Postlingually deafened cochlear implant (CI) adults have large variability in speech perception abilities. While CIs are one of the most successful neural prosthetic devices, they are not able to adequately provide fine structure cues which results in a degraded signal for the listener to interpret. While behavioral measures remain the gold standard for determining speech perception abilities, an objective measure is needed for patients who are unable to provide reliable behavioral responses. Behavioral, cognitive, and neural measures were collected in this study to identify potential neural biomarkers that correlate with speech perception performance. Behavioral experiments evaluated participants' abilities to identify, discriminate, and recognize words as well as sentences in quiet and in noise. Cognitive measures were assessed to determine the roles of attention, impulse control, memory, and cognitive flexibility on speech recognition. Auditory event-related potentials (ERP) were obtained with a double oddball paradigm to produce the mismatch negativity (MMN) response, which has been shown to have associations with phonetic categorical perception at the group level. The results indicated that executive function is highly predictive of speech performance and that the MMN is associated with categorical perception at the individual level. These findings are clinically relevant to determining appropriate follow-up care …