Research methods of the Biological approach

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  • Research methods in the biological approach
    • Twin studies
      • Used to examine the role of genes on behaviour
        • Identical twins share 100% of their genes
          • These are called monozygotic twins (MZ)
            • Even if they live together, MZ twins will have different experiences and environments to one another, even in the womb
            • Have different fingerprints to one another
            • Some genetic characteristics are triggered by the environment and so over time twins can become less identical
              • Epigenetic modification is the term to describe this
              • However some characteristics such as IQ can become more alike over time
        • Identical twins share 50% of their genes
          • Dizygotic twins (DZ)
      • Aid the nature/ nurture debate
        • Nature is based on our genes and what we are born with
        • Nurture is what we experience as we develop from our environment
      • Twins tend to share much of the same environment which makes them bad to study in everyday life
        • Why adoption studies are so strong
          • Here twins live in different environments and so we can examine the role of environment on behaviour
      • Twin studies compare MZ and DZ twins on certain characteristics
        • If there are strong differences then the characteristics are said to be genetic
        • When both sets of twins share a characteristic then there is said to be a concordance rate
        • Twin studies are strong as there is no alternatives, there is no other way to share the exact same DNA as someone
        • Most twins  share the same environment and are treated simply as twins so there should be a lack of extraenous variables
          • However MZ twins may be treated differently to DZ twins as they are identical
        • No twins are exactly identical
    • Adoption studies
      • Enables the role of environment to be examined
      • Where a child is adopted and thus has a different environment to that of its biological family
        • Environment is controlled which is a strength
      • E.g a researcher examining whether schizophrenia is environment or genetically based would use this as the child would share the gene if it existed
      • Similarities with their biological families will be due to genes
      • Often family situations are matched so environments wouldn't have been that different to that of their biological families
        • Adoption is an official process
          • All adoptive families may be the same
      • Developmental trends can be studied as the studies are longitudinal
    • Twins reared apart
      • Another form of adoption study
      • MZ twins separated at birth
      • Usually adopted
      • Controls the similarity of environments
      • A unique method
      • Very few MZ twins have been reared apart
        • Therefore it is hard to draw conclusions
        • Often family members bring up the children
          • Reared apart but as part of the same family
      • Sometimes in these studies it can be hard to tell if the twins are MZ or DZ
      • Unethical to deliberately raise twins apart
    • PET scans
      • Positron emission tomography
      • 1) A radioactive transmitter is injected into the patient
      • 2) This attaches to a chemical in the bloodstream, usually glucose
      • 3) It travels to the brain through the bloodstream and to the areas where energy (glucose) is needed which are the sights of activity
      • 4) A positron is given off that is in the tracer and this shows up as an area of activity
        • Shows what areas of the brain are used for what function
      • Shows blood flow to the brain
      • Having the injection is invasive
        • Unethical as uses radioactive material which could cause harm
        • Could be psychologically harmful to people with claustrophobia
      • More ethical as usually animals would be used using surgery for this purpose
      • High validity
      • Very reliable and easily repeatable
      • It is hard to isolate certain areas of the brain
        • Criticises the validity of PET scans
    • MRI
      • Magnetic resonance imaging
      • 2) A strong magnetic field is passed over the area
      • 3) A cross sectional image is created from this
      • Images are affected by movement so the person has to keep very still
      • Do not show activity to the same extent as PET scans
      • Can measure blood flow
      • 1) A dye (contrast medium) is injected into the body
      • High validity
      • More ethical than surgery but still invasive as uses an injection
      • Replicable
      • They are extremely noisy which can be distressing
      • Limited knowledge can be obtained from these as they only measure body tissue
    • Using animals in lab experiments
      • 8% of research uses animals
        • 90% on rodents and birds
        • 5% on primates
      • Mice have similar enough genes to humans and breed quickly
        • different generations can be quickly and easily studied
      • Most animals used are small and easy to handle
      • Quite a few animals share similar brain patterns and functions
      • Research can be useful for animals as well as humans
        • E.g by understanding their anatomy zoos can care for them better
      • More practical to use animals
        • E.g animals age quicker than humans
      • Extraneous variables such as diet can be monitored easier
      • No animal is identical to a human
      • These studies often don't take into account the complexity of real life
      • Illness' and diseases have to be artificially created in animals, this isn't the same as developing them naturally
      • Lack credibility
      • Studies that can't be carried out on humans cane be carried out on animals
      • We should improve our way of life by any means
      • Advantageous new drugs can be developed
      • Cause harm and so are unethical

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