Single-Sided Deafness (SSD) poses unique challenges for individuals navigating acoustically complex environments. Although many can meet the everyday demands of listening by relying on their functioning ear, this often incurs a substantial cognitive cost— manifesting as mental fatigue, increased listening effort, and depletion of attentional resources. Bone-Anchored Hearing Aids (BAHA) provide a means of restoring audibility in unilateral hearing loss; however, their ability to alleviate cognitive load and listening-related fatigue, dimensions not typically captured by standard clinical assessments, remains uncertain.

To investigate this, we employed a spatially separated adaptation of the Coordinate Response Measure (CRM) task. Speech stimuli were presented to the deaf ear, with competing noise presented to the hearing ear. Participants (N = 16; ongoing) performed two listening conditions: High Load (BAHA off) and Low Load (BAHA on). An additional control group (N=30; normal hearing) was tested with the same set up and simulated SSD (through occluding one ear).

Listening effort and attentional allocation were assessed using three oculomotor measures: Pupil Dilation Response (PDR) as a marker of arousal and effort, Microsaccade Rate (MSR) as an indicator of moment-to-moment attentional allocation, and Eye Blink Rate (EBR) as a measure of general cognitive engagement. Results show that, despite improving behavioural performance on the task, there is little evidence that BAHA reduces arousal under high load, as reflected by PDR. However, BAHA-listening was associated with a higher MSR, suggesting reduced burden of allocation on attentional resources relative to the BAHA-off condition. EBR analyses revealed significant modulation after the sentence keywords, with rebound dynamics differing by load condition— indicating that BAHA may facilitate computation speed. These findings suggest that while BAHA may not fully alleviate all dimensions of cognitive effort, it may support more efficient attentional processing in SSD.

Importantly, these results demonstrate the need to integrate efficient and non-invasive physiological assessments into clinical research, enabling a more comprehensive understanding of the cognitive and perceptual impact of auditory interventions beyond simple, traditional measures of audibility.