A new neuroimaging study provides the strongest evidence to date that unusual shyness in children may result from differences in their brains.

Researchers at Harvard Medical School used functional magnetic resonance imaging (fMRI) to examine adults who had been unusually shy in childhood. When these people were shown pictures of unfamiliar faces, they displayed significantly higher activity in the amygdala than people who had been unusually outgoing as children. The amygdala is a brain structure involved in vigilance and fear.

It has long been hypothesised that extreme shyness, which emerges in infancy and often persists into adulthood, must have some distinctive signature in the developing brain. However, this idea has not been tested directly because it is difficult to conduct brain imaging experiments with very young children.

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