Gian Gonzaga, senior research scientist at eHarmony, said that studies his company had conducted of married people who met through eHarmony and a control group who met in other ways found that those who linked up through eHarmony were happier.

The only trouble, as Professor Lohr points out, is that couples who met through eHarmony had been married only six months and were “still in the honeymoon phase,” while the control group couples had been married about two years.

Mr. Gonzaga acknowledged the difference, but said the study was statistically controlled for length of marriage and other factors.

Mr. Gonzaga is now conducting a five-year longitudinal study following engaged couples — those who met through his Web site and those who found each other through different means.