BIOLOGICAL - RESEARCH METHODS Flashcards
adoption studies
AO1:
->adoption studies involve looking at an individual and their genetically related relatives in comparison to adoptive relatives who are genetically different but share the same environment as the adoptee
->this means the child still shares genetic material with their biological parents even though their environment is different, to study the nature/nurture debate (useful for studying characteristics such as SZ)
->if genetically related relatives show higher degrees of concordance for a condition than adoptive relatives, this suggests that genetic factors are importance in causation (nature)
->if concordance is greater in adoptive relatives, this suggests that environmental factors are more important in disease causation (nurture)
AO3:
STRENGTHS:
->they are a useful way of separating genes from the environment
–>this means we can assume that similarities between biological parent and child are due to genetic similarities
–>therefore we can further understand the nature/nurture debate
->allows for trends in behaviour to be studied
–>adoption studies tend to use the longitudinal method, meaning that they follow the same group of children over long periods
–>this allows trends in behaviour to be studied which can then be linked to genetic influences
WEAKNESSES:
->there may be some validity issues - we may overemphasise the role of genes
–>children tend to be placed in families similar to that of their own, so their birth family and adoptive family are very different
–>this means that the adoptive environment may be very similar to the environment of the birth family, therefore not sufficiently different to the environment they would have grown up in had they not been adopted
->may lack generalisability
–>only certain types of families are accepted as adopters of children
–>adopting families are therefore likely to be very similar to one another, making research and findings less representative
twin studies
AO1:
->this type of study has been of value in enriching our understanding of the contribution of genetic and environmental factors in human behaviour
->genetically, twins can either be MZ (share 100% of DNA) or DZ (share 50% of DNA)
->studying differences in the behaviour of MZ and DZ twins reveals a lot about the influence of genetics (nature) on behaviour
->if MZ and DZ twins behave differently, it suggests nature is at work because the shared environment is not producing the same behaviour, so genetic differences would explain this
->twin studies are measured using a statistic called concordance rate, meaning “agreement”. If one twin shows a behaviour and the other does too, this is concordance
->the concordance rate is usually expressed as a % (100% concordance means all twins shared the behaviour in common, 0% means none did). In a twin study, the concordance rate of MZ twins is compared to that of DZ twins
->twins are said to be concordant for a condition if both develop it (eg. depression, SZ, etc)
AO3:
STRENGTHS:
->high validity
–>although the amount that they share their DNA differs, both MZ and DZ twins share their environment so there is a natural control over their environmental effects
–>this means we can be sure any differences in concordance rates between MZ and DZ twins is unlikely to be due to environmental effects
->they are very useful for studying nature/nurture
–>no other humans share 100% of their DNA, so MZ twins are perfect for this kind of study
–>therefore, there’s no other way to study genetic influences so clearly
WEAKNESSES:
->there may be some validity issues - we may overemphasise the role of genes
–>MZ twins are treated more alike than DZ twins because they are not inly identical, but share gender too
–>we assume that genetic similarity is the reason for higher concordance rates in MZ twins over DZ twins, yet in reality, this may be due to MZ twins having greater environmental similarity to DZ twins
->may lack generalisability
–>twin studies tend to use volunteer sampling
–>as such, this is a biased sample as the volunteers may all have similar characteristics
correlations
what is a correlation?
->a correlation is the measurement of the extent to which pairs of related values on 2 variables tend to change together (measuring 2 variables to see if they are related in any way)
->positive correlation: as variable 1 increases, variable 2 also increases
->negative correlation: as variable 1 decreases, variable 2 increases
->no correlation: no relationship between variables 1 and 2
what are co-variables?
->correlations are described in terms of co-variables
->they can be measured directly from the researcher or gathered from secondary sources, such as medical records, etc
->co-variables are usually plotted on a scatter graph
AO3:
STRENGTHS:
->correlations allow us to investigate otherwise unethical situations
–>it would be unethical to study the correlation between smoking and heart disease as you can’t force an experimental group to smoke or give the, heart disease
–>therefore allowing is to research topics that otherwise cannot be studied
WEAKNESSES:
->they cannot infer C&E
–>in some cases, we don’t fully know which factor is potentially the cause and which is the effect
–>this is because it’s difficult to see what comes first
->a 3rd unaccounted for factor may have cause the relationship with the co-variable
–>this is because we can’t control ppt variables, eg. some ppts may smoke or drink whereas others may not
brain scans: PET scans (1973)
AO1:
->psychologists use PET scans because they show pictures of the living, active brain
–>in psychology the tracer is injected and the ppt is given a task to stimulate the part of the brain the researchers want to look at
–>PET scans detect areas of damage by indicating which parts of the brain are showing abnormal levels of activity, and this can help researchers to not only see where problems exist, but also predict what kind of issues patients might face in relation to the brain activity being shown
how do they work?
