<h3>Heritability estimates of Extraversion (and other Big 5 factors)</h3>

<p>The introduction section of  Loehlin et al (1998) provides a narrative review of heritability estimates of <a href="http://en.wikipedia.org/wiki/Big_Five_personality_traits">big 5 personality</a> traits (i.e., one of which is extraversion).
A brief extract gives a flavour of some of the research that has been conducted:</p>

<blockquote>
  <p>A recent heritability analysis of the Big Five dimensions as measured
  by the <a href="http://en.wikipedia.org/wiki/Revised_NEO_Personality_Inventory">Revised NEO Personality Inventory</a> of Costa and McCrae (1992)
  used a total of 660 monozygotic (MZ) pairs and 380 dizygotic (DZ)
  pairs from pooled Canadian and German twin samples (Jang, McCrae,
  Angleitner, Riemann, &amp; Livesley, 1998). For all five traits a simple
  model involving only additive genes and nonshared environment fit the
  data. Estimates for the heritabilities of factor scales for [Extraversion, Agreeableness, Conscientiousness,
  Neuroticism, and Openness] were .50, .48, .49, .49, and .48, respectively. These
  estimates are obviously very similar—in partic- ular, the heritability
  of Agreeableness is quite in line with the rest.</p>
</blockquote>

<p>They also mention other twin studies, with <a href="http://en.wikipedia.org/wiki/Heritability#Estimating_heritability">heritability estimates</a> for Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness respectively as:</p>

<pre><code>                       E    A    C    N    O
Waller (1999):        .49  .33  .46  .42  .58
Riemann et al (1997):  60  .57  .71  .61  .81
</code></pre>

<p>Thus, in summary, it seems that such estimates for the heritability of extraversion are around 50%.</p>

<h3>Side Point</h3>

<ul>
<li>While inventories like the Myer-Briggs Type Inventory often categorise individuals, into categories, I find a continuous approach to personality traits provides a more accurate description of an individual. Using such an approach, people have a score on an extraversion dimension that is roughly normally distributed (or at least continuously distributed) in the population.</li>
</ul>

<h3>Limitations</h3>

<ul>
<li>I realise this only partially answers your question. It doesn't discuss the dynamic environmental-genetic interactions that cause personality traits , nor does it take a critical perspective on issues related to the measurement of extraversion, and the estimation issues related to heritability. Hopefully, it is a useful starting point.</li>
</ul>

<h3>References</h3>

<ul>
<li>Jang, K. L., McCrae, R. R., Angleitner, A., Riemann, R., &amp; Livesley, W. J. (1998). Heritability of facet-level traits in a cross-cultural twin sample: Support for a hierarchical model of personality. Journal of Personality and Social Psychology, 74, 1556–1565.</li>
<li>Loehlin, J.C. and McCrae, R.R. and Costa, P.T. and John, O.P. (1998). Heritabilities of common and measure-specific components of the Big Five personality factors. <em>Journal of Research in Personality</em>, 32, 4, 431-453. <a href="http://socionics.org/forums/storage/9/421602/hedirity.pdf">FREE PDF</a></li>
<li>Riemann, R., Angleitner, A, &amp; Strelau, J. (1997). Genetic and environmental influences on
personality: A study of twins reared together using the self- and peer report NEO-FFI
scales. Journal of Personality, 65, 449–475.</li>
<li>Waller, N. G. (1999). Evaluating the structure of personality. In C. R. Cloninger (Ed.), Personality and psychopathology (pages 155-197). Washington, D.C.: American Psychiatric Press. <a href="http://genepi.qimr.edu.au/contents/p/staff/CV250.pdf">FREE PDF</a></li>
</ul>

CC BY-SA 3.0
2012-01-31T11:02:08.183Z
2012-02-01T04:41:06.663Z
2012-02-01T04:41:06.663Z
Jeromy Anglim
<p>Genetics is obviously an important cause of whether someone becomes extraverted or introverted. But what percentage is genetics and what percentage is the environment? What factors in the environment are most important in determining this trait?</p>

CC BY-SA 3.0
2012-01-31T15:28:49.383Z
It may seem like the definitions of introverted and extroverted are clear enough, in reality I don't think they are. Do you mean the way I would define it: Does a person re-energize by being alone and doing their own thing (introvert) or do they re-energize by socializing (extrovert). OR do you mean a person is shy and quiet versus outgoing and/or talkative. In the first definition, I think that is all genetics. In the second definition it is almost all environment.
Dunk
CC BY-SA 3.0
2012-01-31T21:13:16.723Z
@Dunk: Interesting point. I mean the first one as that appears to be the psychology definition
Casebash
CC BY-SA 3.0
2012-01-31T21:54:55.203Z
@Casebash-I don't know any studies, just my personal experience with my kids and can certainly say that within the first few weeks/months you can definately tell what the child's personality is going to be. So it has to be genetics. We have one very, very outgoing child and one far more reserved. We have worked hard at getting the reserved one to be sociable and it has been working but I know it is always going to feel like work to him, throughout his life. While for the sociable one, that is what he likes to do. That is his fun.
Dunk
<developmental-psychology><nature-nurture><genetics><personality>
What are the main causes of whether a person becomes introverted or extraverted?
Casebash
# What are the main causes of whether a person becomes introverted or extraverted?

