Biological responsiveness to pheromones provides fundamental and unique insight into olfactory function.

When exposed to the odor of conspecifics, most organisms exhibit an adaptive behavioral response, particularly if the individuals are sexually mature. Evidence increasingly suggests that behavioral responsiveness to these odors, which are termed 'pheromones', reflects neuroethological mechanisms associated with olfactory function. Reproductive pheromones, which are the best understood, are commonly used by both invertebrates and vertebrates. In both instances they are generally comprised of mixtures of compounds and behavioral responsiveness to them is largely instinctual, sexually-dimorphic, and attributable to a specialized component(s) of the olfactory system. While pheromonal responsiveness in some systems (e.g. moths) appears highly stereotypic and symptomatic of a relatively simple 'labeled line', behavioral responsiveness of other animals (e.g. rodents) can be modified by experience, suggesting a more complex underlying central mechanism. In any case, our understanding of these fascinating systems is progressing only because of an active dialogue between behavioral and neurological investigations. This review briefly examines how behavioral studies have provided fundamental insight into the neuroethology of olfactory function by drawing comparisons between some of the better understood sex pheromone systems which have been described in heliothine moths, the goldfish, and the pig. Many similarities between invertebrate and vertebrate pheromone systems are noted.