Often times when referring to symmetry we think of equal, similar parts to things. In our book, "The Extraordinary Powers of Our Five Senses," by Lawrence Rosenblum, it is introduced that we unconsciously smell others body symmetry. Research shows that males with higher symmetry have more intimate partners, and have better genetic health. Those with lower symmetry usually have worse physical and mental health along with IQ. Information acquired shows women during their cycles can smell the odor of physiological processes that relate to men's symmetry. The degree of a mans symmetry relates to how attractive a man is to a woman. A woman who isn't on her cycle will notice no difference or not have a preference.
Pheromones also play their part in the processes. For instance the signaler pheromones send information to the sender regarding sex, kin, and potential of reproduction. Modulator pheromones are said to regulate mood and emotion to the receiving end. There are also releaser pheromones and they are chemically sent when detected by the same species. These can also influence our behavior on how we react to things.