Biological Psychology Flashcards
Monozygotic twins
Identical, share 100% of their genes as they come from one fertilised egg.
What should be considered about MZ twins?
- Do not share the same environment
- There are some physical differences, such as fingerprints
- Can become less identical over time
- Some characteristics, such as IQ and personality might become more alike as twins age
Epigenetic modification
Different environmental influences affect which genes are switched on and off. Younger MZ twins have few epigenetic differences.
Dizygotic twins
Not identical, come from two separate eggs fertilised at the same time. Share 50% of genes
Why are twin studies useful?
If a characteristic comes from genes, MZ twins should be more likely to share it.
Psychologists can compare behaviour between a group of identical twins and fraternal twins to see which group shared the most similarity.
Concordance rate
The extent to which the same behaviour is the same between twins. An agreement rate when both twins have got a characteristic.
Strengths of using twin studies
- Twin studies are the main way of finding out if genes have any influence on behaviour.
- Both twins share their environment, so there should not be many environmental differences between the twins.
Weaknesses of using twin studies
- MZ twins will be treated more like twins than DZ twins, so environments are not the same.
- Epigenetic modification, there are differences between twins. Difficult to say if a characteristic is caused by genes conclusively
Gottesman and Shields (1966) procedure
- 16 year period (longitudinal) using 5 twin studies
- To see if there was a relationship between genetic make up and development of schizophrenia by looking at concordance rate
- 57 twin pairs (24 MZ and 33 DZ)
- Hospital notes and semi-structured interviews
Gottesman and Shields (1966) results
- MZ twins - 42%
- DZ twin - 17%
Gottesman and Shields (1966) conclusion
Genes do play a role in the development of schizophrenia, but can’t conclusively say it is solely due to genes.
Why are adoption studies useful?
It is the only direct way to isolate the influence of genes and the environment.
In what circumstances in adoption studies suggest the roles of genes?
Similarities between child and their biological parents
Kety et al (1994)
- Research in Finland
- Sample of 155
- 9 adopted children, 8 had biological mothers with schizophrenia or a form of psychoses
Strengths of adoption studies
- Developmental trends (patterns) can be studied because studies are longitudinal. Same children can be studied at different times during development.
- Control for environment, separates genes from environment.
Weakness of adoption studies
- Adopted children are often placed into families very similar to their biological families
- They are matched, so the environments might not be as different as thought
What are the 3 main brain scanning techniques?
PET scans, CAT scans and fMRI scans
How do PET scans work?
- inject patient with FDG (radioactive)
- task is given to stimulate the brain
- glucose is used up, radioactive atoms break down, gamma rays produced
- high activity (red)
- low activity (blue)
What are PET scans useful for?
Investigating areas of the brain that are not functioning normally, indicate damage or tumours.
Strengths of PET scans
- Reasonably non-invasive, less dangerous than surgery
- Valid measure
- Reliable because it can be repeated and same results found again
Weaknesses of PET scans
- Invasive
- Ethical implications, need informed consent and a good reason to carry it out
- Can cause panic if claustrophobic
- Difficult to isolate different brain functioning precisely, as they will be using other parts of the brain as well.
Hard to claim exactly what part of the brain is performing which function
How do fMRI scans work?
- uses blood flow of brain to indicate level of activity
- head placed in large electromagnet
Strengths of fMRI scans
- No danger from radiation
- Detection of blood flow is very precise so slight changes can be detected
- Medical use, looking at brain structure and functioning
Weaknesses of fMRI scans
- Cannot look at receptors of neurotransmitters unlike PET scans
- Too much head movement can distort imaging
- The brain is never at rest, so it is not easy to gather a baseline measure
- Risks, such as those with pacemakers and those who are claustrophobic.
How do CAT scans work?
- Multiple X-ray beams passed around the head at different angles
- Detailed 3D image
What are CAT scans useful for?
Detecting areas of brain damage after an accident or position of tumours
Strengths of CAT scans
- Less harmful than PET scans
- Can detect changes in physical structures, so good for detecting tumours or haemorrhages
- Not painful, non-invasive
Weaknesses of CAT scans
- MRI gives a clearer picture
- Involves X-raying which can cause damage, notably cancers.
Research using PET scans
Raine (1997)- investigate whether people charged with murder and pleading NGRI have brain differences that might link to their aggression.
Research using fMRI scans
Dimoka (2010)- if brain function and structure linked to trust and distrust. Found that credibility and discredibility linked to cognitive brain areas in the prefrontal cortex. Benevolence and malevolence linked to emotion area (limbic system)
Research using CAT scans
Betts (2009)- case of Herbert Weinstein, 64 year old man who strangled his wife. Defence was that a cyst had caused pressure on his prefrontal cortex, affecting understanding. CAT scan evidence of differences in his brain relating to schizophrenia.
Correlations
A way of looking at relationships between two variables, not causes. If two variables are correlated, you can predict one from the other.
In a correlation, the SAME person produces the two scores. True or false?
True
What type of data is used in correlations?
Numerical data
What are the three important features of correlation design?
- There is no IV or DV, only two variables of equal importance
- Hypothesis will be about a relationship between two variables (not a difference)
- Hypothesis could be directional as it could predict a positive or negative correlation.
Name an example of co-variables in biological psychology
Measuring the number of genes a person shares (closeness of family relationship) and a behavioural characteristic such as the amount of aggression they show.
What type of graph do you use to show correlations?
Scatter diagrams
Types of correlations
- Positive correlation
- Negative correlation
- Uncorrelated
Which inferential statistic test do you use for correlations?
Spearman Rank Correlation Coefficient
How do you carry out a Spearman’s rho?
- Rank starting from the lowest score (rank 1)
- If there are two or more scores the same, allocate those scores the same rank by finding the middle rank
How can you analyse correlations?
- Spearman’s rho
- Draw a scatter graph then look at the line of best fit
How do you interpret the results of the Spearman’s test?
- If both scores rise, there is a positive correlation. A result of +1 means a perfect positive correlation
- A result of 0 means no correlation
- If one score rises and the other falls there is a negative correlation.
Positive correlation
Both co-variables increase
Negative correlation
When one variable increases and the other variable decreases.