As a followup to a previous column, Irreconcilable Differences, I received an e-mail from a reader asking how she could ensure, ahead of time, investment compatibility with a future spouse.

Unfortunately, like most issues in life, the direct approach does not work. Asking him, Sweetie, how will you invest our 401(k) funds? will only result in getting the answer he thinks you want. Honey, whatever you think is best, will be the answer you will hear. The thought that different investment strategies could result in irreconcilable harm to your future relationship seems remote to him. But we know better. He will say whatever you want in order to move the conversation to supposedly more important questions like, How many kids do you want, five or six? Or, What religion should we raise the kids in? We all know, however, as index investors, that our Investment Gestalt (IG) is the key predictor of future happiness. Fortunately, I have developed a test that will increase the probability of matching your IG with that of a prospective partner.

This is the scenario: Your friend (and I would keep the relationship at a platonic stage until after this first test of compatibility) is driving and you approach a toll on the New Jersey Turnpike. Its 5:30 p.m. and traffic is backed up a quarter mile. Now watch carefully as your friend selects one of 10 lanes to approach the tollbooths. Does he scan the mass of opportunities and abruptly cut across eight lanes of traffic to get into the shortest lane? So far, so good, correct? No, dont jump to any conclusions yet. Wait and see his behavior as his lane stops dead. Does he pull out and squeeze into the fastest moving lane two rows to your left? Even worse, does this behavior continue for the next 10 minutes as he chases the best performing lane? Stay away from this person. Dont give him a kiss goodnight and dont take his calls in the future. His approach is strictly short-term. He chases short-term performance (and he is rude too).

Still confused? The most suitable mate, the one with a similar IG would have randomly selected a lane and not wavered. He realizes that the lane that moves the fastest cannot be determined ahead of time and that short-term performance has no statistical significance to the final outcome. Your Mr. Right would have selected a lane and stayed in it. He would have used the extra time to find your favorite CD and ask how your mom is feeling.

Stay close to this guy. (Please note: With the introduction of express toll booths the validity of the above test has been challenged.) My question to our readers: what are the habits, quirks of personality that help you identify a person with a similar IG? Please share your perspectives with us.

Is it the kind of car he drives? Or the kind of dog he walks? Or how neat he keeps his apartment? Is it important that he calls his mom each night? Or is it totally counterintuitive? Are Indy 500 or Formula One drivers more likely to be index investors, while librarians take very large positions in hedge funds?

Please e-mail me with your insights so that I can share them with our readers.