Study: Are Those Born Shy Always Shy?

June 23 -- When Marti Olsen Laney was growing up, she always felt "weird" but never really understood why.

"Sometimes I could not even think of anything to say," said Laney, a psychologist in Calabasas, Calif., and author of The Introvert Advantage: How to Thrive in an Extrovert World. "They wanted to hold me back in first grade because I was so quiet."

It wasn't until Laney took the Myers-Briggs Type Indicator test in college that she began to understand she wasn't "weird," as she once described herself, but an introvert — someone who is more introspective and requires time alone to re-energize after socializing.

Laney may need time alone, but she is hardly alone in kind.

Estimates are about one in every three people is an introvert, including writer T.S. Eliot, former President Jimmy Carter and NBA star Michael Jordan, among many others.

Scientists in recent years have moved beyond personality quizzes and have begun probing the brain itself to detect the biological foundations of personality.

While it's not clear whether someone born with a quiet temperament will remain that way for life, research results do reveal actual differences in brain activity between introverts and more gregarious extroverts — differences that seem to last from birth to adulthood.

Personality ‘Flavor’ Begins at Birth

Introverts, for instance, experience more blood flow at the frontal lobes while extroverts experience more blood flow at the temporal lobes, found Debra Johnson, a psychologist at the University of Iowa in Iowa City.

Guarded personalities can be traced to smaller sizes of the amygdala — a region in the center of the brain associated with fear and identifying novel things — discovered Paul Costa, chief of the laboratory of personality and cognition at the U.S. National Institute on Aging in Bethesda, Md.

And a new long-term study on human personality finds that inhibition — a trait often associated with introverts — appears to persist from infancy to adulthood in the form of distinct brain activity.