Blame shy on amygdala
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Jun. 20, 2003. 01:00 AM
Shy? Blame it all on that excitable amygdala
WASHINGTON—A tendency to be shy may be an inherited characteristic marked by a specific reaction in the brain to the presence of strangers or novel objects, a study suggests.
And although people may learn to be outgoing as adults, the brain marker for shyness remains.
Researchers at Harvard University took brain scans of 22 22-year-olds. Thirteen had, at age 2, been been classified as inhibited; nine had been deemed outgoing, based on their childhood behaviour.
Those judged 20 years earlier to be inhibited showed on scans that the amygdala structure in their brains responded much more actively to unexpected sights than did those who had been judged as children to be more outgoing, said Jerome Kagan, a researcher in Harvard's department of psychology.
``A lot of the ones who were fearful aren't fearful anymore. They have overcome it. But the questions is, did they still have a very active amygdala?"
Based on the brain scans, the answer is clearly yes. A report on the research appears this week in the journal Science.
"We had assumed, but never measured, that ... the shy, inhibited group had inherited a certain chemistry" in the amygdala, Kagan said.
All the subjects were exposed to a series of pictures of faces with neutral expressions. After they had become accustomed to those pictures, new faces were introduced while the researchers measured the reaction of the amygdala structure in their brains.
The brains of once-shy children were much more active than the other subjects.
"That is support for the notion that the reason they were shy, timid and reserved when they were 2 years old is because they had an excitable amygdala," Kagan said.
This suggests that shyness is a temperament that can be inherited, but the researcher said this temperament does not necessarily determine one's eventual personality.
Kagan said that before any firm conclusions can be drawn, similar research needs to be done using many more subjects than the 22 in the current study.
Although some children are shy and others are outgoing, he said, these traits can change with time and life experiences.
"People overcome their shyness," Kagan said. "You can also acquire shyness."
Extreme shyness can be a precursor for serious disorders, such as social phobias and depression. Kagan said that by finding a biological basis for such shyness, it may be possible to develop drugs to treat patients whose lives are adversely affected.
Other co-authors of the study are Dr. Carl Schwartz, Dr. Christopher Wright, Lisa Shin and Dr. Scott Rauch, all of the Harvard Medical School.