What Really Shapes Your Personality? A Psychological Deep Dive
Personality is one of those things we all recognise instantly, even if we struggle to define it.
You might describe someone as “easy-going,” “high-strung,” or “the life of the party,” and everyone immediately understands what you mean. In psychology, personality refers to the consistent patterns in how we think, feel, and behave over time. While life experiences matter, psychologists have long been interested in why people are so different from one another in the first place.
Two influential psychologists who helped shape our understanding of personality are Gordon Allport and Hans Eysenck. Although they approached personality from different angles, both believed that personality is relatively stable and that biology plays an important role.
Allport: Personality as Individual Traits
Gordon Allport focused on what makes each person unique. Rather than placing people into strict personality “types,” he believed personality is made up of traits — habitual ways of responding to the world. According to Allport, traits help explain why people tend to behave consistently across different situations.
Allport suggested that some traits are more central to who we are than others. For most people, personality is shaped by a handful of core traits that show up regularly in everyday life. For example, someone might generally be dependable, kind, and cautious. These traits influence how they show up at work, in friendships, and in family life.
Some traits only appear in specific situations. Think of the person who is calm and confident most of the time but becomes noticeably anxious when speaking in front of a group. That anxiety doesn’t define their whole personality — it’s more situational.
Allport also described rare cases where a single trait dominates a person’s life so strongly that it defines them. While most of us don’t have a trait this extreme, we still recognise the idea. For example, someone who is relentlessly driven by success may organise their entire life around achievement, status, and recognition.
What makes Allport’s theory especially relatable is that it allows for complexity. You don’t have to fit neatly into a box. You can be warm but introverted, confident but sensitive, organised at work yet chaotic at home. Personality, in this view, is deeply individual.
Eysenck: Personality and Biology
Hans Eysenck took a more biological approach. He believed that personality traits are strongly influenced by genetics and the nervous system. While Allport focused on describing traits, Eysenck wanted to explain where they come from.
Eysenck suggested that much of personality can be understood through a few broad dimensions. One of the most well-known is extraversion and introversion. Extraverts tend to seek stimulation — they enjoy socialising, activity, and excitement. Introverts, on the other hand, feel more comfortable in calmer environments and often prefer smaller groups or time alone.
Eysenck believed this difference is linked to how easily a person’s brain becomes stimulated. Introverts tend to have higher natural levels of arousal, so too much stimulation can feel overwhelming. Extraverts have lower baseline arousal and seek out stimulation to feel energised.
Another key dimension is neuroticism, which relates to emotional stability. People high in neuroticism are more likely to experience anxiety, mood swings, and emotional reactivity. Those lower in neuroticism tend to be calmer and more emotionally resilient.
You can see this in everyday stress. Imagine two people stuck in traffic. One becomes tense, frustrated, and anxious about being late. The other feels mildly annoyed but remains composed. According to Eysenck, these differences are partly rooted in biological sensitivity to stress.
Eysenck also described a third dimension called psychoticism, which relates to traits like impulsivity, tough-mindedness, and lower empathy. This does not mean mental illness — despite the confusing name. Instead, it reflects differences in self-control and interpersonal style.
The Role of Biology
Eysenck’s work highlighted the idea that personality is not shaped by environment alone. Research on twins and families supports this view, showing that traits like extraversion and emotional reactivity are partly inherited. Even siblings raised in the same household can have noticeably different temperaments from an early age.
That doesn’t mean personality is fixed or that experiences don’t matter. Biology provides a foundation, but environment shapes how traits are expressed. For example, a child who is biologically sensitive may thrive with supportive caregivers but struggle in a chaotic or stressful environment.
Is personality malleable?
For a long time, personality was described as something fixed: you’re either “anxious,” “introverted,” or “short-tempered,” and that’s just who you are. While it’s true that we’re born with certain temperamental tendencies, research now shows that personality is malleable — meaning it can shift and adapt across the lifespan.
We start with a temperament, not a finished personality
At birth, we have a basic temperament — things like sensitivity, emotional intensity, and activity level. Some babies are calm and adaptable, others are highly reactive or cautious. These early differences are largely biological, but they’re only the starting point, not the final outcome.
As we grow, experiences shape how those tendencies are expressed. A naturally sensitive child who grows up with emotional support may learn strong self-regulation and empathy. The same child in a chaotic or unsafe environment may develop anxiety or emotional withdrawal. The biology is similar — the expression is different.
Life experiences reshape traits over time
Personality doesn’t stop developing after childhood. Major life experiences can meaningfully shift traits well into adulthood.
For example:
People often become more emotionally stable with age, as they learn coping skills and gain perspective.
Parenthood frequently increases conscientiousness — suddenly routines, planning, and responsibility matter more.
Therapy, trauma recovery, or secure relationships can reduce neuroticism and increase emotional regulation.
New environments (like a job that requires leadership or collaboration) can bring out traits we didn’t realise we had.
These changes aren’t usually dramatic overnight shifts. They’re gradual, shaped by repeated experiences and new ways of responding to the world.
Behaviour can lead personality change
One of the most powerful ideas in modern psychology is that acting differently can eventually change who we are. When someone repeatedly practices new behaviours — setting boundaries, tolerating discomfort, speaking up, or self-soothing — those behaviours can slowly become part of their personality pattern.
For instance, someone who sees themselves as “bad at boundaries” may begin by setting one small limit. Over time, repeated boundary-setting can increase assertiveness, confidence, and emotional stability. The trait didn’t change magically — it changed through practice.
What doesn’t change — and what does
Personality isn’t endlessly flexible. Core tendencies like introversion or sensitivity often remain, but how they’re expressed can change dramatically. An introverted person may always need alone time — but they can still become confident, socially skilled, and emotionally expressive. A sensitive person may always feel deeply — but they can learn to regulate emotions rather than be overwhelmed by them.
Why These Ideas Still Matter
Although modern psychology now uses broader models like the Big Five, the ideas introduced by Allport and Eysenck still underpin how we understand personality today. Allport reminded us that personality is personal and nuanced, while Eysenck helped explain why certain traits appear so early and remain so consistent.
Together, their theories highlight an important truth: personality is shaped by both who we are born as and what we experience along the way.
Understanding this can help us be more compassionate — toward ourselves and others — when we notice differences in how people think, feel, and respond to the world.