Hearing Research Center, Boston University, Boston, MA 02215;
Acoustics Research Institute, Austrian Academy of Sciences, Vienna 1040, Austria.
Proc Natl Acad Sci U S A. 2017 Sep 5;114(36):9743-9748. doi: 10.1073/pnas.1703247114. Epub 2017 Aug 21.
Studies of auditory looming bias have shown that sources increasing in intensity are more salient than sources decreasing in intensity. Researchers have argued that listeners are more sensitive to approaching sounds compared with receding sounds, reflecting an evolutionary pressure. However, these studies only manipulated overall sound intensity; therefore, it is unclear whether looming bias is truly a perceptual bias for changes in source distance, or only in sound intensity. Here we demonstrate both behavioral and neural correlates of looming bias without manipulating overall sound intensity. In natural environments, the pinnae induce spectral cues that give rise to a sense of externalization; when spectral cues are unnatural, sounds are perceived as closer to the listener. We manipulated the contrast of individually tailored spectral cues to create sounds of similar intensity but different naturalness. We confirmed that sounds were perceived as approaching when spectral contrast decreased, and perceived as receding when spectral contrast increased. We measured behavior and electroencephalography while listeners judged motion direction. Behavioral responses showed a looming bias in that responses were more consistent for sounds perceived as approaching than for sounds perceived as receding. In a control experiment, looming bias disappeared when spectral contrast changes were discontinuous, suggesting that perceived motion in distance and not distance itself was driving the bias. Neurally, looming bias was reflected in an asymmetry of late event-related potentials associated with motion evaluation. Hence, both our behavioral and neural findings support a generalization of the auditory looming bias, representing a perceptual preference for approaching auditory objects.
听觉逼近偏见的研究表明，强度增加的声源比强度降低的声源更显著。研究人员认为，与退行声音相比，听众对逼近声音更敏感，这反映了一种进化压力。然而，这些研究仅操纵了整体声音强度；因此，尚不清楚逼近偏见是否真的是对声源距离变化的感知偏见，或者仅仅是对声音强度的感知偏见。在这里，我们在不操纵整体声音强度的情况下，同时展示了行为和神经相关的逼近偏见。在自然环境中，耳廓会产生诱导出外部化感觉的频谱线索；当频谱线索不自然时，声音会被感知为更接近听众。我们操纵了个性化定制的频谱线索的对比度，以创建具有相似强度但不同自然度的声音。我们证实，当频谱对比度降低时，声音被感知为逼近，而当频谱对比度增加时，声音被感知为退行。在听众判断运动方向的同时，我们测量了行为和脑电图。行为反应表现出逼近偏见，即对于被感知为逼近的声音，反应比对于被感知为退行的声音更一致。在对照实验中，当频谱对比度变化不连续时，逼近偏见消失，这表明驱动偏见的是感知到的距离运动，而不是距离本身。从神经学角度来看，逼近偏见反映在与运动评估相关的晚期事件相关电位的不对称中。因此，我们的行为和神经发现都支持听觉逼近偏见的推广，代表了对接近听觉物体的感知偏好。
