Dictionary definition: A chemical substance that is produced by an animal and serves especially as a stimulus to other individuals of the same species for one or more behavioral responses — called also ectohormone-1997 by Merriam-Webster, IncorporatedTo the scientist, pheromones act in a very different way from normal smells. Some years ago, researchers discovered the existence of a small organ in the nose of many animals (known as the VNO), which acts as a “detector” for pheromones much as the nose acts as a detector for odors. One of the first mammals that was found to have such an organ was the domestic pig, and thus much of the early research relating pheromone activity with behavioral actions was done with pigs. Amazingly enough, it was found that the presence of pheromones (even when the olifactory receptors had been removed) had a direct affect on social behavior. The end result of many years of experimentation determined that the VNO/pheromone effect is not dependent on any conditioning through experience, nor is it dependent upon the sense of smell.

Pheromones utilize this special organ (the VNO), which is separate from the normal smelling process. There is still much arguing about the presence of this VNO in humans, but it is well accepted that pigs and cows in the vicinity of the sex pheromones of their species will be rendered “in the mood” even if they have no sexual experience, as long as the VNO is intact. It is now commonly accepted that pheromones regulate many common biological phenomenon in humans such as the commonly observed synchronization of menstrual cycles in households where many women live together.