Personality Is Stable. That Doesn’t Mean It’s Fixed

Ask someone whether personality can change and you will usually get one of two answers. Either people fundamentally remain the same person forever, or they can reinvent themselves completely provided they buy the correct journal, download the correct app and wake up at 5 a.m.

Psychology, inconveniently, suggests something less dramatic.

Personality traits are relatively stable patterns in how we think, feel and behave. Relatively stable is doing important work there. A trait being stable does not mean it is frozen in place, any more than describing the British climate as relatively stable means Tuesday cannot surprise you.

A new randomised controlled trial published in Psychological Science provides unusually direct evidence of that distinction. Amanda Wright and colleagues recruited 446 German-speaking adults who wanted to become less neurotic and tested whether a six-week smartphone intervention could actually shift their personality in that direction (Wright et al., 2026).

The answer appears to be yes.

Trying to Become Less Neurotic

In personality psychology, neuroticism refers broadly to a tendency to experience negative emotions such as anxiety, worry, irritability and emotional instability more readily or intensely. It is one of the Big Five personality traits and is associated with numerous measures of psychological and physical health.

That makes it an obvious target for intervention. Plenty of people would quite like their internal alarm system to stop behaving as though a delayed email constitutes an unfolding national emergency.

Wright and colleagues did not simply tell participants to “think positively” and check back six weeks later. The intervention was specifically designed to test different theories about how personality change might happen.

Some strategies targeted momentary states, attempting to change how participants responded in particular situations. Others targeted habits, aiming to alter repeated patterns of behaviour over time. The researchers also distinguished strategies focused primarily on thoughts from those focused on behaviour.

Across the intervention groups, self-reported neuroticism fell by small-to-moderate amounts. Effect sizes immediately following treatment ranged from approximately d = −0.22 to −0.37. Importantly, much of that change remained two months later, with follow-up effects ranging from around d = −0.16 to −0.33.

That alone is interesting.

But self-report is also where things can become slightly awkward.

If somebody spends six weeks using an intervention explicitly designed to make them less neurotic, it is hardly mysterious that they know which direction their questionnaire score is supposed to travel.

So the researchers also obtained reports from people who knew the participants. On one of the two peer-report measures, these observers also detected reductions in neuroticism at follow-up, with effect sizes of approximately d = −0.18 to −0.30.

That does not eliminate every possible bias, but it makes the result much more difficult to explain as participants merely becoming better at completing a personality questionnaire correctly.

Quick stats note

What does d = −0.22 actually mean?

In psychology, d is a common way of expressing effect size: roughly speaking, how large a difference or change was.

d The measure This tells you the number is an effect size.

− The direction Here, it means neuroticism scores went down.

0.22 The size This tells you how large the change was.

So d = −0.22 does not mean the result was “negative” or bad. It means there was a small reduction in neuroticism.

0.2 Small

0.5 Moderate

0.8 Large

In this study: effects of d = −0.22 to −0.37 mean neuroticism fell by an amount that was roughly small to approaching moderate.

These cut-offs are only rough rules of thumb. Whether an effect is important depends on the context.

Fast Change and Slow Change

Perhaps the most interesting result was not that neuroticism changed, but how different approaches appeared to produce change.

Strategies targeting momentary psychological states tended to produce larger immediate improvements. Their effects, however, were somewhat less durable.

Habit-focused strategies followed almost the opposite pattern. Their initial effects were smaller, but they strengthened over time.

Behaviour-focused strategies performed particularly well, especially when they targeted habits (Wright et al., 2026).

There is an appealingly mundane idea hiding in that finding.

Changing your personality may not require excavating a mysterious “true self” buried somewhere underneath adulthood. It may partly involve changing what you repeatedly do until those behaviours become increasingly characteristic of how you normally respond.

In other words, traits may partly emerge from accumulated patterns of states and habits.

That fits broader work on intentional personality change. A 2024 systematic review identified 30 longitudinal studies involving 7,719 participants. Simply wanting to change one's personality showed only a weak relationship with actual personality change. Interventions, however, produced small but meaningful changes in the desired direction, with some effects maintained or even increasing during follow-up (Haehner, Wright, & Bleidorn, 2024).

Wanting to become more conscientious while continuing to live precisely as before, it turns out, may not represent a particularly aggressive intervention.

Stable Is Not the Same as Permanent

None of this means personality is infinitely malleable.

Personality traits are called traits precisely because they display meaningful consistency. If they changed completely every fortnight, personality questionnaires would have roughly the scientific usefulness of asking what someone fancied for lunch.

People also differ in how much they change, which traits they can change, what circumstances support that change and how long any intervention effects persist.

The current study focused specifically on adults who wanted to reduce neuroticism. It does not demonstrate that all five major personality traits can be modified equally easily, nor that six weeks of smartphone exercises can manufacture whatever personality somebody chooses.

The follow-up period was also only two months. That is enough to show the changes did not disappear immediately, but not enough to tell us whether they will still be detectable in two years.

Researchers working in this area have themselves warned against racing from promising intervention studies to personality engineering. Questions remain about long-term effects, unintended consequences, individual differences and even the ethics of defining certain personality configurations as desirable targets for improvement (Haehner et al., 2026).

That caution matters particularly with neuroticism. High neuroticism is associated with distress and poorer outcomes, but sensitivity to threat is not inherently useless. There is probably an evolutionary reason our ancestors did not thrive by responding to every suspicious noise in the undergrowth with admirable emotional stability.

Simply Put

The genuinely interesting message from this research is therefore neither “your personality cannot change” nor “you can become anyone you want.”

It is that personality appears to occupy the much less marketable territory in between.

Traits are stable enough to describe meaningful differences between people while remaining sufficiently plastic to shift with experience, behaviour and deliberate intervention.

That may sound less exciting than complete personal reinvention, but psychologically it is far more interesting.

You do not wake up one morning with a different personality.

You repeatedly think, feel and behave in slightly different ways. Some of those responses become habits. Those habits become increasingly characteristic of you. And eventually, when psychology asks what kind of person you are, the answer may have moved.

Personality is stable.

It just never promised to stay still.

References

Haehner, P., Wright, A. J., & Bleidorn, W. (2024). A systematic review of volitional personality change research. Communications Psychology, 2, 115. https://doi.org/10.1038/s44271-024-00167-5

Haehner, P., Asselmann, E., Baumgardt, S., et al. (2026). Ten concerns about volitional personality-change interventions—and how to address them. Perspectives on Psychological Science. https://doi.org/10.1177/17456916261466950

Wright, A. J., Haehner, P., Andrae, R., Lubczyk, T., Hopwood, C. J., & Bleidorn, W. (2026). Effects of a theory-based smartphone intervention to decrease neuroticism in the general public. Psychological Science, 37(10), 685–704. https://doi.org/10.1177/09567976261476962