John Tierney in The New York Times:
…Unlike many other Web dating services, eHarmony doesn’t let customers search for partners on their own. They pay up to $60 per month to be offered matches based on their answers to a long questionnaire, which currently has about 200 items. The company has gathered answers from 44 million people, and says that its matches have led to more than half a million marriages since 2005. Dr. Gonzaga, a social psychologist who previously worked at a marriage-research lab at the University of California, Los Angeles, said eHarmony wouldn’t let him disclose its formulas, but he did offer some revelations. He said its newest algorithm matches couples by focusing on six factors:
¶ Level of agreeableness — or, put another way, how quarrelsome a person is.
¶ Preference for closeness with a partner — how much emotional intimacy each wants and how much time each likes to spend with a partner.
¶ Degree of sexual and romantic passion.
¶ Level of extroversion and openness to new experience.
¶ How important spirituality is.
¶ How optimistic and happy each one is.
The more similarly that two people score in these factors, the better their chances, Dr. Gonzaga said, and presented evidence, not yet published, from several studies at eHarmony Labs. One study, which tracked more than 400 married couples matched by eHarmony, found that scores from their initial questionnaires correlated with a couple’s satisfaction with their relationship four years later.
More here.