The Gift of Introversion

Heritability
Personality research conducted on twin subjects suggests that both heritable and
environmental factors contribute to the Big Five personality traits.
Genetically informative research, including twin studies, suggest that heritability and
environmental factors both influence all five factors to the same degree. Among four
recent twin studies, the mean percentage for heritability was calculated for each
personality and it was concluded that heritability influenced the five factors broadly. The
self-report measures were as follows: openness to experience was estimated to have a
57% genetic influence, extraversion 54%, conscientiousness 49%, neuroticism 48%,
and agreeableness 42%.
Non-Humans
The Big 5 personality traits can be seen in chimpanzees.
The Big Five personality traits have been assessed in some non-human species but
methodology is debatable. In one series of studies, human ratings
of chimpanzees using the Hominoid Personality Questionnaire, revealed factors of
extraversion, conscientiousness and agreeableness – as well as an additional factor of
dominance – across hundreds of chimpanzees in zoological parks, a large naturalistic
sanctuary, and a research laboratory. Neuroticism and openness factors were found in
an original zoo sample, but were not replicated in a new zoo sample or in other settings
(perhaps reflecting the design of the CPQ). A study review found that markers for the
three dimensions extraversion, neuroticism, and agreeableness were found most
consistently across different species, followed by openness; only chimpanzees showed
markers for conscientious behavior.
Development During Childhood and Adolescence
Research on the Big Five, and personality in general, has focused primarily on
individual differences in adulthood, rather than in childhood and adolescence, and often
include temperament traits. Recently, there has been growing recognition of the need to
study child and adolescent personality trait development in order to understand how
traits develop and change throughout the lifespan.
Recent studies have begun to explore the developmental origins and trajectories of the
Big Five among children and adolescents, especially those that relate to
temperament. Many researchers have sought to distinguish between personality and
temperament. Temperament often refers to early behavioral and affective
characteristics that are thought to be driven primarily by genes. Models of temperament
often include four trait dimensions: surgency/ sociability, negative emotionality,
persistence/effortful control, and activity level. Some of these differences in
temperament are evident at, if not before, birth. For example, both parents and
researchers recognize that some newborn infants are peaceful and easily soothed while
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