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.

Question

Quizplus · Accepted Answer

If genetic factors are influencing the need for achievement, we would expect monozygotic twins, who share 100% of their genetic material, to have a higher correlation of scores compared to dizygotic twins, who share only 50% of their genetic material on average. Therefore, the correlation between scores for pairs of dizygotic twins would be lower than .50 if genetic factors are influencing the need for achievement.

A Psychologist Conducts Research Using the Twin-Study Method