Source: Pepe174 CC0 via Wikimedia Commons

characteristics reflect key differences between people in their motivations. For example, people who are very open to experiences treat new things as something to be approached and considered, while those on the other end of the spectrum are more likely to away from the unfamiliar.

Personality characteristics are valuable to understand because they are fairly stable. That means that knowing something about a person’s personality characteristics can help you predict how they are likely to act and react in situations.

Although a lot is known about personality in young adults (because college students are frequently the participants in studies) and in older adults, the development of personality from to adulthood is less well understood.

New insights on what happens to personality during this period of life come from a paper in the October 2017 issue of the Journal of Personality and Social Psychology. The researchers analyzed data from a multi-year study of adolescents and young adults (ages 12 to 22) in the Netherlands. Each participant filled out a personality inventory that measured the personality traits— , , , , and (often conceptualized as Neuroticism)—and rated their closeness to siblings and friends that they had recruited to join them in the study.

The researchers explored how much personality traits tended to change over time. Consistent with the idea that personality stabilizes as people reach adulthood, the degree of change from year to year decreased as children got older.

The team was also interested in age-group differences in overall . They looked at this change separately for boys and girls. They found that:

The trait of agreeableness, which partly reflects how much people want to be liked by others, tended to increase over time in both boys and girls.

Conscientiousness, which reflects how much people tend to complete what they start and to follow rules, increased in girls over time. For boys, there was an initial dip as they entered adolescence and then an increase in as they became young adults, though adolescent and young-adult boys were less conscientious on average than girls in the study.

Boys in this sample showed a slight tendency toward more emotional stability over time, reporting decreased ratings on tendencies such as worrying or getting easily upset. Girls showed an initial dip in emotional stability as they reached adolescence, followed by an increase as they reached young adulthood.

The last big question addressed in this paper was whether children’s relationships with friends and siblings affects their personality. While there was a tendency for children to choose to hang out with other people who have traits similar to their own, changes in friends’ traits did not predict changes in a child’s traits. That is, the evidence suggests that kids make friends with people who are like them, but that their personalities are not strongly swayed by the personality shifts that unfold in their friends.