Birds as a Model in Hearing Research

The earliest reference to hearing birds can be traced back to Aristotle who mused about the parallels between birdsong and human language, a theme that continued through Darwin into present times. Technological advancements in the late 1800s and early 1900s set the stage for the first experimental hearing studies on birds in the 1930s–1950s which first began to approach the precision of those performed on humans. In the 1950s, the blending of operant conditioning, psychophysics, and signal-detection methods resulted in an explosion of methodologically rigorous studies on all aspects of hearing in birds. Beginning with detection and discrimination experiments using simple pure tones, tests on a wide variety of avian species provided a solid contrast with what was known about hearing in humans in terms of absolute and differential thresholds for frequency, intensity, and temporal changes. This quickly led to more elaborate studies, which were often motivated by the anatomical foundations of hearing in birds, aimed at understanding how hearing functions in the real world. These studies include the perception of acoustic categories, sound localization, the cocktail-party effect, and auditory scene analysis. In summary, despite a narrow range of hearing and closely spaced ears, birds have evolved an extremely sophisticated auditory system that matches well with the earliest speculations arising from observations on the widespread use and complexity of their learned vocalizations.