Editorial: How, and Why, Does Spatial-Hearing Ability Differ among Listeners? What is the Role of Learning and Multisensory Interactions?

Large individual differences are relatively common in human perception. Spatial hearing is not an exception; for instance, two listeners can perceive the same auditory target to be at very different spatial locations. Such variability cannot be considered as mere experimental noise but as true data that we have to use for explaining the mechanisms underlying the perception of auditory space. The 22 papers of this research topic explore individual differences in almost every aspect of auditory space perception. To determine the position of a sound source on a Left/Right axis (from −90 • at the extreme left to +90 • at the extreme right), listeners use binaural cues: interaural differences in level (ILDs) and in time (ITDs). The auditory system is sensitive to ITDs for stimuli below about 1500 Hz, but this sensitivity declines rapidly at higher frequencies. It has been suggested that this reduced sensitivity at higher frequencies acts as a protective mechanism against ambiguous information that results from the similarity between head radius and the wavelengths for these frequencies. By providing quantitative data, Hartmann and Macaulay reconsidered this explanation and showed that this mechanism would only be effective for heads that are 50% smaller than current adult heads. The authors presented potential developmental and evolutionary processes that could explain how ILDs would replace ITDs for the localization of frequencies above 1500 Hz. Ochi et al. found that individual differences in ITDs and ILDs sensitivities were related to basic non-spatial abilities (i.e., the efficiency of temporal coding for the ITDs and of intensity coding for the ILDs). Gallun et al. reported that temporal coding was influenced both by hearing loss and aging, but these factors were independent. The authors reached this conclusion by applying a linear mixed model on a population of 78 listeners with a large range of hearing thresholds and ages. In older adults, Perez et al. showed that temporal coding could partially predict satisfaction of hearing impaired listeners recently fitted with hearing aids. Specifically, those with better abilities prior to fitting were less satisfied after fitting, presumably due to higher, and so unfulfilled, expectations. In a special case of hearing impairment, single-sided deafness, listeners retain some localization abilities in azimuth, even in the absence of normal binaural cues, but large individual differences are observed (Agterberg et al.). It seems that listeners can use the direction-dependent modifications