Twins Studies And Adoption Studies Flashcards
Concordance rate
Concordance rate- The rate of probability that 2 people with shared genes will develop the same organic disease. (Relates to usefulness of Twin Studies)
Heritability rate
Heritability rate- A measure of how well differences in peoples genes account for differences in their traits. How much variation in a given trait can be attributed to genetic variation. Ranges from 0-1, close to 0 indicates almost all of the variability in a trait among people is due to environmental factors.
MZ Twins
MZ Twins- Identical Twins, share the same egg and 100% of DNA
DZ Twins
DZ Twins- Fraternal twins, 2 eggs and 2 sperm, develop from separate fertilisations, share 50% DNA
Adoption Studies
A01
- Involve looking at an individual and their genetically related relatives in comparison to adoptive relatives who are genetically different but who share the same environment as the adoptee
- If GENETICALLY RELATED RELATIVES show higher degrees of CONCORDANCE for a condition than adoptive relatives, this suggests that genetic factors are important in CAUSATION (NATURE)
- If concordance is greater in ADOPTIVE RELATIVES, this suggest that environmental factors are more important in disease causation (NURTURE)
Adoption Studies
A03- Strength usefulness
Adoption studies can be useful in separating the influence of genes on behaviour such as aggression from the influence environmental factors. If there are similarities between the biological parent and child in terms of aggression, we can assume this is due to genetic similarity.
Adoption studies
A03 strength patterns in behaviour
Adoption studies often utilise a longitudinal method, and follow the same group of children over a long period of time. Therefore, making it easier to identify patterns/trends in behaviour such the manifestation of aggression which can then be linked back to genetic or environmental influences.
Adoption studies
= Heston 1966
A01- Aim
Aim- To see how many adopted children of biological mother with SZ would go onto develop SZ themselves
Adoption studies
= Heston 1966
A01- Sample
Experimental group- 47 ppts
Born between 1915-1945 to SZ mother, from the OREGON STATE PSYCHIATRIC HOSPITAL
Children adopted at birth(within the first few days of life) as their mothers were suffering from SZ
Matched group-
50 adoptees whose mothers were believed to be mentally healthy were also identified- matched for sex, type of eventual placement (adoptive, foster family, institutional) and length of time in child care
Sampling method- Volunteer sample
Adoption studies
= Heston 1966
A01- Procedure
- Subjects contacted by letter, ask to participate in a personal interview
- Adults interviewed to see if any of them had developed SZ themselves. Nearly all of these interview were conducted in the homes of the subject- added to range of possible observations
- Short form of MMPI (Minnesota Multiphasic personality inventory) was given after the interview
- Info was complied on each subject, evaluated blindly and independently by 2 psychiatrists, final evaluation then made by third researcher
- Evaluative measures= score moving from 100-0 with increasing psychop social disability assigned for each subject. Scoring based on Menninger mental health sickness rating scale (MHSRS)
- Control group= important to eliminate possibility that adoption itself might be responsible for SZ
Adoption studies
= Heston 1966
A01- Results
-Out of 47 interviewed whose mother suffered SZ, 5 had been hospitalised with SZ, 3 chronically ill
(5/47)
-10% of adopted children of SZ mother had developed SZ as well= same number expected had they not been adopted but brought up by biological mother. None of control group developed SZ- indicates experience of adoption, not a factor in SZ
-Significant excess of psycho - social disability in of one half of persons born to SZ mothers
Adoption studies
= Heston 1966
A01-Conclusion
- Results provided powerful evidence in role of genetics in SZ
- No evidence emerged of any role at all for environmental factors in development in SZ
Adoption studies
= Heston 1966
A03- Generalisability
Heston used a sample of 47 participants who had been adopted from birth and born to mothers in the Oregon Psychiatric hospital with SZ. The researcher used a volunteer sampling method from to gather the participants which meant they may have shared similar characteristics in being interested in participating in a study focused on SZ and adoption. Therefore, suggesting the sample is not representative of the wider population, limiting the extent in which we can generalise results.
Adoption studies
= Heston 1966
A03- Strength Reliability
Heston conducted standardised interviews with all of the participants, establishing which participants had gone onto develop SZ themselves and involving a standardised set of questions. They were all then given a short form of the MMPI after the interview. This consistent procedure allows the study to easily be replicated to test for reliability in the findings. If similar results are found in terms of the development of SZ this suggests the results are accurate.
Adoption studies
= Heston 1966
A03- Weakness Ethics
Heston drew on sensitive subject matter such as mental illness in investigating the genetic link of SZ and finding some had like their mother developed SZ, 5 out of 47 participants had been hospitalised with SZ, 3 of which were chronically ill. The testing and interviewing of these participants, particularly those who had developed SZ may have been distressing in terms of the purpose of the study, failing to protect the participants from the emotional harm the study may cause.
