University of North Texas graduate student Rigers Memko, 23, kept his wits about him when the market began to swoon and did not sell any stocks when the market fell early this year.

Memko heads the student investment group at the school, which manages $600,000 in assets. Members focus on long-term investing. Their top holding is Apple Inc., followed by such blue chips as Johnson & Johnson, Altria Group Inc., Coca-Cola Co. and AT&T Inc.

"The market right now is affected by global uncertainties and what is happening in China, in Europe, and with Russia, which I believe will pass, and the market will start picking up again," Memko says.

That conservative investing attitude is proving to be typical of millennials, many of whom grew up watching their parents' investments get whacked when the market sank in 2008.

"Conventional wisdom is a younger investor would take more risk," says Mike Loewengart, ETrade Financial Corp.'s vice president of investment strategy. But ETrade's Q1 Streetwise report found millennials (25-34) were more bearish than older millennials, and more interested in diversification — including a higher interest in international exposure, as well as commodities.

Erin Lowry, 26, who writes the Broke Millennial blog (brokemillennial.com), says the careful attitude makes sense. "If you aren't totally sure how the stock market works and if your parents were burned in 2008, you look at it as gambling," says Lowry, who invests almost exclusively in index funds.

Kathy Murphy, president of personal investing at Fidelity Investments, is concerned that millennials are keeping too much cash on the sidelines and not talking advantage of the fact that time is on their side.

Murphy has four basic tips for millennial investors.

• Do not try to time the market. Get into stocks, bonds and other assets. Invest for the long-term.

• A target-date fund, which adjusts its asset allocation as you age, is a great solution to ensure your investments are poorly allocated for retirement.

• Avoid having too much cash. You are "treading water" return-wise if you do not invest it.

• Use time to your advantage. The power of compounding interest is key to achieving savings goals.

When it comes to individual stocks, TD Ameritrade says the stocks most traded by millennials (18-34) so far in 2016 are Apple, Netflix Inc., Amazon.com Inc. and Facebook Inc.

"They are investing in what they know," says Nicole Sherrod, managing director of trading at TD Ameritrade.

Bobbi Rebell writes for Reuters.