PROJECT SUMMARY The goal of this study is to identify the auditory, cognitive, and linguistic processes that support foreign-accented speech recognition for native and non-native listeners. With increasing globalization, foreign-accented speech occurs regularly in real-world human communication and is often a cause of miscommunication. Yet little is known about how non-native speech alters the mechanisms of speech recognition. To understand the mechanisms that support accented-speech recognition and their language-dependent plasticity, 60 middle-aged adults from three different language backgrounds (native English monolingual, Spanish-English bilingual, and Mandarin-English bilingual) are tested on accented-speech recognition, the frequency-following response (FFR), and a battery of cognitive and linguistic measures. The accented-speech recognition test uses sentences of varying linguistic complexity spoken by native-English monolinguals, Spanish-English bilinguals, and Mandarin- English bilinguals, allowing evaluation of non-native speech recognition in individuals whose language backgrounds either match or do not match the talkers. The FFR is a neurophysiological response to complex auditory stimuli that provides fine-grained detail about how multifaceted, overlapping components of sound (e.g., fundamental frequency and harmonics) are transformed into discrete neural components. Thus, the FFR can identify how individual sound components contribute to non-native speech recognition. Additionally, a comprehensive battery of cognitive and linguistic processes thought to be important for non-native speech recognition are measured on these participants. Together, these tests delineate the contribution of auditory, cognitive, and linguistic processes on foreign-accented speech recognition for native and non-native listeners. By identifying the neural mechanisms underlying accented-speech recognition and language-based plasticity of these mechanisms, this project provides the groundwork for developing strategies to improve accented speech recognition. Furthermore, outcomes from this project will aid in our overarching goal of understanding the shared and separate mechanisms that support all types of degraded-speech recognition and how these mechanisms are influenced by language experience. Identifying mechanisms of degraded-speech recognition and their experience dependency will identify ways to improve communication in everyday settings, and will facilitate development of remediation strategies for individuals whose speech recognition difficulties are exacerbated, such as individuals with a hearing impairment or language disorder.