I am looking for information regarding the differences between
introverts, and extroverts. I have already found information as to the
end effects of these differences - that is, the personality traits. I
am seeking to know the differences in the brain structure and
functions of an introvert and an extrovert, and how these differences
develop.

As a subset of this question - I would like to know why society as a
whole tends to reward extroversion and shun introversion.. (Many
introverts are told that something is wrong with them.) What are the
effects of an introvert constantly being pushed to be extroverted? And
is this even really possible to achieve? (given evidence from the
first question)

---

Request for Question Clarification by hedgie-ga on 22 Dec 2005 15:53 PST

"why society as a
whole tends to reward extroversion and shun introversion..."

 This is true for mainstream US society; 
 it is not true for other cultures 
 (and this points to other then genetic causes
since gene pool of EU and US do not differ much)

 Do you want to expand your question to all cultures 
 or concentrate on US
 and focus on cultural rarther then genetic causes?

---

Clarification of Question by darkwolf228-ga on 23 Dec 2005 04:54 PST

I'd like to focus on US culture primarily, however it brings up
another question.. and that is how the US differs in this manner from
other cultures..

As far as the cultural vs. genetic, i'd like to see some info on both,
and maybe evidence as to which plays a bigger role.

---

Request for Question Clarification by hedgie-ga on 24 Dec 2005 02:24 PST

I did have a quick look and there is lot of interesting material
on the web on this topic.
 It looks like you are right: introvert-extrovert dimension is 70% inherited,
only the rest is culture/environment. 
It is an interesting question;  unfortunately, I do not have time
right now to give it it's due, so I hope someone else will pick up tis
question.
 Great article suggested in comment by byrd-ga. Thanks byrd.

---

Clarification of Question by darkwolf228-ga on 10 Jan 2006 08:16 PST

Previous researcher made comment under "request clarification" so
google keeps asking me to clarify...

OK, since no one picked it up, and it is such a good question, 
I decided to look into it. I hope I did not overdid it.

Before jumping into brain structure and function, it's
helpful to familiarize one's self with some of the terms,
concepts, measuring instruments as used in the research.
Looking at C.G. Jung's original theory is also helpful.
So in this answer, we'll proceed from the concepts and
personality measures, to cultural factors and differences,
to research on the brain itself.


1) PERSONALITY TESTS 'put a number' on the degree of introversion

To determine the degree of heredity the

The Introvert - Extrovert dimension 
http://csis.pace.edu/~bergin/patterns/introvertExtrovert.html

needs to be quantified. 

That can be shown as part of Myers-Briggs Personality Index assessment.
The Myers-Briggs adds a fourth dimension or scale to those
originally suggested by C.G. Jung, resulting in 16 possible combinations
or "types," denoted by 16 sets of initials. INTP, for example, stands for
Introverted, Intuitive, Thinking, Perceiving. The complete opposite in type
would be an ESFJ, Extroverted, Sensing, Feeling, Judging personality.

http://www.humanmetrics.com/cgi-win/JTypes1.htm
http://www.humanmetrics.com/cgi-win/JTypes2.asp

or similar, often derived simplified tests
http://www.okcupid.com/tests/take
http://www.nerdtests.com/mq/take.php?id=19
old.danurman.net/psych/ambivert.html

 The Myers-Briggs is based on the work of Freud's coworker, and later rival,
  Carl Jung.  Jung saw universal `types' in human personality 
" These types are all present in all of us, but there tends to be one ..."
http://www.mtnmath.com/whatrh/node98.html
http://www.myersbriggs.org/more_about_personality_type/international_use/multicultural_use_of_the_mbti.asp


"Extroversion and introversion, terms introduced into psychology by
Carl Jung to identify opposite psychological types. Jung saw the
activity of the extrovert directed toward the external world and that
of the introvert inward within himself or herself..."
http://columbia.thefreedictionary.com/extroversion+and+introversion


In the following you will need to now this jargon : 'he is NT or ST ..' type

"..the MBTI T traits for this individual (TJ, TP, NT, ST) .."
http://tap3x.net/EMBTI/j5gonsowski.html

2) THE ORIGINS OF PERSONALITY: THE NATURE-NURTURE DEBATE


"There are some genetic factors that play a part in determining certain aspects
of... Determinants of personality. Heredity. Culture. Family background ...
[
http://cw.raiuniversity.edu/management/mba/
OrganisationalBehaviourandMnagementProcess/lecture_notes/lecture-31.pdf
]                  long URLs in [   ] often need do be pasted into a browser!
(from University of Toronto personality in Eysenck?s framework, )

 vvv THIS IS ONE HALF OF THE ANSWER vvv !!!!!
  ======================================

  " 70% of the variance in extroversion is due to heredity,
Studies examining the extent to which a adoptive parent?s
personality accounts for the child?s personality suggest that
it accounts for about 0-7% of the child?s personality..."

 http://www.psych.utoronto.ca/~joordens/courses/PsyA01/Chapter14/Chapter14.PPT.



