While some children tend to be timid from the start, more are just the opposite: they are born to be talkative, sociable and spontaneous.

When put into situations that make shy babies nervous and fussy, the outgoing infants take it in stride and even seem to enjoy themselves. They look attentively and occasionally grin at bouncing mobiles, funny smells and unusual toys.Psychologist Jerome Kagan of Harvard University estimates that 20 percent of white children - the only children he studied - are born with a tendency to be extremely shy, while about 35 percent are gregarious from their first weeks.

"These babies smile a lot," said Kagan. "They sleep deeply. They are not irritable. Mothers say, `This kid is a dream.' "

Kagan said this trait is often inherited, like shyness, and probably results from differences in the brain.