When we cry, we may be doing more than expressing emotion. Our tears, according to striking new research, may be sending chemical signals that influence the behavior of other people. The research, published on Thursday in the journal Science, could begin to explain something that has baffled scientists for generations: Why do humans, unlike seemingly any other species, cry emotional tears? In several experiments, researchers found that men who sniffed drops of women’s emotional tears became less sexually aroused than when they sniffed a neutral saline solution that had been dribbled down women’s cheeks.