A woman who studied 600 millionaires says successful investors have the same 5 traits - but the wealthiest among them do one thing differently

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Millionaire investors spend more time studying and planning for future investments.

• Successful investors, regardless of net worth, share the same five characteristics, according to a researcher who studied more than 600 millionaires.
• Millionaire investors, however, do one thing differently: They spend more time studying and planning for future investments, she said.
• Millionaires also act simply and commonly invest in index funds, an investing strategy championed by Warren Buffett.

Investing can be intimidating.

But those who do it right tend to share similar characteristics, according to Sarah Stanley Fallaw, the director of research for the Affluent Market Institute. She co-authored "The Next Millionaire Next Door: Enduring Strategies for Building Wealth," in which she surveyed more than 600 millionaires in America.

During her research, she found that five components mark a successful investor, including those who are rich: a personality for risk, a high-risk preference, confidence in investing, composure, and knowledge regarding investments and investing.

But millionaire investors do one thing differently: They make more effort with the final component.

"They spend time building knowledge and expertise in managing investments," Stanley Fallaw wrote.

Millionaire investors spend more time planning for future investments

According to her, millionaire investors spend an average of 10.5 hours a month studying and planning for future investments. That's nearly two hours more than under-accumulators of wealth - defined as those with a net worth less than one-half of their expected net worth based on age and earnings - who spend 8.7 hours a month doing so.

In her study, 55% of millionaires said they believe their investing success is due to their own efforts in studying and becoming educated, rather than advice provided by professionals.

"Their literacy in financial matters means that they are more tolerant of taking investment-related risks," Stanley Fallaw wrote. "Future outlook and financial knowledge typically relate to taking greater financial risk, so the time they spend in managing and researching investments helps in decision-making."

Financial literacy is related to financial "success" outcomes more so than cognitive ability, according to Stanley Fallaw. Having the knowledge required to make appropriate financial decisions - along with a long-term and future-oriented outlook and a calm manner - allows millionaires to make better financial decisions, she said.

Read more: A woman who studied 600 millionaires found how rich you can get boils down to 6 'wealth factors,' no matter your age or salary

Millionaires also favor index funds

Millionaire investors also have something in common when it comes to investing strategies: They act simply, according to John, who runs personal-finance blog ESI Money and retired early at the age of 52 with a $3 million net worth. He interviewed 100 millionaires over the past few years and found that many of them use the same investing strategy: investing in low-cost index funds.

"The high returns and low costs of stock index funds (I personally prefer Vanguard as do many millionaires) are the foundation that many a millionaire's wealth is built upon," he wrote in a blog post.

"Index funds are the most straightforward, cheapest, and most likely way to see strong long-term returns," former hedge-fund manager Chelsea Brennan, who managed a $1.3 billion portfolio, previously wrote in a post for Business Insider. "Index mutual funds offer instant diversification and guarantee returns equal to the market - because they are the market."

Even billionaire investor Warren Buffett has championed low-cost investing, often recommending Vanguard's S&P 500 index fund for the average investor, Business Insider reported. He previously called index funds "the most sensible equity investment."