Clinicians are now focused on which device, at each ear, best provides the perceptual acuity such that age- appropriate spoken language develops. Bilateral CIs (BCIs) are recommended as soon as possible for young children with the most profound hearing losses (HLs). Clinicians are less certain, however, about recommendations for young children with HL varying from severe to profound. Although the long-term consequences of these device decisions are unknown, the expectation is that early perceptual abilities provide a foundation for functional communication and peer interactions critical for navigating academic and social situations in a hearing world. Generally, hearing-device recommendations are based on audiometric thresholds and speech perception scores, usually segmental speech scores (e.g., words understood). Yet suprasegmental perception (perception of intonation, stress, and rhythm), which is also extremely important for spoken language and lexical development, has been largely ignored. Importantly, the acoustic cues associated with suprasegmental perception are not transmitted equally well with CIs and HAs; CIs are typically more effective for conveying segmental cues while HAs, depending on a listener's residual hearing, are more effective for conveying suprasegmental cues. We identified a critical duration of HA use for each of three ranges of HL severity (pure-tone-averages [PTAs] of 72, 92 &110 dB HL) that maximizes both segmental and suprasegmental perception. Both contribute to receptive language, and suprasegmental remains significant for early reading skills. Our results suggest that a child with severe HL (~72 dB HL) who receives BCIs at an early age, and consequently does not experience early extended use of a HA, could be denied good suprasegmental perception and a more-typical language foundation. The long-term benefits, however, of early HA use (moderated by PTA) to spoken language skills, reading, and other perceptual abilities remain unknown. We now propose to establish whether early HA use contributes to, or detracts from, perception skills implicit in “real world” communication, namely audiovisual (AV) speech perception and binaural listening. Early acoustic hearing complements visual speech information and may provide large benefits for AV perception. Alternatively, for developing binaural listening skills, early BCIs, with their somewhat symmetrical stimulation, may be better than bimodal devices for which there is an implicit extended period of acoustic hearing and asymmetrical stimulation. We will examine these two types of perceptual abilities at ages when these skills are thought to be fully-developed and can be reliably assessed. Aim 1a: Determine whether early acoustic hearing contributes to AV perception and binaural listening skills. Aim 1b: Determine the unique contributions of AV perception and binaural listening skills to spoken language, quality of hearing, and social functioning. Aim 2: Determine if contrib...