An adaptive bias in the perception of looming auditory motion

Rising acoustic intensity can indicate movement of a sound source toward a listener. Perceptual overestimation of intensity change could provide a selective advantage by indicating that the source is closer than it actually is, providing a better opportunity for the listener to prepare for the source's arrival. In Experiment 1, listeners heard equivalent rising and falling level sounds and indicated whether one demonstrated a greater change in loudness than the other. In 2 subsequent experiments listeners heard equivalent approaching and receding sounds and indicated perceived starting and stopping points of the auditory motion. Results indicate that rising intensity changed in loudness more than equivalent falling intensity, and approaching sounds were perceived as starting and stopping closer than equidistant receding sounds. Both effects were greater for tones than for noise, Evidence is presented that suggests that an asymmetry in the neural coding of egocentric auditory motion is an adaptation that provides advanced warning of looming acoustic sources.