Although many people with hearing impairments can accurately recognize words and sounds with proper treatments (hearing aids or cochlear implants), they often report fatigue and stress from doing so. These individuals need to exert more auditory cognitive processing effort to hear well, especially in adverse listening environments or when engaging in competing tasks. We hypothesize that the allocation of these auditory cognitive resources, or auditory cognitive “X-Factors,” can explain variability in outcome across cochlear implant users. To find the “X-Factors,” we use pupillometry as a physiological measure of cognitive load across auditory cognitive domains including short term memory (forward digit span) working memory (backward digit span), cognitive load (Paced Serial Addition Task), listening effort (speech in noise tests) and personality traits (motivation, self-efficacy, and adaptability). A custom-built eye tracking system using Pupil Labs software provides a cost-effective, dynamic, and fully m...