Why can’t monkeys talk, while humans can? It’s an interesting question that many of us may have pondered, as humans are the only primates that are capable of speech. But a new study hints at the answer to that question and suggests that monkeys may actually be able to talk, but aren’t able to do so intelligibly due to other reasons.
A new study published Friday in Science Advances and cited by the Christian Science Monitor suggests that the vocal anatomy of macaques make them capable of “human-like speech.” The researchers analyzed these patterns first by capturing X-ray video of the apes in the process of vocalizing, eating, and making various facial expressions. They then created computer models from the data, which allowed the scientists to determine the capabilities of the macaque’s vocal tract.
While macaques cannot be understood by humans when they “talk,” researcher Asif Ghazanfar from Princeton University said that they may make some sounds humans are capable of making.
“The range of different sounds that a living macaque can produce actually overlaps quite a bit with the sounds that a human can produce.”
According to study co-author W. Tecumseh Fitch from the University of Vienna, monkeys have vocal tracts capable of producing “hundreds, (even) thousands” of words, and several types of sounds. In theory, he believes that the vowels in words such as “bit,” “bet,” “bat,” “but,” and “bought” are among the possible sounds monkeys can make.
The New York Times wrote that people were able to correctly recognize the sounds when the researchers played the macaque recordings back. And it even got to a point where Fitch and his fellow researchers were able to string recognizable sentences together based on the sounds the macaques created. But as for the reason why monkeys can’t talk coherently like humans do, Ghafanzar attributed this shortcoming to the animals’ brains.
“If they had the brain, they could produce intelligible speech.”
Aside from the animals’ brains, there is also another shortcoming preventing monkeys from achieving human-like speech. The Christian Science Monitor wrote that Brown University professor emeritus Phillip Lieberman, who created an early computer model of macaque speech in 1969 based on the vocal tract of a dead ape, observed that monkeys cannot enunciate the /i/ vowel, as used in words such as “beet.” He singles out this vowel sound as a unique aspect of human speech, and one curiously missing in macaque speech patterns.
“We could talk without these sounds. But it wouldn’t be an effective means of communication.”
Max Planck Institute for Psycholinguistics cognitive scientist Marcus Perlman also shared his own insights on the new study with the CSMonitor. In an email to the publication, he wrote that the ability to speak may extend to great apes, and may “characterize a baseline” for our hominid ancestors. In other words, the answer to why monkeys can’t talk may not be related to their vocal tract.
Perlman, who was not involved in the study, also suggested that non-human primates, as well as our ancestors, may have had vocal tracks capable of enunciating certain consonants. One example was the “talking” chimpanzee Viki, who was able to string the words “mama,” “papa,” and “cup” together, representing three different consonants.
“Considering all of the current evidence, it appears clear that our great ape ancestors would have had a vocal anatomy capable of articulating enough vowels and consonants to provide a fairly substantial substrate for a spoken language,” he said.
In all, the authors of the new study agree with other scientists who believe that macaques and other non-human primates don’t have the neural pathways to produce coherent speech. But it may take more than simply eliminating the vocal tract theory when it comes to figuring out the exact reason why monkeys cannot talk.
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