Taking something as slippery as the concept of love into the laboratory is not something most social psychologists would take lightly, thus, credit must be given to Joshua Ackerman, assistant professor of marketing at MIT and colleagues Vladas Griskevicius, and Norman Li who together have published a paper, the Journal of Personality and Social Psychology, showing that it's not women who most often utter those first words of love, it's men; though their motivation for doing so might be different then for women.
The Study
To find out which gender most often says "I love you" first, the researchers conducted six studies, all done via surveys spread out over a series of months in several different locations. The multi-part questionnaires were designed to be answered by couples (and former couples) regarding the circumstances that led to one or the other confessing their love for the other. In addition to asking about who said what first, the researchers also sought to find out how the couples involved felt about the way things went for them, and whether they thought the timing was right.
Results
To their surprise the researchers found that two thirds of the couples studied reported that it was the man who expressed his love first and even then most were holding back apparently, as most of the men studied admitted that they'd been thinking of spilling the beans up to six weeks earlier than most of the women reported.