Mechanisms underlying auditory looming bias: Behavioral perspective
Approaching or looming sounds are more salient than receding sounds. In order to study this auditory looming bias, moving sensations are mostly created by intensity changes, while increasing intensity elicits a looming sensation and decreasing intensity a receding sensation. Alternatively, manipulating spectral cues can also elicit looming bias. Here, the direction-dependent filtering caused by the reflections of the listeners’ individually shaped pinnae, head, and shoulders provide the necessary spatial information: flattening the magnitude spectrum makes the sound appear looming (even into the listener’s head), while sharpening the magnitude spectrum leads to a receding sensation. To directly and independently compare both types of sound manipulation, we conducted an experiment playing smoothly cross-faded pairs of Schroeder-phase harmonic complex tones to elicit a moving sensation. As a control condition, we presented static sound-pairs without movement. The listeners judged the direction of the movement for every sound-pair. We expected to find a looming bias in the accuracy rates (higher accuracies for looms than recedes) as well as response times (shorter for looms) for both intensity and spectral-magnitude changes. The results will be discussed with regards to the different sound manipulations and their potential for studying the neural substrate of looming bias.