Project Summary/Abstract: In real-world listening environments, individuals must integrate distinct auditory features such as pitch, onset time, and spatial location to perceive auditory objects amidst background noise. This feature integration is particularly important for deciphering sequential sounds with converging features, such as speech or music. Hearing loss, especially in single-sided deafness (SSD), can disrupt feature integration leading to challenges like impaired speech comprehension in noise. This study adapts a perceptual illusion, the auditory kappa (AK) effect, to investigate feature integration in the healthy and impaired auditory system. In the AK effect, changes in pitch bias relative timing judgments in sound sequences such that sequential tones that are closer in pitch are perceived as closer in time. Leveraging this effect, we introduce the auditory spatial kappa (ASK) task to investigate how acoustic spatial and temporal cues are integrated to bias time perception and to test the effect of SSD on spatio-temporal feature interactions underlying auditory object perception, with and without a cochlear implant (CI). While temporal onsets are preserved in CI signal processing, individuals with CI and SSD face unique challenges due to impairments in spatial localization and auditory stream segregation. Although SSD patients recover some sound localization abilities with CI, it is crucial to identify disruptions in spatio-temporal features binding in this population. Our research objectives include establishing spatio- temporal feature interactions in normal hearing (NH) adults and determining which cues for spatio-temporal auditory perception are restored with CI in the SSD population. Aim 1 establishes baseline measures of spatial biases on timing judgments in NH adults. Participants will report the relative timing of sequential sounds presented at distinct horizontal locations. Building on our previous research studying the AK effect and preliminary data, we predict an ASK effect where smaller spatial separations result in shorter perceived time intervals due to auditory grouping. We hypothesize that grouping sounds based on spatial proximity biases perceived temporal proximity. Aim 2 examines the effect of SSD on this task and determines the extent of restored spatio-temporal feature interaction in SSD patients with CI. The ASK task will be adapted to compare fine-grained localization and more coarse lateralization in SSD individuals with and without CI. Based on preliminary data, we predict poor localization performance and a lack of feature interaction, measured as perceptual bias, without CI and a bias restoration for higher frequencies with CI due to reintroduction of bilateral interaural level cues. Findings from this research may provide an easy, objective measure of feature integration for auditory training tasks and improve rehabilitation strategies, especially in addressing challenges like speech comprehension in noi...