Teens smoke, take drugs, have unprotected sex and ride with drunk drivers, not because they think they are invulnerable or haven't thought about the risks, says a new Cornell study.

In fact, they are more likely to ponder the risks, take longer (about 170 milliseconds more) weighing the pros and cons of engaging in high-risk behavior than adults -- and actually overestimate the risks. It's just that they often decide the benefits -- the immediate gratification or peer acceptance -- outweigh the risks, says Valerie F. Reyna, professor of human development at Cornell.

With Frank Farley of Temple University, Reyna reviewed the scientific literature on why adolescents make bad decisions, and on how interventions could help them do the right thing more often. The findings are published in the September issue of the journal Psychological Science in the Public Interest.

The researchers found that while adults scarcely think about engaging in many high-risk behaviors because they intuitively grasp the risks, adolescents take the time to mull over the risks and benefits.

"In other words, more experienced decision-makers tend to rely more on fuzzy reasoning, processing situations and problems as gists [the essence of their actions] rather than weighing multiple factors," said Reyna.

In another study, published September's Journal of Experimental Psychology: Applied, she found that doctors make better decisions by processing less information and making sharper black-and-white distinctions among decision-making options. "This leads to better decisions, not only in everyday life but also in places like emergency rooms where the speed and quality of risky decisions are critical," she said.

The findings on teenagers imply that interventions that use risk data regarding smoking or unprotected sex, for example, may actually backfire if young people overestimate their risks anyway. Instead, interventions should help young people develop "gist-based" thinking in which dangerous risks are categorically avoided rather than weighed in a rational, deliberative way.