Trivia question: Why were local phone numbers originally seven digits long? The answer is that in the early days of local phone service, researchers found that seven digit numbers were about as long as most people could remember without forgetting or making errors. (One oft-quoted study on the “seven” topic is The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information by George A. Miller.)

If it’s hard to remember more than seven digits, how many complex concepts can we process and/or keep track of? I don’t think that research has been conducted, but a New York Times interview with Cristóbal Conde, president and C.E.O. of SunGard, suggests one solution:

A boss once told me: “Cris, you’re a smart guy, but that doesn’t mean that people can absorb a list of 18 things to do. Focus on a handful of things.” Very constructive criticism, and the way I’ve translated that is, when I do reviews, everything is threes.

So, “Look, Charlie, these are the three things that are going well. These are the three things that are not going well.” Now, that’s very important because then people know that everybody’s going to get three positives and three things they should do differently. Then they don’t take it personally. I’ve found that to be an incredibly valuable tool. [Emphasis added. From New York Times Corner Office - Structure? The Flatter The Better.]

Now there may not be research to show that three is some kind of hard-wired limit like the average number of digits we can retain is, but Conde’s limit of three makes a lot of sense. When the number of things to focus on keeps growing, that focus will eventually be lost.

I think the Rule of Three can be applied not just to performance reviews but other business topics as well. How about the three things I absolutely must complete today? The top three products needing sales attention? The list could go on and on. Now there may be nothing magical about “3,” but one can’t argue that using the Rule of Three won’t simplify a complex focus and increase the probability of achieving those three objectives.

Do you have any simplification rules to manage your life or business activity? Do you let lists grow as long as needed, or do you have a cutoff number that helps you (or your employees) focus?