The goal of this study is to determine the mechanisms underlying functional consequences of asymmetry for bilateral and single-sided deafness cochlear implant (CI) listeners. The project will focus on two phenomena that likely limit outcomes: “bilateral speech interference” (speech presented in one ear impedes speech understanding in the other) and “interaural loudness mismatch” (bilateral stimuli that are equally loud when presented sequentially produce a distorted spatial map when presented simultaneously). This knowledge will guide programming and rehabilitation to optimize CI performance.