Research Methods

• Correlations

  Correlations do not use an IV or a DV. They use Co-Variables.

  Co-variable: Those characteristics which will be measured in a correlation.

  Correlations are shown on scatter graphs.  Correlation co-efficients tell us about the strength of the relationship. A co-efficient of +1 is a perfect positive correlation, -1 a perfect negative correlation and 0 no correlation. 
• Positive Correlation +1

  This means that as one variable increases the value of the other variable will also increase
• Negative Correlation -1

  This means that as one variable increases the other variable being measured decreases
• No Correlation 0

  There is no significant relationship between the two co-variables
• Outline TWO strengths of the correlational method of collecting data

  • Allows researchers to see if there is a relationship + if follow up research could be done 
  • more ethical to measure two covariables than to manipulate an IV. 
• Outline TWO weaknesses of the correlational method of collecting data

  • Only quantitative data rather than qualitative so no reasons are given for why covariables are related 
  • cannot establish cause + effect. Lowers scientific value as could just be chance.
• fMRI scans

  Functional magnetic resonance imaging, or fMRI, is a technique for measuring brain activity. It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area. fMRI can be used to produce activation maps showing which parts of the brain are involved in a particular mental process.
• PET Scans

  • PET scans use a radioactive glucose tracer which is usually injected or swallowed in order to see activity in the brain.
  • Once in the bloodstream, it flows through the brain and oxygen and glucose accumulate in brain areas that are metabolically active.
  • As the glucose is used in the active parts of the brain, the radioactive material breaks down and gives off a neutron and a positron. This is picked up by the scanner, showing areas of activity as ‘hotter’ colours
• CAT Scans

  Computed tomography (CT) scanning builds up a picture of the brain based on the differential absorption of X-rays. During a CT scan the subject lies on a table that slides in and out of a hollow, cylindrical apparatus. An x-ray source rides on a ring around the inside of the tube, with its beam aimed at the subjects head. After passing through the head, the beam is sampled by one of the many detectors that line the machine’s circumference. Images made using x-rays depend on the absorption of the beam by the tissue it passes through. Bone and hard tissue absorb x-rays well, air and water absorb very little and soft tissue is somewhere in between. Thus, CT scans reveal the gross features of the brain but do not resolve its structure well. 
• Twin Studies

  They look at the concordance rate (degree of similarity) of twins with respect to the disorder being considered. Concordance rates means the probability of one twin having the disorder if the other already has it expressed as a percentage.

  In a twin study, MZ (identical) and DZ (non-identical) twins are compared. Whilst MZ twins have a greater degree of genetic similarity, both types of twin pair grow up in identical environments. So if we discover that MZ twins have a higher concordance, this cannot be because their environments are more similar than those of DZ twins; it must therefore be because their genes are more similar. When interpreting twin study data, we look for the following features:
• Adoption Studies

  Adoption studies are carried out because the environment of adopted children is not the same as their biological parent. In these situations the child has the genes of the biological parent but the environment created by the adoptive parent.

  Similarities between the child and the biological parent would suggest a role for genes.

  Similarities between the child and adoptive parent would suggest a role for the environment.

  In adoption studies the child and their adoptive parents are compared. The children are often followed up in adulthood to see whether similarities between them and the adoptive parents persist once they have left the adoptive home.
• Adoption Studies - Mednick - Aim

  To investigate whether people become criminals because of their genes or because of the environment in which they are brought up in. If genetics is the cause of criminal behaviour then the children who had biological criminal parents were more likely to be criminals themselves regardless of whether their adoptive parents were law-abiding. On the other hand, if criminality is caused by the environment then children adopted by law-abiding parents would be less likely to commit crimes.
• Adoption Studies - Mednick - Procedure

  Mednick et al took all the court convictions between 1927 and 1947 in a small European country and found over 14000 adoptees. They then investigated the biological and adoptive relatives of these people.

  The following information was obtained:

  • Court histories as an indicator of criminal involvement 
  • Conviction rates
• Adoption Studies - Mednick - Findings

  Biological Parents with criminal record Adoptive Parents with criminal record % of sons with criminal record 

  The closer the biological relationship the higher the level of adoptee convictions. There was a statistical significance between the biological father and the adopted child. 

  In addition if the biological parents were reoffenders the adopted child was also more likely to reoffend. This was strongest for property crimes such as theft but not violent crimes. This gives more support for the genetic basis of criminality.

  
• Adoption Studies - Mednick - Conclusion

  The study shows that there is a relationship between the criminal convictions of the biological parent and their adopted children. No relationship was found between the type of crime. Mednick et al. concluded that some genetic “factor” was transmitted by criminal parents that increased the likelihood of their children becoming criminals.