Twin Study (Gottesman and Shields (1966)) Flashcards
What do twin studies enable psychologists to determine?
If characteristics are down to nature, nurture or a mix of both.
What are Monozygotic twins?
100% genetically similar
Identical
What are Dizygotic twins?
50% genetically similar
Non-identical
What is the twin study?
Gottesman and Shields (1966)
What was the aim of Gottesman and Shields (1966)?
To find out if schizophrenia was genetic.
To replicate other studies that had found a genetic link to schizophrenia.
Describe the sample of Gottesman and Shields (1966)
57 pairs of twins
from 392 same sex twins that had been admitted to Bethlem and Maudsley Psychiatric Hospital
24 monozygotic twin pairs
33 dizygotic twin pairs
27 pairs were female
30 pairs were male
Age range 19 - 64
How many twin pairs are monozygotic or dizygotic? (Gottesman and Shields (1966)
24 monozygotic twin pairs
33 dizygotic twin pairs
How many pairs of twins were there in Gottesman and Shields (1966)?
57 pairs of twins
How was data collected in Gottesman and Shields (1966)?
Hospital Notes
Case Histories
Interviews with patients and their parents
Tape recordings from a semi-structured interview to look at verbal behaviour
MMPI (personality test)
An object sorting task looking at thought disorder
How were the patients concordance measured? (Gottesman and Shields (1966))
Grade 1 - if both twins had been diagnosed with schizophrenia
Grade 2 - if both twins had been diagnosed with psychiatric disorders, but they were different diagnoses
Grade 3 - if one twin had schizophrenia and the other had some psychiatric abnormality that may have been found by GP or during the testing
What was Grade 1? (Gottesman and Shields (1966))
Grade 1 - if both twins had been diagnosed with schizophrenia
What was Grade 2? (Gottesman and Shields (1966))
Grade 2 - if both twins had been diagnosed with psychiatric disorders, but they were different diagnoses
What was Grade 3? (Gottesman and Shields (1966))
Grade 3 - if one twin had schizophrenia and the other had some psychiatric abnormality that may have been found by GP or during the testing
What were the results of Gottesman and Shields (1966)?
Grade 1 - MZ 42%, DZ 9%
Grade 2 - MZ 12%, DZ 9%
Grade 3 - MZ 25%, DZ 27%
Normal - MZ 21%, DZ 55%
What was the conclusion of Gottesman and Shields (1966)?
That schizophrenia was partially genetic, but not totally, as there was not a 100% concordance rate between MZ twins
The environment also plays a part and can trigger SZ if there is a genetic predisposition
