Interaural Grouping and the Precedence Effect Bernhard U Seeber MRC Institute of Hearing Research, Nottingham, UK The precedence effect describes our ability to suppress detrimental effects of reflections on localization of sound sources in rooms. We recently demonstrated for bilateral cochlear implant patients and for cochlear implant simulations that precedence can break down such that the echo is audible in addition to the leading sound. This triggered our interest in the effects of parameters that can facilitate grouping. Studies on auditory scene analysis showed that spectral relationships, particularly harmonic relationships, common onsets, offsets, and interaural binaural cues as well as coherent amplitude and frequency modulation help group components into auditory objects. We will present first results of a study that takes the view that lead and lag are grouped into one object in the precedence effect when the delay is shorter than the echo threshold. We will facilitate interaural fusion by enhancing parameters known to be relevant for monaural grouping of spectral components.