Personality and temperament: what is the difference?

Temperament and personality are often used interchangeably in everyday speech, and the distinction between them is genuine — though it is one of degree rather than a clean line.

The conventional distinction

Temperament refers to constitutionally based individual differences in reactivity and self-regulation, observable very early in life and relatively stable. Infants differ from the first weeks in how strongly they respond to novelty, how easily they are soothed, how much they approach or withdraw. These differences precede any meaningful learning history, which is the core of the argument that they are constitutional.

Personality refers to the broader, more elaborated patterns of thinking, feeling and behaving that characterise an adult. It includes temperament as a foundation but adds everything built on top: values, beliefs, characteristic adaptations, identity, the strategies a person has developed for handling their own reactivity.

The metaphor most often used is that temperament is the raw material and personality is what experience makes of it.

Where it comes from

The modern research programme starts with Thomas and Chess's New York Longitudinal Study in the 1950s, which followed infants and identified nine temperament dimensions later grouped into easy, difficult and slow-to-warm-up patterns. Kagan's work on behavioural inhibition in the 1980s showed that a subset of infants who react strongly to novelty at four months remain more inhibited into adolescence, with measurable physiological differences.

Rothbart's model, now the most influential, reduces temperament to three broad factors: surgency or extraversion, negative affectivity, and effortful control. Buss and Plomin's earlier EAS model proposed emotionality, activity and sociability.

Where the line blurs

The clean distinction runs into trouble at both ends.

The adult trait dimensions look a great deal like grown-up temperament dimensions. Rothbart's surgency corresponds to extraversion, negative affectivity to neuroticism, effortful control to conscientiousness. That is three of the Big Five with a different developmental label. If adult traits are largely elaborated temperament, the categories are not describing different things so much as the same things at different ages.

Heritability estimates do not separate them either. Both temperament and adult personality traits show heritability in the range of 40 to 60 percent — temperament is not uniquely biological and personality is not uniquely learned.

And temperament is not fixed. Kagan's inhibited infants were more likely to become inhibited adolescents, but a substantial share were not. Early temperament shifts the odds; it does not determine the outcome.

Why the distinction is still worth keeping

Even blurred, it does useful work.

It explains why change is possible but slow. If part of what you are working against was present before you had any say in it, effort produces gradual movement rather than transformation — and expecting transformation is a good way to conclude wrongly that nothing is changing.

It also separates reactivity from regulation, which everyday language conflates. Two people can have the same intensity of emotional response and differ enormously in what they do with it. The second is far more trainable than the first, and interventions that target regulation rather than reactivity are the ones with better evidence.

In measurement terms

Adult instruments measure personality, not temperament. Temperament assessment is done with infant and child instruments, often through parent report or observation, and does not translate to adults.

What an adult questionnaire captures is the current state of a system with constitutional foundations and decades of history layered on it. That is why a trait score is best read as a description of where you are now — informative, moderately stable, and not a statement about what was inevitable.