Study: Are Those Born Shy Always Shy?

June 23, 2003 -- 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.

"It's clear we all start off with a particular 'flavor,' " said Carl Schwartz, director of the developmental psychopathology lab at Massachusetts General Hospital in Boston and lead author of the temperament study in the most recent edition of the journal Science.

Schwartz added: "We found the correlation between early behavior and brain activity differences in adulthood is incredible."

Lifespan Tests

Schwartz' new research is based on studies that began decades ago. He worked with a set of 22 young adults who had been analyzed as 2-year-olds by Jerome Kagan, a psychology researcher at Harvard University in Cambridge, Mass.

In 1984, Kagan made hourlong observations of 200 children and determined that among the group there were at least 22 especially inhibited or uninhibited children.

"Some of the children were very avoidant — unfamiliar people and objects bothered them," said Kagan. "Another 20 percent didn't appear affected by strangers or an unfamiliar room. They were more spontaneous."

Kagan selected children from these two groups and then followed up with further observations when they were 3, 4, 5 and 13 years old.

In 1998, Schwartz suggested that he and Kagan check in on the same group of people again but this time they'd use a new tool — functional magnetic resonance imaging, or fMRI — to look for differences in brain activity among the now 20-something-year-old subjects.

The fMRI device allows researchers to trace conscious brain activity by monitoring blood flow, with no harm to the patient. By tracing brain activity, the pair hoped to find footprints of earlier temperaments, even if people had developed into adults with less extreme personalities.

The differences were striking.

Quiet Mind, Active Amygdala, Steady Heart

When Schwartz and colleagues showed the subjects pictures of unfamiliar faces, the amygdala lit up in both sets of patients. But among the inhibited subjects, activity hummed at unusually high levels.

"It was a very subtle test," said Schwartz. "I was surprised we saw such different reactions in the two sets of people."

Inhibition in its extreme form could be a risk factor for social problems, he adds. Among the 22 people he tested, two were diagnosed with social anxiety disorder — and both were from the group that had been classified as inhibited when young.

Three additional people from Kagan's original group of inhibited children could not participate in the study because they were taking medication for depression or social anxiety and medications would have skewed the results.

By comparison, none of the original uninhibited group of children showed signs of social anxiety or depression.

Ned Kalin, director of the Health Emotions Research Institute at the University of Wisconsin Medical School in Madison, said the results make sense. His own experiments with primates have shown the animals become less timid (as well as less anxious) when researchers chemically suppress activity in their amygdalae.

The fMRI results also appeared to parallel interesting differences detected in the subjects when they were 13.

Kaplan's earlier work showed the inhibited 13-year-olds had more regular heartbeats than the uninhibited children. And when asked to respond to certain problems, the young teens in the inhibited group had more marked increases in blood pressure than their counterparts.

Said Kaplan: "They retained their basic biology at 13 and these new tests show they retain it still."

Nurture vs. Nature

Does that mean people born shy remain so throughout their lives? Perhaps internally, says Kagan, but biology isn't everything.

"Just because you're born with a biology that favors introversion or extroversion doesn't mean you'll become that way," Kagan said. "How you were raised and your current environment can also influence behavior."

Case in point: Laney argues introversion should not be mistaken for shyness. Depending on their life experiences, she says, extroverts are just as likely to have timid personalities.

"It's a separate issue," she said. "For extroverts, lacking external stimuli and social skills can become a greater problem because they need it more. So there are probably many extroverted people who are shy or socially inhibited."

Many argue that society is generally tailored to the extrovert by favoring people who interact easily and quickly. The famously extroverted Bill Clinton, for example, might have quashed introverted Jimmy Carter had they ever debated, even though both men were known for their intellect.

But Schwartz points out most of the people in his study had found careers and lifestyles that suited their inherent personalities. The most inhibited member of his test group, for example, is pursuing a doctorate in math while the most uninhibited is starting a career in tabloid journalism.

Laney says simply understanding her identity as an introvert has been socially liberating. Once she realized she needed alone time to refuel, she found herself more able to deal with social situations and more able to recognize her own personal strengths.

"Many introverted people are not shy or have social anxiety," she says. "In fact, we're usually gifted people, we can take in a lot of complexity, we're good listeners and we're usually rather responsible and self-sufficient."