on behavior is easier to study in boys because they have only one copy whereas girls have two, one for each of their two X chromosomes. For each boy, Caspi and Moffitt collected information on the presence and frequency of their antisocial behavior and whether they were raised by parents who were caring,

other hand, typically experience intense feelings of social isolation even though they are physically around more people than before they left home. Caspi and colleagues (23) found that perceived social isolation in adolescence and young adulthood predicted how many cardiovascular risk factors (e.g., bo