We seek to understand how structural and biochemical changes within the central nervous system regulate behavior. One effective method for investigating this topic is the exploitation of naturally occurring differences in behaviors. We study courtship and copulatory displays because they are stereotyped, sexually differentiated, and in many species displayed seasonally. Therefore, we can evaluate mechanisms regulating behaviors within a sex in and out of the breeding season, as well as between the two sexes. We focus on factors involved both in organizing critical regions of the brain, spinal cord and muscles during development, as well as those that confer varying levels of plasticity in adulthood. Members of my lab are working with two model systems, songbirds and anole lizards. These species have the potential to not only increase understanding of the evolution of the processes regulating behavioral differences, which have commonly been studied in mammals, but also to address the ubiquity of the mechanisms employed in diverse situations. Our techniques currently range from molecular to behavioral, with emphases also on measurements of steroid hormones, their receptors and metabolizing enzymes, and the morphology of anatomical structures related to reproduction. Integrating work across multiple levels of analysis and appreciating the differences and similarities across diverse vertebrate systems facilitates our understanding of factors controlling nervous system structure and function.