Twin Studies
Twins are used to determine whether behaviour is biological and universal to all or if behaviour is due to nurture (environment)
MZ twins are identical twins which share 100% of their DNA. DZ twins are non identical and share 50%.
Concordance rates look at the likelihood of if one twin has a particular trait, the other will also have it e.g. schizophrenia
If there is a high concordance rate for MZ twins it suggests there may be a genetic cause
If twins raised apart show similar traits this suggests a strong genetic influence
+ Twins are tested for zygosity using blood tests, visual appearance and fingers prints, this makes them a reliable method
+ Twin studies are useful to society as they can isolate specific genes
- Data is only useful if it is collected in a valid, reliable way e.g. IQ is difficult to measure
- Separated twins may be difficult to compare – age of separation, different circumstances, similar environment
- Difficult to collect a large sample of twins and for there to be similarities e.g. in age of the pp's
- MZ twins are more likely to be treated the same
- May not be able to generalise to others- most people are not twins
- Difficult to find twins that fit the criteria
Adoption Studies
Adopted children share no genes in common with their adopted family but share the same environment. They share 50% of genes with their biological parent but not the same environment,
This allows for similarities to be looked at between the child and their biological parents and the child and their adoptive parents
E.g If studying intelligence, if the child shows a high IQ and so does the biological mother, and the adoptive mother shows an average IQ this could suggest that genetics are the main influence.
+ Direct comparison of nature vs nurture – isolate influence of genetics from environment
+ can investigate a range of behaviours using a range of methods and samples e.g. trans-racial adoption
- Representativeness of the sample – not everyone is adopted and other factors may influence adoption
- Adopted children are often placed with families similar to their biological family
Animal Studies
Animals are used in studies when humans cannot be used
They can be used biologically to look at how genes and hormones play a role in behaviour
Clinically, they can be used to test new drugs and to identify biological causes of disorders
They can also be used to study learning – e.g. training through positive reinforcement
+ It is more ethical to use animals – they can be used when we are unable to use humans
+ It is more practical – animals are easy to handle, have shorter life spans and gestation
+ Fairly generalisable – some animals are similar to humans e.g. primates e.g. brain, chromosomes
+ Using animals is reliable as you can careful control variables e.g. diet and this can easily be replicated
- Research can be limited as researchers need to follow the guidelines, so some research may not be allowed
- Hard to generalise – differences that make animals useful e.g. life span, make it difficult to compare to humans
- Human behaviour more complex
- Credibility – it is difficult to trust all findings from animal studies and apply them to humans
Ethical guidelines for animals
The law – failure to comply = prosecution
Cost benefit analysis - Bateson
Species – knowledge of their natural history
Minimal number of animals
No endangered species
Caging and social environment
Consideration of animal’s normal living habitat
Home office licence
Lesion studies
This is where damage is caused to the brain and the change in behaviour can be measured.
This can be permanent – by removing parts of the brain or by damaging connections; or temporary where drugs can be used to shut off parts of the brain. IV = damage to the brain; DV = changes in behaviour
Studies using animals
Genes:
Mice can be used to see whether a particular gene causes an abnormality
Rats have been used to study Parkinson’s Disease – rats injected with drugs to replicate the symptoms, then gene therapy used to treat the symptoms
The nervous system:
Rats used to study the effects of antipsychotic drugs
Mice used to investigate changes in neurotransmitters when under stress
Brady (1958) Monkeys used to study the effects of stress
Functions of the brain
Rats initially used to find out the effects of antipsychotic drugs on the brain.
Lashley (1950’s) used rates to investigate brain function by removing brain parts to see what effects this would have on memory.
Twins are used to determine whether behaviour is biological and universal to all or if behaviour is due to nurture (environment)
MZ twins are identical twins which share 100% of their DNA. DZ twins are non identical and share 50%.
Concordance rates look at the likelihood of if one twin has a particular trait, the other will also have it e.g. schizophrenia
If there is a high concordance rate for MZ twins it suggests there may be a genetic cause
If twins raised apart show similar traits this suggests a strong genetic influence
+ Twins are tested for zygosity using blood tests, visual appearance and fingers prints, this makes them a reliable method
+ Twin studies are useful to society as they can isolate specific genes
- Data is only useful if it is collected in a valid, reliable way e.g. IQ is difficult to measure
- Separated twins may be difficult to compare – age of separation, different circumstances, similar environment
- Difficult to collect a large sample of twins and for there to be similarities e.g. in age of the pp's
- MZ twins are more likely to be treated the same
- May not be able to generalise to others- most people are not twins
- Difficult to find twins that fit the criteria
Adoption Studies
Adopted children share no genes in common with their adopted family but share the same environment. They share 50% of genes with their biological parent but not the same environment,
This allows for similarities to be looked at between the child and their biological parents and the child and their adoptive parents
E.g If studying intelligence, if the child shows a high IQ and so does the biological mother, and the adoptive mother shows an average IQ this could suggest that genetics are the main influence.
+ Direct comparison of nature vs nurture – isolate influence of genetics from environment
+ can investigate a range of behaviours using a range of methods and samples e.g. trans-racial adoption
- Representativeness of the sample – not everyone is adopted and other factors may influence adoption
- Adopted children are often placed with families similar to their biological family
Animal Studies
Animals are used in studies when humans cannot be used
They can be used biologically to look at how genes and hormones play a role in behaviour
Clinically, they can be used to test new drugs and to identify biological causes of disorders
They can also be used to study learning – e.g. training through positive reinforcement
+ It is more ethical to use animals – they can be used when we are unable to use humans
+ It is more practical – animals are easy to handle, have shorter life spans and gestation
+ Fairly generalisable – some animals are similar to humans e.g. primates e.g. brain, chromosomes
+ Using animals is reliable as you can careful control variables e.g. diet and this can easily be replicated
- Research can be limited as researchers need to follow the guidelines, so some research may not be allowed
- Hard to generalise – differences that make animals useful e.g. life span, make it difficult to compare to humans
- Human behaviour more complex
- Credibility – it is difficult to trust all findings from animal studies and apply them to humans
Ethical guidelines for animals
The law – failure to comply = prosecution
Cost benefit analysis - Bateson
Species – knowledge of their natural history
Minimal number of animals
No endangered species
Caging and social environment
Consideration of animal’s normal living habitat
Home office licence
Lesion studies
This is where damage is caused to the brain and the change in behaviour can be measured.
This can be permanent – by removing parts of the brain or by damaging connections; or temporary where drugs can be used to shut off parts of the brain. IV = damage to the brain; DV = changes in behaviour
Studies using animals
Genes:
Mice can be used to see whether a particular gene causes an abnormality
Rats have been used to study Parkinson’s Disease – rats injected with drugs to replicate the symptoms, then gene therapy used to treat the symptoms
The nervous system:
Rats used to study the effects of antipsychotic drugs
Mice used to investigate changes in neurotransmitters when under stress
Brady (1958) Monkeys used to study the effects of stress
Functions of the brain
Rats initially used to find out the effects of antipsychotic drugs on the brain.
Lashley (1950’s) used rates to investigate brain function by removing brain parts to see what effects this would have on memory.