Final answer:
Psychologists can compare personality traits, social behaviors, and environmental influences when studying twins, gaining insights into the nature versus nurture debate.
Step-by-step explanation:
Psychologists studying twins are able to compare various aspects to understand the influence of genetics versus the environment on human behavior. By researching identical and fraternal twins who have been raised apart or together, such as in the Minnesota Study of Twins Reared Apart, investigators gain insights into the heritability of traits like personality, obedience, and stress resistance. Studies have shown that identical twins, whether raised together or apart, generally have very similar personality traits, indicating a high degree of genetic influence. However, examining twins also allows for the observation of differences that arise due to different social environments, highlighting the complex interplay between nature and nurture.