Date: May 31, 2017
No experience with human speech is necessary for budgerigars to perceive the difference between "d" and "t," according to a study published May 31, 2017 in the open-access journal PLOS ONE by Mary Flaherty from The State University of New York, Buffalo, USA, and colleagues.
The debate over speech perception is unresolved, with some evidence supporting a speech-specific mechanism and other evidence supporting a general auditory mechanism. The latter case holds that, in the absence of extensive experience with speech, there should be no difference between speech and nonspeech perception. To investigate this scenario, Flaherty and colleagues used budgerigars, vocal mimics that are similar to people in their ability to perceive consonant and vowel tokens. The researchers divided 25 budgerigars into groups before hatching, raising some in complete isolation from human speech and others with extensive exposure to human speech.
After the birds fledged, the researchers trained them to peck keys in response to synthetic speech sounds that began with "d" or "t." Then they tested the birds' perception of speech sounds that varied in two cues: voice onset time and the frequency of the first formant (formants are resonating frequencies of the vocal tract). For comparison, they likewise tested the perception of speech sounds in 25 people.