Are some people naturally more likely to take risks than others? Or does it depend on a social situation? A time of year? A time of life?

The research isn't conclusive — but here's a selection of what the science tells us thus far.
Happier people take more risks.

If you're feeling high on life, you see the odds as in your favor.
"When we're happy we take more risks, are more trusting, more generous," writes University College London professor Noreena Hertz. "It's why a country's stock market tends to rise off the back of a national team's win at football. (Not something England needed to worry about this year, sadly.)"

Sunny summer days open people up to risk.
Research suggests that when the days get shorter, people are more averse to risk.

Behavioral finance scholar Lisa Kramer has found that it gets more intense the further north you go — traders in Stockholm get more skittish in autumn than their peers in Frankfurt, for example.

"As the exposure to daylight diminishes, we respond in a biological way to the change in exposure to daylight," Kramer said in an interview. "We're not that different than ancestors who would retreat in the winter time. When the seasons changed, they had to become a lot more conservative; they had to adopt a lot more conservative practice. We're still those same people."

Correspondingly, if you want to pitch someone on an outlandish proposal, she says to wait until the spring.

Teens like to take "unknown risks."

While teens are thought to be rollicking risk-takers, the research shows the opposite — they overestimate risks around sex and drug use. In one study, adolescents thought that a sexually active teen girl had a 60% chance of catching HIV, when the chance is tiny in real life.
Fascinatingly, even though teens overestimate known risks, they are more likely than adults to make risky decisions if the outcome is ambiguous.

Here's TIME's account:

"Relative to adults, adolescents engage more in unknown risks than they do in known risks," says Agnieszka Tymula, a postdoctoral student at New York University and the lead author of the study, which was published in the Proceedings of the National Academy of Sciences. Teens, it seems, love the unknown.

They may get lost in the details about specific risks and overly focused on possible rewards, while ignoring the overall "gist" of the problem — i.e., the ultimate consequences. In the case of unprotected sex, for example, even if the odds of contracting HIV are low, a bad outcome would be irreversible. Unlike teens, adults tend to focus on the end result and the consequences.

In other words, teens are cool with not knowing what's going to happen. Therein lies the risk.
Some genes predict risk-taking.

Kellogg management professor Camelia M. Kuhnen has found that a gene called DRD4 — which regulates hormone levels in the reward center of your brain — predicts whether you're likely to become a pathological gambler or a risk-loving stock market trader.
"If you carry the long version of DRD4, you tend to take about 25% more risk in your portfolio than other people," she tells Marketplace.

People who like to stay up late do riskier things.

Psychologists have fun words for being an early-bird or a night-owl: morningness and eveningness, respectively.

According to one Stanford study, people with a high degree of eveningness seek sensations, are more impulsive, and — you guessed it — take more risks. Although it might also be explained by sleep deprivation.

A follow-up University of Chicago study found that the correlation held for evening-oriented women, but not men.

If you're used to taking risks, you'll keep taking risks.

In his book "The Click Moment," Frans Johansson tells the story of the Cypres device, which was designed to help keep skydivers from dying.

For some people, skydiving is totally chill.

But it didn't.

Here's why:
The Cypres eliminated "no-pull" or "low-pull" deaths. These types of accidents are exactly what they sound like — deaths resulting from divers pulling the cord too late or not at all. The Cypres opens the parachute automatically if the diver is seconds away from impact.

Great innovation, right? In fact, in 1998, Cypres devices recorded 12 "saves" and there were no low-pull deaths that year. In 1991, before the Cypres penetrated the market, there were 14 deaths. The technology of the Cypres worked to make skydiving safer.

But people were still dying during skydives. And in roughly the same number. What was going on?

The divers were trying riskier landings.

With the added safety of the Cypres device, divers started trying to execute more difficult landings to impress their friends. Called a "hook turn," the diver makes a 90 or 180 degree turn just before landing — and probably dies if he doesn't get it right.

When the Cypres device became standard issue — and the chance of a "no-pull" death plummeted — hook turns became popular.

The reason: risk homeostasis.
"The Cypres device practically eliminated the risks of parachute malfunctions — so skydivers compensated by trying to get themselves killed in other ways," writes the Agile Lifestyle blog.
You experience this in your own life. If you're driving down a rainy, winding street, you'll slow down to stay safe. But if that road opens up into a clear, dry, highway, you'll probably speed up — yet the chance of getting into an accident is about the same either way.
The takeaway: We all have an appetite for risk. In extreme cases, we'll risk our lives to keep it sated.