Personality: What the Research Tells Us About Who We Are and How We Change
When we talk about personality, we are referring to patterns of thinking, feeling, and behaving that are relatively stable over time. Personality is what makes each of us feel consistent to ourselves and others, even across different situations and stages of life.
A central question in psychology is whether personality is shaped more by genetics or by environment. The answer, based on decades of research, is that it is both, but genetics appears to play a particularly strong role in core personality traits (Bouchard & McGue, 2003).
Is Personality Genetic or Learned?
Research using adoption and twin studies has provided some of the strongest evidence for the genetic basis of personality.
Studies comparing adopted children with their biological and adoptive parents show an interesting pattern: there is often very little correlation between adopted children and their adoptive parents in core personality traits. In contrast, there is a much stronger similarity between children and their biological parents, even when they have had limited contact (Bouchard & McGue, 2003).
This suggests that traits such as sociability, emotional reactivity, and levels of extraversion are strongly influenced by genetics.
However, this does not mean environment is unimportant. Values, attitudes, and beliefs about life tend to be more strongly shaped by upbringing, culture, and social learning.
Twin research further supports this conclusion, showing that even identical twins raised apart are more similar in personality than fraternal twins raised together (Bouchard & McGue, 2003).
In simple terms, genetics tends to influence how we are wired, while environment shapes what we do with that wiring.
Stability and Change Across the Lifespan
Personality is not completely fixed, but it does show a pattern of both stability and change across the lifespan.
Temperament, the early building blocks of personality, can be observed as early as six months of age. This suggests that some core aspects of personality are present very early in development (Costa & McCrae, 1992).
However, personality is more variable during childhood and adolescence, when cognitive, emotional, and social development is still taking place.
As people move into adulthood, personality becomes more stable. Traits such as extraversion, conscientiousness, and emotional stability tend to remain relatively consistent over time (Roberts, Walton, & Viechtbauer, 2006). However, this stability is not absolute. Gradual changes do occur, often reflecting psychological maturity, for example, increases in conscientiousness and emotional regulation.
Importantly, stability does not mean personality cannot change. It means that change typically happens slowly and is influenced by meaningful life experiences rather than small day-to-day events (Roberts, Wood, & Caspi, 2008).
Life Events and Personality Change
Research shows that major life transitions can influence personality traits over time, including unemployment, widowhood, parenthood, marriage, divorce, and retirement (Roberts, Wood, & Caspi, 2008).
These experiences can lead to shifts in traits such as neuroticism, conscientiousness, extraversion, openness, and agreeableness depending on the context and individual differences.
These findings highlight an important point: personality is shaped by both internal dispositions and external life circumstances. When environments change significantly, people often adjust psychologically and behaviourally in response.
Personality and Health Behaviour
Personality traits are strongly linked to health-related behaviours and outcomes.
Research has consistently shown associations between personality and behaviours such as smoking, substance use, physical activity, dietary habits, risk-taking behaviours, sunscreen use, and dangerous driving (Smith & MacKenzie, 2006).
One of the most robust findings is that higher neuroticism is associated with greater stress reactivity, while higher conscientiousness is associated with healthier behaviours and better adherence to health recommendations (Costa & McCrae, 1992).
Personality therefore plays an important role not only in emotional wellbeing but also in long-term physical health outcomes.
Personality, Wellbeing, and Mental Health
Personality traits are also linked to psychological wellbeing. Higher extraversion is associated with positive affect and social engagement, higher conscientiousness is linked to better self-regulation, and higher neuroticism is associated with increased vulnerability to stress, anxiety, and depression (McCrae & Costa, 2008).
These traits do not determine mental health outcomes on their own, but they influence how individuals respond to stress and life challenges.
Can Personality Be Changed?
One of the most important findings in psychological research is that personality is not fixed.
While genetics provide a baseline, environmental influences and intentional behavioural change can lead to gradual shifts in personality traits over time.
However, meaningful change typically requires sustained effort and significant life experiences rather than short-term interventions.
Implications for Psychological Therapy and Health Interventions
An important finding in clinical psychology is that the type of therapy used is not always the strongest predictor of change. Instead, client characteristics and presenting difficulties often play a larger role.
Research suggests that individuals presenting with anxiety disorders or personality-related difficulties often show greater change in therapy compared to those with conditions such as eating disorders or substance use difficulties (Soldz & Vaillant, 1999).
This highlights the importance of personalised psychological intervention.
Understanding a client’s personality traits during assessment can help clinicians tailor interventions more effectively.
Therapy does not aim to change personality itself, but rather to help individuals work with their natural tendencies in a way that improves wellbeing and functioning.
So what does this all mean?
Personality is best understood as the result of both genetic and environmental influences. It shows stability across adulthood but also meaningful change across the lifespan, particularly in response to major life events.
Rather than being fixed, personality is dynamic over time, shaped by both who we are and what we experience.
Understanding personality helps us make sense of how people think, feel, behave, and respond to stress. It also plays an important role in tailoring psychological interventions to individual needs.
Written by Victoria MulcahyProvisional Psychologist
References
Bouchard, T. J., & McGue, M. (2003). Genetic and environmental influences on human psychological differences. Journal of Neurobiology, 54(1), 4–45.
Costa, P. T., & McCrae, R. R. (1992). Revised NEO Personality Inventory (NEO PI-R) and NEO Five-Factor Inventory (NEO-FFI) professional manual. Psychological Assessment Resources.
McCrae, R. R., & Costa, P. T. (2008). The five-factor theory of personality. In O. P. John, R. W. Robins, & L. A. Pervin (Eds.), Handbook of personality: Theory and research (3rd ed.). Guilford Press.
Roberts, B. W., Walton, K. E., & Viechtbauer, W. (2006). Patterns of mean-level change in personality traits across the life course. Psychological Bulletin, 132(1), 1–25.
Roberts, B. W., Wood, D., & Caspi, A. (2008). The development of personality traits in adulthood. In O. P. John, R. W. Robins, & L. A. Pervin (Eds.), Handbook of personality: Theory and research (3rd ed.). Guilford Press.
Smith, T. W., & MacKenzie, J. (2006). Personality and risk of physical illness. Annual Review of Clinical Psychology, 2, 435–467.
Soldz, S., & Vaillant, G. E. (1999). The Big Five personality traits and the life course. Journal of Personality and Social Psychology, 77(3), 532–562.
