We will evaluate a variety of auditory processing tests in MZ and same-sex DZ twins. This initial phase of the study is designed to provide data so that the performance of MZ twin pairs can be compared to the performance of DZ twin pairs. Statistical modeling will be used to estimate the relative contributions of heredity and environment to auditory processing skills. In addition, we will examine variation in auditory processing skills in the general population of twins. This will allow us to identify auditory processing skills and tests that have the greatest heritable components, and to establish normative data for the tests we administer.