3) THE EFFECT OF CULTURE

"Distributions of the sixteen types differ across different cultures.
However, distribution patterns are similar across all the cultures
studied.  STJ types predominate in all cultures.
..
People in the same profession often have similar types. For example,
law enforcement officers in Australia, the United Kingdom, and the
United States show preferences for ISTJ and ESTJ.
..
As a result, preferences may not look the same in different cultures.
Britain and the United States offer good examples. The type
distributions of business groups are almost the same, yet Britain
appears to have more people with preferences for Introversion and the
United States more people who prefer Extroversion....."

 The reason? Perhaps because US is more market-oriented than Europe.
In United States, employees are taught to 'sell themselves,' or just
to highlight their achievements, talents, etc.  In other cultures
this is considered gauche or crass. 


In the US extroversion is considered part of 'leadership' and is valued
http://66.249.93.104/search?q=cache:vO9ZqBwcE0MJ:www.uncp.edu/mpa/papers/professionalpapers/leadership.pdf++Myer-Briggs+Heredity&hl=en&lr=lang_en&client=opera

In other cultures, such as some in Europe and Asia, American's version
of extroversion can be seen as 'being pushy' or arrogant, or as not
listening to others. In a society where for decades or even centuries,
everyone has had to keep opinions to oneself, or within a close group
of trusted friends,
it's possible that the cultural push is toward introversion, to be
strongly "innerwardly referenced."

In a culture where introverts are in the minority, introverts may feel
constantly pushed and may also have difficulty coping with
"significant others" or their children who are
extroverts.

The book reviewed here deals with the topic extensively.
http://books.slashdot.org/article.pl?sid=03/07/16/2143241

  vv   THE OTHER HALF OF THE  ASNWER  vv
 =================================

Connects introversion to autism, schizofrenia, talent and genius.
We are just beginning to undertand neurological processes involved,
and what we learn about the extreme cases, MAY apply to introversion.


4) Introversion : AUTISM TALENT and MATHEMATICS, GENIUS AND MADNESS

The 'Missing Link' Between  Madness And Genius" is the summary of this section.
http://www.rense.com/general66/madness.htm

    Autistic savant
Autism is a puzzling disorder characterized by developmental delays. A
person with autism often has problems understanding the meaning and
purpose of body language and the spoken and written word. They find
social interaction difficult, confusing and scary.
http://www.betterhealth.vic.gov.au/BHCV2/bhcarticles.nsf/pages/Autistic_savant?open

  Math and Myers-Briggs  types: 

"Q. Is it possible for an NT to be horrible at mathematics and the
hard sciences? -- Anonymous
 From what I've found out so far they are usually introvert or ENTP.
Martin, for recommending the Simon Singh's book "Fermat's Last Theorem" .."

http://www.socionics.com/advan/qa.htm?1119815531


 Mathematics and schizophrenia 


" The link between genius and madness
is a complex one. The fortuitous
convergence of a number of factors in
one person, including a minimum level
of intelligence, the ability to join ideas
from different domains, the ability to
record these ideas, independence and
flexibility of thinking, intense focus, self-
discipline, perseverance,...."
 http://www.sma.org.sg/sma_news/3403/commentary.pdf


  The popular belief (or myth?) that

 ? Many great scientists and philosophers ? have had similarly strange
and solitary personalities.   ? Among them she includes Rene
Descartes, Ludwig Wittgenstein, Immanuel Kant, Thorstein Veblen, Isaac
Newton and Albert Einstein. From the witty Veblen to the ponderous
Kant, from the humanitarian Einstein to the misanthropic Newton, a
more diverse gang of rowdies is hard to imagine. If they had anything
is common it was a tendency to introversion:"

is harshly criticized in this review:

   " It was in the period of his [Nash's] employment by MIT that Nash produced 
the 3 remarkable results that make him famous among mathematicians:
the differentiable manifold-real algebraic varieties  papers (1952); 
the solution to the isometric embedding problem  (1954-56); and his work on 
bounding estimates for multi-dimensional parabolic partial differential 
equations  (1957) ....."

