastes and
particular aptitudes – are due to differences in their
experience or environment.
Recessive and dominant genes
• A gene can be recessive or dominant.
• A recessive gene only shows if the individual has
two copies of the recessive gene. For example, the
gene for blue eyes is recessive. You need two copies
of the gene to have blue eyes.
• A dominant gene always shows, even if the
individual only has one copy of the gene. For
example, the gene for brown eyes is dominant. You
only need one copy of the gene to have brown eyes
(and two copies will still give you brown eyes!).
Example
Heterozygous and homozygous genes
• heterozygous – the
genotype consists of two
different genes, for
example Bb
• homozygous - the
genotype consists of two
genes that are the same,
for example BB
Summary
•Genotype is something
you cannot see with
your eyes (examples:
dominant, recessive,
heterozygous genes,
etc.)
•Phenotype are things
that can be seen with
your eyes. (example:
colours, growth, etc.)
Evolution and behaviour
Evolution: the changes in inherited characteristics in
a biological population over successive generations
Charles Darwin emphasised two main
concepts in evolutionary theory:
•natural selection
•sexual selection
Natural selection
• Animals with particular traits that provide them with an
advantage are more likely to survive and reproduce thereby
passing on their ‘adaptive traits’ to their offspring.
• These behaviours need to adapt to the environment that the
animal is living in which is dependent on three principles:
 the principle of diversity - the variety within a species
the principle of interaction - which is how this variety of
species adapt and fit in with the environment e.g. animals
that breathe air wouldn’t be able to permanently live under
water
the principle of differential amplification - those who
adapt to their environment will reproduce and those that do
not will die out.
Sexual selection
•Males have an abundance of sperm and
can reproduce with as many females as
they want.
•Females however, are limited by the
amount of eggs she produces and the fact
that she has to carry the baby for 9
months and then raise it till the age of 18.
•Females therefore will be more particular
about who fathers their children due to
the investment they have to make.
Research methods
• The biological approach
draws on concepts from the
hard sciences and research
tends to be highly scientific
in nature
• The most common
methods include laboratory
experiments and
observations
• Objective brain recording
and scanning techniques
are also used
Strengths of biological approach
• It is a scientific approach. This suggests that we can find
cause and effect relationships of both physiology and
behaviour.
• Scientific approach lends credence to study of psychology –
establishes psychology as a respectable science
• Impact of biology on behaviour can lead to treatment and
intervention to those suffering
• Understanding how an abnormal brain works can shed light
on normal brain functioning
• Measurements can be objective as it can be performed by
machines which have no vested interest in the outcome e.g.
PET scans, EEGs etc. Use of complex machinery allows
accurate and precise measurements
Limitations of biological approach
• It is a deterministic approach as it believes that we are determined by our
physiological, genetic or evolutionary make-up. Thus stating that there is no
free will.
• This approach is reductionist by stating that all human behaviour can be
explained through biological processes and we are therefore not unique as
individuals. It is also dehumanising to present humans as ‘biological machines’
• Biological approach ignores the role of the environment etc. it should be used
in combination which is known as the biosocial approach.
• Research may focus on rare conditions that have little impact on the everyday
lives of most people
• Complex machinery operated by humans and therefore measurements could
be subject to human error
• Correlations frequently employed – cannot determine cause and effect
• Small or restricted samples make findings difficult to generalise
• Laboratory experiments lack ecological validity
Can you?
1. Explain what is meant by genotype and phenotype (2
marks each)
2. Outline the influence of genes on behaviour (3 marks)
3. Using an example, explain how neurochemistry can
influence behaviour (3 marks)
4. Outline the relationship between evolution and behaviour
(4 marks)
5. Outline two weaknesses of the biological approach in
psychology (4 marks)
• Answer the ‘Check it’ questions on page 113
Essay title
Can you answer the question?
Discuss the biological approach in
psychology. Refer to at least one other
approach in your answer (12 marks)
Homework
Ensure you have written up your class notes to
include the following:
• The assumptions of the biological approach
• the influence of genes, biological structures and
neurochemistry on behaviour,
• genotype and phenotype,
• genetic basis of behaviour,
• evolution and behaviour.
• The strengths and weaknesses of the approach