The ability to perceive the sound quality known as “pitch” can no longer be listed as unique to humans. Johns Hopkins researchers — including auditory neuroscientist and Professor of Biomedical Engineering, Xiaoqin Wang — report new behavioral evidence that the highly-vocal marmoset monkey, with a hearing range similar to that of humans, appear to use auditory cues similar to humans to distinguish between low and high notes.
The research, Complex pitch perception mechanisms are shared by humans and a New World monkey, was published online in the journal Proceedings of the National Academy of Sciences. In addition to Dr. Wang other authors of the report include graduate student Xindong Song, Research Associate Michael Osmanski and graduate student Yueqi Guo of the Department of Biomedical Engineering. The paper appeared on the cover of PNAS, vol. 113 no 3, January 19, 2016.
The discovery infers that aspects of pitch perception may have evolved more than 40 million years ago to enable vocal communication and songlike vocalizations.
Wang’s previous research discovered a region in the marmoset brain where nerve cells “fired” after exposure to sounds with pitch, like a melody’s shift from high to low notes. Human brains show similar activity in that region. What researchers were missing, though, was behavioral evidence that the marmosets could perceive and respond to pitch in the same way humans do. Wang’s team spent years developing ways to test pitch perception, including training a group of marmosets to lick a waterspout only after hearing a change in pitch. Through a series of hearing tests, with waterspout licks as a readout, Wang’s team, led by graduate student Xindong Song, determined that marmosets share the three specialized features of pitch perception once thought to be unique to humans.
Humans first of all are better at distinguishing pitch at low frequencies rather than high. Second, they’re able to pick up on subtle changes in the spread between pitches at low frequencies. And lastly, a person’s sensitivity to rhythm appears to dictate their ability to detect pitch differences among simultaneous tones.
“Now that we have a primate relative we can study behaviorally and physiologically,” Wang says, “tone deafness and perfect pitch may be studied to determine whether those traits are inherited or learned.”