Perceptual salience is insufficient for auditory streaming in eastern gray treefrogs ( Hyla versicolor )

Auditory streaming underlies a receivers ability to organize complex mixtures of auditory input into distinct perceptual "streams" that represent different sound sources in the environment. During auditory streaming, sounds produced by the same source are integrated through time into a single, coherent auditory stream that is perceptually segregated from other concurrent sounds. Based on human psychoacoustic studies, a prominent hypothesis regarding auditory streaming is that any perceptually salient acoustic difference between sounds can promote their segregation into distinct auditory streams. Here, we used the eastern gray treefrog, Hyla versicolor, to test this hypothesis in the context of vocal communication in a non-human animal. In this system, females choose their mate based on perceiving features of a males pulsatile advertisement calls in social environments (choruses) characterized by mixtures of overlapping vocalizations. We employed an experimental paradigm from human psychoacoustics to design interleaved pulsatile sequences (ABAB...) that mimicked key features of the species advertisement call, and in which alternating pulses differed in pulse rise time, which is a robust species recognition cue in eastern gray treefrogs. Using phonotaxis assays, we found no evidence that perceptually salient differences in pulse rise time promoted the segregation of interleaved pulse sequences into distinct auditory streams. These results suggest the hypothesis that any perceptually salient acoustic difference can be exploited as a cue for stream segregation is not supported in all species. We discuss these findings in the context of cues used for species recognition and auditory streaming.