1) patients are injected with a radioactive tracer in the brain cells, uptake of oxygen in the water or glucose happens, and the tracer decays and emits positrons
2) when positrons are emitted, they collide with electrons giving gamma rays and this is what produces the images of activity
3) PET scans are used to identify damages or tumours and show malfunctions via the levels of activity (blue=low // red=high)
EXAMPLE RESEARCH:
->Raine et al (1997) used PET scans to investigate differences between the brains of murderers NGRI and non-murderers
–>using PET scans they were able to measure any abnormal brain activity in the murderers group in the areas of the brain associated with impulsivity and risk taking behaviour, which may explain increased aggression they found in murderers as they had less glucose activity in some parts of the brain linked to violent behaviour
AO3:
STRENGTHS:
->ethical procedure
–>although PET scans involve an injection, they are a relatively non-invasive and painless technique of studying the brain
->highly valid
–>consistent results are always found as the same areas of the brain are consistently found responsible for particular activities
->high reliability
–>standardised procedure (injection -> positrons emitted & collide with gamma rays -> shows brain activity, blue=low, red=high)
–>therefore can be replicated
WEAKNESSES:
->there may be long term effects
–>the use of radioactive tracers is invasive and ethical guidelines should be closely followed by the researcher(s)
–>the radioactive tracer can cause harm so there must be a good reason for doing the test
->we can’t pinpoint exact locations, which decreases validity
–>this is because it is difficult to isolate different brain functions precisely, so it is difficult to establish C&E
–>therefore lowering internal validity
brain scans: CAT scans (1971)
AO1:
->CAT scans can be used to take images of any part of the body, including the brain
–>they are very quick to conduct and can give accurate details of brain structure, which can help guide clinicians in decision making regarding treatment or surgery
–>a CAT scan may help a surgeon to better plan a procedure before surgery takes place as it provides an accurate layout of brain structure
how do they work?
1) CAT scans of the brain involve passing x-rays into the head. Multiple beams are passed around the head from different angles to gather more information, as - when scanning something as complex as the brain - more info is needed
2) the info from the multiple x-ray beams can be interpreted by a computer and a detailed image of the structure of the brain can be seen. This is useful for detecting areas of brain damage following an accident, or the position of a tumour in the brain
EXAMPLE RESEARCH:
->Betts (2009) discussed the case of Weinstein,, whose defence used CAT scanning to show that he had damage to his brain that might’ve lead to his aggression (he strangled his wife)
–>the scans showed some damage and the evidence persuaded the jury that he did not sufficiently know right from wrong
–>Betts suggested that 60-77% of people pleading NGRI have psychosis, and 10% of those have psychosis that is neurologically based
AO3:
STRENGTHS:
->quick and effective
–>good for when surgeons/doctors need to make a fast decision in medical procedures
–>therefore is very practica;
->objective and scientific
–>provides highly detailed images of brain structure, revealing abnormal structures, and is higher quality than x-rays
WEAKNESSES:
->practically difficult
–>ppts must remain very still as even tiny movement can distort the images, meaning they have to restart which is costly
–>therefore, it can be an inconvenient method of brain scanning
->limited use due to radiation
–>the use of CAT scans involve exposure to radiation and it is advised that they are only used when the possible benefits in relation to diagnosis outweigh the potential risks
brain scans: fMRI scans (1990)
AO1:
->fMRI scans enable images of brain activity to be gathered without the use of radiation, and are often the procedure of choice for psychologists researching brain activity
–>they allow us to see the structure of the brain and whether damage of tumours need treatment
–>the idea behind this technique is that brain activity is used to gather the information by the scanner to produce still pictures of the brain, much like an x-ray (many slices of the brain). As neural activity increases, so does blood flow
how do they work?
1) the patient is placed in a large scanner which passes a strong magnetic field through the head. The nuclei of some atoms in certain molecules spin a certain way when placed against a magnet, which gives the still pictures. Nuclei emit hydrogen concentrations in different areas, which produce the detail of the scan
2) as neural activity increases in the brain so does blood flow in the active areas (this is to keep up with the demand for oxygen). The oxygen repels a magnetic field but when it has been deoxygenated it will follow the direction of the magnetic field; and it is these changes that the scanner will detect to create an image
EXAMPLE RESEARCH:
->Li et al (2013) used fMRI scans to investigate how heroin effects different parts of the brain
–>they found in the cue induced task that activation of the PFC and other brain regions in the heroin group compared to the control group
AO3:
STRENGTHS:
->fMRI is the preferred method by psychologists as it is the safest
–>there’s no radiation involved as it uses magnets and is less invasive as there’s no injection needed
–>therefore it is the most ethical brain scanning technique
->highly reliable
–>uses a standardised procedure and gains highly accurate and precise results
–>therefore is also highly objective and valid
WEAKNESSES:
->not available for everyone
–>people with pacemakers fitted cannot have an fMRI scan due to the magnetic field, also people who are claustrophobic or anxious/unnerved by loud noises may find it distressing
->practically difficult to conduct
–>ppts must remain very still as even tiny movement can distort the images, meaning they have to restart which is costly
–>therefore, it can be an inconvenient method of brain scanning
