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What Really Is The Difference Between Introverts And Extroverts?

The internet is teeming with quizzes about whether you're an introvert or an extrovert, and most of them are backed by dubious evidence, if any at all. But there have actually been quite a few scientific studies to uncover the real differences in this continuum of personality types, and many of them might surprise you.

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When Science Gives You Lemons

In 1964, D. W. J. Corcoran measured the amount of saliva 11 adults produced before and after applying a drop of lemon juice to their tongues. Corcoran compared these results to personality tests the subjects took and saw that the introverts reliably produced more saliva than the extroverts. Scientists think this has to do with activity in an area of the brain stem known as the reticular activating system, or RAS, which responds to stimuli such as food and social contact. Introverts' increase in saliva production suggests more activity in the RAS, which could explain the feeling of overstimulation that some experience after prolonged social interactions.

Look In, Look Out

There are more differences still: PET scans of introverts' brains show more blood flow to the regions involved with recalling events, making plans, and solving problems (their inner life) while extroverts have more blood flow to areas involved with interpreting sensory information (the outside world). Other studies have suggested that extroverts pay more attention to human faces than introverts.

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Beautiful illustrations of author Susan Cain's lessons on introversion.

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Key Facts In This Video

  1. Studies indicate that there's no correlation between being a charismatic speaker and having the best ideas. 00:21

  2. Steve Wozniak, who invented the Apple computer, is a self-described introvert. 01:45

  3. In business, some of the most effective teams are ones that combine introverts and extroverts. 02:29

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