@article {320025,
	title = {Orangutans show active voicing through a membranophone},
	journal = {Nature Scientific Reports},
	volume = {9},
	year = {2019},
	month = {2019/08/23},
	pages = {12289},
	abstract = {<p>Active voicing {\textendash} voluntary control over vocal fold oscillation {\textendash} is essential for speech. Nonhuman great apes can learn new consonant- and vowel-like calls, but active voicing by our closest relatives has historically been the hardest evidence to concede to. To resolve this controversy, a diagnostic test for active voicing is reached here through the use of a membranophone: a musical instrument where a player{\textquoteright}s voice flares a membrane{\textquoteright}s vibration through oscillating air pressure. We gave the opportunity to use a membranophone to six orangutans (with no effective training), three of whom produced a priori novel (species-atypical) individual-specific vocalizations. After 11 and 34 min, two subjects were successful by producing their novel vocalizations into the instrument, hence, confirming active voicing. Beyond expectation, however, within \&lt;1 hour, both subjects found opposite strategies to significantly alter their voice duration and frequency to better activate the membranophone, further demonstrating plastic voice control as a result of experience with the instrument. Results highlight how individual differences in vocal proficiency between great apes may affect performance in experimental tests. Failing to adjust a test{\textquoteright}s difficulty level to individuals{\textquoteright} vocal skill may lead to false negatives, which may have largely been the case in past studies now used as {\textquotedblleft}textbook fact{\textquotedblright} for great ape {\textquotedblleft}missing{\textquotedblright} vocal capacities. Results qualitatively differ from small changes that can be caused in innate monkey calls by intensive months-long conditional training. Our findings verify that active voicing beyond the typical range of the species{\textquoteright} repertoire, which in our species underpins the acquisition of new voiced speech sounds, is not uniquely human among great apes.</p>
},
	isbn = {2045-2322},
	doi = {https://doi.org/10.1038/s41598-019-48760-7},
	url = {https://www.nature.com/articles/s41598-019-48760-7},
	author = {Lameira, Adriano R. and Shumaker, Robert W.}
}
