Temporal and spatial coherence as cues for across-frequency grouping in treefrogs

Abstract

Humans exploit environmental regularities in sounds to perceptually bind acoustic energy occurring simultaneously at different frequencies. Such abilities influence vowel perception in speech and timbre perception in music. Other animals solve similar binding problems in the recognition of species-specific acoustic signals. Moreover, they commonly do so using auditory systems that differ in notable ways from that of mammals. This study of two treefrog species investigated temporal and spatial coherence as cues that promote grouping of two spectral bands emphasized in their acoustic signals. In two-alternative choice tests, females preferred temporally and spatially coherent calls over alternatives in which the onsets/offsets of the two bands were time-shifted by more than 25 ms or in which the two bands were spatially separated by 7.5° or more. These results, which suggest temporal coherence and spatial coherence promote across-frequency auditory grouping, are notable given differences in how the two spectral bands are processed by the anuran auditory system. Sound energy in the high- and low-frequency bands primarily enters the auditory system via different pathways (tympanum and body wall, respectively) and is encoded primarily by different papillae in the inner ear (basilar papilla and amphibian papilla, respectively).