ROBOTIC weapons? Terrifying. Robo cars? Controversial. Robo investment managers? They're a great way to start or continue investing. In the 15 years since their introduction, computer programs that automatically design and maintain portfolios tailored to an individual's goals and risk tolerance have grown rapidly. Robo advisers currently manage more than $500 billion of investors' money. One reason for their success is that they can steer investors away from emotion-driven mistakes. "When an investment doesn't do as well as we'd like, or the headlines are screaming, the best thing investors can do is stay the course and rebalance their portfolio, if necessary. A robo adviser can be really helpful since it can do that automatically," says Bradley Hilton, an Atlanta-based certified financial planner.

Research published last year found that do-it-yourself investors who switched to a low-cost robo service that also offers access to human advisers (known as a hybrid service) ended up with more-diversified portfolios that were less vulnerable to significant losses and earned higher risk-adjusted returns. The researchers—Georgetown University finance professor Alberto Rossi and Stephen Utkus of the University of Pennsylvania—also found that robo customers spent less time dealing with their investments, gaining an average of six hours a year of free time.

To help you determine whether a robo investment option is right for you, Kiplinger has analyzed 10 major robo firms' offerings, costs and, with help from robo-tracker Condor Capital Wealth Management, portfolio returns. But before you zero in on specific robo offerings, consider some general guidelines.