A longitudinal study examining personality changes between 10 and 16 years of age found that conscientiousness and agreeableness tend to decline from age 12 to 16. Neuroticism increased during the studied period, but only in girls. The paper was published in Personality and Social Psychology Bulletin.
Personality is the relatively stable pattern of thoughts, emotions, motivations, and behaviors that makes each person distinctive. It influences how people perceive situations, interact with others, respond to challenges, and make decisions. Personality develops through a combination of genetic influences, early experiences, social relationships, culture, and life events.
One of the most widely used scientific models of personality is the Big Five model. One trait in this framework, openness to experience, describes curiosity, imagination, creativity, and a willingness to consider new ideas. Conscientiousness refers to being organized, responsible, disciplined, dependable, and focused on achieving goals. Extraversion involves sociability, assertiveness, enthusiasm, energy, and a tendency to seek stimulation from other people.
Agreeableness reflects kindness, cooperation, empathy, trust, and concern for the needs of others. Neuroticism describes a tendency to experience negative emotions such as anxiety, sadness, irritability, and emotional instability. Underneath these broad categories are narrower traits called facets. For example, conscientiousness includes the specific facets of order and self-discipline, while neuroticism includes anxiety and depression.
Study author Silje Steinsbekk and her colleagues explored how these overarching traits and their specific facets change as children mature. They noted two opposing views about the developmental trajectory of personality. One view expects that as children mature, they become more conscientious, agreeable, and emotionally stable. An opposing idea, the disruption hypothesis, suggests temporary declines in certain aspects of personality maturation during adolescence as teenagers face new social and biological challenges.
To investigate this, the research team analyzed data from the Trondheim Early Secure Study. In 2007 and 2008, all four-year-olds born in Trondheim, Norway, alongside their parents, were invited to participate in a project examining psychosocial development. Researchers eventually selected just over a thousand participants to attend the first assessment.
This particular analysis focused on data collected from the time the participating children turned 10 years old. Ten was the age when participants started completing self-reported personality tests. In total, the researchers looked at 805 children who provided data at ages 10, 12, 14, or 16. The number of children at individual assessment points ranged from 635 to 704, with girls making up slightly more than half of the group.
The results generally supported the disruption hypothesis. Contrary to the idea of steady maturation, the conscientiousness and agreeableness of participating children decreased from age 12 onward. A closer look at the narrower facets revealed that a drop in self-discipline drove the decline in conscientiousness. Meanwhile, a reduction in compliance and altruism pushed agreeableness downward.
Neuroticism decreased between 10 and 12 years of age in boys and then remained relatively stable. In contrast, girls experienced an increase in neuroticism from age 12 to 16. Examining the specific facets showed that rising anxiety levels fueled this upward trend in girls. Extraversion also decreased between 14 and 16 years of age in both sexes, largely due to a substantial drop in the activity facet.
Openness decreased in girls throughout the study period. In boys, this trait decreased between 10 and 14 years of age and remained relatively stable afterward. “Our results predominantly support the disruption hypothesis, showing declines in conscientiousness and agreeableness across sexes from age 12, with an increase in neuroticism observed solely for girls. The findings further demonstrate that maturation disruptions vary at the facet level, suggesting a complex developmental process,” the study authors concluded.
The study contributes to the scientific understanding of personality development. However, all study participants came from a single city in Norway, meaning findings in other cultures might not be identical. Additionally, the study relied on self-reports from children as young as 10. Younger children are generally less reliable reporters of their own behavior, which could have affected the accuracy of the early assessments.
The paper, “Personality From Age 10 to 16 years. A Four-Wave Cohort Study of Development and Sex Differences in the Big Five and Its Facets,” was authored by Silje Steinsbekk, Lars Wichstrøm, and Tilmann von Soest.