WASHINGTON (AP) -- A new brain-scan study may help explain what's going on in the minds of financial titans when they take risky monetary gambles -- sex.

When young men were shown erotic pictures, they were more likely to make a larger financial gamble than if they were shown a picture of something scary, such as a snake, or something neutral, such as a stapler, university researchers reported.

The arousing pictures lit up the same part of the brain that lights up when financial risks are taken.

"You have a need in an evolutionary sense for both money and women. They trigger the same brain area," said Camelia Kuhnen, a Northwestern University finance professor who conducted the study with a Stanford University psychologist.

Their research appears in the current edition of the peer-reviewed journal NeuroReport.

The study involved 15 heterosexual young men at Stanford University. It focused on the sex and money hub, the V-shaped nucleus accumbens, which sits near the base of the brain and plays a central role in what you experience as pleasure.

When that hub was activated by the erotic images, the men were far more likely to bet high on a random chance game that would earn them either a dollar or a dime. Each man made more than 50 gambles under brain scans.

Stanford psychologist Brian Knutson, a lead author of the study, says it's all about the power of emotion and arousal and our financial decisions. The trigger doesn't have to be sex -- it could be chocolate or a winning lottery ticket.

"It didn't matter if the sexy woman didn't tell you anything about the odds of winning a roulette game," Knutson said. "What really matters is that the sexy woman is having an emotional impact. That bleeds over into your financial decisions."

Kuhnen said the same link could hold true for women, but they didn't test it because it is more difficult to find an erotic image that would appeal to many different heterosexual women compared to heterosexual men.

The link between sex and greed goes back hundreds of thousands of years, to men's evolutionary role as provider or resource gatherer to attract women, said Kevin McCabe, professor of economics, law and neuroscience at George Mason University, who wasn't part of the study.

"Risk-taking is a natural way of increasing your relative success, but, of course, there's a downside to it, what we're seeing right now in the economy," McCabe said.

The results of the study jibe with real life on the trading floor, said Phil Flynn, a former Chicago, Illinois, commodities floor trader and current analyst at Alaron Trading Corp.

"I'm not shocked that it may be part of the deal," Flynn said Friday. "When you talk about all the euphemisms for trading [on the floor], they can be used for sex as well."

("Massaging the market" and "hardcore" were the cleanest he and his colleagues could come up with.)

The study conforms with recent research that indicates men shown a pornographic movie were more likely to make riskier sexual decisions. Another suggests straight men think less about their financial future after being shown pictures of pretty women.

One still-to-be-published study at Harvard University found a link between higher testosterone levels and financial risk-taking.

But the study conducted at Stanford, funded by the National Institutes of Health, went deeper, using functional magnetic resonance imaging machines. It's part of a new but growing field called neuroeconomics that attempts to take the hard-wired science of brain biology and mix it with the softer sciences of psychology and economics to figure out why we make the financial decisions we do.

An earlier study by the same team found that the brain's reward area lit up at about the same time as risky decision-making.

The erotic pictures experiment was designed to find which was the cause and which was the effect. The answer: Lighting up the reward area, in this case with soft-core pictures, caused the risk-taking, Kuhnen said.

"The more activation there you have, the more prone you are to taking more risk," Kuhnen said. "It could be a feedback loop."

The flip side was that the photos of snakes and spiders activated the portion of the brain often associated with pain, fear and anger. And those people were more likely to bet low.

This all makes sense to Harvard economist Terry Burnham, author of the book "Mean Genes." Burnham said it could be all summed up in a famous line from the movie "Scarface."