(Asked by: username_0 on 2012-01-31)

Genetics is obviously an important cause of whether someone becomes extraverted or introverted. But what percentage is genetics and what percentage is the environment? What factors in the environment are most important in determining this trait?

**Tags:** developmental-psychology, nature-nurture, genetics, personality

> **Comments:**
> **username_1**: It may seem like the definitions of introverted and extroverted are clear enough, in reality I don't think they are. Do you mean the way I would define it: Does a person re-energize by being alone and doing their own thing (introvert) or do they re-energize by socializing (extrovert). OR do you mean a person is shy and quiet versus outgoing and/or talkative. In the first definition, I think that is all genetics. In the second definition it is almost all environment.  
> **username_0**: @username_1: Interesting point. I mean the first one as that appears to be the psychology definition  
> **username_1**: @username_0-I don't know any studies, just my personal experience with my kids and can certainly say that within the first few weeks/months you can definately tell what the child's personality is going to be. So it has to be genetics. We have one very, very outgoing child and one far more reserved. We have worked hard at getting the reserved one to be sociable and it has been working but I know it is always going to feel like work to him, throughout his life. While for the sociable one, that is what he likes to do. That is his fun.  

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## 1 answers

### Answer by username_2 on 2012-01-31. Score: 9 | Accepted answer

Heritability estimates of Extraversion (and other Big 5 factors)
The introduction section of  Loehlin et al (1998) provides a narrative review of heritability estimates of big 5 personality traits (i.e., one of which is extraversion).
A brief extract gives a flavour of some of the research that has been conducted:

A recent heritability analysis of the Big Five dimensions as measured
  by the Revised NEO Personality Inventory of Costa and McCrae (1992)
  used a total of 660 monozygotic (MZ) pairs and 380 dizygotic (DZ)
  pairs from pooled Canadian and German twin samples (Jang, McCrae,
  Angleitner, Riemann, & Livesley, 1998). For all five traits a simple
  model involving only additive genes and nonshared environment fit the
  data. Estimates for the heritabilities of factor scales for [Extraversion, Agreeableness, Conscientiousness,
  Neuroticism, and Openness] were .50, .48, .49, .49, and .48, respectively. These
  estimates are obviously very similar—in partic- ular, the heritability
  of Agreeableness is quite in line with the rest.

They also mention other twin studies, with heritability estimates for Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness respectively as:
                       E    A    C    N    O
Waller (1999):        .49  .33  .46  .42  .58
Riemann et al (1997):  60  .57  .71  .61  .81

Thus, in summary, it seems that such estimates for the heritability of extraversion are around 50%.
Side Point

While inventories like the Myer-Briggs Type Inventory often categorise individuals, into categories, I find a continuous approach to personality traits provides a more accurate description of an individual. Using such an approach, people have a score on an extraversion dimension that is roughly normally distributed (or at least continuously distributed) in the population.

Limitations

I realise this only partially answers your question. It doesn't discuss the dynamic environmental-genetic interactions that cause personality traits , nor does it take a critical perspective on issues related to the measurement of extraversion, and the estimation issues related to heritability. Hopefully, it is a useful starting point.

References

Jang, K. L., McCrae, R. R., Angleitner, A., Riemann, R., & Livesley, W. J. (1998). Heritability of facet-level traits in a cross-cultural twin sample: Support for a hierarchical model of personality. Journal of Personality and Social Psychology, 74, 1556–1565.
Loehlin, J.C. and McCrae, R.R. and Costa, P.T. and John, O.P. (1998). Heritabilities of common and measure-specific components of the Big Five personality factors. Journal of Research in Personality, 32, 4, 431-453. FREE PDF
Riemann, R., Angleitner, A, & Strelau, J. (1997). Genetic and environmental influences on
personality: A study of twins reared together using the self- and peer report NEO-FFI
scales. Journal of Personality, 65, 449–475.
Waller, N. G. (1999). Evaluating the structure of personality. In C. R. Cloninger (Ed.), Personality and psychopathology (pages 155-197). Washington, D.C.: American Psychiatric Press. FREE PDF


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