Think back to who you were at 19. Now think about the people you know in their fifties. Most of us notice a difference, and it is not just more grey hair. Older friends often seem steadier, more patient and better at getting things done.
That is not your imagination, and it is not just nostalgia. Personality psychologists have tracked thousands of people across decades and found a consistent pattern of change so reliable it has a name: the maturity principle. Here is what shifts, when it happens and why.
What the maturity principle says
The term was popularised by personality researchers including Brent Roberts and Avshalom Caspi in the mid-2000s. It describes a simple observation: on average, as people move through adulthood, their personalities change in ways that help them function in adult life.
Using the Big Five model, that typically means:
- Conscientiousness rises. People become more organised, dependable and self-disciplined.
- Agreeableness rises. People become warmer, more patient and more cooperative.
- Neuroticism falls. People become calmer and more emotionally stable.
These are the traits most linked to holding down a job, keeping relationships going and caring for others. In that sense, personality tends to "mature".
If you want a refresher on what each trait measures, our guide to the Big Five personality traits explains them in detail.
What the research found
The landmark study here is a 2006 meta-analysis by Brent Roberts, Kate Walton and Wolfgang Viechtbauer. They combined 92 longitudinal studies that measured the same people more than once, across ages from adolescence to old age.
Their key findings:
- Most traits showed meaningful average change across adulthood.
- The biggest changes happened between about 20 and 40, not in adolescence as many people assume.
- Emotional stability and conscientiousness increased steadily through young and middle adulthood.
- Agreeableness rose too, with some of its largest gains later in life.
- One part of extraversion, social dominance or assertiveness, increased, while another part, social vitality or the appetite for lively social stimulation, rose in adolescence and declined in older age.
- Openness rose in adolescence and early adulthood, then dipped in older age.
How your traits shift decade by decade
The changes are gradual, so you rarely notice them happening. But across 40 years they add up.
| Age range | What tends to change | What it often looks like |
|---|---|---|
| Teens | A temporary dip in conscientiousness and agreeableness for some | Moodier, less organised, pushing against rules |
| 20s | Fastest rise in conscientiousness and emotional stability | Building routines, taking on responsibility |
| 30s | Continued gains in stability and conscientiousness | Calmer under stress, more consistent habits |
| 40s and 50s | Agreeableness keeps rising, neuroticism keeps easing | More patient, more forgiving, less reactive |
| 60 and beyond | Personality becomes more stable overall; openness may ease | Settled preferences, fewer big swings |
Research using large cross-sectional samples, including work by Christopher Soto and colleagues, suggests that early adolescence can bring a temporary dip in some of these traits before they climb again. So the path from 12 to 20 is not always smooth.
Stable and changing at the same time
The maturity principle can sound like it contradicts the idea that personality is stable. It does not.
Psychologists distinguish between two kinds of stability:
- Mean-level change is the average shift in a trait across a whole group. This is what the maturity principle describes.
- Rank-order stability is whether people keep their position relative to each other. If you were the most conscientious person in your friendship group at 25, you are likely to be among the more conscientious at 55.
A 2000 meta-analysis by Brent Roberts and Wendy DelVecchio found that rank-order stability rises through adulthood and peaks in later middle age. So you tend to become calmer and more reliable, but so do your peers. You change, while largely keeping your place.
Why personality matures
Adult roles shape us
The leading explanation is social investment theory. The idea is that committing to adult roles, such as a steady job, a long-term partner or raising children, rewards certain behaviours. Turning up on time, managing frustration and putting others first become everyday habits, and over years those habits shift the underlying traits.
Some evidence supports this. People who take on a first serious job or a committed relationship often show increases in conscientiousness or emotional stability around that time. And a cross-cultural study led by Wiebke Bleidorn found that in societies where people take on adult roles earlier, personality maturation also tends to happen earlier.
Biology plays a part too
Not everything is about roles. Twin studies suggest that some personality change is genetically influenced, and the general pattern appears in many different cultures. Most researchers now think both biology and life experience are involved.
Experience and feedback
Living longer means more feedback about what works. Losing your temper with a colleague, missing a deadline or hurting a friend all teach lessons, and many people gradually adjust.
What the maturity principle does not mean
A few common misunderstandings are worth clearing up:
- It is an average, not a rule. Plenty of people do not follow the pattern, and some change in the opposite direction.
- It is not a moral ranking. Becoming more agreeable is not the same as becoming a better person. Different traits suit different situations.
- It does not stop at 30. Change slows, but it continues well into middle age and beyond.
- It is not purely automatic. Life roles and effort matter. You can influence the direction of your own change, as we discuss in can your personality change?.
What this means for you
If you are in your twenties and feel scattered or anxious, it may help to know that, for most people, these traits tend to improve with time and experience. If you are older and wonder why you care less about nightlife and more about calm weekends, the shift in social vitality is a normal part of the pattern.
You can also use this knowledge actively. Choosing roles and habits that reward reliability and patience may speed up the changes you want. Small, repeated behaviours such as planning tomorrow before bed or pausing before reacting are the raw material of personality change.
Curious where you sit right now? You can take our free Big Five personality test and compare your scores with how you see yourself. Retaking it every few years is a neat way to watch your own maturity principle in action. For a closer look at the trait most people hope will fall, see high neuroticism.
The bottom line
The maturity principle describes how, on average, people become more conscientious, more agreeable and more emotionally stable between their twenties and their sixties. The biggest shifts happen in early adulthood, driven by a mix of biology, adult roles and experience. It is a gentle, gradual trend, not a fixed script, and you have some say in how it unfolds for you.
FAQ
What is the maturity principle in psychology?
It is the finding that, on average, people become more conscientious, more agreeable and less neurotic as they move through adulthood. These are traits linked to functioning well in adult roles like work and relationships.
At what age does personality change the most?
Large studies suggest the biggest average changes happen between about 20 and 40. Change continues more slowly after that, and personality becomes increasingly stable in later middle age.
Does everyone become more mature with age?
No. The maturity principle describes averages, and individuals vary a lot. Some people change little, and some shift in other directions depending on their experiences.
Why do people become calmer as they get older?
Researchers think it is a mix of genetic influences, the demands of adult roles such as work and family, and years of experience in handling stress and conflict.
