Based on the outcomes of Phase 1, auditory processing tests of skills with the highest heritable component will be selected for evaluation of probands. Those who score in the top and bottom 10th percentile will be eligible for participation as probands in this phase of the study. Variation of these skills in the general population, as determined by the twin data (Phase 1) or published norms, when they are available, will be used to determine the top and bottom 10th percentiles. This same test set will be administered to probands and at least two first-degree relatives allowing us to determine whether traits related to auditory processing occur within the family at a rate greater than chance.