Twin Studies

Question 1

What two ways can you carry out a twin study experiment?

Answer 1

1) hold genetics steady and vary environment (MZ twins together vs MZ twins apart)
2) hold environment steady and vary genetics (MZ twins vs DZ twins when twins in a pair have same environment)

Question 2

What is concordance rate?

Answer 2

% of cases in which a trait is present for one twin when you know it is present in the other

Question 3

What does it suggest if concordance rate for MZ and DZ twins were equal?

Answer 3

No significant genetic component is affecting/contributing to the behaviour

Question 4

Weakness of Christianson 1977?

Answer 4

Only twins from Denmark so not generalisable as only includes one culture

Question 5

Sample of Christianson 1977?

Answer 5

3500 twin pairs from Denmark MZ and DZ, male and female
Used twin registry for large representative sample

Question 6

Monozygotic (MZ) vs Dizygotic (DZ) twins?

Answer 6

MZ are identical - one zygote split into two early in development (100% DNA shared)
DZ are non identical - 2 sperm and 2 eggs (50% DNA shared)

Question 7

Explain the twin study of Christianson (1977) and results?

Answer 7

-Concordance rates of criminality were measured for MZ and DZ twins that were both male and female.
-Each twin of a pair had the same environment
-Higher concordance rate of criminality for MZ suggesting there is a genetic component to criminality.
-Males had much higher concordance scores than females suggesting gender to affect criminality.

Question 8

2 pros of your twin study ?

Answer 8

Assumes MZ and DZ twins equally share the same environment so a higher concordance rate on MZ than DZ means the difference must be due to genetics
Sample comes from a twin registry so you can have a large representative sample of twins

Question 9

2 example strengths of Christianson 1977?

Answer 9

Reliable as large 3500 sample so reduced impact of participant variables
OR
Used twin registry for large representative sample so high population validity

Question 10

2 cons of twin studies?

Answer 10

-Construct validity = Cannot identify specific genes involved- moreso useful as a starting point for future research
-MZ twins often have a more similar environment than same sex DZ twins. E.g wear same clothes every day same hair etc. The environment of MZ is more similar than DZ so higher concordance rates aren’t just due to genetics