Chemoreception is a physiological process whereby organisms respond to chemical stimuli. Humans and most higher animals have two principal classes of chemoreceptors: taste (gustatory receptors), and smell (olfactory receptors). Though our sense of smell assists us in distinguishing among tastes, the gustatory and olfactory receptors are different in many respects—not only in their locations but also in terms of their chemical and neurological makeup. Capabilities of taste and smell vary widely among people, as a function of genetics, age, and even personal habits. Likewise, culture influences attitudes toward taste and smell. As for the animal kingdom, certain creatures are gifted with exceedingly acute senses, particularly where smell is concerned, but for some invertebrates, such as worms, there is really little distinction between taste and smell. Among the most interesting aspects of chemoreception in animals is the use of smell for communication, particularly through the release of special chemicals called pheromones. As to whether pheromones, which function as sex attractants, play a role in human interaction, many scientists remain skeptical.