T-type

Dr. Frank Farley of Temple University refers to risk-takers as T-types, the "T" standing for thrill-seekers. He said that T-types had traditionally been males, but that more girls were becoming risk-takers as social barriers dropped. T-types often have symptoms parents can recognize as early as age 2.

"They're very exploratory. They're the kid who wanders off into the woods. They don't cling to you. They show fearlessness," Farley said.

Dr. Farley has studied risk behavior for 30 years.