            This relates to a 
movie
http://www.imdb.com/title/tt0268978/
and book:
http://www.amazon.com/gp/product/0743224574/103-7594500-8510243?v=glance&n=283155
 Sylvia Nasar: A Beautiful Mind,

 The two, movie and the book are actually are quite different,
 book is more true to the real story and more profound.

 Book was harshly  critiqued by this mathematician:

http://www.maths.ex.ac.uk/~mwatkins/isoc/nash.htm

other examples of Introversion - schizophrenia - genius:
http://members.optushome.com.au/vergil/blog/2003/12/autism-savants-genius-and-male-brain.html
http://en.wikipedia.org/wiki/Ramanujan

 Current research in the area of Autism and Savant Syndrome

 "Savants can be categorized according to level of ability. The first
are prodigious savants. ..."
http://ehlt.flinders.edu.au/education/ iej/articles/v2n4/YOUNG/PAPER.PD

confirms that statistically significant correlation DOES EXISTS:

"Personality traits associated with creativity in scientists
? Openness to experience, flexibility of thought
? Drive, ambition, achievement
? Self-confidence, dominance, arrogance, hostility
? Autonomy, introversion, independence"
            -------------
Source: Handbook of Creativity. Cambridge University Press.
http://news-service.stanford.edu/news/2002/june12/crazy_genius.html



5) THE NEUROLOGICAL BASIS OF TYPOLOGY
   This is not well understood as yet
http://www.innerexplorations.com/catpsy/t2c12.htm


but is the topic of academic research
http://www.personality-project.org/perproj/readings-theory.html


"The neurological basis of introversion-extroversion: Gray's Theory.
 Terms Animals Behavior, Animal Cerebral Cortex/physiology* ..."
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&
db=PubMed&list_uids=4992318&dopt=Abstract

"Introversion correlated with increased activation in several regions, ...
right-handed (32), and screened for psychiatric or neurological
problems by using ..."
http://www.pnas.org/cgi/content/full/102/45/16502

"Trends in the psychophysiology of individual differences.
Higher Nervous Activity Human Individuality* Inhibition (Psychology)
Introversion (Psychology) Models, Neurological Models, Psychological ..."
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&
db=PubMed&list_uids=934717&dopt=Abstract -

"Series of neurological interactions are responsible for variable ...
 Extroversion and Introversion, Psychology and Psychiatry ..."
http://serendip.brynmawr.edu/biology/ b103/f03/web1/nkrimgold.html


"One study showed that with pallidotomy (PDT), there is a change in
hypochondriasis, hypo-mania score and with thalamotomy there is a
change in depression and social introversion. The numbers of subjects
in this study were very small, and patients were not randomized,"
http://0-accessible.ninds.nih.gov.portia.nesl.edu/
news_and_events/proceedings/cognitive_meeting_2001.htm

... that a series of neurological interactions are responsible for variable ...
1) 1 Up Info: Extroversion and Introversion, Psychology and Psychiatry ...
serendip.brynmawr.edu/biology/ b103/f03/web1/nkrimgold.html

SEARCH TERMS: personality test, introvert, heredity
               genius madness introversion
                neurobiology, Myers-Briggs, C.G. Jung


Hedgie    (rating appreciated)

Introverts produce more saliva.  it was on TV last night...

Here's one of the best discussions on the subject I've ever seen
(speaking as an introvert!):
http://www.theatlantic.com/doc/200303/rauch?ca=0gNycTGz%2F1opoMG3VXTOcBAMDoJYmtPtbhYj0biJx88%3D

Perhaps the society pressures people towards extroversion because it
makes them easier to manipulate....

Yeah, I like the article Byrd posted. It sure does expose society's
folly in branding introverts as deviants. Sure told me a lot about
myself too. hehe

Gosh, maybe I am one too, and married to a "think by talking" extrovert!
I doubt if introverts produce more saliva; they just don't spread it
around or let their mouths dry out by having them open so much.  ;)

Hello darkwolf228,
I peeked into probably the most popular work on Introversion, The
Introvert Advantage by Marti Olsen Laney, at my local bookstore and it
contained a section on the differences between extrovert and introvert
brains. Unfortunately I couldn't find an equivalent of that
explanation on the Internet, so I am planning to buy the book - it's
probably a good read if you believe yourself to be an introvert.

By the way, on the saliva bit, I guess introverts produce more saliva
because they actually have more left from speaking less. Extroverts
probably talk more as they see more people to talk to and their saliva
dries as they do it. Lesson: if you're an extrovert, try to babble
less. :P

Here's yet another article that can complement the one Byrd posted:

The Tyranny of the Extroverts
http://allendowney.com/essays/tyranny.html