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Tests for Call Restoration in the Gray Treefrog Hyla versicolor

Joshua J. Schwartz, Kenneth Huth, Sherryll H. Jones, Robert Brown, Jacqueline Marks & Xiaoliang Yang (2010). Tests for Call Restoration in the Gray Treefrog Hyla versicolor. Bioacoustics, Volume 20 (1): 59 -86

 

Abstract: 

Phonemic restoration, a form of temporal induction, occurs when the human brain compensates for masked or missing portions of speech by filling in obscured or non-existent sounds. We tested for temporal induction and related abilities in females of the Gray Treefrog Hyla versicolor. The number of pulses in calls is used by females for assessment of males. Accordingly, an ability to “restore” or interpolate between masked or otherwise sonically degraded portions of calls could help females during mate choice in noisy choruses. In phonotaxis experiments, we employed unmodifed calls and those that had a centrally placed gap, a region overlapped by a portion of another call or filtered noise, or replaced with filtered noise. When offered call alternatives with equivalent numbers of clear pulses, we found that females discriminated against calls with gaps two or more times greater than the natural 25 ms interpulse interval. When a gap was replaced with a zone of call overlap or noise (so, again the call durations of the alternatives were unequal), females discriminated either in favour (overlap) of the modified stimuli or failed to discriminate (noise). However, when the unmodified and modified stimuli were the same duration, females discriminated against the latter. Normal calls were also chosen when paired against calls with multiple noise sections. Pulses formed from noise bursts were attractive, but less so than normal pulses. In single speaker tests, standardized rates of movement did not differ between calls containing noise segments of different duration. Our results therefore do not indicate that females of the Gray Treefrog employ a form of temporal induction that is fully restorative. However, the data indicate that acoustically anomalous sections of calls can retain attractive potential provided acoustic energy and pulses are present.

Keywords: 
gray treefrog, communication, temporal induction, phonemic restoration, acoustic interference