I began with a theory. Since antiquity, poets, philosophers, and physicians have classified people into four styles of temperament. For Plato, they were the Artisan, Guardian, Idealist, and Rational. I have come to call them the Explorer, Builder, Negotiator, and Director. Each basic type, I suspect, is associated with a distinct cluster of genes—along with the expression of certain brain chemicals and a unique collection of personality traits. When people pair up, I propose, they tend to fall for a type different from their own, pulled by an unconscious biological appetite to create more genetic variety in their young and to raise their children with a wider array of parenting skills. Furthermore, each kind of pair will have its own joys and challenges, so a Builder married to a Director might face one set of highs and lows; a Negotiator-Explorer couple, another.
To see how these ideas play out in the real world, we e-mailed thousands of married O readers and asked each spouse to complete our online survey independently (once partners hit "submit," they couldn't read each other's answers). Part of the survey consisted of questions I had originally developed for the new dating/relationship site Chemistry.com (see "Do We Click?" ) to determine a person's love type. Other questions addressed issues that might cause friction in the relationship—money, sex, respect, boredom—as well as levels of general happiness.
Then I studied the hundreds of pages of data collected by Beta Research Corporation, the company that carried out the survey for us, on 500 couples who answered our questionnaire. With some respondents as young as 21 and others in their 60s, the average age for women was 47 and for men, 49. Some 83 percent of couples had children, many still living at home. And on average, the spouses had been married 16 years. Were some pairings more compatible than others? Are certain types better left unwed?