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. From an evolutionary perspective, the problem of anticipating an approaching ob-ject is an important task. A listener with a perceptual bias to detect approaching ob-jects might gain a selective advantage by better preparing for the object’s arrival. In vision, the topic of looming has been widely studied, with investigations ranging from the study of gannets who time their wing folding to coincide with contact with the water when diving for fish (Lee Reddish, 1981) to baseball outfielders who ar-rive at the correct position in the field to catch fly balls (McBeath, Shaffer, Kai-ser, 1995). The problem has also been studied to a lesser extent in the auditory domain.