Dent M L, Brittan-Powell E F, Dooling R J, Pierce A
Department of Psychology, University of Maryland, College Park 20742, USA.
J Acoust Soc Am. 1997 Sep;102(3):1891-7. doi: 10.1121/1.420111.
Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover, there are only a handful of avian species that are known to be good mimics of human speech. One such species is the budgerigar (Melopsittacus undulatus), which is a popular mimic of human speech and learns new vocalizations throughout adult life. Using operant conditioning procedures with a repeating background task, we tested budgerigars on the discrimination of tokens from two synthetic /ba/-/wa/ speech continua that differed in syllable, but not transition, duration. Budgerigars showed a significant improvement in discrimination performance on both continua near the phonetic boundary for humans. Budgerigars also showed a shift in the location of the phonetic boundary with a change in syllable length, similar to what has been described for humans and other primates. These results on a nonmammalian species provide support for the operation of a general, nonphonetic, auditory process as one mechanism which can lead to the well-known stimulus-length effect in humans.
