Jerome Kagan Study of Shyness

When a stranger walks into a nursery full of toddlers, most of them stop playing, look at the stranger for a few seconds, and then resume playing. About 10% of the toddlers are overly shy or inhibited and will not resume play until the stranger leaves. Another 10-15% are outgoing. These “bold” children will walk up to the stranger and start asking questions.
Jerome Kagan, a psychologist at Harvard University has studied social behavior for over 20 years. He has found that shy toddlers frequently grow up to be adults with significant social anxiety. Shy children are different even in utero in that they will have a much greater increase in fetal heart rate in response to a loud noise. Bold toddlers grow up to be extroverts and in some cases may even grow up to be criminals. The bold toddler’s fetal heart rate doesn’t change in response to loud noises. These as well as other studies strongly support genetics as the primary underlying cause of social anxiety disorder.