In nature, vinegar flies are exposed to a wide variety of odor mixtures, which contain both attractive and repellent odors. Scientists at the Max Planck Institute for Chemical Ecology have now discovered that repellent odors suppress the perception of pleasant smells. This happens because certain brain structures that respond to attractive odors are inhibited by a repellent one. These processes in the brain are also reflected in the behavior of the flies: The flies avoid attractive odor sources when a repellent odor is added. This helps them to avoid spoiled or infected food sources, which would have fatal consequences for the flies and their offspring.