Directional Hearing in Fishes

Abstract

Directional hearing and sound source localization by fishes has several related meanings that arise from our assumptions about localization by human beings and assumptions about the cognitive capacities of fishes. For human listeners, we assume that when we determine the position of a sound source in the space around us, we know in a cognitive sense where the source is located, we can point to it with some accuracy, and we can move directly toward it and remember where the source is. Furthermore, we have the capacity to segregate in perception and locate multiple, simultaneous sources that make up an auditory scene (Bregman, 1990). The quantitative measure of localization for human listeners is the minimum audible angle (MAA), usually defined as the minimum angular deviation (usually in azimuth) required for reliable discrimination between two source locations. In a MAA experiment, we simply assume that not only can we discriminate the difference between two source locations, but that we “know” the direction to both sources in an absolute sense. We also often make the reasonable assumption that most other animal species function the same way: that they too “know” where the sound sources are located. But how well founded is this assumption in the case of fishes? This question arises for several reasons, including that fishes are thought not to use the same binaural acoustic cues as terrestrial animals, that the underwater environment makes source localization an exceedingly difficult, and sometimes impossible task, and that fishes may have few or any of the cognitive capacities required to “know” anything at all. In addition to these considerations, the history of research on source localization by fishes is contradictory and confusing. This chapter summarizes the literature on sound source localization in fishes and concludes that the evidence for a localization ability is strong, but that the mechanisms of sound source localization remain a fascinating question and an essential mystery in need of further experimentation and theoretical analysis.