Lack of right wiring in primates’ brains prevents them from producing human-like speech

Lack of right wiring in primates’ brains prevents them from producing human-like speech

Monkeys have a vocal tract capable of producing human-like speech but they are unable to produce words because they lack the right wiring in their brains, according to a new study.

Researchers have long been intrigued by primates’ failure to talk like humans. On Friday, a group of researchers reported that their study suggested that monkeys have the required vocal tract but they don’t have the right wiring required to produce words.

The researchers reported, “A monkey’s vocal tract would be perfectly adequate to produce hundreds, thousands of words … This suggests that what makes people unique among primates is our ability to control the vocal apparatus, not the apparatus itself.”

Human speech is produced by contracting muscles and a complicated choreography of flowing air. Humans give the vocal tract a particular shape to produce a particular sound. The vocal tracts of primates contain same elements as ours but their geometry is different.

However, some researchers are not convinced with the results of the study. They argue that human speech’s evolution had to involve changes in both the vocal tract and the brain.

Results of the new study were published in the Dec. 9th edition of the journal Science Advances.

"This suggests that what makes people unique among primates is our ability to control the vocal apparatus, not the apparatus itself," Thore Jon Bergman, an evolutionary biopsychologist at the University of Michigan said in a report published by CS Monitor. Bergman was not directly associated with the study.

The CS Monitor report further informed, "The new research suggests that the monkeys can produce five vowel sounds like humans, but they are missing a crucial one, says Lieberman, who is now a professor emeritus at Brown University in Providence, R.I.. The /i/ vowel, like in "beet," is thought to be particularly special for human speech. And the macaques' vocal anatomy doesn't appear to be capable of making that sound."

"As soon as you had a brain that was ready to control the vocal tract," Fitch says, "the vocal tract of a monkey or nonhuman primate would be perfectly fine for producing lots and lots of words."

The real issue is that monkeys' brains do not have direct connections down to the neurons that control the larynx and the tongue, he says. What's more, monkeys don't have critical connections within the brain itself, between the auditory cortex and motor cortex, which makes them incapable of imitating what they hear in the way that humans do.

Tags: 
Category: