Do Personalities Remain Stable Across a Lifetime?

Introduction

Personality psychology has long sought to determine whether the characteristics defining individuals remain constant through life or change based on environmental interaction. Personality can be defined as a unique, dynamic configuration of characteristics or behaviour in social and environmental contexts (APA: Dictionary of Psychology, 2018). The most popular personality framework is the Big Five Model (Costa & McCrae, 1992), explaining personality across five broad categories: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Each dimension provides insight into how personality behaves over time, displaying a comprehensive perspective of individual differences. Factor-analytic research (Goldberg, 1990) supports its effectiveness in discussing personality. The Big Five Model illustrates personality as relatively stable dispositions that remain steady across time and context. However, the assumption of lifelong stability has been opposed by developmental psychologists, arguing that personality may change in response to biological maturation, environmental influence, or social roles. Personality stability across the lifespan has implications beyond theoretical psychology, having also been linked to life outcomes (Friedman et al., 2014). The debate of personality stability can be evaluated by the familiar nature-nurture discussion: broader debates involving biological predispositions and environmental experiences. Evidence from genetics, developmental psychology, longitudinal studies, and social theory can suggest that personality traits depict continuity but may demonstrate change across a lifetime.

Instead of being completely fixed or completely malleable, this essay will argue that personality follows trajectories, moulded by the coalescence of nature and environment.

The genetic case for stability

Personality stability is strongly associated with biological and genetic evidence. Genetic research, in association with behaviour, has demonstrated that personality traits possess a relatively moderate inheritance, proposing that individual differences are partly influenced by genetic factors; this is supported by meta-analytic evidence (Vukasović & Bratko, 2015; Power & Pluess, 2015), which indicates that 40-50% of the variability in personality traits is linked to genetic influences. Furthermore, twin studies of monozygotic twins raised apart, researchers (Bouchard et al., 1990) found significant similarities in personality traits — suggesting a genetic influence of ~50% in personality. However, it’s important to note that heritability doesn’t directly indicate immutability but rather a predisposition that can be influenced by potentially negative, stressful environmental conditions — the Diathesis-Stress Model (Zubin & Spring, 1977). While genetic evidence and high concordance rates support the stability of personality traits, it doesn’t provide evidence of a fixed structure across the lifespan nor consider the crucial role of life experiences in the shaping of personality. Furthermore, twin studies that often support these findings rely on equal environmental context assumptions, which, in practice, often aren’t the case. It can also be argued that many psychological characteristics, not just bound to personality traits, are influenced by polygenic processes (Plomin & von Stumm, 2021). This reinforces the view of predisposition, providing a foundation, but it lacks direct demonstration of fixed personality or accounting for significant developmental factors across the lifespan.

Early temperament and developmental trajectories

Developmental studies of early temperament also provide evidence for biological stability in personality. Investigations classified a large sample of infants as ‘behaviourally inhibited’ (Kagan et al., 1988), an avoidance of unfamiliar stimuli which, in turn, leads to an increased likelihood of behaviour that demonstrates increased rates of anxiety and introversion in later childhood and adolescence. These findings suggest that these early temperamental effects possibly form the foundations for later personality expression. Additionally, theories surrounding Life-Course-Persistent (LCP) and Adolescent-Limited (AL) (Moffitt, 1993) offenders both support and contradict nature’s deterministic aspects of the personality stability argument. LCP offenders bring deviant acts from childhood into adulthood, the main reasoning being neuropsychological deficits (e.g., cognitive ability, temperament) or high-risk environments — supporting the reinforcement of personality stability over time. Moreover, the much more common AL offender, whose crimes begin in early adolescence and end by young adulthood, challenges stability as deviant traits decrease significantly post-maturity. Both studies from Kagan et al. and Moffitt indicate that biological predisposition plays a role in personality development; therefore, predispositions can provide a biological baseline for the shaping of personality, but the expression of these traits may vary across different environmental contexts. Thus, while early temperament supports personality continuity, the variation between LCP and AL offenders exemplifies that trajectories of personality are not fixed.

