Twin & Adoption Studies

Question 1

Define ‘monozygotic twins’

Answer 1

Identical twins who share 100% of their DNA due to coming from the same egg

Question 2

Define ‘dizygotic twins’

Answer 2

Non-identical twins who share 50% of their DNA due to coming from different eggs like siblings but being born at same time

Question 3

Define ‘concordance rate’

Answer 3

The probability of one twin sharing a certain characteristic of the other twin

Question 4

Which set of twins will have a higher concordance rate if a behaviour is due to nature?

Answer 4

Monozygotic

Question 5

List 2 strengths of twin studies

Answer 5

1- High reliability; fertility treatments + having babies later = number of multiple births are increasing so can replicate easily as there’s more twins available
2- High internal validity; MZ and DZ twins sharing the same environment whereby there is a natural control over extraneous variables of each

Question 6

List 2 weaknesses of twin studies

Answer 6

1- Low generalisability; MZ twins may not be representative of other twins in a different environment
2- Low ethics; risk of children being made to feel different as they share DNA, may damage confidence

Question 7

List 2 strengths of adoption studies

Answer 7

1- High reliability due to allowing us to study trends in behaviours via longitudinal methods of following the same group of children for long periods of time
2- High ethics; anonymity preserved, respects privacy + dignity

Question 8

List 2 weaknesses of adoption studies

Answer 8

1- Low generalisability; circumstances in which a child will be split up from their parent will be unique and cause different environmental variables for the adopted child that wouldn’t represent a normal child
2- Low validity; children tend to be placed in families similar to their own so their birth family and adopted family will match very closely, making it harder to tell if upbringing is at work