Bouchard et al 1990

• Aim - To examine the influence of genes on determining psychological qualities in twins
• Participants - 100 MZ twin pairs (56 reared apart, 44 together) recruited through word of mouth. They chose MZ twins so they could act as each other's controls
• Procedure - each participant completed approximately 50 hours of testing on nearly every human dimension possible (personality trait scales, aptitude and occupational interest inventories, two personality tests). They also filled in a family environment scale, completed a life history interview and sexual history interview.
• Results - The twins reared apart and together showed same levels of similarity, disproving the argument that twins reared together would be more similar because of growing up in the same environment. The correlations for characteristics were remarkably similar (close to 1.00 and no lower than 0.70), hence shared environment doesn't have a significant impact on concordance rate
• Bouchard et al was a true laboratory experiment
• Conclusion - genetic factors account for most of the variation in a remarkable variety of human characteristics, suggesting that while environmental factors also play a role, they are less impactful.
• Method:

  • strong cause and effect
  • standardized
  • internal validity
  • but theres no total control, artifical environment, interview bias, ethics
• Alternative explanations: twins could have grown up with similar environments even if reared apart, so their concordance rates may have also been influenced by selective placement or how much time the twins spent together before being separated
• Gender and ethics - study wasn't gender biased, study was ethical cus there was informed consent, not deceived, identities were confidential... HOWEVER there is mental harm because being reunited with a twin could be a life-changing event
• A population can be defined as: A group of organisms of the same species living in an area at one time
• Members of a population interact with each other and can breed together. A population can be isolated from other populations of the same species due to living in a different area. This isolation means that members of separate populations cannot breed together and gene exchange cannot take place between them
• Abundance refers to the number of different species or the number of individuals of a particular species in a given area
• Distribution of a species is where it's found within an ecosystem. This is probably where the suitable habitat of that species is found
• In random sampling the positions of sampling points are selected random which avoids researcher bias. In systematic sampling the sampling points are at fixed intervals, as this avoids accidentally missing out sections of habitat due to chance. This allows researchers to investigate the presence of certain environmental features on species distribution (like a river)
• A sampling error is the difference between an estimated population size and a true population size. This occurs when a sample is not truly representative of a whole population