Neuroscience and rank-order stability

Furthermore, neuroscientific research supports the argument of fluctuations in personality as individuals mature. The development of the prefrontal cortex, associated with emotional regulation, continues from adolescence to early adulthood (Casey, Getz & Galvan, 2008). Meta-analytic research (Roberts & DelVecchio, 2000) established ‘rank-order stability’, which indicates the levels at which individuals maintain their position compared to others on personality traits. Rank-order stability increases proportionally to age; results also indicate higher stability in adulthood as opposed to higher levels of variability in earlier life. These findings demonstrate that personality is progressive into adulthood with increasing stability. Following on, this increasing stability carries over from the age of 30 to 50s and 60s; therefore, it’s implied that personality shows flexibility during a lifespan while following an overall trajectory of increasing stability with age, opposing the notion of deterministic continuity from an early life stage onwards. However, it’s important to note that brain development and personality change are examples of correlation, not causation.

When genes meet environment

On the other hand, environmental factors on personality should not be overshadowed compared to biological perspectives. The space between nature and nurture is identified by research into the environmental and genetic interactions that influence personality. For example, serotonin transporter genes were studied and linked to stressful life experiences in predicting depression (Caspi et al., 2003). The findings propose that genetic predispositions are significant but are not the sole determinant; rather, they interact with environmental influence to shape behaviour. Some predispositions may also only be expressed whilst under environmental stress stimuli. Although this study focuses on depression, it is able to extend its findings to personality by demonstrating that predispositions are activated or suppressed based on environmental context. This challenges the idea of fixed traits, insisting on a dynamic model of personality instead, dependent on environmental context. Even so, the link established between genetics and depression may be considered contested, as meta-analytic research found no strong evidence for the interaction (Risch et al., 2009); thus, inconsistent findings of the relationship between specific genes and depression employ the concept as debatable or more polygenic than originally proposed.

Social roles and reinforcement

Environments in social contexts can also influence personality. The Social Investment Theory (Hudson, Roberts & Lodi-Smith, 2012; Roberts, Wood & Smith, 2005) suggests that personality traits in individuals can alter based on social roles such as parenthood, marriage or employment. These roles employ expectations which reward behaviour such as emotional regulation, ability to cope under stress, and co-operation — all of which demonstrate behavioural change to attune to familiar environments. Repeatedly engaging in these behaviours, which is often required, can lead to reinforcement of relevant tendencies over time (Skinner, 1963), leading to long-term changes in personality. For example, entering a stable career would encourage responsible behaviour from an individual; long-term relationships also require maturity and emotional stability as a necessity for healthy communication (Overall & McNulty, 2017). Thus, societal roles contribute to personality, challenging purely biological perspectives of personality stability.

Longitudinal evidence

To understand the environmental impacts on personality stability, researchers often resort to longitudinal studies due to their rich data, which are analysed both scientifically and socially. Longitudinal research reflects a general maturation process through age (Bleidorn et al., 2013), such as conscientiousness (Costa & McCrae, 1992) and emotional stability. Both age-related development and life experiences appear to play a crucial role in the shaping of personality — signalling the relationship between personality and life events could be bidirectional, with personality heavily influenced by major life transitions (Specht, Egloff & Schmukle, 2011). Personality development could be described as a systematic process, structured by multiple social factors. This longitudinal evidence provides a strong challenge against complete personality immutability, employing a gradual personality development instead of a strictly fixed stability.

Culture and context

Cultural context is also a major factor in personality psychology. Cross-cultural research (McCrae, 2002; Triandis, 1995) demonstrates that while the structure of the Big Five Model is universal, as suggested previously, its physical and behavioural indications are culturally relative. For instance, extraversion may be encouraged in individualistic societies, while often looked down upon in collectivist societies. Although underlying traits remain relatively stable, cultural context-dependent factors criticise claims of high stability in individuals; personality cannot be considered stable across sociocultural contexts. This suggests that while the Big Five model’s trait definitions may be universal, said expressions are context-dependent.

Conclusion

To conclude, on one hand, biological evidence supports continuity across individuals (particularly in rank-order stability), and on the other, the nurture-based side of the argument suggests environmental influences contribute to a slow, gradual change over the lifespan. Additionally, the definition of stability itself can be open to interpretation, which implies that both change and continuity exist. The significance of this balance is showcased by research into traits, such as conscientiousness, in predicting long-term outcomes in an individual’s lifespan, some of which include longevity (Friedman et al., 2014). Overall, personality is best interpreted as a constrained plasticity, following certain trajectories yet simultaneously given room to follow different paths specific to each individual.

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