Question

A psychologist conducts research using the twin-study method. He administers a need for Achievement scale to sets of monozygotic and dizygotic twins and finds a correlation of .50 between the scores for pairs of monozygotic twins. If this study is to demonstrate evidence for a genetic influence on need for Achievement, what would we expect the correlation to be between scores for pairs of dizygotic twins?

a) Higher than .50
b) Lower than .50
c) Very close to .50
d) There is no way to demonstrate a genetic influence with these data.

Answer 1

For a genetic influence on the need for achievement to be suggested, the correlation between scores for pairs of dizygotic twins would be expected to be lower than .50, as they share less genetic material than monozygotic twins.

Step-by-step explanation:

When assessing the influence of genetics on personality traits such as the need for achievement, psychologists use twin-study methods. The given research shows a correlation of .50 for monozygotic twins (identical twins). For this study to provide evidence of a genetic influence, we would expect the correlation for dizygotic twins (fraternal twins), who share only about 50% of their genetic variation, to be lower than .50. This is because monozygotic twins share almost all their genes, and if their scores are correlated highly, it implicates genetic factors. On the other hand, dizygotic twins, sharing fewer genetic similarities, would have a lower correlation if genetics are a significant contributor to the trait being studied. Should the correlation be lower for dizygotic twins, it would suggest that genetic factors do play a role in the need for achievement, although not to the extent as in monozygotic twins.