Understanding the genetic and neurobiological mechanisms underlying social behavior will provide insights into determining how these systems go wrong in individuals with developmental disorders including autism. Using a naturalistic animal model, this study will examine the genetic influences on social behavior using two different species of rodents called voles. One species, the prairie vole, forms strong social bonds, while the other, meadow voles, does not. Previous research has suggested that the difference in this social behavior may be due to a “microsatellite” region of genetic material that is located outside the area which transcribes the gene for the peptide hormone receptor avpr1. The molecules on which this receptor works, called oxytocin and vasopressin, have been shown to regulate this social affiliative behavior. Therefore, these researchers will create markers for these microsatellites as well as establish different strains of voles which show differing levels of social behaviors. What this means for people with autism: This set of molecular markers, used in conjunction with selectively bred lines of voles that differ in their ability to form social bonds, will allow for the discovery of genes that contribute to variations in social behavior. This strategy may ultimately lead to novel pharmacological interventions to selectively treat the social deficits associated with ASD.