A growing body of literature is providing evidence that women's mating psychology undergoes changes across the menstrual cycle. Yet, the physiological mechanisms that may regulate such changes are largely uninvestigated. A number of projects in our lab are using salivary hormone assays to test possible mediators of such cycle phase shifts. These studies are also directed toward empirical tests of a novel functional theory that seeks to explain the evolution of mechanisms that may calibrate mating psychology to hormone concentrations.