Size-Distance Scaling With Absolute and Relative Auditory Distance Information

In the dynamic 3D space, it is critical for survival to perceive size of an object and rescale it with distance from an observer. Humans can perceive distance via not only vision but also audition, which plays an important role in the localization of objects, especially in visually ambiguous environments. However, whether and how auditory distance information contributes to visual size perception is not well understood. To address this issue, we investigated the efficiency of size-distance scaling by using auditory distance information that was conveyed by binaurally recorded auditory stimuli. We examined the effects of absolute distance information of a single sound sequence (Experiment 1) and relative distance information between two sound sequences (Experiment 2) on visual size estimation performances in darkened and well-lit environments. We demonstrated that humans could perform size-distance disambiguation by using auditory distance information even in darkness. Curiously, relative distance information was more efficient in size-distance scaling than absolute distance information, suggesting a high reliance on relative auditory distance information in our visual spatial experiences. The results highlight a benefit of audiovisual interaction for size-distance processing and calibration of external events under visually degraded situations.