The invention provides a method of identifying a compound that alters vigilance. The method consists of contacting an invertebrate with a candidate compound, evaluating a vigilance property in the contacted invertebrate, and determining if the candidate compound alters the vigilance property in the contacted invertebrate. A candidate compound that alters the vigilance property in the contacted invertebrate is identified as a compound that alters vigilance. The invention also provides a method of identifying a vigilance enhancing compound that modulates homeostatic regulation or a vigilance diminishing compound that modulates homeostatic regulation. The method consists of contacting an invertebrate with a compound that increases or decreases vigilance, and determining the effect of the compound on a homeostatic regulatory property of vigilance. A compound that alters the homeostatic regulatory property is characterized as being a vigilance enhancing compound or a vigilance diminishing compound that modulates homeostatic regulation.