" Moodiness also functions as an assessment device to test the strength of the bond.17 Women use moodiness to impose small costs on their mates and then use men’s reactions to the costs as a gauge of their degree of commitment. If a man is unwilling to tolerate these costs, it is a cue that his commitment is low. Men’s willingness to tolerate the costs and to be responsive to the increasing demands for investment signals a greater level of commitment. Either way, the woman gains valuable information about the strength of the bond. "

― David M. Buss , The Evolution Of Desire: Strategies of Human Mating