Auditory object formation in Cope's gray treefrogs (Hyla chrysoscelis)

Hearing and acoustic communication in 'real world,' multi-source environments require animals to group sound elements produced by the same source into perceptually coherent 'auditory objects.' However, research on nonhuman animal communication rarely investigates perceptual processes involved in forming auditory objects of communication sounds. We tested the hypotheses that spectral and spatial proximity promote the sequential integration of temporally separated sounds produced by the same source into coherent auditory objects of acoustic signals. Male gray treefrogs produce a pulsatile advertisement call; females prefer longer calls (= more pulses) to shorter calls and discriminate against calls missing pulses. We gave females a choice between a short but spectrally and spatially coherent call (25 pulses) and a longer call (35 pulses) in which alternating groups of 5 pulses had different frequencies (ΔF, 0-12 semitones) and came from different locations (A9, 0° or 90°). Females generally preferred the longer call at smaller values of ΔF and ΔΘ, indicating a role for spectral and spatial proximity in sequential integration. Under some conditions, however, subjects showed a surprising willingness to integrate pulses despite large AFs. Together, these data shed light on the perceptual cues that receivers exploit to form coherent auditory objects of communication sounds.