If you're like me, you may occasionally wish that one day you'll read the results of a study finding that eating a lot of ice cream is very good for you. Or that vigorous exercise isn't as good for you as sitting on a couch is. Based on something I read the other day, though, I've not been aiming high enough in my little fantasies.

Get this: According to a study by the folks at Stanford University's Graduate School of Business, the kind of people who make the best investment decisions are "functional psychopaths." That's right. Forget about looking for the upside to ice cream and movies. There's an upside to some mental states, at least in the investment arena, where it seems that abnormal brain patterns can be beneficial.

Let me explain a little more. What makes functional psychopaths succeed in investing is their inability to experience and respond to emotions. So while many of us succumb to fear or greed when buying and selling stocks -- or when not selling, or not buying -- functional psychopaths generally don't.

The study's findings were based partly on an experiment involving participants being given $20 each and invited to bet $1 repeatedly on a coin toss on which they'd get $2.50 if they won. The most rational response would be to bet each time, based on a cost-benefit analysis. Those with brain damage affecting their emotions took the bet in 84% of the rounds, versus just 58% of the control group.

According to a Bloomberg News report, "The results help to explain the 'equity premium puzzle,' or why more people invest in bonds than stocks, when equities historically offer a higher average return. ... A study co-author noted, 'Investors are not behaving in their own best financial interest . all research suggests that, even after taking into account fluctuations in the market, overall, people are better off investing in stocks in the long term.'"

Buffett and emotions
It's not just academics who warn of emotion interfering with performance. Look at Berkshire Hathaway's Warren Buffett. I don't think he's a psychopath, but his extremely rational way of investing and tuning out emotions suggests he may have a few things in common with the folks who have funky brain waves. In his 1983 letter to shareholders, Buffett noted: "If the holders of a company's stock and/or the prospective buyers attracted to it are prone to make irrational or emotion-based decisions, some pretty silly stock prices are going to appear periodically."

Four years later, in his 1987 letter, he discussed the concept of "Mr. Market," introduced by his mentor, Benjamin Graham:

"[Graham] said that you should imagine [stock prices] as coming from a remarkably accommodating fellow named Mr. Market, who is your partner in a private business. Without fail, Mr. Market appears daily and names a price at which he will either buy your interest or sell you his. Even though the business that the two of you own may have economic characteristics that are stable, Mr. Market's quotations will be anything but. For, sad to say, the poor fellow has incurable emotional problems. At times he feels euphoric and can see only the favorable factors affecting the business. When in that mood, he names a very high buy-sell price because he fears that you will snap up his interest and rob him of imminent gains. At other times, he is depressed and can see nothing but trouble ahead for both the business and the world. On these occasions, he will name a very low price, since he is terrified that you will unload your interest on him."

This kind of representation of the market should ring true to most ears. Most of us do, after all, respond to fear and greed when investing. ("The market's swooning? Oh, dear -- I'd better sell!" "My stock is up 50% and is well above what I think is its intrinsic value? Well, I'll just hang on a little longer -- maybe it will go up some more.")

The upside of mental health
If you're thinking of hitting yourself in the head with a frying pan in the hope of becoming a better investor, snap out of it. The Bloomberg report explained that "emotions aren't all bad. Those who can't experience feelings tend to make 'disadvantageous' social decisions, losing their jobs and their friends."

The good news is that you can do well with the brain you have. Many CEOs are finding that this is true, as they fine-tune themselves.

CEO emotion coaching
A 2002 Business Week article described the not-so-uncommon practice of CEOs getting coached in managing their emotions to make them more effective in their jobs and lives.

For example, former Charles Schwab (NYSE:SCH) CEO David Pottruck, after getting a stinging performance review that said people didn't like working with him and didn't trust him, signed up with "executive coach" Terry Pearce, a former IBM executive. Part of his treatment included a spiritual cleansing by a shaman. Pottruck did make some changes, including taking no bonus and a 93% pay cut to $603,000 (from, apparently, nearly $9 million).

The article noted that not only are more and more CEOs seeking out coaches, but some boards are also "insisting" on them. Some CEOs cited as having used them, include eBay's (NASDAQ:EBAY) Meg Whitman, Pfizer's (NYSE:PFE) Henry McKinnell, Unilever Group's (NYSE:UL) Anthony Burgmans and Niall FitzGerald, and bigwigs at American Express (NYSE:AXP). The story also noted that, of course, "there are plenty of hacks, as well as 1-800 numbers promising coaching skills in just hours and schools offering mail-order degrees. There's no industry regulation: Hairdressers require more credentials. Worse, companies can be naive consumers, failing to conduct even basic background checks. Ford (NYSE:F) once hired a coach who had lost a sexual harassment suit."

Fool s and emotions
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Charles Schwab and eBay are Motley Fool Stock Advisor recommendations. Pfizer is a Motley Fool Inside Value selection, and Unilever is an Income Investor pick.

Selena Maranjian 's favorite Fool discussion boards include Book Club , Eclectic Library, and Card & Board Games. She owns shares of Berkshire Hathaway, eBay, and Pfizer. For more about Selena, viewher bio and her profile. You might also be interested in these books she has written or co-written:The Motley Fool Money GuideandThe Motley Fool Investment Guide for Teens. The Motley Fool is Fools writing for Fools.