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First published online August 30, 2006
Journal of Experimental Biology 209, 3652-3663 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02420

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Perturbation of auditory feedback causes systematic perturbation in vocal structure in adult cotton-top tamarins

S. E. Roian Egnor^*, Carmen G. Iguina and Marc D. Hauser

Harvard University, William James Hall, 10th Floor, 33 Kirkland Street, Cambridge, MA 02138, USA

View larger version (26K): [in a new window]   Fig. 1. Example spectrograms of CLCs from individual JG. (A) Spontaneously produced CLC. In this case the call consists of a short, downward frequency modulated `chirp', followed by three relatively constant frequency `whistles'. (B) A CLC that received 1 s white noise feedback with a delay of 0.5 s, showing that the final whistle has been omitted. (C) The same CLC as in B with white noise feedback removed (see Materials and methods for details).

View larger version (15K): [in a new window]   Fig. 2. CLC duration histograms for modified feedback (black bars) and normal feedback (open bars) for four male (A-D) and four female (E-H) cotton-top tamarins. Modified feedback stimuli were 1 s long white noise bursts, presented at a delay of 0.5 s, with a feedback probability of 50%. Data are from the Random condition.

View larger version (22K): [in a new window]   Fig. 3. Interruption rate as a function of session. Interruption rate for early sessions (white bars) and later sessions (dark bars) for the Begin, End and Random experimental conditions. Interruption rate was lower in the Begin condition than in either the End or Random conditions, and interruption rate was lower in later sessions than in early sessions in all three conditions, however, neither of these trends were significant. Values are means ± s.e.m. (for number of calls in each condition, see Table 1).

View larger version (22K): [in a new window]   Fig. 4. Interruption rate as a function of time within a session. Interruption rate for the first call (white bars) and last call (dark bars) for the Begin, End and Random experimental conditions. There was no difference in interruption rate between the first and last calls in a session in any of the experimental conditions. Values are means ± s.e.m. (for number of calls in each condition, see Table 1).

View larger version (24K): [in a new window]   Fig. 5. Call amplitude as a function of time relative to modified feedback. In the Begin condition (A) calls with modified feedback (MFB, dotted lines) were louder than those with normal feedback (NFB, broken lines), which were not significantly different from Baseline calls (Base, gray lines). In the End condition (B) neither modified feedback nor normal feedback calls were significantly different each other or from Baseline. Although there was no amplitude difference between normal feedback and modified feedback calls in the Random condition (C), both modified and normal feedback calls were louder than baseline calls. In Begin and Random conditions calls were only significantly louder than Baseline calls in the portion of the call that received modified feedback. Values are means ± s.e.m. (for number of calls in each condition, see Table 1).