Audiovisual estimation of time to collision in road traffic assessed in bilateral cochlear implants users

In order to cross a road safely when a car is approaching, one must be able to estimate the time remaining until a potential collision (time to collision TTC). This is usually done both visually and auditorily. Individuals with cochlear implants (CI) have impaired auditory perception compared to normal hearing (NH) subjects in both the frequency domain and the dynamic range. In this work, we investigated whether audiovisual TTC estimation varies between subjects with CI and those with normal hearing. Thirteen bilateral Cl subjects and 15 NH participated in the study. Subjects estimated contact times for visual and audio-visually presented accelerating vehicles in an audiovisual VR simulation, varying the actual TTC. Visual presentation was realized via VR glasses, and Higher-Order Ambisonics (TASCAR Toolbox) was used for the auditory simulation. With visual presentation alone, TTC was increasingly overestimated with increasing actual TTC, compatible with an inadequate consideration of acceleration known from previous studies. With present vehicle noises, the estimations were significantly more accurate. Therefore, the acoustic information supported the assessment of the TTC. No significant differences were found in the estimation of TTC between Cl and NH subjects. Despite the limited auditory perception of bilateral Cl users, they appear to achieve comparable audiovisual integration in the task examined, as people with normal hearing.