PROJECT SUMMARY Although individuals with complete vision loss can compensate by relying on audition, much less is known about whether such sensory substitution is used by individuals with residual vision, who represent a much larger portion of the visually impaired population. Few studies measured judgments of collision, which are essential for safe mobility, or the relative weights assigned to different sources of visual and auditory information, which is important for training and rehabilitation. We will address these gaps by measuring the relative contribution of visual and auditory information used by visually impaired individuals to make judgments of collision with obstacles in the environment. Results will advance a more individualized approach to rehabilitation and the development of assistive technologies, and will advance theories of collision perception. We will measure the abilities of 180 people to use visual and auditory information in judgments of collision, comparing those with central vision loss to age-matched as well as younger individuals with normal vision. We will create novel and compelling visual and acoustic computer simulations of approaching 3D vehicles, and compare judgments when auditory and visual information are presented concurrently to judgments when each is presented alone. By measuring judgments of when a collision would occur, and whether it is safe to cross a street in traffic, the proposed research will be the first to measure the degree to which auditory information is used during collision judgments when residual vision is available, and how much weight is assigned to different sources of visual and auditory information. Building on our collective expertise in collision perception, visual impairments, psychoacoustics, statistics, and 3D simulations, we will achieve three aims: 1) determine whether individuals who have partial vision loss compensate by relying on their hearing while making collision judgments, 2) determine whether individuals with partial vision loss achieve better collision judgments when they have auditory information in addition to their residual vision, compared to residual vision alone, and 3) measure how much weight individuals with partial vision loss assign to reliably accurate information (e.g., invariant of tau) compared to less reliable heuristics (e.g., depth cue of relative size) during collision judgments, and compare the weights to individuals with normal vision. Our pilot study showed that individuals with partial vision loss used their residual vision during collision judgments, placed more weight on visual cues than auditory cues, and placed more weight on less reliable heuristic cues. They also had smaller safety margins and more collisions during street-crossing judgments. By investigating multisensory processes in tasks essential for navigation by the visually impaired, we will help to fulfill the mission of the National Eye Institute to reduce the burden of eye dise...