Psychology › Personality & intelligence › Heritability: nature and nurture
Temperament in infants
1956 (Thomas & Chess)· Concept
Well replicatedStrong, repeated evidence.
Babies differ from birth in mood, activity and reaction to new things; these early, partly inborn styles are called temperament.
See it on the Psychology map →What it says
In 1956 psychiatrists Alexander Thomas and Stella Chess began the New York Longitudinal Study, following 133 children. Rating traits like activity, mood and adaptability, they classed about 40 percent as 'easy' babies, 10 percent 'difficult' and 15 percent 'slow to warm up'; the rest were mixed. In the 1980s Jerome Kagan showed that roughly 15 to 20 percent of infants react strongly to novelty and tend toward shyness later, though many grow out of it.
Why it matters
It shifted blame away from parents: a fussy baby is not proof of bad parenting. Thomas and Chess stressed 'goodness of fit' between a child's style and their surroundings.
The evidence
Long-term cohort studies, parent and observer ratings, and lab tests of infants' responses to new toys and strangers. Twin studies and heart-rate and brain measures tie it to biology.
Open questions
How strongly infant temperament predicts adult personality is debated; links are modest. Why some sensitive children thrive in supportive homes but struggle in harsh ones is still studied.
Connections (3)
▸Ainsworth's Strange Situation and attachment styles is partly confounded with Temperament in infantsMixed evidence
The connection
The Strange Situation classifies babies by how they react when a parent leaves and returns. Critics such as Jerome Kagan argued these reactions partly reflect inborn temperament, how easily a baby gets upset, rather than the quality of care. Studies suggest temperament affects how much babies cry more than whether they are classed as securely attached.
Who showed it and when
Debated from the early 1980s by Kagan at Harvard and attachment researchers; tested in many infant studies through the 2010s.
How solid is it?
Babies often have different attachment classifications with mother and father, which temperament alone cannot explain; meta-analyses find only weak links between temperament and security.
Open questions
How temperament and caregiving interact: some argue easily upset babies are the most affected by the quality of care they receive.
▸Temperament in infants is an early root of The Big Five personality traitsWell replicated
The connection
Infant temperament dimensions map onto adult traits: negative emotionality resembles neuroticism, surgency (energetic, outgoing behavior) resembles extraversion, and effortful control resembles conscientiousness. As children grow, experience elaborates these early tendencies into fuller personality traits.
Who showed it and when
Mary Rothbart's temperament model from the 1980s; New Zealand's Dunedin study of about 1,000 children born in 1972–73; a 2003 review by Rebecca Shiner and Avshalom Caspi.
The evidence
In the Dunedin study, temperament observed at age 3 modestly predicted personality at age 26. The structural overlap is well documented.
Open questions
Whether temperament and personality are the same thing at different ages, and why links from infancy to adulthood are only modest.
▸Temperament in infants is partly explained by Heritability: nature and nurtureWell replicated
The connection
Twin studies show temperament traits like activity level, shyness and fussiness are moderately heritable, with estimates often between about 20 and 60 percent. The rest reflects environment, including prenatal conditions, parenting and chance. Shared home environment matters more for some infant traits, like positive mood, than it does later in life.
Who showed it and when
Twin studies of infants and toddlers since the 1980s, including work by H. Hill Goldsmith and Jerome Kagan's research on shy, inhibited children.
The evidence
Identical twin babies resemble each other more than fraternal twins on observed and parent-rated temperament, in several countries.
Open questions
Few specific genes have been identified. Some children seem especially sensitive to environment, for good or ill, a 'differential susceptibility' idea still being tested.