Cheap mutual funds may save investors from their worst impulses, says an article in Barron’s.

According to the article, investors in the highest-cost funds “suffer the double whammy of first being set back by high fees, and then buying and/or selling at the wrong time,” citing supporting data from a recent Morningstar study. One theory, the article explains, is that “investors who buy low-fee funds are smarter than their peers and don’t overtrade.” Another, says CFRA director of mutual fund and ETF research Todd Rosenbluth, is that “investors are more patient with strategies that cost less.”

Many investors, the article says, can’t endure downside volatility (even if the potential upside is hefty) and therefore sell at the worst times. “For skittish investors in actively managed funds,” it says, “higher-cost volatile ones—even top performers—are a nemesis. Such folks would do better to stock with cheaper, more stable funds, though the discipline of automated investing, such as via a 401(K) plan, could mitigate the impulse to trade.”

“In sum,” the article concludes, “for the average investor, boring and cheap are beautiful.”